Help! I made a 52v battery but it’s cutting out at 50-51v

[SurRonny]

Hey guys,

I made a 52V battery out of tested laptop batteries.

Battery chargers to 58.8 which is perfect.

I have hooked a BMS up which is all connected properly, when it gets to 51V on my handlebar volmeter the LCD display goes off and the voltmeter dies. When I switch it back on it fluctuates to 10-20-30v then goes off again.

Is it something to do with balancing ?

Bad cell ?

Settings on the KT LCD5 display ?

Little bit stuck.

Be great if you guys could point me in the right direction I’d be very grateful.

Thank you

Nathan

This is the BMS I have got - https://m.aliexpress.com/i/32977028591.html 30A


Battery pic 1 - https://ibb.co/2KbKJxW

Battery pic 2 - https://ibb.co/5F8HGMz

 

[StuartsProjects]

I made a 52V battery out of tested laptop batteries.

How did you test the batteries ?

 

[soundwave]

 

[Nealh]

One suspects the cells are shot or very saggy, probably both.
51v is an even 3.64v but my guess is that some cells are simply collapsing once the voltage gets low and have high internal resistance, it only takes 0.4 - 0.5v sag to hit lvc.

Used laptop cells are just that and certainly won't be the high grade high current cells e bikes need.

 

[Nealh]

I can see some panny cells but no idea of the rest.
Are they all the same mah and current rating if not, the the battery is only as good as the lowest rated cell.
You won;t get ant more form the battery with such a mish mash of used cells, there is one thing one is asking for and that is likely fire. So be very careful.

 

[SurRonny]

Batteries were charged on xstar 8plus @ 500ma.

any below 4.15 we’re binned. Any that had a high internal resistance were also binned.

I let the rest sit for a week and noted voltage on each cell.

Any that dropped more than .10v were also binned.

Is it dangerous using tested cells ?