Alternative Power sources - DC generator vs DC Converter

Author

DC generator vs DC Converter

JoeSixPack

2005-10-15, 11:21 am

Charging 4 T-105s that run a 2000W Go-Power puresine inverter. What's the
efficiency of using an AC generator to charge the batteries through the 12V
converter vs. using some sort of gasoline-powered DC generator, such as a
gas engine-driven automotive alternator? How much efficiency do you lose by
using the AC? The converter is all solid state 45 amp, regulated, and has a
15 amp breaker behind the battery-charging circuit. All equipment is less
than 2 years old.

Steve Spence

2005-10-15, 11:21 am

JoeSixPack wrote:
> Charging 4 T-105s that run a 2000W Go-Power puresine inverter. What's the
> efficiency of using an AC generator to charge the batteries through the 12V
> converter vs. using some sort of gasoline-powered DC generator, such as a
> gas engine-driven automotive alternator? How much efficiency do you lose by
> using the AC? The converter is all solid state 45 amp, regulated, and has a
> 15 amp breaker behind the battery-charging circuit. All equipment is less
> than 2 years old.
>
>
The "converter" may not have the 3 stages necessary for good battery
health. Most dc chargers don't either.

for dc charging you need something similar to:

http://www.amplepower.com/products/sarv3/index.html

for ac charging you need something similar to:

http://tinyurl.com/9jskw

either will do a good job. if you have some non-inverter ac loads, an ac
charger will be a better bet. if everything you have can run on the
inverter, then dc is a good deal.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Ulysses

2005-10-15, 2:21 pm

"JoeSixPack" <olegp@telus.net> wrote in message
news:9D74f.13803$y_1.2650@edtnps89...
> Charging 4 T-105s that run a 2000W Go-Power puresine inverter. What's the
> efficiency of using an AC generator to charge the batteries through the
12V
> converter vs. using some sort of gasoline-powered DC generator, such as a
> gas engine-driven automotive alternator? How much efficiency do you lose
by
> using the AC? The converter is all solid state 45 amp, regulated, and has
a
> 15 amp breaker behind the battery-charging circuit. All equipment is less
> than 2 years old.
>
>
As Steve Spence pointed out the converter will not do a good job of charging
your batteries. I also suspect it will go well over 14.5 volts when the
batteries are fully charged.

I am charging four 220 Ah batteries using a Honda eu2000 generator and a
Vector 40 amp Smart Charger. The charger is fully regulated and 3-stage.
However, I am working on a engine-driving-an-alternator generator and I use
it (still in the process of configuring it for best functionality and
portability, weather resistance, etc) to drive a MSW inverter which in turns
powers the Vector charger. My last Honda eu2000 lasted around 12,000 hours
but when the engine finally wore out I discovered it was unrepairable (well,
$800 to fix it and a new one was $900). The alternator I have is driven by
a Honda 4 HP engine. I now have the option of using many different engines,
alternators, and inverters for future repairs or upgrades. The most
expensive component is the engine and they are currently selling for about
$150 new. With a good 85 Ah 12 volt battery and the 65 amp alternator it
will supply at least (tested so far) around 1300 watts for a limited time.
It will supply over 800 watts for extended times. It has plenty of power
for other AC appliances while charging the batteries. The fuel consumption
is approximately the same as for the Honda generator. The engine is running
at only about 2000 rpm so I expect a long life and some extension on oil
changes. As far as effeciency goes I am looking at the long term repair
costs as part of the equation. Ease of repair is also a definate
consideration. If you try to use an alternator to directly charge your
batteries it will be difficult to regulate the current and voltage. With my
Vector charger I don't have to worry about them and they will likely last
much longer than with other types of battery chargers.

My next step will be to try and get the engine/alternator contraption to run
from wood gas.

Steve Spence

2005-10-15, 5:21 pm

Ulysses wrote:
> "JoeSixPack" <olegp@telus.net> wrote in message
> news:9D74f.13803$y_1.2650@edtnps89...
>
>
> 12V
>
>
> by
>
>
> a
>
>
> As Steve Spence pointed out the converter will not do a good job of charging
> your batteries. I also suspect it will go well over 14.5 volts when the
> batteries are fully charged.
>
> I am charging four 220 Ah batteries using a Honda eu2000 generator and a
> Vector 40 amp Smart Charger. The charger is fully regulated and 3-stage.

> If you try to use an alternator to directly charge your
> batteries it will be difficult to regulate the current and voltage. With my
> Vector charger I don't have to worry about them and they will likely last
> much longer than with other types of battery chargers.
>
>
>
I forgot to mention that I have 6 T105's powering a AC Delco 2500 watt
inverter. I use a schumacher 40amp 3 stage charger from Walmart, very
similar to the Vector. This system powers my house.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Loren Amelang

2005-10-15, 5:21 pm

On Sat, 15 Oct 2005 13:38:13 GMT, "JoeSixPack" <olegp@telus.net>
wrote:

>Charging 4 T-105s that run a 2000W Go-Power puresine inverter. What's the
>efficiency of using an AC generator to charge the batteries through the 12V
>converter vs. using some sort of gasoline-powered DC generator, such as a
>gas engine-driven automotive alternator? How much efficiency do you lose by
>using the AC? The converter is all solid state 45 amp, regulated, and has a
>15 amp breaker behind the battery-charging circuit. All equipment is less
>than 2 years old.

Other posts didn't directly address the efficiency question. I'd say
it all depends on the relative sizes of your generators, chargers, and
battery banks, and whether they are your only charging source or you
have solar as well.

In my system, both DC (truck alternator on Honda engine) and AC (Dual
switching chargers running from 5KW Onan) sources can usually run
flat-out and stay within the acceptance range of my battery bank. When
the batteries are so close to full that that is no longer true, I just
let the solar finish the job (the generators are only for extended
low-sun emergencies).

My take on efficiency is that even running two "75 Amp" AC to DC
chargers doesn't use but a small fraction of the Onan's output, and
the old Onan is not very efficient (or happy) at low power draws.
Unless I need lots of AC for other uses, using the Honda saves fuel
dollars. And considering another kind of efficiency, it wears out a
$300 machine rather than a $3000 machine.

If you don't have significant solar capability and need to fully
charge your batteries with a generator, or your battery bank can't
accept the full output of your generator even when discharged, the
problem of the load decreasing to very low levels gets even worse. If
I had to deal with that I'd look into one of the new
inverter-generators where the engine can slow to idle at very low
power draws.

Loren

Rob

2005-10-15, 5:21 pm

"Ulysses" <therealulysses@yahoo.com> wrote in
news:11l2c8ss61o26e0@corp.supernews.com:

>
If
> you try to use an alternator to directly charge your batteries it will
> be difficult to regulate the current and voltage. With my Vector
> charger I don't have to worry about them and they will likely last
> much longer than with other types of battery chargers.
>

I'm still trying to figure this all out. I have an almost identical 4hp
engine driving an 80 amp alt, charging two t605's while the batts run a
msw inverter. My thoughts were that the internal regulater of the alt
would handle the current and voltage regulation. I see the extra benifits
of running an inverter to charger to batt set up, but the third stage of
battery charging is a long slow process (correct me if I'm wrong) and as
such, a fairly fuel consuming process on a gas generator. Would it not be
more economical to use the 12v generator to charge the batts up to say 80%
(bulk charge)then let them run down to say 50% before recharging?

