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Hi. I am so pleased to re-discover Greyarro.
About 5 years ago I spent quite a lot of money on a MAVIC PRO and ancillary equipment including 5 quite expensive batteries. I fairly soon crashed and smashed it but replaced it. Time has passed and the batteries have sat idle for years mostly due to house moving. I have recently discovered that leaving the batteries for any length of time causes them to die. I desperately need help to get back into the air.
I have retained my legal licence to fly.
Regards in expectation. David Bingley.
Sadly I think the batteries may not be of use now. I have not heard of intelligent batteries being brought back to life. If this is possible then I am sure someone here will be able to give you some advice. I am not a pro and reasonably new to it but I am aware that none use will cause problems.
P.s. Welcome back
If not looked after and charged regularly they unfortunately die
Lots of topics on this very issue
https://greyarro.ws/search?context=topic&context_id=67047&q=Mavic%20pro%20battery&skip_context=true
Yes they will hold their charge for a reasonable amount of time, even months but if not recharged at some point they will eventually just die completely. Once they are depleted you gotta bin them safely
Hi. If you look on YouTube, there seems to be several ways to salvage the batteries. My four have been idle for about Five years. I can’t accept that, because of the price of theses things, that there isn’t a way to bring em back. I’ll keep trying hoping that someone will say. Oh! Yes, I can fix them for you. Or I will die trying.
You could probably change the cells but then you would need to reactivate the BMS
This can be done but you will need to open the battery, be able to solder and will need some kit to flash the BMS
Thanks for that but it sounds a bit above my pays ale.
I’m somewhat annoyed that there wasn’t anywhere near enough warning of the battery problem. Spent about £360 having more than enough batter power only to find that it was wasted money. I hate that! The price of batteries has come down just a tad. There are some for sale on ebay. Looks a risky deal though. Know anyone who has bought batteries on Ebay?
Have you reached out to DJI 
No. Good idea. Didn’t occur to me. Cheers.
Not sure many batteries would survive 5 years left to mind their own business
I agree. But I’ve moved house twice during that time plus, I assumed that if they were stored full charged, they would be fine. Expensive mistake! 
A few weeks ago I bought a big Samsung S8 14in tablet. Samsung were doing a £200 off if you traded in a working tablet. I dug out a couple of old HTC tablets that had sat in a drawer unused for around 12 years or more [yes, I know, must clear out more often…]. I charged them both up. Yes, first surprise, they both charged up. Second surprise…they both held charge for a week until I selected one to post off to Samsung. A few days later I got an email from them confirming the receipt of a working tablet and £200 paid in to my account. I’m not sure that I paid £200 for these tablets when they were new.