So far this season, we’ve apparently had two PCP’s go bad on us. It’s not that they don’t deliver power, it’s that we seem to have issues with the robot draining new, fully powered batteries within a few seconds of driving them. Literally 10 feet and we drop from 119% to the 80% range. When diagnosing the issue the first time, we swapped out the equipment from the PCP to the battery, and everything worked as it was supposed to. We opened the bottom of the PCP and the soldier points inside looked odd. They were pitted and peaked…in short, they looked like there were issues with the connections. We thought that maybe some aluminium had gotten into it from drilling that had been done and maybe the PCP hadn’t been covered well enough.
We encountered the same problem a week or so later, swapped the panel out with our last known good one, and the problem went away again. Inspecting the panels’ inside showed similar patterns, but we were very much more careful about covering the electronics. We don’t know if that’s the way they are supposed to look…mostly because I’m unwilling to open up our last good one.
So, long story short, is there a good way to test to see if the PCP is malfunctioning? Is there a way to diagnose whether that is truly the problem and test it’s functionality?
Firstly, it is PDP, Power Distribution Panel
I think Omar browses these forums so I would defer to him but the first thing I’d think of is a short- are you shorting your motor leads (can be either to or from the motor controllers) somewhere? either you have the wires exposed and they’re touching each other or ground, your crimps aren’t secure, you are putting connections in parallel, etc.
Have you measured your current draw through the PDP and the items hooked into it? I’ve never seen a PDP (or the former PDB) go bad like you are describing before.
Have you kept track of which batteries you are using each time you drive? The batteries ca. Suffer internal damage that would cause them to suddenly drop a large voltage amount in the way you describe. Do your batteries show any external damage from being dropped?
If you’re really using that much power that quickly, there should be something very warm on the robot.
i don’t know what I was thinking with the PCP thing…
We have been monitoring the batteries and they didn’t seem to be an issue. The heavy gauge wires were very hot and a motor was hot, but the connection seemed fine. Nothing crossed or exposed. I suspect that most likely we missed something, twice, but I just wanted to see if we could test the panel without it being on the bot.
How old are your batteries? Even if they still charge up to 12-12.5V doesn’t mean they’re still in usable condition. We still have a battery from 2009 that charges up to 12.5, and will stay there for a long time under small loads, but discharges very quickly when used on a robot. We keep it for the scouting system, and for testing individual mechanisms.
Brand new. Bought this year.
If you are draining brand new batteries in just a few seconds, you are likely to have some issue such as two motors on the same side of the drivetrain that are fighting each other. Please start by follow the instructions in the 43 post of the following thread.
I would think that too, but when we swapped panels, the problem went away. That doesn’t mean they weren’t wired incorrectly into the panel, however, that’s really unlikely as that we check and double checked the wires coming in before we swapped. Occam’s Razor would lead us to think that its fighting motors, but that didn’t seem to be the case.
That’s why I was wondering if there was a way to test the panel off the bot.
That said, I’ve copied off your troubleshooting steps, formatted them for a word document and am printing them off to post in our room as just plain a good idea.
By heavy gauge wires do you mean the wires going between the battery and PDP and the main breaker? Or the wires going to a motor and motor controller?
When using the “bad” PDPs, what voltage do you see on the driver station when the robot is just sitting still with a fresh battery?
Does anything get hot while the robot just sits there turned on?