I relize the importance of topping up the batts to 100% (between uses) I'm
refering to my not too often power outages. It seems to me that putting
all 80(?) amps for a while into the batts, then shutting down when the amps
drop to 2 or 3 would work? (BTW with a 4" pully on the engine, its not too
far off idle to put out 65 amps (65amps best I ever got )).

I do hook up to a 3 stage charger when the grid returns.

Rob..........

Robert Morein

2005-10-15, 7:21 pm

George Ghio

2005-10-15, 8:21 pm

Steve Spence wrote:
> Ulysses wrote:
>
>
>
> I forgot to mention that I have 6 T105's powering a AC Delco 2500 watt
> inverter. I use a schumacher 40amp 3 stage charger from Walmart, very
> similar to the Vector. This system powers my house.
>
He also forgot to mention the bloody great diesel generator. Steve is
being a bit misleading here.

If you have a charger and a generator use it.

If you use a motor/alternator combination you have two choices;

1) A good charge regulator to control it or

2) Learn to control it manually.

As an aside the T105's are not a great choice for the job.

Vaughn

2005-10-15, 10:21 pm

"George Ghio" <AKA@nomailhere.com> wrote in message
news:43518870_1@news.chariot.net.au...
>
> If you use a motor/alternator combination you have two choices;
>
> 1) A good charge regulator to control it

westmarine.com will be happy to sell you a variety of three stage
regulators for alternators. Be prepared to spend about $200.00.

Vaughn

JoeSixPack

2005-10-16, 1:21 am

"Steve Spence" <sspence@green-trust.org> wrote in message
news:rIc4f.24102$Ge5.17588@fe10.lga...
> Ulysses wrote:

It's been holding battery voltage very steady at 13.8 for several weeks now.
I hope this converter will maintain the batteries in good condition until
they go back into service with the PV array in the spring.

At that time, I'm undecided whether to invest in a quiet inverter-generator
to run for long periods to supplement the P.V. array, or to get an
gas-engine driven alternator to charge them more quickly for shorter
periods. I could live with 75% overall efficiency running an AC generator
thru a converter to charge the batteries, but if it's lower than that, I'd
look more seriously at running a gas powered alternator to charge the
batteries directly.
[color=darkred]
>

What's wrong with the internal regulator in the alternator? It seems to keep
car batteries well-charged for years at a time.
[color=darkred]
> I forgot to mention that I have 6 T105's powering a AC Delco 2500 watt
> inverter. I use a schumacher 40amp 3 stage charger from Walmart, very
> similar to the Vector. This system powers my house.
>

I also have the option of plugging in a solid state battery charger which
has a setting for deep-cycle batteries. I don't see the need to use it, as
I have no reason to believe it would do a better job than the converter is
already doing.

nicksanspam@ece.villanova.edu

2005-10-16, 3:21 am

Robert Morein <nowhere@nowhere.com> wrote:

>Ripple current will kill a battery.

Because of the heating effect?

>An engine driven alternator has too much ripple to float a battery...

How much is too much?

Nick

wmbjk

2005-10-16, 12:21 pm

On Sun, 16 Oct 2005 04:11:42 GMT, "JoeSixPack" <olegp@telus.net>
wrote:

>What's wrong with the internal regulator in the alternator? It seems to keep
>car batteries well-charged for years at a time.

A Home Power Magazine article on the subject. Read the paragraph
that's 7th from the bottom.

http://www.greenspun.com/bboard/q-a...l?msg_id=001BAG

Wayne

JoeSixPack

2005-10-16, 1:21 pm

"wmbjk" <wmbjkREMOVE@citlink.net> wrote in message
news:ijp4l15t1d2aespvn496dg0dqaqs0b1v5n@4ax.com...
> On Sun, 16 Oct 2005 04:11:42 GMT, "JoeSixPack" <olegp@telus.net>
> wrote:
>
>
>
> A Home Power Magazine article on the subject. Read the paragraph
> that's 7th from the bottom.
>
> http://www.greenspun.com/bboard/q-a...l?msg_id=001BAG
>
> Wayne

I pasted the paragraph in question for your convenience:
Car Voltage Regulators Car voltage regulators will not work well in deep
cycle applications. The regulator makes its decisions based only on the
systems voltage. This is fine with the average car battery which is cycled
to less than 1% of its capacity before being refilled. However, the deep
cycle battery is almost empty when it is recharged. The car voltage
regulator attempts to instantly bring the systems voltage to 1415 Volts. A
12 Volt deep cycle lead-acid battery will not reach a voltage of 14 Volts
until it is almost filled. The net result is that the car regulator dumps
the entire output of the alternator into the batteries until they are full.
This is almost always too much energy too fast for a fully discharged
battery. To compound the problem, the car regulators voltage limit is set
too low for deep cycle service. This low voltage limit means that the
batteries are charged too slowly when they are almost full, resulting in
many extra hours of generator operation to totally fill the battery pack.
Since the car regulator is set at about 14 Volts, we are unable to raise the
system voltage up to over 16 Volts for the essential equalizing charges.

None of those concerns are mine for this application. My intention is to
supplement the charging of the photovoltaics when they can't keep up. This
will mostly happen towards the end of summer before I go on the grid for the
winter. When I run the generator, the batteries will probably start at about
75%, and I want to bring them up to about 95% fairly quickly. A 30-60 amp
charge for a few hours from an alternator shouldn't damage four 225AH
deepcycle batteries, I should think. From there, the photovoltaics can bring
them up to full charge during the day with a 5-15A regulated charge rate. I
am trying to decide whether I need to use an regular AC generator (+solid
state charger) or an automotive alternator for this purpose.

RF Dude

2005-10-16, 2:21 pm

Why do you need a generator if you have grid? Sounds like the 3-stage AC
charger is for you.

An AC switch regulated charger efficiency is 87% or better. But your gas
engine is terrible. I was just looking at the input BTU/hr numbers for home
standby gennies (~11 kW) and noticed they are about 17% (full load)
efficient when compared to the input BTU required.

>"JoeSixPack" <olegp@telus.net wrote:
>This will mostly happen towards the end of summer before I go on the grid
>for the winter.

Solar Flare

2005-10-16, 2:21 pm

Engine driven automobile alternators are usually 3 or more phases and the ripple
from fullwave rectified 3 phase is next to nothing.

<nicksanspam@ece.villanova.edu> wrote in message
news:dispfs$loe@acadia.ece.villanova.edu...
> Robert Morein <nowhere@nowhere.com> wrote:
>
>
> Because of the heating effect?
>
>
> How much is too much?
>
> Nick
>

JoeSixPack

2005-10-16, 3:21 pm

"RF Dude" <post@thisnewsgroup.com> wrote in message
news:gev4f.199$ns3.59425@news20.bellglobal.com...
> Why do you need a generator if you have grid? Sounds like the 3-stage AC
> charger is for you.

