Battery won't turn off (!)

[Saturn49]

I pulled my Mavic air out of storage where it sat for the last 6 months or so. 2 of the 3 batteries are fine and started charging (from 2-3 lights). The 3rd wouldn't charge though, and the multi-charger showed a red light. Hitting the button didn't do anything either. I figured it was completely dead. However, after much futzing, plugging, unplugging, holding the button down, etc, it eventually showed 2 lights, solid (not in the middle). On a whim I plugged it into the air and it powered on immediately. Back in the charger and it started charging. Not with the incremental blinking, but rather solid lights, increasing to 4 lights. Now it is fully charged but still won't turn off.

I tried updating the firmware on the Air with DJI Assistant 2 and the wonky battery plugged in... the Air "refreshed" its firmware (already on 1.00.0.620) fine, but the battery still won't turn off.

I'm guessing the controller in the battery has either locked up or otherwise failed, but I don't have any way to reset it.

Anyone ever heard of such a thing?

 

[Deleted member 94047]

This is a new one to me and a puzzling one. If the battery has indeed charged, why not put in the MA and drain it completely and then charge it back again? Perhaps that may fix it? I don't know. I am just thinking out loud here.

 

[Saturn49]

Well, this morning it was still on (fully charged, on the charger) and wouldn't turn off. Then I picked it up, hit the button a few times (nothing) and set it down on a table and it turned off. Now I can't turn it on again.

If I put it on the charger, the charger lights up green (not red anymore).

It's almost acting like just the button is not working (which would be a really stupid way for an $85 battery to die). But no amount of pushing, holding or bumping while pushing can get the lights to light up.

 

[Saturn49]

After futzing some more, I'm convinced that the button is actually shorted out, and when held just right, it sometimes disconnects, registering a button press. I got it to turn off and on once while holding it upside down (button facing down) and just barely touching the button. The lights were acting as if I was pushing the button really quickly.

I contacted support but got nowhere, as my batteries are ~11 months old.

Seems really dumb to throw out a battery because of a bad micro-switch but it looks like these batteries are REALLY difficult to get apart. And then once it is apart, what are the chances of getting it back together?

 

[Saturn49]

Well, I was able to get the battery apart without destroying it, and it was almost certainly the button. I dropped a little 99.9% isopropyl alcohol directly on the button and it started working properly. It looks like replacing the switch would be quite difficult - it is a surface mount component very near the battery connection, and the battery connections appear to be spot welded with many extremely tiny spots each.

So while it is currently working, I have to decide if I'm ever actually going to use it in my drone again, considering it may act up again and turn itself off mid-flight...

 

[Deleted member 94047]

If there is even a small chance that it could turn off mid flight, better to retire it or at least use it for purely ground work. Not worth risking losing your drone.

 

[Saturn49]

For those following along at home, the battery eventually returned to its defective state.

More as a challenge to myself, I acquired a (cheap) hot air rework station, flux, solder paste and kapton tape and a replacement switch. From what I can tell, this is a near exact replacement for the push-button switch:

TL3340AF160QG E-Switch | Switches | DigiKey

Order today, ships today. TL3340AF160QG – Tactile Switch SPST-NO Side Actuated Surface Mount, Right Angle from E-Switch. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

Manufacturer: E-switch
Part #: TL3340AF160QG

I wouldn't attempt it without a hot air station though, there's just not enough room to get a soldering iron on the contacts without disconnecting the batteries.

I was able to replace the switch and it has been working fine since, though I haven't exposed the battery to any appreciable humidity or anything. I haven't yet run the battery in the drone either...

I did notice while replacing the switch that even the very mild conductivity of the flux before it was dry was enough to activate the switch. This indicates it has a VERY weak pull-up on it, though I did confirm it didn't appear to be entirely floating (which would also cause random activations).