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Multiple SLA Batteries in Parallel
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|
| Neil - Salem, MA USA 2005-06-18, 6:25 pm |
| I have never been to this newsgroup before, so I apologize if this question
has been posted before.
I am thinking of building a miniature backup power system for my living room
using eight 12-volt Sealed Lead Acid (SLA) batteries connected in parallel.
(There will be no series connections.) During a power outage, I'll use an
inverter to make my AC power from this battery assembly.
I have no need for a rapid charging process, and I have read that a
Float-Charge is safest for SLA batteries. I have not been able to determine
how much current a single 12-volt SLA battery would draw during a
Float-Charge. Whatever that current might be, I would need a Float Charger
that can supply 8 times that amount of current during a Float-Charge for
this parallel set of 8 batteries.
I am looking for any an all kinds of advice. Is my plan workable? What
Float Charger would you recommend that could Float-Charge eight 12-volt SLA
batteries in parallel? What SLA batteries would you recommend?
Thank you very much in advance,
Neil
Salem, MA USA
| |
| Charles Foot 2005-06-18, 11:25 pm |
| Neil - Salem, MA USA wrote:
quote:
> I have never been to this newsgroup before, so I apologize if this question
> has been posted before.
>
> I am thinking of building a miniature backup power system for my living room
> using eight 12-volt Sealed Lead Acid (SLA) batteries connected in parallel.
> (There will be no series connections.) During a power outage, I'll use an
> inverter to make my AC power from this battery assembly.
>
> I have no need for a rapid charging process, and I have read that a
> Float-Charge is safest for SLA batteries. I have not been able to determine
> how much current a single 12-volt SLA battery would draw during a
> Float-Charge. Whatever that current might be, I would need a Float Charger
> that can supply 8 times that amount of current during a Float-Charge for
> this parallel set of 8 batteries.
>
> I am looking for any an all kinds of advice. Is my plan workable? What
> Float Charger would you recommend that could Float-Charge eight 12-volt SLA
> batteries in parallel? What SLA batteries would you recommend?
>
> Thank you very much in advance,
>
> Neil
> Salem, MA USA
>
>
My recommendation would be: do not put 8 batteries in parallel! It's
asking for trouble. Seen it done, seen the hassles it can cause. Two in
parallel maybe, but preferably not even that. I'm sure everybody in the
NG will agree.....
| |
| SQLit 2005-06-18, 11:25 pm |
|
"Neil - Salem, MA USA" <Neil@Salem.Massachusetts.USA> wrote in message
news:lr6dnfbg5feJ4infRVn-hA@comcast.com...
quote:
> I have never been to this newsgroup before, so I apologize if this
question
quote:
> has been posted before.
>
> I am thinking of building a miniature backup power system for my living
room
quote:
> using eight 12-volt Sealed Lead Acid (SLA) batteries connected in
parallel.
quote:
> (There will be no series connections.) During a power outage, I'll use an
> inverter to make my AC power from this battery assembly.
>
> I have no need for a rapid charging process, and I have read that a
> Float-Charge is safest for SLA batteries. I have not been able to
determine
quote:
> how much current a single 12-volt SLA battery would draw during a
> Float-Charge. Whatever that current might be, I would need a Float
Charger
quote:
> that can supply 8 times that amount of current during a Float-Charge for
> this parallel set of 8 batteries.
>
> I am looking for any an all kinds of advice. Is my plan workable? What
> Float Charger would you recommend that could Float-Charge eight 12-volt
SLA
quote:
> batteries in parallel? What SLA batteries would you recommend?
>
> Thank you very much in advance,
>
> Neil
> Salem, MA USA
I will be the first to say I do not know what a SLA battery is.
8 batteries is 16 connections and places for a failure.
Bigger batteries less connections.
Are you planning on putting this contraption in the house??? ( humor
intended)
Have you thought about out gassing?
Ya out gassing, oh these batteries are sealed, right. Wrong, all batteries
out gas sooner or later. unless they are solid, no liquid.
Your charger would need to be large enough to not only float charge but full
charge the array.