I go off the grid in the summer. At these northern latitudes, the solar
energy is about 10X greater in June than it is in December. Solar energy
becomes irrelevent about the end of August, and some other power source is
needed.

I tried the 3-stage charger, and it worked well, but the 115-12V converter
seems to be holding the batteries at a constant 13.8 V, and until someone
convinces me there's a better way, I can leave it at that.

>
> An AC switch regulated charger efficiency is 87% or better. But your gas
> engine is terrible. I was just looking at the input BTU/hr numbers for
> home standby gennies (~11 kW) and noticed they are about 17% (full load)
> efficient when compared to the input BTU required.

The efficiency is a concern between the two types of gasoline-powered
chargers. That's my only option in the summer whan I'm off-grid. I don't
want to invest in a gas engine powered alternator if the efficiency of going
from an AC generator thru a charger is nearly as good.

JoeSixPack

2005-10-16, 3:21 pm

"Solar Flare" <sflare@hotmail.com> wrote in message
news:tbednYjif6qfFs_enZ2dnUVZ_sudnZ2d@golden.net...[color=darkred]
> Engine driven automobile alternators are usually 3 or more phases and the
> ripple
> from fullwave rectified 3 phase is next to nothing.
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:dispfs$loe@acadia.ece.villanova.edu...

I don't want to float the battery, I just want a quick charge. The
photovoltaics do the final charge.

RF Dude

2005-10-16, 3:21 pm

Concern for efficiency ($ per kW) would keep you on the grid! ;-))

Diesels are more efficient converting fuel to energy. Add some wind
generators if you can. They will compensate when the sun isn't shining. If
you get some surplus Programmable Logic Controllers, you can set yourself up
with a "Cycle Charged" energy approach as used in many isolated
communications sites (helicopter access). Without getting specific, I can
tell you there are cycle charged sites in Canada using wind and solar where
the generator rarely ever has to start up. Wind and sun provide all needs
with the rare top up by generator. To make this work, a very large battery
is required so that you can go a few days without worring about low output
from wind or sun. The PLC can shed load if necessary, or convert excess
load to other useful purposes. It can tweak the charge regime to make sure
all resources are running at full efficiency. For instance, the generator
is never used to fully charge the battery... not efficient. But excess
energy from sun or wind can bring the battery to 100%. Etc.

Your 13.8V should be OK for float. You won't get the battery to 100%
efficiently with a generator / charger set to this voltage. Battery float
charging is an exponential curve. It may take a battery a few hours to get
to 90%, but a week to get to 100% capacity on float voltage alone. Not
acceptable for engine charging systems. Thus engines are used to get the
battery to ~90% only. The smart chargers change this scenario somewhat, as
you can keep flowing energy into the battery closer to the desired 100% by
raising the voltage (to 14.4 say). But the trick is to back it off to safe
float voltage before damage (or gassing) results.

RF Dude

Solar Flare

2005-10-16, 4:21 pm

I doubt one would have to worry about ripple heating effect when just bulk
charging.

Sitting on float with charge going in every peak waveform and out between
waveforms 24/7 is most likely the problem with cell wear and tear.

"JoeSixPack" <olegp@telus.net> wrote in message
news:Xrw4f.37639$ir4.21423@edtnps90...
>
> "Solar Flare" <sflare@hotmail.com> wrote in message
> news:tbednYjif6qfFs_enZ2dnUVZ_sudnZ2d@golden.net...
>
> I don't want to float the battery, I just want a quick charge. The
> photovoltaics do the final charge.
>
>

Ulysses

2005-10-16, 4:21 pm

"JoeSixPack" <olegp@telus.net> wrote in message
news:2qk4f.30842$S4.2780@edtnps84...
>
> "Steve Spence" <sspence@green-trust.org> wrote in message
> news:rIc4f.24102$Ge5.17588@fe10.lga...
the[color=darkred]
a[color=darkred]
lose[color=darkred]
the[color=darkred]
>
> It's been holding battery voltage very steady at 13.8 for several weeks
now.
> I hope this converter will maintain the batteries in good condition until
> they go back into service with the PV array in the spring.
>
> At that time, I'm undecided whether to invest in a quiet
inverter-generator
> to run for long periods to supplement the P.V. array, or to get an
> gas-engine driven alternator to charge them more quickly for shorter
> periods.

My engine-driven alternator is not a whole lot louder than my Honda eu2000.
Since it is running at reduced rpm the noise is less annoying. I also stuck
an additional muffler (riding lawnmower type, $3 at Home Depot) on it and it
greatly reduces the projected noise.

If I had not already bought the secone eu2000 I would go with the engine,
altenator, battery, and probably a 1500 watt MSW inverter. It should do
just about everything the Honda will do plus it can still supply power (up
to 800 watts) when the engine is off.

It may seem absurd to be using a battery to charge batteries but it works
well and you need some way to stabilize the voltage so the inverter doesn't
shut down from overvoltage (or get fried).

I could live with 75% overall efficiency running an AC generator
> thru a converter to charge the batteries, but if it's lower than that, I'd
> look more seriously at running a gas powered alternator to charge the
> batteries directly.
>
a[color=darkred]
3-stage.[color=darkred]
>
>
> What's wrong with the internal regulator in the alternator? It seems to
keep
> car batteries well-charged for years at a time.
>
last[color=darkred]
>
> I also have the option of plugging in a solid state battery charger which
> has a setting for deep-cycle batteries. I don't see the need to use it,
as
> I have no reason to believe it would do a better job than the converter is
> already doing.
>
>

I don't either.

Ulysses

2005-10-16, 5:21 pm

"Rob" <beprivat@here.org> wrote in message
news:zsSdnWye-7nX_MzeRVn-sQ@rogers.com...
> "Ulysses" <therealulysses@yahoo.com> wrote in
> news:11l2c8ss61o26e0@corp.supernews.com:
>
> If
>
> I'm still trying to figure this all out. I have an almost identical 4hp
> engine driving an 80 amp alt, charging two t605's while the batts run a
> msw inverter. My thoughts were that the internal regulater of the alt
> would handle the current and voltage regulation.

Well, I don't have an ammeter connected yet and when I tried using the
alternator directly to charge the batteries they did not appear to be
charging. From what I've read the built-in regulator will stop charging the
batteries long before they are done. I doubt that overvoltage would be much
of a problem with the size of battery array you have.

OTOH the built-in regulator seems to do a great job of keeping my 85 Ah
battery charged and easily supplies an 800 watt inverter for extended times.
And, like I said, I can also run another 700 watt inverter which will draw
it's power from the battery, at least for a limited time. I have not
measured how much current the battery is drawing while running under the 800
watt load limit (65 amp alternator's abilities) but the battery voltage
always reads just a little higher than before I started the whole thing up.

Now, if I can ever find out how to use the sine wave inverter in my old,
worn out eu2000...

I see the extra benifits
> of running an inverter to charger to batt set up, but the third stage of
> battery charging is a long slow process (correct me if I'm wrong) and as
> such, a fairly fuel consuming process on a gas generator.

