Hi I am having issues with my battery packs having undervoltage errors. They never tend to be able to stay on for more than around 3 minutes before turning off and flashing the LED closest to the button 5 red 5 times per second. I plugged it in to the brain and ran the battery medic program on it and everything seems normal at first except for the high over and under voltage error counts.
After a while, each cell one by one turns red, and then the pack voltage turns red and drops drastically, and then the brain shuts down and the red flashing light on the battery occurs again.
Your capacity and pack/ cell voltages are not in sync for some reason. Put that battery on charge for a couple of hours, ignore the capacity and green LEDs. Then run it again on a brain with battery medic running, see how long it lasts before turning off.
Wasn’t it the promise that LiFePO4 chemistry used in the V5 batteries would provide more reliability and resilience (over regular Li-ions) at the expense of some extra weight?
I am somewhat puzzled why V5 batteries have so many failures both from long storage and imbalanced cells. Should’t the built-in battery firmware take care of, at least, some of those issues automatically?
The V5 Batteries are surprisingly decent in terms of power for its weight and size. However I have a seemingly similar issue with practically all of the batteries I use drain within 5-6 minutes of a robot’s runtime without even moving. Even though I am just displaying text onto the V5 Brain, just by having motors connected and not running them, the robot’s battery drains eerily quick. Does the V5 Brain consume a significant amount of power when there are like 12-14 motors connected, not moving, and idling? Or could it be that the two processors on the V5 Brain are decently power-hungry?
It does, but balancing is tricky, we really only know when cells are not balanced near the end of charging. If the battery gets pulled of the charger early then balancing may not finish. The V5 batteries have a different use situation to most other rechargeable batteries we use in daily life, a fast high current discharge often followed by only partial recharging. I guess this situation does happen with hybrid and BEV, but I will admit that our battery firmware is probably nowhere near as sophisticated as the auto manufacturers.
You should be getting far longer than that.
Look at the brain dashboard and it will show battery current.
At 1A discharge you should be seeing 45-60 minutes of use.
When we were doing the battery evaluation back in 2018 we would usually discharge at 3A (and also higher) when testing. At 3A a typical battery would run for about 18 minutes.
Honestly… I didn’t time it but now that I realize it, perhaps it could be me while coding the robot for a long time without realizing 45 minutes has gone by, and I practically would gaslight myself to thinking it’s only 5 minutes when the robot dies.
I’ve been having fun making a more powerful OkapiLib for VEXCode with machine learning and path generation, and I perhaps am having fun coding it that time flies by before I know it.
We’re having what we believe to be the same problem as OP, seeing the battery quickly shut off (outwardly appears as if the battery had died) with the 4th (closest to the button) LED flashing 5 times per second. This happens every time we run the robot, most commonly while attempting to run a motor/pneumatic, frequently while not doing anything, and occasionally while idling (without the program running).
We can confirm the battery is not at fault. We have tried a total of 4 different batteries (2 of which have been confirmed to work separately), and the problem still occurs. We swapped the battery cable for another which is known to work, but the problem still occurs.
The problem started ~1.5 months ago, and has been progressively getting more frequent and severe (the battery will work for at most 30 seconds before shutting down). Our coach believes this issue may originate from static electricity around the brain as the gears in the drivetrain and conveyor mechanism are both close to the brain, and a pneumatic tank is also close (acting as a capacitor, he theorizes).
Another possible origin, though I have no idea what would have caused it, is the programming. My team uses object-oriented python (both static and instance methods), also using constructs like lambda functions. I don’t say this because they are notable, but my coach advises me the code could be an issue. Verification from others who use these python features would be much appreciated.