Just how long do you plan on using this setup? Days, weeks?
| |
| Neil - Salem, MA USA 2005-06-18, 11:25 pm |
| "Charles Foot" <chaz@equinet.co.nz> wrote in message
news:1119130429.605009@ftpsrv1...
quote:
> Neil - Salem, MA USA wrote:
> My recommendation would be: do not put 8 batteries in parallel! It's
> asking for trouble. Seen it done, seen the hassles it can cause. Two in
> parallel maybe, but preferably not even that. I'm sure everybody in the NG
> will agree.....
An power engineering company I found on the Internet wrote the following:
"PARALLELING BATTERIES
"You should parallel batteries only to create a battery bank with a higher
capacity. We do not recommend paralleling batteries only for charging
purposes, the weaker batteries can hog all the charging current.
"When you parallel batteries, do so with batteries that are the same
voltage, same AH rating and with the same past history. We recommend using
new (identical) batteries. Don't connect new batteries in parallel with old
batteries. Don't connect 7 AH batteries in parallel with 100 AH batteries.
You should charge each battery separately, let them rest at least 12 hours,
and then connect in parallel to create a battery bank. No two batteries are
the same. Once connected, the weaker batteries will draw down the stronger
batteries and eventually all the batteries in the bank will equalize. Until
then, the weaker batteries will hog all the charging current."
Charles, is your recommendation to *not* put batteries in parallel because
of possible problems with charging the bank, as mentioned in the above
quote? If so, I could do as the quote suggests: I could charge them
separately and then connect them.
I thank you for your response.
Neil
Salem, MA USA
| |
| Vaughn 2005-06-18, 11:25 pm |
|
"Neil - Salem, MA USA" <Neil@Salem.Massachusetts.USA> wrote in message
news:lr6dnfbg5feJ4infRVn-hA@comcast.com...
8 batteries is a lot to parallel, a REAL lot. I can think of no reason for
doing this unless you already have the batteries. I don't admit this often, but
I have had 4 in parallel for several years and it works just fine, but I agree
that it is not good practice. Why do I do it? Because I have the batteries and
I got them for free! (and because they are matched, identical batteries)
If you have not already obtained the batteries, I suggest that you buy
fewer, larger batteries, and/or go to a 24 volt or 48 volt system.
Vaughn
| |
| Charles Foot 2005-06-18, 11:25 pm |
| Neil - Salem, MA USA wrote:
quote:
> "Charles Foot" <chaz@equinet.co.nz> wrote in message
> news:1119130429.605009@ftpsrv1...
>
>
>
> An power engineering company I found on the Internet wrote the following:
>
> "PARALLELING BATTERIES
> "You should parallel batteries only to create a battery bank with a higher
> capacity. We do not recommend paralleling batteries only for charging
> purposes, the weaker batteries can hog all the charging current.
>
> "When you parallel batteries, do so with batteries that are the same
> voltage, same AH rating and with the same past history. We recommend using
> new (identical) batteries. Don't connect new batteries in parallel with old
> batteries. Don't connect 7 AH batteries in parallel with 100 AH batteries.
> You should charge each battery separately, let them rest at least 12 hours,
> and then connect in parallel to create a battery bank. No two batteries are
> the same. Once connected, the weaker batteries will draw down the stronger
> batteries and eventually all the batteries in the bank will equalize. Until
> then, the weaker batteries will hog all the charging current."
>
> Charles, is your recommendation to *not* put batteries in parallel because
> of possible problems with charging the bank, as mentioned in the above
> quote? If so, I could do as the quote suggests: I could charge them
> separately and then connect them.
>
> I thank you for your response.
>
> Neil
> Salem, MA USA
>
>
The basic problem is that the entire battery bank will only be as good
as the weakest battery. As one starts to 'fade' it will pull all the
others down with it, and you will have to disconnect the entire array to
find the weak one. Take some advice based on many years of living on an
island where there is no grid supply.... just use one large battery, or
a number of lower voltage ones in series. (Especially in the case of SLA
batteries, which don't have the longevity of flooded cells).
| |
| Robert Morein 2005-06-18, 11:25 pm |
|
"Neil - Salem, MA USA" <Neil@Salem.Massachusetts.USA> wrote in message
news:lr6dnfbg5feJ4infRVn-hA@comcast.com...
quote:
> I have never been to this newsgroup before, so I apologize if this
question
quote:
> has been posted before.