I don't know how many Ah the T605s are but with my 440 Ah at 12 volts if I
used them all night and all the next day and then charge them in the evening
it takes about 4-5 hours to bring them to about 98% charge with the Vector
charger (I never run them down very far though). It starts out at 40 amps
(actually I prefer to start at 20, run it for a couple hours and then
switch to 40 to reduce the load on the engine) so the initial charging is
fairly quick and the final charging stages (once it drops below 20 amps)
complete in an hour or two. With a 4 HP engine we are talking about
approximately 1 gallon of gas to do the job.

Would it not be
> more economical to use the 12v generator to charge the batts up to say 80%
> (bulk charge)then let them run down to say 50% before recharging?
>
> I relize the importance of topping up the batts to 100% (between uses) I'm
> refering to my not too often power outages. It seems to me that putting
> all 80(?) amps for a while into the batts, then shutting down when the
amps
> drop to 2 or 3 would work? (BTW with a 4" pully on the engine, its not
too
> far off idle to put out 65 amps (65amps best I ever got )).

I started out with a 5" pulley and I was able to run my engine a bit slower
and it seemed to be using somewhat less gas but it was an aluminum pulley
and it didn't last very long. The biggest steel pulley I could find was 4".
I suspect that the best size pulley for our purposes is about 4 1/2" to 5".

BTW which way is your alternator turning? I read info in at least 3 places
that indicated that it *should* be turning clockwise as seen from the pulley
end but all of the instructions I found had it going counterclockwise. If
your alternator is turning the wrong way is it possible you may not be
getting your full 80 amps because it's overheating?

>
> I do hook up to a 3 stage charger when the grid returns.
>
> Rob..........

JoeSixPack

2005-10-16, 5:21 pm

<nicksanspam@ece.villanova.edu> wrote in message
news:dispfs$loe@acadia.ece.villanova.edu...
> Robert Morein <nowhere@nowhere.com> wrote:
>
>
> Because of the heating effect?
>
>
> How much is too much?
>
> Nick
>

That's a bit confusing, because it's my understanding that a storage battery
does a fine job of leveling off the peaks and troughs in any circuit
connected to it.

Harry Chickpea

2005-10-16, 8:21 pm

>To compound the problem, the car regulators voltage limit is set
>too low for deep cycle service. This low voltage limit means that the
>batteries are charged too slowly when they are almost full, resulting in
>many extra hours of generator operation to totally fill the battery pack.
>Since the car regulator is set at about 14 Volts, we are unable to raise the
>system voltage up to over 16 Volts for the essential equalizing charges.

Intriguing. For home use of a system, lets figure a 24 hour duty
cycle. That means getting a full float charge on a system is nigh on
impossible and Pb/Acid batteries should be failing right and left.
Would battery life be extended significantly if there were two battery
banks, and there was an additional 24 rest period where each bank
would be float charged on alternate days?

Next question - What if an alternator was used to fast charge a
(third) small "topper" bank of more forgiving batteries -say NiMH-
that were then used to power an inverter/charger to provide the float
charge over that 24 hr period to the Pb/Acid banks? Would that be
practical or cost-effective?

Where I'm going is the idea of a system where an engine/alternator
operates for the peak 2 to 4 hours per day, also supplying hot water
and heat as co-gen, but then the battery/inverter system coasts the
lighting and less energy intensive appliances through the rest of the
day - but (and this is the big but) the system can operate in this
mode indefinitely.

Is something like this feasible?

Solar Flare

2005-10-16, 9:21 pm

It does, but does a lot of work to do it. iT has to take a charge at the peak
voltage and carry the load between peaks of waveforms. This is like charging and
discharging your bank 120 times per second. Much wear and tear on the battery
bank.

"JoeSixPack" <olegp@telus.net> wrote in message
news:o6y4f.38400$ir4.3404@edtnps90...
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:dispfs$loe@acadia.ece.villanova.edu...
>
> That's a bit confusing, because it's my understanding that a storage battery
> does a fine job of leveling off the peaks and troughs in any circuit
> connected to it.
>
>

George Ghio

2005-10-16, 10:21 pm

JoeSixPack wrote:
> <nicksanspam@ece.villanova.edu> wrote in message
> news:dispfs$loe@acadia.ece.villanova.edu...
>
>
>
> That's a bit confusing, because it's my understanding that a storage battery
> does a fine job of leveling off the peaks and troughs in any circuit
> connected to it.
>
>

The danger here is just too much bad advice. Now from your post:

"None of those concerns are mine for this application. My intention is
to supplement the charging of the photovoltaics when they can't keep up."

You can do this. You will need a regulator to control the charge.

You have three choices:

1) The reg built into the alt. Only if you are desperate.

2) A purpose built reg. Better control, better charging.

3) The reg you have between your ears. Works well, runs on full logic
but requires you to stay awake.

I believe you said 4 225Ah batteries. If that is in fact 500Ah all up (4
T105s series/parallel) then a 30 amp alt will be fine, 60A would be
pushing the friendship a bit. C10 would be 50A. But you want to bring
your batteries up faster than ten hours.This means you need a charging
regime to suit your needs.

My charger:

5hp motor, 35A Bosch alt(external reg type, reg not used) Rheostat for
field control. This is the famous 150A rated ceramic Rheostat scrounged
from a spot welder.

Take the state of charge in your batteries. Yes it is important that you
not let them remain at a low state of charge for long periods, on the
other hand they do not need to reach 100% charge every single day
either. I will run the little generator to charge my batteries if they
drop to 12 Volts (but like the fine print says ”Conditions Apply”)

Condition: Batteries read 12 volts at four o’clock in the afternoon

Condition: I know the sun won’t be out tomorrow.

Condition: I need to use the computer for several hours that night.
(This condition has been negated due to better computer.)

Condition: There will be three hours of Red Dwarf on TV that night.

It takes at least two of these conditions to warrant the running of the
generator. It may be that your "required" conditions will be different.

And when it comes to charging the batteries I am not trying to bring
them up to 100%. I am doing what I call ”Maintenance Charging” which is
to say that I only require that they be in the top twenty per cent of
their capacity. The sun usually does the rest.

When required I run the gen for less three hours. This is for a battery
set of 840Ah. During winter this may be as much as 3 hours a week or as
little as 1-2 hours/month.

Will this harm your batteries, only if you're stupid and don't pay
attention to what you are doing.

Oh, I also run a logger on my system so I know what is going on, at all
times.

George

Harry Chickpea

2005-10-16, 10:21 pm

George Ghio <AKA@nomailhere.com> wrote:

>Condition: There will be three hours of Red Dwarf on TV that night.

Smegging right, but there are only so many episodes. :-)

nicksanspam@ece.villanova.edu

2005-10-17, 6:21 am

Solar Flare <sflare@hotmail.com> wrote:

>...This is like charging and discharging your bank 120 times per second.
>Much wear and tear on the battery bank.

How much is too much?

