Problematic charging

Freshblood

1 mW
Joined
Aug 27, 2017
Messages
11
HI,
I have built a 9S 6P 32.4V battery pack with a 10S BMS. I bought a 10S 42V charger off ebay and the fuse keeps blowing.This happens the moment charger makes contact with batter pack. With limited electrical experience I am trying to figure out why.
There is 32.4 V on the charging port which i thought was strange but the wires for charge/discharge is connect in series so I guess it should be.
Pack does not appear to have any shorts. Each cell is checked at BMS end and it all registers. Also discharge potential is 32.4V.
Any way to troubleshoot this?
 
Most likely thing to cause that, is you are connecting + to - when you plug it in. I mean you have your charger wired backwards.

Done it enough times to suspect you did it too.
 
Thanks for the advice here. Talking about the charger, the live wire(usually blue/ positive) I matched up with + and the neutral (brown/negative) I matched up with -. I will switch these two wires and check again, once I bought more fuses :)

Regarding using 10S charger with 9S battery. Well I am not sure why they call it is 10cell charger. They call it a 36v 42V 48V 10s 5A charger but it definitely does not control cell charging. Only positive and ground going into battery. My BMS deals with individual charging.
 
Freshblood said:
Talking about the charger, the live wire(usually blue/ positive) I matched up with + and the neutral (brown/negative) I matched up with -.

I've never seen a positive wire to be blue.
 
I had a charger time ago.... positive blue negative red..... I am glad I always check wires with multimeter.
 
Freshblood said:
Thanks for the advice here. Talking about the charger, the live wire(usually blue/ positive) I matched up with + and the neutral (brown/negative) I matched up with -. I will switch these two wires and check again, once I bought more fuses :)
You need to use a multimeter to measure it. When you connect the meter, if it shows a - sign in front of the voltage, then you have + connected to - on the meter, and should swap them.

FWIW, you can't trust wire color on pretty much anything "cheap from china"; I've seen so many things with "wrong" colors (that don't match any standard, or even matching the labels on the device) and even stuff with all the same color wires.


Regarding using 10S charger with 9S battery.
You don't want to do that. If your BMS does not shut charge off for any reason you'll overcharge your cells, potentially causing a fire (and damaging the cells even if they don't burn). Each cell would get at least a 0.46v overcharge, bringing htem up to almost 4.7v per cell, instead of 4.2v.


Well I am not sure why they call it is 10cell charger. They call it a 36v 42V 48V 10s 5A charger
I suspect the three voltages on there mean it's switchable or adjustable inside, but possibly only at the factory. You'd have to check with teh manuacturer to be certain of that, but they probably won't reply or even if they do probably won't be able to help you change it.

But a 42V charger for 10s means it would charge 10 series cells to 4.2v each (assuming they're all well-balanced).


The 5A means it will output a max current of 5A, so when the cells are at their lowest (most discharged) it will charge them at 5A (and taper off as it gets closer to full).
 
billvon said:
thunderheart said:
I've never seen a positive wire to be blue.
In NEC compliant wiring, white is return and black/red/blue are hot.
tell that to a chinese 6 year old.
 
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