Charging 48V battery with 36V charger + 12V power supply

[cybug]

Nothing really new here, I post it for noobs (like me) who ask themselves how to do an emergency charging without the proper charger ...

I needed to charge my "48V" battery pack (12S2P RC LiPo, Max. 50.4V) but have blown my RC charger. I only have a "36V" battery charger (42V/2.5A) so the pack only charged at 42V which means 3.5V per cell instead of 4.2V

So I added a 12V (30A) power supply trimmed to the minimum (9.6V) in serie with the charger. Because the charger is current limited to 2.5A, the power supply aligned to it and delivered no more current. Monitoring during charge was done with a wattmeter and a battery medic. I stopped the charge when all cells were at 4.1xV.

Here's a video :
http://youtu.be/kOP343mixtg

(youtube BB code isn't working so I post it an URL)

 

[dnmun]

you can use a 12S lipo BMS also and then adjust the charger voltage down a little so your total in series is the 50.2V and you won't have to monitor it. the BMS would then balance it to the 4.2V/cell.

 

[cybug]

I only have 10S BMS handy so I had to monitor for hours (2.62A) balancing with only one battery medic 6S at a time.

A 12S BMS is planned for this pack