Nick

Robert Morein

2005-10-17, 10:21 am

"Solar Flare" <sflare@hotmail.com> wrote in message
news:tbednYjif6qfFs_enZ2dnUVZ_sudnZ2d@golden.net...
> Engine driven automobile alternators are usually 3 or more phases and the
ripple
> from fullwave rectified 3 phase is next to nothing.
>
I have a NATO 2KW 28VDC field generator. The rating is 5% ripple.

Robert Morein

2005-10-17, 10:21 am

<nicksanspam@ece.villanova.edu> wrote in message
news:divk1t$mab@acadia.ece.villanova.edu...
> Solar Flare <sflare@hotmail.com> wrote:
>
>
> How much is too much?
>
> Nick
>
The battery manufacturers want perfect DC, like that provided by a regulated
power supply.
As Solar Flare remarks, they want it that way with the battery disconnected.
The battery will level it, but at the cost of constant erosion of the
plates.

Ulysses

2005-10-17, 12:21 pm

"George Ghio" <AKA@nomailhere.com> wrote in message
news:4352ee42_4@news.chariot.net.au...
>
>
> JoeSixPack wrote:
battery[color=darkred]
>
> The danger here is just too much bad advice. Now from your post:
>
> "None of those concerns are mine for this application. My intention is
> to supplement the charging of the photovoltaics when they can't keep up."
>
> You can do this. You will need a regulator to control the charge.
>
> You have three choices:
>
> 1) The reg built into the alt. Only if you are desperate.
>
> 2) A purpose built reg. Better control, better charging.
>
> 3) The reg you have between your ears. Works well, runs on full logic
> but requires you to stay awake.
>
> I believe you said 4 225Ah batteries. If that is in fact 500Ah all up (4
> T105s series/parallel) then a 30 amp alt will be fine, 60A would be
> pushing the friendship a bit. C10 would be 50A. But you want to bring
> your batteries up faster than ten hours.This means you need a charging
> regime to suit your needs.
>
> My charger:
>
> 5hp motor, 35A Bosch alt(external reg type, reg not used) Rheostat for
> field control. This is the famous 150A rated ceramic Rheostat scrounged
> from a spot welder.

When using the rheostat what exactly is happening? Are you able to control
both the voltage and current or just the current and shutting down when the
voltage reaches it's peak?

>
> Take the state of charge in your batteries. Yes it is important that you
> not let them remain at a low state of charge for long periods, on the
> other hand they do not need to reach 100% charge every single day
> either. I will run the little generator to charge my batteries if they
> drop to 12 Volts (but like the fine print says ”Conditions Apply”)

This is a very good point concerning effeciency--the batteries do not
necessarily have to reach a 100% charge every day. I do not know how to
tell the difference between, say, a 90% and 100% charge. My hydrometer will
read "full charge" but my Vector charger may still be charging at 5 amps or
so. I would go so far as to say that the hydrometer's reading is probably a
good enough indicator and if it says full then the batteries are adequately
charged. About every few days, however, I do let my Vector run until it
shuts down and says "full."
>

> Condition: Batteries read 12 volts at four o’clock in the afternoon
>
> Condition: I know the sun won’t be out tomorrow.
>
> Condition: I need to use the computer for several hours that night.
> (This condition has been negated due to better computer.)
>
> Condition: There will be three hours of Red Dwarf on TV that night.
>
> It takes at least two of these conditions to warrant the running of the
> generator. It may be that your "required" conditions will be different.
>
> And when it comes to charging the batteries I am not trying to bring
> them up to 100%. I am doing what I call ”Maintenance Charging” which is
> to say that I only require that they be in the top twenty per cent of
> their capacity. The sun usually does the rest.
>
> When required I run the gen for less three hours. This is for a battery
> set of 840Ah. During winter this may be as much as 3 hours a week or as
> little as 1-2 hours/month.
>
> Will this harm your batteries, only if you're stupid and don't pay
> attention to what you are doing.
>
> Oh, I also run a logger on my system so I know what is going on, at all
> times.
>
> George
>
>
>
>

nicksanspam@ece.villanova.edu

2005-10-17, 2:21 pm

Robert Morein <nowhere@nowhere.com> wrote:

>I have a NATO 2KW 28VDC field generator. The rating is 5% ripple.

Is that too much?

Nick

nicksanspam@ece.villanova.edu

2005-10-17, 2:21 pm

Robert Morein <nowhere@nowhere.com> wrote:

>The battery manufacturers want perfect DC...

Ah. So 1 microvolt is too much.

Nick

Bruce in Alaska

2005-10-17, 3:21 pm

In article <4352d539.34092689@localhost>,
hchickpeaREMOVEME@hotmail.com (Harry Chickpea) wrote:

snipped for brevity

> Where I'm going is the idea of a system where an engine/alternator
> operates for the peak 2 to 4 hours per day, also supplying hot water
> and heat as co-gen, but then the battery/inverter system coasts the
> lighting and less energy intensive appliances through the rest of the
> day - but (and this is the big but) the system can operate in this
> mode indefinitely.
>
> Is something like this feasible?

This is basically how I use my system. I have twin 20Kw Gensets
that I run for a totall of 10 hours a day. (7Am to noon, and 5Pm to 10Pm)
That takes care of the main High Power Loadings of Breakfast and Dinner
and the charging of all the battery banks for the twin inverter systems
connected. It also keeps the four freezers at better than -10F on a
24/7 basis, and the telco equipment battery bank charged. I have had
really good luck with both a 1200Amp/hour 24Vdc L16HD bank, as well
as a 800Amp/hour 24Vdc Absolyte II AGM battery bank. These are on
the inverter systems. L16 bank is over 4 years old, and replaced a
800Amp/hour bank that was 12 years old. The Absolyte II bank is 8 years
old now and still has 95% of the new capacity.

Bruce in alaska
--
add a <2> before @

wmbjk

2005-10-17, 3:21 pm

On Mon, 17 Oct 2005 08:03:40 -0700, "Ulysses"
<therealulysses@yahoo.com> wrote:

>When using the rheostat what exactly is happening? Are you able to control
>both the voltage and current or just the current and shutting down when the
>voltage reaches it's peak?

The latter. But if you *know* how many Amp-hrs you want to replace and
the charge rate of the generator, then a spring-wound timer can be
used to somewhat automate the process. Ideally the timer would shut
off the field current, and then shut down the engine after a short
delay to allow some unloaded cool-down time. This outfit
http://www.ifg.thomasregister.com/ supplies affordable timers with
custom contact arrangements and delays.

>
>This is a very good point concerning effeciency--the batteries do not
>necessarily have to reach a 100% charge every day. I do not know how to
>tell the difference between, say, a 90% and 100% charge. My hydrometer will
>read "full charge" but my Vector charger may still be charging at 5 amps or
>so. I would go so far as to say that the hydrometer's reading is probably a
>good enough indicator and if it says full then the batteries are adequately
>charged. About every few days, however, I do let my Vector run until it
>shuts down and says "full."

