We are having a few issues with our drivetrain, we are experiencing large current spikes when driving (going up to 150A). This causes our voltage to drop from 12V to 8V while we are driving around. This issue appears to be an exclusive drivetrain issue, running other mechanisms seems to have no impact on our brownout issue. This issue began occurring a few days after our first district event and we are unsure of the cause. Our drivetrain is a West Coast Drive with a dual shifting gearbox driven by four (2 on each side) Falcon 500s. Our gear ratios are 7.95:1 (high) and 16.36:1 (low). Our robot is near max weight ~150lb (bumpers +battery). We are using 6 inch Omnis on the corners and 6inch Colsons in the middle, no drop center, 3 wheels per side. Any help or any troubleshooting steps would be greatly appreciated!
Things we’ve already tried:
Retensioned chain
Used old reliable code (pre-competition)
Looked through gearbox (gears seemed to be meshing well)
Redid drivetrain wiring
Checked breaker connections
Put a current limit on your motors.
150 amps isn’t that much coming from 4 falcons. Each can easily pull 100 amps. Even current limited to 60 amps, you are still looking at 240 amps of peak draw.
I’m not sure what part of this issue would have suddenly appeared out of nowhere.
Consider purchasing better batteries, upgrading to thicker wire, and applying software current limiting on the supply side.
Have you tried adding more grease to gearbox and cheking battery internal resistance?
Surges to 150 amps should not be enough to brown out a battery that was charged. How long are you trying to drive on one battery, and how long are you charging it?
Agreed that 150 seems low for brownout. We’ve previously limited at 180 and been fine.
Low soc and internal resistance of the battery is not the only source of resistance in the system, either.
A couple years ago we busted a 6awg lug underneath the heat shrink/tape and didn’t figure it out for three matches. Symptoms of brownout, escalating to a full power cycle and big spark. Root cause was the robot side sb50 wasn’t locked down and was yanking on the lugs during plug/unplug.
For sure check all connections in the primary power loop, including on all batteries. Track which batteries you see this with, and under what conditions (charging at an event can be sub-optimal). You can use the log viewer to check current draw for individual PDP/H slots (and hence, motors). You want to see fairly even current across motors. One motor, or one side of the drivetrain, using more current invites further scrutiny.
We’ve got similar problems, so sympathy from here 
For ours we think we have a bad SparkMax and possibly a bad current amplifier. We seem to be discharging the battery significantly just sitting there… One of the six SparkMaxes shows zero current, which is super suspicious… Infra-red camera time!
Check that all the bolted electrical connections (battery, main breaker, PDP, older motor controllers) are all tight enough that the wires/cables cannot be moved with finger pressure.
Do a pull test on each and every connection/crimp, individually, with finger pressure. If it pulls out, the connection/crimp needs to be redone and retested.
Are your batteries fully charged? A fully charged battery should read around 13 V.
A picture might help…
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