Chief Delphi - 12V Battery Maintenance

Quote:

Originally Posted by eugenebrooks

C/10 is a reasonable value to test the capacity of a battery at, but your goal should be to evaluate the batteries as close to the actual robot loading as is possible with your tester. I would test right below the continuous power limit of your tester, with enough margin that you are sure that you won't damage the tester. Assuming 13 volts, the 100 watt limit is 7.7 amps. You are looking at close to 2 hours for a fresh battery.

The highly variable current loading in a competition is actually much higher than this (on average), and most would call it abuse of the battery, but that is what we are doing in the robot...

All,
There are two types of tests I would perform when given the chance. The first is at c/10 to insure that the battery meets specs +/- 10%. Then I would perform an average match draw to see what you leave in a battery for the next match. My conclusion, rule of thumb actually, is that if you are unable to run three matches from the same battery, you have a problem with mechanical design that puts too much load on the battery. With these new computer controlled testers it would be great to simulate a match and run a test under those conditions. There is a formula for determining approximate battery life for portable radio operations. (QRP for you hams out there.) It is based on how much a typical radio contact will be in transmit and how much the receiver runs in between.
Match simulation can be a more valid test now that the RC has a backup battery. The deciding factor had always been to not exceed the current draw that would pull the output below 8 volts. All things being equal that was about 350 amps on a fully charged battery. Modeling an actual match would be a great help. Has anyone compiled valid current data (sampled throughout a match) for their robot or others?

As a side note, do not attempt to draw this much current from our battery without safety precautions, knowing the risks and using a circuit cutout in case all else fails.