Robot weaker after new brain

Edit: we tried connecting the drive ports to the old brain and testing that, same issue which makes us think that it’s something other than the brain, we have 3 batteries and ones brand new and they all behave the same so we dont think that’s the issue either.
We had to switch out our robot’s brain because static blew a bunch of ports, but when we put the new brain on the robots drive was significantly weaker. We also switched out the drive motors which were the motors in particular that we noticed are weaker (the rest of them seem okay) and that didnt fix it. Previously our robot was able to push 2 goals just fine but now it struggles to push 1. Also on low battery percentages the drive is so weak it cant go to full speed without any goals being pushed or carried is the brain defective or is there something else that I am unaware of?

For your brain dying id reccomend something like this to protect it. Your problem could be with the program, battery, or it could be a mechanical issue. A picture of the drivebase and/or code would help distinguish the issue

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Here’s a picture of the drive base, we inspected everything mechanically and code wise but havent found any issues, also nothing has changed mechanically other than the new motors but it was doing it with the old motors too. The code hasn’t changed either, only thing that changes was the old brain to the new brain

Do you have a 3rd spare (brain) that you could try?

I would check in with you advisor if you have one, but overall it might be a fault brain. Second thoughts: it might be that’s the rpm is down for the motors on the brain’s side of things.

There’s no condition in the brain that I can think of that would directly affect motor power. The battery is routed to the smartports and the motors themselves decide output power based on control values sent from the user code.

How old was the brain you replaced ? Was it updated with latest vexos or was it on an old version ?


The brain is about a year old but has barely been used at all. We just updated the firmware a little while ago but the condition hasn’t changed

I was going to ask if you use custom code or the built in drive program, but then noticed you mentioned keeping the old code.

Then I was going to ask what motor cartridges (green or red) you used, but then you mentioned that old motors were doing the same thing.

When you say “weak” do you mean pushing force or speed?

Have you tried different wires? Are those official vex wires or custom made?

Do you see any signs of oxidation on wires, or battery, or motor ports?

Might just well cycle through several connect/disconnect cycles for every port to make sure all contacts are capable to carry full current.

Also, what happens if you control individual motors manually from the V5 brain test screen? Can you go 100% and what is approx speed by counting number of full rotations per, let say, 10 seconds?


Hi guys, thanks for your replies and sorry from disappearing from thos topic for a while. Luckily we managed to get our drive working as intended, and we concluded several reasons as to why the drive wasn’t working as intended.
#1 not properly maintained, the motors overheat fast, we lubricated them and that greatly helped the robot
#2 vex OS, I previously mentioned that the vex OS was up to date because we had updated it that night, but later that same night we discovered that the computer did fail to download one of the updates.
#3 a slight difference in the lift limiter, we never expected this but there was a slight difference in the lift’s limiter due to it being loose that caused an issue when the lift attempted to push a goal on the ground.
(The drive started working properly after we updated the firmware and fixed the limiter)
#4 overuse, we were using the drive a bit extensively that night, our robot is heavy so naturally the motors heat up fast, so we know now that we have to give the robot frequent breaks to cool down. So far we have had very little issues with the drive in the couple of competitions we had since we had this issue.