>
> I am thinking of building a miniature backup power system for my living
room
quote:
> using eight 12-volt Sealed Lead Acid (SLA) batteries connected in
parallel.
quote:
> (There will be no series connections.) During a power outage, I'll use an
> inverter to make my AC power from this battery assembly.
>
The other posters are correct.
Don't do this.
Your intuition might tell you that the load and wear will be shared equally
between the batteries, but this is not the case.
Batteries are close to constant-current devices. Minute differences between
the voltages of the batteries will cause a "pecking order", where the
strongest battery takes the beating.
Also, if these are gel cells, there is a real possibility that a short could
cause things to get very hot. Keep an axe handy to sever all the
connections!
The conventional wisdom is that no more that three batteries should be
paralleled, and that it's a second rate idea at that. A single string
completely eliminates the problem of battery imbalance.
| |
| Neil - Salem, MA USA 2005-06-19, 4:25 am |
| "Robert Morein" <herethereeverywhere@nowhere.com> wrote in message
news:OMmdnSgaeOJDICnfRVn-2A@comcast.com...
quote:
>
> "Neil - Salem, MA USA" <Neil@Salem.Massachusetts.USA> wrote in message
> news:lr6dnfbg5feJ4infRVn-hA@comcast.com...
> question
> room
> parallel.
> The other posters are correct.
> Don't do this.
> Your intuition might tell you that the load and wear will be shared
> equally
> between the batteries, but this is not the case.
> Batteries are close to constant-current devices. Minute differences
> between
> the voltages of the batteries will cause a "pecking order", where the
> strongest battery takes the beating.
>
> Also, if these are gel cells, there is a real possibility that a short
> could
> cause things to get very hot. Keep an axe handy to sever all the
> connections!
>
> The conventional wisdom is that no more that three batteries should be
> paralleled, and that it's a second rate idea at that. A single string
> completely eliminates the problem of battery imbalance.
Well ...I think you folks have convinced me! OK ...perhaps I can achieve my
goal of a backup power system using a series of 12V SLA batteries ..or maybe
I'll just stick with one big 12V battery.
My initial ambitions were probably excessive. I really only need a backup
power system that can handle 5 amps at 110 volts for 5 to 10 hours, without
overly discharging the batteries. (SLA batteries don't like to be
discharged too much.) I probably could achieve that with one 100 or 140
Amp-Hour 12V SLA battery, couldn't I?
Sincerely and gratefully,
Neil
Salem, MA USA
| |
|
| Neil - Salem, MA USA wrote:
quote:
> "Robert Morein" <herethereeverywhere@nowhere.com> wrote in message
> news:OMmdnSgaeOJDICnfRVn-2A@comcast.com...
>
>
>
> Well ...I think you folks have convinced me! OK ...perhaps I can achieve my
> goal of a backup power system using a series of 12V SLA batteries ..or maybe
> I'll just stick with one big 12V battery.
>
> My initial ambitions were probably excessive. I really only need a backup
> power system that can handle 5 amps at 110 volts for 5 to 10 hours, without
> overly discharging the batteries. (SLA batteries don't like to be
> discharged too much.) I probably could achieve that with one 100 or 140
> Amp-Hour 12V SLA battery, couldn't I?
>
> Sincerely and gratefully,
>
> Neil
> Salem, MA USA
>
>
120v at 5a is about 48a DC 12.6v. A 100 or 140ah battery would not last
more than maybe two hours at most and you would be below the 20% level.
