3.8 volts is required to fully charge a battery. But at 3.8 volts, the battery can be overcharged without the use of a controller correct? What if I don't care if the battery is fully charged? In the case of our family boat, I just installed a new radio, so I'm a little worried about power consumption. So now for the real question; If I hook a 2 volt panel to the batteries, do I need to worry about overcharging them? Or will the batteries stop the charging process once they reach 2 volt?I built the panel myself, it's 8 volts at 3.5 amps open circuit. I have tabs at every 3 volt increment on the panel so that I can use less voltage than 8 if I want to power something directly, (ex:2 volt radio)So I'm using the 2 volt tab at 3.5 amps(approx) for a total of approx 48 watts
It is cheaper to have a solar regulator to extend the battery lifespan. A lead acid battery can vent hydrogen if charged too much and run out of electrolytes. The battery would cost more than a $30 5 amp solar regulator.
Batteries will not stop charging on their own. The will stop charging when the battery voltage equals the supply voltage. Solar panel open circuit voltage is typically around 20V. Batteries will just boil dry before reaching 20V. One rule of thumb, above 0W you need a controller for sure.
can I use a 2volt .5 amp solar panel on a 2 volt battery in a boat that i use for trolling motor and if I can can I leave it hooked up when using the trolling motor ? Plus how long would it take to charge a half drain battery with this panel??
I have been using solar panels for over ten years never until recently bothered to use a charge controller, it depends really on how much power your batteries can hold how often they will be drained from use of the connected dc-ac inverters. While constant daylight charging at 8v 3.5a/hr is quite heavy it is not excessive, 2v lead acid battery chargers give a voltage output of appx 4.8v but the fluctuating output of a solar panel means you may well charge at 8v for some time but with occasional shade etc it will more likely average at 5v which I think is quite acceptable.