You might consider adding a Trimetric, Link 10, etc. It will keep
track of Amps in and out, and automatically take Peukert's equation
into account. Here's a link to the user manual for the Link 10, see
page 40. http://www.xantrex.com/web/id/72/docserve.asp

Wayne

wmbjk

2005-10-17, 3:21 pm

On Mon, 17 Oct 2005 10:21:12 +1000, George Ghio <AKA@nomailhere.com>
wrote:

>My charger:
>
>5hp motor, 35A Bosch alt(external reg type, reg not used)

Such examples are useful to readers who might be interested in
building a similar setup. But your choice of engine and alternator is
confusing considering your previous claims that a unit with about
twice the Watts per hp was grossly overpowered. Please clarify.

>field control. This is the famous 150A rated ceramic Rheostat scrounged
>from a spot welder.

Anyone who decides to go this route will need to know what size
rheostat to use. Is there some reason you can't simply give the
resistance range of that rheostat, or better yet, the values required
for your alternator's speed and output?

> I will run the little generator to charge my batteries if they
>drop to 12 Volts

That may work well on your setup, but I expect that only a minority of
systems have the predictable extended period without any
charge-discharge that's needed for a useful state-of-charge
measurement by voltage alone. Many, probably most, owners will find it
inconvenient at best to use voltage as a gauge, since it's a near
useless indicator on systems such as those with full-time inverter
loading, those that are powering say, electric refrigeration, or on
hybrid systems with multiple charging sources. It's generally
recommended that such systems are best equipped with a Trimetric or
similar.

Wayne

Steve Spence

2005-10-17, 3:21 pm

JoeSixPack wrote:

>
> What's wrong with the internal regulator in the alternator? It seems to keep
> car batteries well-charged for years at a time.

it's not designed to keep house batteries charged properly for off-grid
applications. deep cycle batteries won't last 7+ years with a automotive
charger regulator. I can drive screws with a hammer, but it's not the
right tool.

>
>
>
>
> I also have the option of plugging in a solid state battery charger which
> has a setting for deep-cycle batteries. I don't see the need to use it, as
> I have no reason to believe it would do a better job than the converter is
> already doing.

if your converter isn't a 3 stage charger, it's reducing the life of
your batteries. if it doesn't have a deep cycle setting, don't use it on
deep cycle batteries.

>
>

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

JoeSixPack

2005-10-17, 4:21 pm

<nicksanspam@ece.villanova.edu> wrote in message
news:dj0e25$n6l@acadia.ece.villanova.edu...
> Robert Morein <nowhere@nowhere.com> wrote:
>
>
> Ah. So 1 microvolt is too much.
>
> Nick
>

I don't believe any of it. The generator gives a quick charge for an hour or
two, then the photovoltaics take over with the smoothest charging waveform
you could wish for.

Please don't offer advice if you're just guessing.

Thanks.

Ulysses

2005-10-17, 4:21 pm

"wmbjk" <wmbjkREMOVE@citlink.net> wrote in message
news:nho7l15lcmth8uob2kcjnp29uuog6304gg@4ax.com...
> On Mon, 17 Oct 2005 08:03:40 -0700, "Ulysses"
> <therealulysses@yahoo.com> wrote:
>
>
control[color=darkred]
the[color=darkred]
>
> The latter. But if you *know* how many Amp-hrs you want to replace and
> the charge rate of the generator, then a spring-wound timer can be
> used to somewhat automate the process. Ideally the timer would shut
> off the field current, and then shut down the engine after a short
> delay to allow some unloaded cool-down time. This outfit
> http://www.ifg.thomasregister.com/ supplies affordable timers with
> custom contact arrangements and delays.
>
you[color=darkred]
will[color=darkred]
or[color=darkred]
probably a[color=darkred]
adequately[color=darkred]
>
> You might consider adding a Trimetric, Link 10, etc. It will keep
> track of Amps in and out, and automatically take Peukert's equation
> into account. Here's a link to the user manual for the Link 10, see
> page 40. http://www.xantrex.com/web/id/72/docserve.asp
>
> Wayne

Thanks. I'll look into it.

Ulysses

2005-10-17, 4:21 pm

"wmbjk" <wmbjkREMOVE@citlink.net> wrote in message
news:smo7l1pm58t3ugtedih5npnii3nin2mm90@4ax.com...
> On Mon, 17 Oct 2005 10:21:12 +1000, George Ghio <AKA@nomailhere.com>
> wrote:
>
>
> Such examples are useful to readers who might be interested in
> building a similar setup. But your choice of engine and alternator is
> confusing considering your previous claims that a unit with about
> twice the Watts per hp was grossly overpowered. Please clarify.
>
>
> Anyone who decides to go this route will need to know what size
> rheostat to use. Is there some reason you can't simply give the
> resistance range of that rheostat, or better yet, the values required
> for your alternator's speed and output?
>
>
> That may work well on your setup, but I expect that only a minority of
> systems have the predictable extended period without any
> charge-discharge that's needed for a useful state-of-charge
> measurement by voltage alone. Many, probably most, owners will find it
> inconvenient at best to use voltage as a gauge, since it's a near
> useless indicator on systems such as those with full-time inverter
> loading, those that are powering say, electric refrigeration, or on
> hybrid systems with multiple charging sources. It's generally
> recommended that such systems are best equipped with a Trimetric or
> similar.
>
> Wayne

I agree with what you are saying. For me the best indicator of the need to
charge my batteries is experience and familiarity with the particular system
and how much it's used. OTOH I find that with a cheapo MSW inverter it will
start screaming or beeping when it's time to recharge and this is based upon
voltage. Of course the load also has to be considered and the inverter may
start protesting much sooner with more load but may have plenty of reserve
at 10.5 volts. But just sticking a voltmeter on there and trying to use
that as an indicator never worked for me especially if there is a weak cell
and the voltage is always under 12 volts (or whatever) with even the
slightest load.

Steve Spence

2005-10-17, 5:21 pm

JoeSixPack wrote:
> <nicksanspam@ece.villanova.edu> wrote in message
> news:dj0e25$n6l@acadia.ece.villanova.edu...
>
>
>
> I don't believe any of it. The generator gives a quick charge for an hour or
> two, then the photovoltaics take over with the smoothest charging waveform
> you could wish for.
>
> Please don't offer advice if you're just guessing.
>
> Thanks.
>
>

He's not guessing, he's giving some folks a bit of rope ....

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Loren Amelang

2005-10-17, 5:21 pm

On Mon, 17 Oct 2005 10:21:12 +1000, George Ghio <AKA@nomailhere.com>
wrote:

>5hp motor, 35A Bosch alt(external reg type, reg not used) Rheostat for
>field control. This is the famous 150A rated ceramic Rheostat scrounged
>from a spot welder.
>
>Take the state of charge in your batteries. Yes it is important that you
>not let them remain at a low state of charge for long periods, on the
>other hand they do not need to reach 100% charge every single day
>either. I will run the little generator to charge my batteries if they
>drop to 12 Volts (but like the fine print says ”Conditions Apply”)
>
>Condition: Batteries read 12 volts at four o’clock in the afternoon
>
>Condition: I know the sun won’t be out tomorrow.
>
>Condition: I need to use the computer for several hours that night.
>(This condition has been negated due to better computer.)
>
>Condition: There will be three hours of Red Dwarf on TV that night.
>
>It takes at least two of these conditions to warrant the running of the
>generator. It may be that your "required" conditions will be different.
>
>And when it comes to charging the batteries I am not trying to bring
>them up to 100%. I am doing what I call ”Maintenance Charging” which is
>to say that I only require that they be in the top twenty per cent of
>their capacity. The sun usually does the rest.

