Unusual Battery Issue

MapMaker53 · Jul 25, 2015

Because I have 5 batteries and tend to cycle using them, none have yet reached the 20 charges point requiring a maintenance drain-down - though some have more charges on them than others. But two of the youngest batteries are suddenly unable to charge to 100% today, leaving the last LED blinking. One has eleven previous charges and the other only six. I have occasionally had to store them in the case in a very hot car (95+ temps outside) during my field assignments, but I can't see how that can be avoided -- unless I possibly use a cooler for future assignments. The other 3 older batteries experienced the same high temp environment but are still charging to 100 percent. Has anyone seen this problem before? I would upload my screen grabs but for some reason I am unable to upload photos to the site lately.

MapMaker53 · Jul 25, 2015

UPDATE: Okay.. I had tried charging with the batteries while still on since they were mostly charged, but that didn't help. I then figured if the problem was caused by some sort of heat damage to whatever molecular chemical structure is in the Lipos maybe cold would "reset" that chemical structure. I put the batteries in the fridge for about an hour and then tried charging while on again. Wouldn't you know.. the first one completed the charge and is indicating 100 percent. Second one is on the charger now.

MapMaker53 · Jul 25, 2015

Well, that did it. Both batteries are now charged to 100 percent. Go figure. Maybe I just came up with a Fridge Trick of some sort. We'll see how the batteries perform this week on another job. This time, I might bring a small cooler for the batteries. Supposed to be in the 90s again.

RoyVa · Jul 25, 2015

Good job we may need to put that info in the ole memory bank for future use.

yorlik · Jul 26, 2015

MapMaker53 said:
Well, that did it. Both batteries are now charged to 100 percent. Go figure. Maybe I just came up with a Fridge Trick of some sort. We'll see how the batteries perform this week on another job. This time, I might bring a small cooler for the batteries. Supposed to be in the 90s again.

be careful; charging a lipo <50F needs to be limited to less than 4.1v per cell and even lower if freezer temp! dji charges to 4.2 - that can cause fire or damage your cells.

MapMaker53 · Jul 27, 2015

Thanks for that info, yorlik. I'll keep that in mind and make any fridge cool down a very brief one.

yorlik · Jul 27, 2015

no, fridge is good! I put a puffed one in and a day later the puff was gone. I am not saying dont put in fridge, I am saying let it warm back up some before you charge it is all. I do not know if dji uses a temp sensor to measure ambient temp in their smart batteries and then adjust max charge voltage accordingly, but I would not assume it, especially when I can just make sure it is not too hot or too cold before charging.

MapMaker53 · Jul 27, 2015

Got it. Thanks.

RichWest · Jul 27, 2015

Great info @MapMaker53 , thanks for the observation. I'll be trying this out on my remaining batteries. We are hitting +100F out in the open, so both man and machine are showing signs degradation.

@yorlik IIRC, I believe they do have a temp sensor in the smart circuitry, based on the log data people were discussing a few months ago.

PaganLinuxGeek · Jul 27, 2015

Wow good info to have! Thanks all for sharing!

yorlik · Jul 27, 2015

RichWest said:
I believe they do have a temp sensor in the smart circuitry, based on the log data people were discussing a few months ago.

yes, they do - for battery temp. they are typically used to watch for overtemp condition but I have never heard of anyone using them to adjust the max voltage of the CV final charge sequence. normally these are non linear ptc or ntc thermistors and not the more expensive linear temp sensors. just a go/no-go output. that would be a good use though!

RichWest · Jul 27, 2015

yorlik said:
...normally these are non linear ptc or ntc thermistors and not the more expensive linear temp sensors

Justifiable, quite a cost spread between the two. It's a simple controller to charge the cells, it was never meant to be precision...or be costly.

RoyVa · Jul 30, 2015

I treat my batteries with the upmost respect. They keep me in the air or not. I know what low battery autoland means.

MapMaker53 · Aug 3, 2015

UPDATE... As I do not want to spread misinformation. Turns out my problem was the charger. I use two chargers on my jobs and must have used the good one to successfully fully charge the batteries after taking them out of the fridge. I discovered one charger was just weakly blinking red and a meter confirmed it was just outputting a little over 2 volts -- while the other was outputting the normal 12.6 volts.

RichWest · Aug 4, 2015

I did the refrig test and felt the batteries didn't even warm during/after charged. Can't attest to any improved flight times since I was landing at 30%. Was over a lake the majority of the flights, so I was imagining a potential failure with the batteries.

I never really noticed before, but my charger does get fairly hot/warm. Guess I need to check its voltage as well.

yorlik · Aug 4, 2015

Richwest,

I tried disconnecting the cells from the smart pcb board in your battery with 'bad cell' pop up in assitant. That did not reset the red LED on the pcb or stop the pop up. So unless dji replies to my request for a method to reset the smart battery board, I guess we are done with trying to revive batts once they get that pop up.

It is like they write a bit to their eeprom and never let it reset after they decide 'bad cell.'

I also have same question "how to reset the smart pcb' in to a few chinese battery mfgrs who show replacement cells for these. Unless there is a way, replacement cells won't do any good of course.

BTW, by charge/disch each cell pair individually, the dji assistant changed from your and my original 3600mah capacity to 4000mah.... so individual balancing seems to increase capacity some - at least it did on your old battery.