Small solar charger system...
I am interested in using a basic solar panel with my camper to charge one or two 12V batteries. I would want to be able to run the water pump, a light or two and a 12V fan. Any suggestions of how to a...
Forum Discussion
pianotuna wrote:
Hi,
Voltage is a poor way to check state of charge. It is only valid when the battery is at rest for 24 hours with neither loads nor charging going on.
If you had measured specific gravity that would be a valid indicator of state of charge.
I suspect the panels are amorphous in your 45 watt system. The do better in low light levels than many other types, which explains part of your results.
The other side of the coin is that you simply don't use much power on a daily basis.
Going lower than 50% state of charge is inadvisable with all lead acid battery types. It will shorten the life span, sometimes dramatically. Your batteries are some what forgiving--but even the die hard six volt crew avoid going below 50%.timjcarter9 wrote:
At the end of the trip I took voltage measurements and was still at 70%.
You can safely discharge to 50% (or lower on six volt batteries) without damaging your batteries. They are made for that. You don't have to charge them to 90% each day.
The voltage reading is not as acurate as specific gravity but gives a good idea. I am not carrying one of those around but always have a volt meter.
I go by the chart on this page which is for batteries attached with no load. It is close enough.
Some people do discharge to 40 - 45% on 6 volt deep cycle batteries though I have never done it. With the led lights it would take a long time to get them down that low.
