I plug my batteries into my vex brain and within 5 minutes the robot suddenly turns off and the red light starts flashing. The green lights still turn on but the battery refuses to work this happened with 4 different batteries and we also changed the battery cable. This would make sense if it were a brain issue but the red light continues to flash still minutes after it is unplugged. Does anyone know what the issue is and how to fix it.
1 Like
Just gonna hit you with some general troubleshooting on this.
Unplug all items except battery.
Update firmware on brain and batts to latest.
Go into brain, go to battery, view the individual cell statuses and pack cycles.
Report back here.
most likely a bad cell, the battery is shutting down due to an undervolt situation. Use the battery medic program to view internal cell status. How old are the batteries ?
(also available in the VEX VSCode extension)
2 Likes
how do you update the firmware of the batteries?
Update the brain. It will update every single thing your plug into it (motors, sensors, batteries, wireless transmitter, etc).
I’m curious. Could it be more than a bad battery? OP says it happens with 4 different batteries… it feels really unlikely that 4 batteries all are bad.
unLESS of course, the OP accidentally grabbed all 4 from their org’s battery graveyard. 
It is really strange this all happened last night. This morning I ran the robot for around 15 minutes and there were no issues so maybe it was a temporary issue
It sounds to me like you forgot to charge them.
2 Likes
When the batteries stopped working in addition to the flashing red light all of them had at least 2 green lights
The green LED give an estimate of capacity only, depending on how the battery has been used (ie. was it allowed to fully charge) that may be inaccurate. The estimated capacity is also separate from the battery management deciding to shutdown due to either low pack or low cell voltage. A bad cell will tend to reach a critical low voltage before others, even if the others have remaining charge and good voltage, the bad cell will cause the entire pack to shutdown.
How old are the batteries ? I would expect a battery used on a competition robot to only last a couple of seasons.
1 Like
Some of the batteries are brand new some are a few years old I don’t know which are which however the issue seems to have dissappeared as today everything is working fine.
(This is for the people in the future that have this problem)
We had this happen to us this year and by replacing the brain cord it stopped killing batteries, so try that first.
We are on year 5 with our packs.
But we follow a couple of general rules
- don’t leave packs on charge longer than needed
- if a pack is run down till the protection kicks in (avoid at all costs) we charge it immediately
- the packs are NOT left fully charged for long periods of time, especially over summer break
- packs are handled like the expensive, reasonably fragile items they are… no dropping/etc
- packs are rotated if possible… avoid using/charging one pack all the time
1 Like
This may have been are issue at first when I changed the cord it did nothing but I left the robot and came back the next day and it was working so i think this may have been the issue
I’m not a fan of the connector used for that cord. The ‘socket’ that the pins go into wears and loosens over time. It was not the best choice for a fairly high current connection. If your cable ends are warm/hot after a run, then I’d replace the cord.
1 Like