Electric Scooter Forum for Scooter Enthusiasts, Scooter Chargers, and Scooter Mechanics.

Discuss the Xiaomi mijia mi M365 original and pro versions in this forum. Topics include hardware, software, hacking, riding, and everything in between.
By OLL
Posts
#12808
Hi All,

I am trying to diagnose/repair an M365 battery problem and I am out of my depth.

The scooter won't charge. When I plug the charger in, the BMS blinks RED four times, then stops - no more red, no blue, nothing. The charger has a steady green light.

The contact tabs on the battery all seem solid and sturdy, but I have not opened up the shrink wrap. The battery is 36V model NE1003-H.

When I check the battery voltage, the readout is NEGATIVE –14.66, even though it's connected red-red, black-black. The DIY videos all show low voltage as an issue, but I have not seen any with NEGATIVE voltage. I don't even know what negative voltage means.

What should/can I do to get this working again? I wish I could just buy an affordable (and authentic) battery pack and swap it out, but at >$100+, that seems wasteful.

Please help! Thanks

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By Ben J
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#12811
It seems one or more of your battery cells are reversed polarity.
Its not at all common thing, I only encountered a few times with lead acid batteries what were being abused.
You probably have to cut open the pack and measure individual cell groups.

Come to think of it, Really 'dunno if lithiums can be reversed, at any rate lithiums are hazardous if they get out of balance.
Be careful.
By jaysonjehsen
Posts
#12814
alternatively make sure the leads of the voltmeter are plugged into the voltmeter the right way as well- they could be reversed-- the black should be ground (GND) and red should be +V. I've never seen a battery pack go negative like that though, and yeah batteries can explode (see macbook, samsung note 7, etc), so be careful
By Butch456
Posts
#12818
hi
was the scooter working ok before. If so then chances are something went wrong with battery.
Have you checked your meter to make sure working correctly.
It is difficult to repair the battery if you havent done it before. There are used batteries can buy reasonable and justmake sure output voltage is good.
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