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Home > Archive > Alternative Power sources > September 2005 > Do solar battery chargers work?
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Do solar battery chargers work?
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| Anthony Matonak 2005-09-24, 2:21 am |
| chad@chadphillips.org wrote:
> I have a project that would have a small embeded computer running about
> 1 hour a day. It takes about 15 watts to run. I was thinking about
> powering it with one of those "battery saver" solar chargers.
>
> Would a 5 watt or 11 watt battery trickle charger work for this?
Well, one hour a day drawing 15 watts would be 15 watt-hours/day.
Figure 20% off the top for panel heating and advertising effects,
another 20% (to be on the safe side) for battery inefficiency in
charging/discharging. That gives us (15/.80/.80=) about 24 wh/day.
Figure you'll get an average of at least 3 'sun-hours' at your
location even in the middle of winter (most of the USA) and your
panel will need to be (24/3) 8 watts.
You might squeak by on a 5 watt panel except during winter but I
would error on the side of caution and use the 11 watt panel.
You'll need a battery too, of course. If you want to run the
thing 5 days without sunlight you would need (5 * 15W) 75 Wh.
If this is a 12V battery that would be (75Wh/12V) 7 amp-hours.
Anthony
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| Scott Willing 2005-09-24, 11:21 am |
| On Fri, 23 Sep 2005 22:13:16 -0700, Anthony Matonak
<anthonym40@nothing.like.comcast.net> wrote:
>chad@chadphillips.org wrote:
>
>Well, one hour a day drawing 15 watts would be 15 watt-hours/day.
>Figure 20% off the top for panel heating and advertising effects,
....advertising effects?
Qu'est-ce que c'est ?
-=s
>another 20% (to be on the safe side) for battery inefficiency in
>charging/discharging. That gives us (15/.80/.80=) about 24 wh/day.
>Figure you'll get an average of at least 3 'sun-hours' at your
>location even in the middle of winter (most of the USA) and your
>panel will need to be (24/3) 8 watts.
>
>You might squeak by on a 5 watt panel except during winter but I
>would error on the side of caution and use the 11 watt panel.
>
>You'll need a battery too, of course. If you want to run the
>thing 5 days without sunlight you would need (5 * 15W) 75 Wh.
>If this is a 12V battery that would be (75Wh/12V) 7 amp-hours.
>
>Anthony
| |
| Anthony Matonak 2005-09-24, 2:21 pm |
| Scott Willing wrote:
> On Fri, 23 Sep 2005 22:13:16 -0700, Anthony Matonak
> <anthonym40@nothing.like.comcast.net> wrote:
>
>
> ...advertising effects?
Advertising typically uses numbers that, while technically
accurate, do not reflect real world conditions. This is why
few people get the mileage shown on their cars window sticker
and nobody considers a single can of coke two servings.
This applies to solar PV panels in two forms. The first is the
STC (standard test conditions) using a temperature lower than
the panels will usually experience and, if I recall correctly,
illumination slightly more than typically found at ground level.
The second is that the warranties are usually only for 80% of
that figure. Technically, they can ship panels with slightly
less output than advertised and stay this side of the law.
You'll see this in the case of wind turbines also. The Air-X
is advertised as a 400W wind turbine but it only generates
this in hurricane force winds. It's really more of a 100-200W
wind turbine in day to day service.
You see this in generators also. That 3kW generator may only
be able to do 3kW for a very short time and it's continuous
rating may only be half that.
Advertising effects are simply the tendency of advert writers
to stretch the truth as much as they can without going to
jail. In the case of PV, some companies are better than others
in this regard.
Anthony
| |
| Solar Flare 2005-09-24, 6:21 pm |
| My BP panels produce much more than they are rated at and their guarantee
point, after one year is 95%. I believe the rating power is at 25 degree C.
My Sharp panels are guaranteed at a little less and haven't been through a
winter yet to know about this factor. Last winter my BP3160s produced over
200W each for 160W rated panels. They were purchased used. I do not know
their age. Oh yeah. They were hung vertical on my deck from a rafter on my
deck.
From the excepts I have read the Air X will never produce much over 200watts
because it furls before it's rated output. Most articles doing testing have
revealed it as a rip-off and a hoax.
"Anthony Matonak" <anthonym40@nothing.like.comcast.net> wrote in message
news:L8-dnWbZLPx8HqjenZ2dnUVZ_sydnZ2d@comcast.com...
Scott Willing wrote:
> On Fri, 23 Sep 2005 22:13:16 -0700, Anthony Matonak
> <anthonym40@nothing.like.comcast.net> wrote:
>
>
> ...advertising effects?
Advertising typically uses numbers that, while technically
accurate, do not reflect real world conditions. This is why
few people get the mileage shown on their cars window sticker
and nobody considers a single can of coke two servings.
This applies to solar PV panels in two forms. The first is the
STC (standard test conditions) using a temperature lower than
the panels will usually experience and, if I recall correctly,
illumination slightly more than typically found at ground level.
The second is that the warranties are usually only for 80% of
that figure. Technically, they can ship panels with slightly
less output than advertised and stay this side of the law.
