VERY new to Solar

System · November 2011

I bought a solar-powered LED rope light at Home Depot to light the inside of an outbuilding at night. It worked great the first night after perfect sunshine, but the second day it was partly cloudy and that night the LED's were so dim as to be useless. I need this lighting system to work, but I'm frustrated with the low quality of the panel/battery.

I'm not sure where the problem lies (w/the panel or the battery), I'd like to keep the light string but provide them with sufficient power to illuminate properly. The only specs that came with the product are as follows:

- one 18500 Lithium, 600mAh, 3.2V rechargeable battery

The SKU on this thing is 905-007 if that will help.

Anyway, I'd like to replace the panel with one that will actually give a charge to the battery (it seemed like the battery ran the string perfectly the first night...~9hrs). I'd like to keep the on-at-dusk, off-at-dawn capability since I am not always available to turn on/off the lights.

Any help on this would be appreciated.

spike481

mike95490 · November 2011

Re: VERY new to Solar

1) charge the battery ASAP

LiIon batteries will be ruined with only 1 deep discharge.

When it's full, (2 or 3 days of charging) Power up the LED's and measure how much power they consume.

And if you can give us any #'s off the packageing about the panel and light, that will help too.

BB. · November 2011

Re: VERY new to Solar

Several keys to a happy solar pv system and happy owner;):

Conservation: Almost always easier/cheaper to conserve than to generator power. Check--sounds like you have very efficient lights.
Turning stuff off: Leaving lights on when not needed--Would be better if you could use a switch/motion detector to turn on when needed. You are not using a large amount of power, so the expense of a motion controller/timer may not be worth it.
Battery... Deciding how large the battery needs to be to meet your needs. For lighting, typically you would want several days of operation without sun (a string of a few days of cloudy weather would kill your lights in the evening without alternative power).
Solar Array + Charger, big enough to charge the battery on sunny days (you don't want it to take a week to recharge you battery pack).

So, looking at your specs and assume it ran it for 10 hours :

one 18500 Lithium, 600mAh, 3.2V rechargeable battery
0.6 AH bat capacity * 3.2 volts * 1/10 hours runtime = 0.192 Watt load (possible--that is not a very bright LED--but enough for a small work area or to prevent tripping).

Also, 0.6 AH for a 18500 Rechargeable Lithium Ion battery sounds a bit on the small side (closer to 2-3x as much energy in a "good" cell?).

Assume a minimum of 3 hours of sun per day (you want lights during winter too? You could down to assuming 2 hours of sun in many regions). Assume 30% efficiency (inexpensive panel, some recharge able chemistries are not very efficient at recharging):

0.192 watts power * 1/0.30 system eff * 10 hours of run time * 1/3 hours of sun = 2.13 watt of solar panel

The above is a wild guess--but at least it gives you some ideas of what your system should look like.

Ideally, you should measure the current (and voltage) presented to the LED string to get a better estimate of how much energy it pulls (lots of guesswork above).

-Bill

waynefromnscanada · November 2011

Re: VERY new to Solar

spike481 wrote: »

I bought a solar-powered LED rope light at Home Depot to light the inside of an outbuilding at night.

spike481

Unfortunately most of these kinds of things are meant to be more or less toys / conversation pieces that may provide an hour or two of light as we sit around the patio in the evening, drink in hand. That's pretty much it. Sorry.

VERY new to Solar

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