At last some common sense in this thread! I'm not sure where home
power people have collected the ideas that lead-acid batteries are so
fragile. I learned about them from a fork lift guy and from long
experience, and the fact is they are very forgiving.

The main charging guideline is the C-rate, which is given as some
fraction of the amp-hour size of the battery. Bulk charging flooded
batteries at "C/5" is typically considered safe, even in home power
circles. If you have 300 AH of battery, a C/5 rate would be 60 amps,
and (ignoring the significant losses in the charging process) would
take 5 hours from full discharge to full charge.

The reason charging is not that simple is that as the charging voltage
rises, more energy and water is lost to heat and electrolysis, rather
than going into actually charging the battery. For a flooded 12V
battery, there is some point between 14.6 and 15.2 volts where the
proportion of loss begins increasing much more rapidly. The exact
point, and the steepness of the inflection in the graph of loss vs.
voltage, depends on the battery construction and on its current state
of charge.

If you have un-sealed, liquid flooded batteries and don't mind wasting
charging current and replacing lots of water, you can ignore the
electrolysis and worry only about the heating effect. Fork lift people
have no fear of removing the battery caps to allow more venting, and
charging at rates above C/1. For those of us who must make our own
charging current, being more patient is highly recommended for
efficiency. But provided you replace the lost water and avoid reaching
temperatures that physically damage the battery structure,
electrolysis does not harm the battery. (If you have sealed or gelled
batteries, electrolysis becomes a serious problem and must be
avoided.)

So charging is a matter of staying below the electrolysis inflection
point. With a manually controlled charger (like an automotive
alternator controlled by a rheostat) just crank it up until you hear
the batteries start to bubble continuously, and back it off until they
only gurgle occasionally. As the charge increases, it will take less
and less current to reach this point, but about the same voltage. You
will quickly learn how much voltage your particular bank can take, and
how it varies at different states of charge.

If your regulated charger limits voltage to 14 volts, like many
auto-shop boosters and most automotive alternators with built-in
regulation, it is being much too cautious, and will require far more
engine running time than a charger capable of higher voltages. But
eventually it will get the job done - anything that provides more
current than the self-discharge rate of the battery will _eventually_
get it charged.

But this thread began with a question about efficiency, and since
making electricity from carbon fuel in a mechanical heat-engine is by
far the most inefficient part of the charging process, we want to use
that engine at its most efficient point. Typically that is somewhere
near its full rated power, so we want to choose an engine that
provides about the same output as the bulk charge rate our batteries
can accept.

BTW, my last set of L-16s lasted 13 years under this regime, and my
main bank of big 2V cells is still going strong after 18 years.

I don't believe the superstition about charging "ripple" harming
batteries, either. All of my chargers have been totally unfiltered, as
are huge fork lift chargers. In fact, I believe batteries love
disturbances during charging. Consider the anti-sulfation devices that
intentionally provide a pulsed charge current...

My system uses only shunt regulation, in the form of switching a
rather large water pump on and off. When the batteries can no longer
handle the full output of my solar array and their voltage rises above
the electrolysis inflection point, the pump comes on. Mid-day, the
voltage drops to maybe 13V, a nice float charge, but near the end of
the day the pump may actually draw current from the batteries. When
the pump stops (after a fixed time) charging resumes. I believe this
cycling is much better for battery life than a steady, even charge.

Loren

Solar Flare

2005-10-17, 10:21 pm

It's called "trolling" or "pot shotting", asking rhetorical questions.

Nothing to add but interesting points to consider.

"Steve Spence" <sspence@green-trust.org> wrote in message
news:oYS4f.9718$1X1.7294@fe12.lga...
> JoeSixPack wrote:
>
> He's not guessing, he's giving some folks a bit of rope ....
>
> --
> Steve Spence
> Dir., Green Trust, http://www.green-trust.org
> Contributing Editor, http://www.off-grid.net
> http://www.rebelwolf.com/essn.html

Bob Adkins

2005-10-17, 11:21 pm

On Sat, 15 Oct 2005 09:51:39 -0400, Steve Spence <sspence@green-trust.org>
wrote:

>for ac charging you need something similar to:
>
>http://tinyurl.com/9jskw

I think this one is the same charger as the Black&Decker I saw at Wal-Mart
for $94. Cosmetic differences, but looks like the same chip and functions.
--
Bob

Robert Morein

2005-10-18, 2:21 am

<nicksanspam@ece.villanova.edu> wrote in message
news:dj0duv$n66@acadia.ece.villanova.edu...
> Robert Morein <nowhere@nowhere.com> wrote:
>
>
> Is that too much?
>
> Nick
>
Yes, way too much. It has to be well under 1%.

Robert Morein

2005-10-18, 2:21 am

<nicksanspam@ece.villanova.edu> wrote in message
news:dj0e25$n6l@acadia.ece.villanova.edu...
> Robert Morein <nowhere@nowhere.com> wrote:
>
>
> Ah. So 1 microvolt is too much.
>
> Nick
>
For a Hawker Energy Systems Powersafe AGM battery, the spec is ripple < 1%
between 5% and 100% charger load. The precision of the charging system
depends upon the expense of the battery bank. For a $10K AGM system of
stationary batteries, which have a 20 year lifetime, it pays to be precise.
Hawker wants the float voltage verified with a 4 digit DVM every six months.

Cheaper batteries receive less precision. Auto batteries, for example, are
charged with plenty of ripple, and overcharged every time they are driven.

nicksanspam@ece.villanova.edu

2005-10-18, 5:21 am

Robert Morein <nowhere@nowhere.com> wrote:

>For a Hawker Energy Systems Powersafe AGM battery, the spec is ripple < 1%
>between 5% and 100% charger load.

That seems more reasonable, esp. at 100%, which heats the battery more.

But we were concerned about ripple during float charge, no? That might
overheat the battery and shorten its life, above (say) 80 F. How much
ripple can we tolerate at 5% without heating the battery over 80 F in
a 70 F room? Maybe a lot, given I^2R and the low equivalent series R of
a lead-acid battery. Below a 90% state of charge, the coulombic ("round
trip energy") efficiency is close to 100%, so the charging itself (vs
I^2R) makes little heat.

Heating a 1' cube with 6 ft^2 of surface and a 9 Btu/h-F airfilm
conductance 10 F requires 10Fx9Btu/h-F = 90 Btu/h, ie 26 watts of
I^2R dissipation. R = 0.001 ohms would make I = 161 amps...

