Battery problem

[mrzealot]

Hello all!

First time posting here, and I'd like to lead with the fact that I'm very much out of my depth on the hardware side, so please just assume I don't know the first thing about whatever we're gonna talk about...

With that said, I bought a bluefruit ble board for a keyboard project, and it works fine while powered by the USB cord, but turns off as soon as I unplug it. I had some no-name 3.7V lipos from earlier that measured around 4 volts raw. Then I spliced a jst connector onto the first one, and it still measured 4 volts. Then I plugged it in the bluefruit, and it dropped to 0.46 volts instantly, which is clerly not enough to power the board. If I then disconnect the battery, it still remains at 0.46 volts. Assumed that maybe the battery was defective somehow, and did the same process with another one, to the same results. The board doesn't heat up when plugged into USB, and works as expected.

Did I do something obviously wrong? How do I go about debugging this? Have I killed the batteries? Any insight would be very much appreciated. Thanks!

[adafruit_support_bill]

What size were the batteries you are using? Do they have built-in protection circuits? Many LiPos (including all the ones we carry in the store) have built-in protection against overload or over-discharge. If you managed to overload the cell, it may take a while for the protection circuit to reset.

Another thing to check is the polarity. There are 2 ways to wire a jst connector and the gaming industry chose to do it the opposite way from the cell-phone industry. All of our batteries and boards are based on the cell-phone standard connector polarity. Connecting a cell with reverse polarity might have caused an overload.

[mrzealot]

1500 mah, with built-in protection circuitry. And it's very reassuring that you mentioned reset and "taking a while" as I was just about to update my post that even tho the battery measured 0.46V right after it was disconnected, now I did another measurement and it's back to normal. So I probably haven't killed it...

Re: reversed polatity, is it safe if I just try it the other way as well? Worst case I just overload it again? Or is there a more "sophisticated" way to test this? Thanks a lot!

[mrzealot]

Nevermind, went with the non-sophisticated way of just reversing it, and it now works! Thanks again for the tip about the competing standards!

[adafruit_support_bill]

Good to hear you have it working now. Thanks for the follow-up.