I have 9, 130ah wet, 12v batterys hooked parallel with a shutoff switch
hooked to each bank of three. I can turn on 3, 6 or 9 or shut off all if
I want. The shutoff switches are hooked to a 3 foot long piece of angle
iron that allows me to run off either of the three banks. Most of the
time I run of all three banks. I do this because I want a lot of backup
power. So far the power has went off a couple of times and I was the
only house with the lights still on and watching tv like nothing
happened.. I only have 21 amps of solar panels and that is no where
enough to pull all 9 batteries up to bulk charge while under load
(barely can with no load)or EQ the bank. So I had to split them up.
Works great. The water bubbles and I am able to float all 4 in my gage.
I will buy two panels at a time till I have 60 amps and then I plan to
never break the bank apart again. But I know nothing about GEL. So I'm
just guessing and willing to bet Neil is correct.
Jmar
| |
| nospam.clare.nce@sny.der.on.ca 2005-06-19, 4:25 am |
| On Sat, 18 Jun 2005 18:15:35 -0400, "Neil - Salem, MA USA"
<Neil@Salem.Massachusetts.USA> wrote:
quote:
>"Charles Foot" <chaz@equinet.co.nz> wrote in message
>news:1119130429.605009@ftpsrv1...
Very easy answer to this part of the question. Hawker Genesis EP
Series batteries - pure lead (not alloyed) plates - EXTREMELY low
internal resistance, and accept very high charging currents,plus very
long life. Not cheap, but quality seldom is.[vbcol=seagreen]
>
>An power engineering company I found on the Internet wrote the following:
>
>"PARALLELING BATTERIES
>"You should parallel batteries only to create a battery bank with a higher
>capacity. We do not recommend paralleling batteries only for charging
>purposes, the weaker batteries can hog all the charging current.
>
>"When you parallel batteries, do so with batteries that are the same
>voltage, same AH rating and with the same past history. We recommend using
>new (identical) batteries. Don't connect new batteries in parallel with old
>batteries. Don't connect 7 AH batteries in parallel with 100 AH batteries.
>You should charge each battery separately, let them rest at least 12 hours,
>and then connect in parallel to create a battery bank. No two batteries are
>the same. Once connected, the weaker batteries will draw down the stronger
>batteries and eventually all the batteries in the bank will equalize. Until
>then, the weaker batteries will hog all the charging current."
>
>Charles, is your recommendation to *not* put batteries in parallel because
>of possible problems with charging the bank, as mentioned in the above
>quote? If so, I could do as the quote suggests: I could charge them
>separately and then connect them.
>
>I thank you for your response.
>
>Neil
>Salem, MA USA
>
| |
| nospam.clare.nce@sny.der.on.ca 2005-06-19, 4:25 am |
| On Sun, 19 Jun 2005 10:53:54 +1200, Charles Foot <chaz@equinet.co.nz>
wrote:
quote:
>The basic problem is that the entire battery bank will only be as good
>as the weakest battery. As one starts to 'fade' it will pull all the
>others down with it, and you will have to disconnect the entire array to
>find the weak one. Take some advice based on many years of living on an
>island where there is no grid supply.... just use one large battery, or
>a number of lower voltage ones in series. (Especially in the case of SLA
>batteries, which don't have the longevity of flooded cells).
Charge multiple batteries separately, and discharge separately. When
one battery reaches a given depth of charge switch to the second
battery with a "make before break" switch.
And don't paint all SLAs with the same brush. some can, and regularly
do, outlast FLA batteries.
| |
| Ron Rosenfeld 2005-06-19, 12:25 pm |
| On Sat, 18 Jun 2005 21:53:23 -0400, "Neil - Salem, MA USA"
<Neil@Salem.Massachusetts.USA> wrote:
quote:
>Well ...I think you folks have convinced me! OK ...perhaps I can achieve my
>goal of a backup power system using a series of 12V SLA batteries ..or maybe
>I'll just stick with one big 12V battery.
>
>My initial ambitions were probably excessive. I really only need a backup
>power system that can handle 5 amps at 110 volts for 5 to 10 hours, without
>overly discharging the batteries. (SLA batteries don't like to be
>discharged too much.) I probably could achieve that with one 100 or 140
>Amp-Hour 12V SLA battery, couldn't I?
