All 3 MA battery cells read 4.2 Volts but battery wont turn on.

[mporter]

I have 2 MA batteries that show no lights when you press the button to turn on or while on the charger. It's not the charger because I have a third battery that still charges. I decided to take one apart & check the voltage of the individual cells. All three cells have a voltage of 4.2. When this happened, I was in cold weather with snow. Turned on, got GPS signal, took off, immediately got the critically low voltage error & started to land itself. Turned it off myself. Tried the second battery, same thing. Took them inside and put one on the charger after it warmed to room temp. It took longer than normal to fully charge, but it did charge all the way up. Proceeded to try & fly again, same thing happened. Critically low voltage, landed itself, then I turned off. Both batteries are nonresponsive when I try to turn on or charge. Got curious & took one apart to check the cells. Like I said, all 3 cells read 4.2 volts. Anybody have any thoughts or ideas? Some sort of temp sensor go bad? Any way to reset battery or bypass whatever is keeping battery from turning on? I have seen a video on YouTube with some guy connecting the battery to the computer via some other gadget to revive the battery through some kind of software, but I hear that process is expensive & so is the software. Any truth to any of this? Is it even real?

Thanks in advance!

 

[everBit]

Your batterries got locked due-to low voltage event. The reason of this is partially weared cells and cold weather. Unlocking is possible but require special software.

 

[mporter]

Your batterries got locked due-to low voltage event. The reason of this is partially weared cells and cold weather. Unlocking is possible but require special software.

No way to bypass it other than special software? Batteries are just junk then? If i replaced the old cells with new cells, would it work again or would the motherboard still need to be reset with that software?

 

[slup]

...Batteries are just junk then?...

That they take charge to 4,2V isn't at all a guarantee that the cells is healthy ... far from it.

Most probably the internal resistance in the cells now are so high that they can't keep the voltage up during amp draw from a drone ... instead they rapidly falls under 3V & by that initiate DJI's critical low battery auto landing.

If you attach one of the flight logs from one of those flights where it start to land just a short while after take off & we can have a look at how the cells behave.

Read up here (under section 3.) on how to retrieve the .TXT log that are stored in the mobile device you flew with --> Mavic Flight Log Retrieval and Analysis Guide then attach it in a new post here.

 

[everBit]

No way to bypass it other than special software?

Some crazy people put jumpers across the MOSFETs to allow power-up the drone. But me could not recommend this in any case due to safety concerns.
Another way is to use daily license to resetting software which specialising workshops offer so batteries could be fixed in budget way. But keep in mind even you unlock the BMS logic, it could be locked again if you will use the batteries in cold state. Their internal resistance increases significantly at low temperatures so voltage drop could be drastically. While batteries are new they have good reserve to pass initial drop and to heatup during the flight to working temp. But being in service for some years should be preheated first to 20...30*C before flight to allow them reduce impedance. DJI even offers battery preheaters as optional accessory for cold weather usage.

it work again or would the motherboard still need to be reset with that software?

Yes, even you put new cells the PCB will be kept locked because error event is stored in the chip eeprom.