Faulty Battery Advice

[David Kirkpatrick]

I bought a kit from these guys https://www.aliexpress.com/item/12-Parts-Whole-Set-E-Bike-Refit-Kit-With36V-500W-Battery-LED-Display-Controller-Motor-Brake/32524917815.html?spm=a2g0s.9042311.0.0.774a4c4dEmsx8L.

Has been working fine until now. The bike has done 1000 miles and probably about 60 charge cycles. The battery charges fully, show 42V on full charge. However when riding now voltages fluctuates widely, power cuts out regulatory and sometimes the bike computer just shuts down. With a bit of experimentation with the throttle voltage is steady until I get above 2 Amps but above that starts fluctuating. Thought maybe I had a loose connection in my wiring somewhere but with this behaviour I am thinking its the battery. Is this the kind of problem you would get if the battery was dodgy.

I have fairly limited electrical skills (I know how to use a multi-meter and could do some very cack handed soldering). Given that is it worth trying to fix.

If not any recommendations for batteries in the UK.

Thanks,
David.

 

[Nealh]

It will depend on the quality of the cells inside and their actual spec, they might be branded knock off cells or just cheap China cells in which case what you are seeing is to be expected. For sure at the mo they can't handle much load.
Only opening the case will you only know what cells they are and also the rating of the controller.

Also some China batteries are known for terrible battery builds, often no where near enough series connections to spread the amp load in series, so this can lead to overload and poor amp draw as you are experiencing. Open the case peel off any covering and take a pic of the cells from both side so we can see the series connections.

Soldering cells is no good as usually to much heat is transferred for to long so causing internal heta damage, spot welding is really the only option.