How I test my batteries

Equipment - (1) Multimeter good for measuring up to 10A DC Current, and DC Voltage.
- (1) 2 x 6 with (4) side marker lights mounted and wired in parallel. (not LED lights, the old fashioned lights) Not wired in series either want to avoid the one goes out, they all go out Christmas Light problem. Style points awarded for the mad scientist steam punk look of the test rig.

I put one battery in the glider, set the multimeter for current put it in series with the battery, turn everything on and measure the glider's normal amp draw, then push the radio's transmit button and get that current draw.

When you are finished with that, hook the battery and the multimeter still measuring current up to your side marker lights. Add or remove bulbs until you get the desired current draw. My choice is above your gliders normal load and below the radio transmit current draw. Don't over think it, sorta close is good enough.

Get the multimeter out of the circuit. Immediately change it back to its measuring voltage configuration. Or skip this step and find out which fuse your meter uses, and what store sells them (it will be closed when this happens or currently out of stock for this size fuse). If you have a meter without a fuse in the current circuit, take a hammer to it, smash it to bits, and go out and buy one with a fuse. I saw one of those blow up one time (480V), it wasn't pretty, and there were a lot of reports to fill out afterwards.

After fully charging the Battery(s) I hook them up to the lights, measure the voltage under load every half hour and write the numbers down until it drops to 11.5 volts. Near the end you may want to check on it more often. Just for fun use the timer on the stove and drive your wife crazy for the better part of the day. Or take it to work and explain to everyone what those red lights are for in your office, or the bomb squad, if you don't catch everybody with the explanation, and leave it unattended with the door open..

Amps X Hours of run time = Ah

SF