You'll see this in the case of wind turbines also. The Air-X
is advertised as a 400W wind turbine but it only generates
this in hurricane force winds. It's really more of a 100-200W
wind turbine in day to day service.
You see this in generators also. That 3kW generator may only
be able to do 3kW for a very short time and it's continuous
rating may only be half that.
Advertising effects are simply the tendency of advert writers
to stretch the truth as much as they can without going to
jail. In the case of PV, some companies are better than others
in this regard.
Anthony
| |
| Scott Willing 2005-09-25, 11:21 am |
| On Sat, 24 Sep 2005 09:50:34 -0700, Anthony Matonak
<anthonym40@nothing.like.comcast.net> wrote:
>Scott Willing wrote:
>
>Advertising typically uses numbers that, while technically
>accurate, do not reflect real world conditions. This is why
>few people get the mileage shown on their cars window sticker
>and nobody considers a single can of coke two servings.
OK, just wanted to make sure I knew what you meant.
-=s
>This applies to solar PV panels in two forms. The first is the
>STC (standard test conditions) using a temperature lower than
>the panels will usually experience and, if I recall correctly,
>illumination slightly more than typically found at ground level.
>The second is that the warranties are usually only for 80% of
>that figure. Technically, they can ship panels with slightly
>less output than advertised and stay this side of the law.
>
>You'll see this in the case of wind turbines also. The Air-X
>is advertised as a 400W wind turbine but it only generates
>this in hurricane force winds. It's really more of a 100-200W
>wind turbine in day to day service.
>
>You see this in generators also. That 3kW generator may only
>be able to do 3kW for a very short time and it's continuous
>rating may only be half that.
>
>Advertising effects are simply the tendency of advert writers
>to stretch the truth as much as they can without going to
>jail. In the case of PV, some companies are better than others
>in this regard.
>
>Anthony
| |
|
| chad@chadphillips.org wrote:
> I have a project that would have a small embeded computer running about
> 1 hour a day. It takes about 15 watts to run. I was thinking about
> powering it with one of those "battery saver" solar chargers.
>
> Would a 5 watt or 11 watt battery trickle charger work for this?
>
> Here are two I am looking at:
> http://www.northerntool.com/webapp/...865&R=200306865
> http://www.northerntool.com/webapp/...904&R=200315904
>
> thanks
> chad
>
some thing to think about is posably reducing the batt voltage so as to
reduce the power wasted though the voltage reg for the micro controler .
| |
| SpiderG 2005-09-26, 10:21 pm |
|
"Anthony Matonak" <anthonym40@nothing.like.comcast.net> wrote in message
news:QqOdnQd6lYXufaneRVn-ug@comcast.com...
> chad@chadphillips.org wrote:
>
> Well, one hour a day drawing 15 watts would be 15 watt-hours/day.
> Figure 20% off the top for panel heating and advertising effects,
> another 20% (to be on the safe side) for battery inefficiency in
> charging/discharging. That gives us (15/.80/.80=) about 24 wh/day.
> Figure you'll get an average of at least 3 'sun-hours' at your
> location even in the middle of winter (most of the USA) and your
> panel will need to be (24/3) 8 watts.
>
> You might squeak by on a 5 watt panel except during winter but I
> would error on the side of caution and use the 11 watt panel.
>
> You'll need a battery too, of course. If you want to run the
> thing 5 days without sunlight you would need (5 * 15W) 75 Wh.
> If this is a 12V battery that would be (75Wh/12V) 7 amp-hours.
Wouldn't that completely discharge the battery? Should you not consider the
Depth of Discharge calculation before using the 7 Ah as the needed capacity?
-SpiderG
>
> Anthony
| |
| Steve Spence 2005-09-26, 10:21 pm |
| SpiderG wrote:
> "Anthony Matonak" <anthonym40@nothing.like.comcast.net> wrote in message
> news:QqOdnQd6lYXufaneRVn-ug@comcast.com...
>
>
>
> Wouldn't that completely discharge the battery? Should you not consider the
> Depth of Discharge calculation before using the 7 Ah as the needed capacity?
>
> -SpiderG
>
>
>
>
>
>
A Walmart Deep Cycle Type 27 battery costs $55 and is rated at 115ah. We
use them with our inverter/generator kits.
--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html
| |
| Anthony Matonak 2005-09-26, 10:21 pm |
| SpiderG wrote:
> "Anthony Matonak" <anthonym40@nothing.like.comcast.net> wrote in message
....
>
> Wouldn't that completely discharge the battery? Should you not consider the
> Depth of Discharge calculation before using the 7 Ah as the needed capacity?
Sure it would completely discharge the battery and perhaps even
damage it. It would still work at least once.  One needs to
balance this against the cost of replacing that 7 amp-hour
battery and how often you expect to get 5 days in a row with no
sunlight whatever.
The message wasn't meant to be a full system design as I clearly
left a lot of things out (charge controller, fuses, disconnects,
wires, options for tracking, mounting, grounding, boxes, etc.)
and I don't even know if the orginal posters location even gets
3 sun-hours a day (on average) in the winter.
Anthony
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