Nick

George Ghio

2005-10-18, 5:21 am

wmbjk wrote:
> On Mon, 17 Oct 2005 10:21:12 +1000, George Ghio <AKA@nomailhere.com>
> wrote:
>
>
>
>
> Such examples are useful to readers who might be interested in
> building a similar setup. But your choice of engine and alternator is
> confusing considering your previous claims that a unit with about
> twice the Watts per hp was grossly overpowered. Please clarify.
>
>
>
>
> Anyone who decides to go this route will need to know what size
> rheostat to use. Is there some reason you can't simply give the
> resistance range of that rheostat, or better yet, the values required
> for your alternator's speed and output?
>
>
>
>
> That may work well on your setup, but I expect that only a minority of
> systems have the predictable extended period without any
> charge-discharge that's needed for a useful state-of-charge
> measurement by voltage alone. Many, probably most, owners will find it
> inconvenient at best to use voltage as a gauge, since it's a near
> useless indicator on systems such as those with full-time inverter
> loading, those that are powering say, electric refrigeration, or on
> hybrid systems with multiple charging sources. It's generally
> recommended that such systems are best equipped with a Trimetric or
> similar.
>
> Wayne

All this from a man who can't even define his "claimed" two days
autonomy. And that at a magical reduced load.

Robert Morein

2005-10-18, 6:21 am

<nicksanspam@ece.villanova.edu> wrote in message
news:dj29jo$o64@acadia.ece.villanova.edu...
> Robert Morein <nowhere@nowhere.com> wrote:
>
1%[color=darkred]
>
> That seems more reasonable, esp. at 100%, which heats the battery more.
>
> But we were concerned about ripple during float charge, no? That might
> overheat the battery and shorten its life, above (say) 80 F. How much
> ripple can we tolerate at 5% without heating the battery over 80 F in
> a 70 F room? Maybe a lot, given I^2R and the low equivalent series R of
> a lead-acid battery. Below a 90% state of charge, the coulombic ("round
> trip energy") efficiency is close to 100%, so the charging itself (vs
> I^2R) makes little heat.
>
> Heating a 1' cube with 6 ft^2 of surface and a 9 Btu/h-F airfilm
> conductance 10 F requires 10Fx9Btu/h-F = 90 Btu/h, ie 26 watts of
> I^2R dissipation. R = 0.001 ohms would make I = 161 amps...
>
> Nick
>
I have quoted the spec, but I don't understand why ripple hurts a battery at
a low state of charge. At float, for an AGM, there is one obvious reason.
The float voltage is optimally maintained at a very tight value constrained
by the need for minimal electrolysis and avoidance of sulfation. For a
flooded battery, I do not see why ripple is bad.

Vaughn

2005-10-18, 8:21 am

<nicksanspam@ece.villanova.edu> wrote in message
news:dj29jo$o64@acadia.ece.villanova.edu...
>
> But we were concerned about ripple during float charge, no? That might
> overheat the battery and shorten its life, above (say) 80 F. How much
> ripple can we tolerate at 5% without heating the battery over 80 F in
> a 70 F room?

To throw a bit more $hit in the game, there are "pulse" chargers which
claim great benefits over "plain" chargers. That would be the same as a huge
amount of ripple no?

Vaughn

JoeSixPack

2005-10-18, 11:21 am

"Robert Morein" <nowhere@nowhere.com> wrote in message
news:yNmdnQv7xds34sneRVn-1g@giganews.com...
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:dj0e25$n6l@acadia.ece.villanova.edu...
> For a Hawker Energy Systems Powersafe AGM battery, the spec is ripple <
> 1%
> between 5% and 100% charger load. The precision of the charging system
> depends upon the expense of the battery bank. For a $10K AGM system of
> stationary batteries, which have a 20 year lifetime, it pays to be
> precise.
> Hawker wants the float voltage verified with a 4 digit DVM every six
> months.
>
> Cheaper batteries receive less precision. Auto batteries, for example, are
> charged with plenty of ripple, and overcharged every time they are driven.
>
>

14.5 V I believe. In colder weather a higher voltage is beneficial. Most
auto batteries retain a voltage of 12.5-13V when parked.

Solar Flare

2005-10-18, 9:21 pm

I think this has been explained several time already but here goes again.

Between the peaks of voltage charging your battery (with ripple) there is no
charging current available to charge it or carry the load burden connected to
it. This means your battery has to carry the load and is in discharge mode. This
is a lot of charging and discharging current on your battery 120 times per
second.

This shouldn't be a problem if you have no load connected.

"Robert Morein" <nowhere@nowhere.com> wrote in message
news:gNqdnc2nf51dL8neRVn-ug@giganews.com...
>
> <nicksanspam@ece.villanova.edu> wrote in message
> news:dj29jo$o64@acadia.ece.villanova.edu...
> 1%
> I have quoted the spec, but I don't understand why ripple hurts a battery at
> a low state of charge. At float, for an AGM, there is one obvious reason.
> The float voltage is optimally maintained at a very tight value constrained
> by the need for minimal electrolysis and avoidance of sulfation. For a
> flooded battery, I do not see why ripple is bad.
>
>

nicksanspam@ece.villanova.edu

2005-10-19, 5:21 am

Solar Flare <sflare@hotmail.com> wrote:

>Between the peaks of voltage charging your battery (with ripple) there is no
>charging current available to charge it or carry the load burden connected to
>it. This means your battery has to carry the load and is in discharge mode.
>This is a lot of charging and discharging current on your battery 120 times
>per second.

How does that hurt the battery? Does this all come down to heating?

Nick

Robert Morein

2005-10-19, 9:21 pm

<nicksanspam@ece.villanova.edu> wrote in message
news:dj4sql$pbb@acadia.ece.villanova.edu...
> Solar Flare <sflare@hotmail.com> wrote:
>
no[color=darkred]
connected to[color=darkred]
mode.[color=darkred]
times[color=darkred]
>
> How does that hurt the battery? Does this all come down to heating?
>
> Nick
>
If you have a load connected, it's just this: ions are being transferred
between the plates and the aqueous solution 120 times per second. It amounts
to a mini charge-discharge cycle at that rate. It adds up.

JoeSixPack

2005-10-19, 11:21 pm

"Bruce in Alaska" <bruceg@btpost.net> wrote in message
news:bruceg-3CEDA4.09250217102005@netnews.worldnet.att.net...
> In article <4352d539.34092689@localhost>,
> hchickpeaREMOVEME@hotmail.com (Harry Chickpea) wrote:
>
>
>
> snipped for brevity
>
>
>
> This is basically how I use my system. I have twin 20Kw Gensets
> that I run for a totall of 10 hours a day. (7Am to noon, and 5Pm to 10Pm)
> That takes care of the main High Power Loadings of Breakfast and Dinner
> and the charging of all the battery banks for the twin inverter systems
> connected. It also keeps the four freezers at better than -10F on a
> 24/7 basis, and the telco equipment battery bank charged. I have had
> really good luck with both a 1200Amp/hour 24Vdc L16HD bank, as well
> as a 800Amp/hour 24Vdc Absolyte II AGM battery bank. These are on
> the inverter systems. L16 bank is over 4 years old, and replaced a
> 800Amp/hour bank that was 12 years old. The Absolyte II bank is 8 years
> old now and still has 95% of the new capacity.
>
> Bruce in alaska
> --

Ain't he da man?

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