First of all, as others have written, paralleling multiple batteries to
increase current output is not a good strategy. Your output will be
limited by the weakest battery, and the lifetime of the bank will be
shortened. This is due to the inevitable differences in internal
resistance that will develop over time. Two strings in parallel is
acceptable; three strings is borderline. You're better off with a single
string of the required current.
Second -- I am assuming from your writing that your SLA batteries are NOT
deep discharge batteries. As such, you should probably plan to not
discharge them more than 20%.
So, to do the math:
5A * 110V = 550W
550W * 10hrs = 5500Wh
Factor for Inverter efficiency -- 0.85
--> AC load expressed as DC = 5500/0.85 = 6471Wh
System Voltage -- 12V (your specification)
Total load -- 6471/12 = 539Ah (Ampere-hours)
At this point, we will assume -- *unrealistically* -- ZERO system losses.
Also, from your writings, I am assuming that your SLA batteries are NOT the
deep discharge type, so I am using a maximum discharge of 20% capacity.
Required battery bank size at 12V:
539 / 20% = 2696Ah !!
That's obviously quite a bit more than a 100Ah 12V battery can supply.
If you are serious, I would suggest looking at true deep discharge
batteries, like the Trojan L16 or Surrette CH-375, and setting up a 24V
system with four batteries in series.
The CH-375 can be discharged as much as 80%, and still have an acceptable
life span. It is a flooded lead acid battery and will require some
maintenance as well as ventilation and a proper enclosure; but it should be
able to handle your stated requirements.
If your stated requirements are not accurate, then you may need to adjust
the battery bank size. But this should be done initially, as adding new
batteries to an old bank is also not a good idea.
Good luck!
-- ron (off the grid in Downeast Maine)
| |
| Vaughn 2005-06-19, 12:25 pm |
|
"Ron Rosenfeld" <ronrosenfeld@nospam.org> wrote in message
news:c9pab1d1hursq9pok951e9atk4dbqe4o1d@4ax.com...
quote:
> On Sat, 18 Jun 2005 21:53:23 -0400, "Neil - Salem, MA USA"
>
> Your output will be limited by the weakest battery,
While I agree that paralleling many batteries is a strategy to be avoided,
the above, often repeated, statment is simply not true for paralleled batteries
and should not go unchallenged. Multiple batteries in series can be redrawn as
a series-parallel circuit with ideal batteries in series with resistors that
represent the internal resistance of the batteries. As the batteies age, their
internal resistance increases at a rate that varies among even identical
batteries. The "weaker" batteries will thus have a higher internal resistance
and will contribute less current to the load, but the total currrent available
is limited only by the equivilant parallel resistance of all of the internal
resistances, not by the "weakest batery".
In the case of a series string of batteries, the output is limited by the
weakest battery because all of the internal resistances are in series.
quote:
>and the lifetime of the bank will be shortened.
Possibly true: In the case of series-parallel strings, one bad battery
effectively removes an entire string which can dramatically increase the DOD for
the remaining string(s) and drastically reduce battery life.
The real danger of paralleling batteries is if one of the cells in one of
the batteries should develop a short. Depending on how "bad" the short is, you
could develop very high currents which could cause a fire and/or cause batteries
to spew acid fumes. If you are lucky you might just see what looks like a large
leakage current and a battery bank that never seems to be at full charge.
quote:
> This is due to the inevitable differences in internal
> resistance that will develop over time.
True only in the case series or series-parallal connections, because of
what I have written above.
quote:
> Two strings in parallel is
> acceptable; three strings is borderline. You're better off with a single
> string of the required current.
I have been struggling with the above for years and I have not yet made up
my mind. In my work, I deal with large UPS's that use strings of many
batteries. One bad battery in a system that consists of a single string means
that you are finished, but parallel strings have their own problems. Which is
best? Get back with me in 10 years.
