95 has a problem much like this. We are using a 4 wheel 4 motor drive (2 CIMs and two drills, plus two van doors and globes being used as steering motors). After about a minute of driving, any movement will cause us to lose contact with the bot, undoubtley because the RC reset due to low voltage. We do not need to be heading up the ramp.
At first, I suspected a short to the frame (why don’t inspectors check for this?). I am now 99% sure this is not the case. Nothing on the multimeter and every connection is tight and insulated, no damaged wires.
We to use worm gears. We did some current draw tests on our motors and found they were drawing around 10 amps, no load. Wow.
That is really high, under load that number will climb even higher. But, we’ve never tripped the main breaker or the 40 amp breakers, the battery voltage always drops below 8 volts and the controller resets after a minute of hard driving, probably before the breakers heat up. With no load on the battery, it will settle at around 11-12 volts.
Doesn’t that seem wrong? That is a very large voltage drop in so short a time, even with the high current draws. I had always thought that to lower the voltage that far with out tripping the beakers would require a short to the frame or a bad battery. Should the voltage stay lower when it is under no load?
I’m puzzled. On one hand, I know for a fact our motors are drawing way to much power. On the other, I am having trouble trusting these batteries. I guarantee our crates dropped well below zero (in the north east anyways). But, few teams have this problem that I know of, and they all seem to be running on worm gears.
I hope that by getting those gears loosened up we can cut our current draw. We believe that attaching a capacitor across the power terminals of the RC helped prevent resets (when voltage dropped to low the capacitor would drop power into the RC to compensate). Yes, we checked with the inspectors and this was legal. I would suggest that teams having problems with brownouts try this. In any case its a stopgap and doesn’t fix the real problem.
Perhaps the batteries are devolping mild internal shorts as they heat up? Could it be that when they heat up, some plates will warp and short to other plates and then when cool lose contact and appear normal? I don’t know nearly enough about these batteries, that just popped into my mind.
I just wish I knew for sure what is causing this. It’s probably a combination of things. I highly suspect its just binding gears, but…