New V5 Battery, no lights, no charge

We have a new V5 battery purchased several months ago. When the button is pressed, there is no response. We have reset it several times with no change. Measuring between the third and any other terminal, it reads 0.9V. None of this has changed after a week of charging uninterrupted. We are using the V5 battery charger and have confirmed that the charger is working using a multimeter.

If none of the leds are on when charging, then it sounds like it is dead. I guess call vex support and try to RMA it, it may not have liked sitting around for several months without ever being used or charged.


That’s what I was thinking as well, but I was hoping there was a different solution. If I don’t figure anything out soon, I’ll go ahead and do that.

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So here is the rub - we were not allowed in buildings for months in some district - mine included. We are coming back to buildings and will find such situations - so it would be more helpful to have a procedure to bring back to life for those instances and those who were out for summer. As this appears to be the new normal.

[our custodians have been taught to turn off things when school is out to conserve power.]

I would not be too concerned. The battery the OP had may have been DOA, all we know is that it has no life at this stage, but I don’t know why.

LiFePO4 batteries have low self discharge rate, although it does increase at high temperatures. I just checked some of my old development batteries that have been inactive for over a year, they are all fine (in as much as they will power on and charge). The capacity as indicated by the LED will be incorrect I would assume, we do not monitor capacity when the battery is inactive (ie. by that I mean we completely shutdown the battery after a few minutes if it is disconnected from the V5 brain). so loss of capacity due to self discharge will not be know by the firmware.

For batteries that have been inactive for several months, charge them up, run them until shutoff on a V5, then charge back up to 60% before placing back into storage. Don’t try to change if they are really cold, get them up to a normal room temperature (15-20 deg C) before doing that.

There’s not much can be done for a battery that will not respond to charging or (as a last resort) using the reset button.


I did some research on LiFePO4 batteries. They have a long shelf life, so leaving them sitting shouldn’t be a problem. However, I found that they can be permanently damaged if a cell discharges below 2.5V, so ~10V total for the 4 cell battery.