I agree with all that Ron has written below:
Vaughn
quote:
> Second -- I am assuming from your writing that your SLA batteries are NOT
> deep discharge batteries. As such, you should probably plan to not
> discharge them more than 20%.
quote:
> So, to do the math:
>
> 5A * 110V = 550W
>
> 550W * 10hrs = 5500Wh
>
> Factor for Inverter efficiency -- 0.85
> --> AC load expressed as DC = 5500/0.85 = 6471Wh
>
> System Voltage -- 12V (your specification)
> Total load -- 6471/12 = 539Ah (Ampere-hours)
>
> At this point, we will assume -- *unrealistically* -- ZERO system losses.
>
> Also, from your writings, I am assuming that your SLA batteries are NOT the
> deep discharge type, so I am using a maximum discharge of 20% capacity.
>
> Required battery bank size at 12V:
> 539 / 20% = 2696Ah !!
>
> That's obviously quite a bit more than a 100Ah 12V battery can supply.
>
> If you are serious, I would suggest looking at true deep discharge
> batteries, like the Trojan L16 or Surrette CH-375, and setting up a 24V
> system with four batteries in series.
>
> The CH-375 can be discharged as much as 80%, and still have an acceptable
> life span. It is a flooded lead acid battery and will require some
> maintenance as well as ventilation and a proper enclosure; but it should be
> able to handle your stated requirements.
>
> If your stated requirements are not accurate, then you may need to adjust
> the battery bank size. But this should be done initially, as adding new
> batteries to an old bank is also not a good idea.
>
> Good luck!
>
>
> -- ron (off the grid in Downeast Maine)
| |
| Ron Rosenfeld 2005-06-19, 11:25 pm |
| Vaughn,
Thank you for your further discussion of this area. I have always been
taught that a single string of appropriate current carrying capacity is
best, in terms of utilization of battery capacity and longevity. Although
I have two strings myself.
Do you believe that cross-tying helps with series-parallel setups? It is
mentioned in the Trace SW manual as desireable if there are multiple,
paralleled strings.
-- ron (off the grid in Downeast Maine)
| |
| Charles Foot 2005-06-20, 4:26 am |
| Ron Rosenfeld wrote:
quote:
> Vaughn,
>
> Thank you for your further discussion of this area. I have always been
> taught that a single string of appropriate current carrying capacity is
> best, in terms of utilization of battery capacity and longevity. Although
> I have two strings myself.
>
> Do you believe that cross-tying helps with series-parallel setups? It is
> mentioned in the Trace SW manual as desireable if there are multiple,
> paralleled strings.
>
>
> -- ron (off the grid in Downeast Maine)
I've read numerous sources eschewing the merits of cross-tying and I can
see the advantages in it, however when you consider the inevitable
eventuality of one or more batteries starting to die, it's going to make
fault-finding just that much more of a hassle (Murphys Law dictates that
it will always happen at the most inconvenient times, in the foulest of
weather). IMHO simpler is better, simplest is best.
| |
| Ron Rosenfeld 2005-06-20, 4:26 am |
| On Mon, 20 Jun 2005 14:42:07 +1200, Charles Foot <chaz@equinet.co.nz>
wrote:
quote:
>I've read numerous sources eschewing the merits of cross-tying and I can
>see the advantages in it, however when you consider the inevitable
>eventuality of one or more batteries starting to die, it's going to make
>fault-finding just that much more of a hassle (Murphys Law dictates that
>it will always happen at the most inconvenient times, in the foulest of
>weather). IMHO simpler is better, simplest is best.
Well, I did not do it. I just wondered if any had practical experience
with the methodology.
Simplest would be a single, series string of cells of sufficient capacity.
-- ron (off the grid in Downeast Maine)
| |
| Vaughn 2005-06-20, 12:25 pm |
|
"Ron Rosenfeld" <ronrosenfeld@nospam.org> wrote in message
news:2sobb1lg4fr9305kos1jdhrg16v6k9tr8e@4ax.com...
quote:
> Vaughn,
..
quote:
>
> Do you believe that cross-tying helps with series-parallel setups? It is
> mentioned in the Trace SW manual as desireable if there are multiple,
> paralleled strings.
I have never seen it done. I could list multiple theoretical advantages
and disadvantages, but have no personal experience to offer.
