New to Solar Few Questions about not draining battery too much

Re: New to Solar Few Questions about not draining battery too much

A good place to start would be to read a Battery FAQ. Not because I am lazy (well, I am, but that is a different story :roll: )... But because it gives you a pretty good holistic view of a storage battery.

Short answer, there are several ways of seeing how much energy there is left in a flooded cell storage battery.

1. Use a hydrometer (and thermometer) to measure the specific gravity of the electrolyte. Messy but accurate.

2. Let the battery rest (no charging or discharging) for several hours and use an accurate DVM to measure the resting voltage. Less accurate and a pain in that you can only do this after the battery has sat unused for a few hours.

3. Use a "cumulative" amp*hour or watt*hour meter that keeps track of the current going into/out-of the battery. Accurate and represents the state of charge at anytime (use, charging, setting unused).

There are not cheap battery monitors (there is at least one Xantrex high end model that does include a programmable output that can be set to 50% battery capacity transition), and there are relatively inexpensive ones that are used by RC hobbyists.

To turn off loads if the battery is over 50% discharged... Not easy to do... The output voltage of a battery is load, charge, and temperature dependent. So a simple "voltage sensor" will not be very accurate at setting the 50% decision point.

Programmable voltage controlled switch

Or you can use mechanical timers (from Home Depot, etc.) so that the lights are on only if the kids are their (turns off after 1 hour automatically).

Or there are electronic timers:

Flexcharge DC Timer Controller

Or, if you have not purchased a charge controller, you can pick one that has a Low Voltage Disconnect (LVD).

MorningStar Charge Controllers

Also, to ensure the battery is not run dead--look at using very low power lamps (CFL, LED, etc.) instead of filament bulbs.

Questions?

-Bill