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Recovering e-scooter battery packs 72V Li-ion
#1
Hello, after following this forum for some time and working a lot with electric scooters and batteries. I have a question that I am tinkering in my head and just want to clarify if anyone has more experience than me (someone has for sure).

Case: Scooter has a 72V Li-ion battery pack which is undercharged to for example 30-40V. Now since I have experience with different brands some batteries have under-voltage protection and in that case, BMS cut output voltage to 5V and disables charger from recharging the battery. But this brand doesn't have that and is clearly showing 36V (on the multimeter) on the battery output terminal. Since there are no input/output blockers from the BMS side, it has to be from the charger. It would be awesome that I can save these battery packs without dismantling battery and I know that some services in the area do that. But they are not telling me how Big Grin . So looks like BMS won't block any input like with other brands it is more like monitoring that management (but has balancer with outside signal).

Idea: With all this in mind and some surfing I got to idea to buy a laboratory power supply where I can carefully manage power input to the battery pack to recover it. Now I see there exists a lot of 60V power supply which are very affordable but I don't think stock battery charger would pick up at that voltage I would prefer 72V and then connect to stock charger like some services do. So I have found this laboratory power supply (EA Elektro-Automatik EA-PS 2084-10B Bench PSU - cant post link to it), it looks like it could serve my purpose without any problems. Has more current output than stock charger (stock charger has 7A) of course I think that batteries should be recovered with low amperage? Right? Or do any of you think that should not be the case? So then I am looking in some other units from this brand which have 5A max on 2 channels so that would be 2.5A on 1 channel. That would give me the ability to work with two battery packs at once.

Here is were I stuck and I am seeking advice from some more experienced here. What do you think about how much current I need to safely recover the under-voltage battery pack?

Any comment or advice is welcome, I would love to hear anything from someone with more knowledge and/or experience...
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#2
(05-05-2020, 03:45 PM)MrKaos Wrote: Here is were I stuck and I am seeking advice from some more experienced here. What do you think about how much current I need to safely recover the under-voltage battery pack?

Generally speaking, the highest amp per cell during recovery is a slow trickle of about 50mA per cell. Charge at that level until they reach about 2.8-3.0V and then resume normal charge
Proceed with caution. Knowledge is Power! Literally! Cool 
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