Vaughn
| |
|
| "Neil - Salem, MA USA" <Neil@Salem.Massachusetts.USA> wrote in message
news:lr6dnfbg5feJ4infRVn-hA@comcast.com...
quote:
> I have never been to this newsgroup before, so I apologize if this
question
quote:
> has been posted before.
>
> I am thinking of building a miniature backup power system for my living
room
quote:
> using eight 12-volt Sealed Lead Acid (SLA) batteries connected in
parallel.
quote:
> (There will be no series connections.) During a power outage, I'll use an
> inverter to make my AC power from this battery assembly.
>
> I have no need for a rapid charging process, and I have read that a
> Float-Charge is safest for SLA batteries. I have not been able to
determine
quote:
> how much current a single 12-volt SLA battery would draw during a
> Float-Charge. Whatever that current might be, I would need a Float
Charger
quote:
> that can supply 8 times that amount of current during a Float-Charge for
> this parallel set of 8 batteries.
>
> I am looking for any an all kinds of advice. Is my plan workable? What
> Float Charger would you recommend that could Float-Charge eight 12-volt
SLA
quote:
> batteries in parallel? What SLA batteries would you recommend?
>
> Thank you very much in advance,
What do you need this power for?
The only thing I can think of for a living room is to power a TIVO type
device or cordless phone. You aren't going to be watching TV for long with
something like this.
I use a Cyberpower UPS 1500 (Uninterruptible Power Supply) for my TIVO, and
a much smaller and cheaper one for my phone. The cost of the Cyberpower is
about $250, unless you can find it on sale, and although it's one heavy
bugger, it's about the same size as standard audio components. It uses four
standard SLA batteries, keeps them charged, monitors discharge, and is
fairly quiet. This is what I recommend for the above.
If you want to power your entire entertainment setup for more than a couple
minutes, you'll need a small generator, or a very huge and expensive battery
setup. SLA batteries simply won't cut it.
As for SLA batteries, how much current they'll draw and supply depends
entirely on how big they are. My lawnmower starter battery is quite small,
somewhere around a 4ah, and it gets something like 150 milliamps for a
trickle charge. Then there's the 7ah battery, probably the most common.
This goes all the way up to 38ah and beyond. Then there's 6 volt batteries,
and so on. However, none of these batteries will take a heavy charge very
well, such as that from a car battery charger, even a 'lower power' one
labeled as a "Float Charger". Perhaps a bunch of them in parallel might be
ok, but then there's all the other posters who don't like the idea of eight
or so SLA batteries wired up like that, and I agree.
You might get by on a few deep cycle marine batteries, but with that you've
just exceeded the cost of a generator, and a generator will last much longer
and be much more portable.
You also have the problem of the inverter. Inexpensive inverters do not
produce a nice, smooth sine wave your equipment is expecting, but rather a
'modified sine wave'. Without going through all the technical details,
while this will power your more complex gear just fine, (often it won't
power simple things where there's just a motor and such...mine refused to
power the electronic ignition on my stove) it will produce noise in your
speakers and headphones. If you want nice, clean power, you'll have to
spring for a high end inverter, which again exceeds the cost of a generator.
I keep coming back to the generator. This is the most elegant and simple
solution. If you have frequent power outages, this is your best bet,
especially if the power is out for several hours (or days) at a time. You
can power your toys during the day, and the fridge at night, possibly even a
small air conditioner or heater, depending on size. You can either run
extension cords from the generator (not recommended in the rain, especially
if you can't put the generator in the garage or something), or have certain
circuits in your home wired up to a switch. With this you can choose to
power your circuits from the power lines or the generator with the simple
flip of a switch. This setup is somewhat pricey, but much cheaper than a
coffin, should you plug a wet cord into a wet generator, while standing on
wet ground.
Or you could do what I do when the power goes out. All you need is a
lantern and a few good books. :-)
Pagan
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| meshach@allstream.net 2005-06-30, 12:25 pm |
| If you have the batteries already, use them. I have 7 in parrellel and
they are doing well. They are different AH and different ages. They
work, what more do you need? They are all sealed AGM batteries . No
gasing.
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