Electronic – Charging 12v batteries with direct connection to 20v solar panels

batteriesbattery-chargingchargingsolar cell

I want to charge a 12v Sealed Lead Acid car battery off of a solar panel (20v) and then draw about 10-20W of power from it via an inverter (the load).

I'm wondering if its okay to connect it together like this:
Wiring diag

And what downsides, if any, are there and can I avoid them? Is it a problem hooking up the battery to solar panel without a load?


Best Answer

Yes, it's okay, on condition that you never let the battery voltage exceed a maximum.

The maximum is typically around 14.4V to 14.8V at 21C temperature. If the maximum is exceeded for minutes to hours, the battery will be permanently damaged. The damage occurs around the same time that flammable gas is generated and vented, so there is a risk of gas explosion near the battery.

Your setup would require constant monitoring, especially if the load is disconnected or turned off. Check the voltage every hour, and disconnect the solar panel as the voltage approaches the maximum.

To find the maximum voltage, check the manufacturer's label or datasheet for the battery.

You can make your setup safer by adding a charge controller to protect the battery (so you don't have to monitor), by ensuring there is air flow, by removing any sources of ignition for the gas, and by keeping the battery away from things it might damage as a result of an explosion.