V5 Battery Blinking Red Light - Even Charged

We have 25 new V5 robots for our school and within just a few charges 2 of them are not working. They are fully charged (at least they show to be with 4 green lights) but get a fast blinking red light as soon as we plug them into the brain and the brain will not power on. The only way to make the red blinking lights go away it to put it on the charger but it goes right back to red the second we plug it back into the brain. The firmware is up to date but the cells show approximately 2.8 volts per cell where the ones that work show approximately 3.2 volts per cell. Any thoughts or help?

How fast is it blinking, and at what position?

EDIT:
Check out this Vex KB article: Interpreting V5 Battery Lights and Errors – STEM Library (vex.com) This may help.

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It doesn’t but thank you for the reply.

Just as soon as it’s plugged into the brain it starts blinking fast red nonstop until we plug it in and then it shows four green lights. It does this every time we try. The reset button does nothing.

which led is flashing red ? Have you tested using battery medic ? If so, can you post a screen shot (I assume you have if you already know the cell voltages)

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We have started having this problem too. It seems we have a cortex that when any battery is plugged into it the start flashing red on the first LED.
We couldn’t get the cortex on long enough to do an update, till I plugged the battery into charge at the same time as running the cortex. I’ll try the Battery medic tomorrow.
Wondering if it is because we have competed much in the last two years, so batteries have been hardly used.