I need to access my BMS: What is this stuff shown in the photo?

Hammick

Member
Region
USA
My battery won't charge. I want to try to wake up the BMS. Charging through the discharge port didn't wake it up. I need to access the BMS so I can try to wake it up by removing then reinserting the cell connector plug while the charger is connected. I also want to check the individual pack voltages to make sure I don't have one or more that is bad. I'm pretty sure the BMS is right below the wires encased in the black glue. However I have no idea if the green/silver area circled in the photo carries current or is just insulating tape.

This is a 48v 13ah Silverfish battery.

Thanks for any advice.

UPDATE: Turns out it was just reinforced strapping tape. Since it is transparent the green paper underneath made it look like a ribbon cable.
 
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harryS

Well-Known Member
How about the other end. Is there a removeable cover? Might be a BMS on that end.

Otherwise, you have to push the shrink wrapped cells out. The last time I did this (different style battery), the shrink wrapped block was held in with rubber cement.. It was quite hard to get out. Then I removed the wrap at both ends and discovered the BMS underneath. It's basically a discovery process, unless someone else has done so,
 

harryS

Well-Known Member
Ah, I didn't see that you already got it out. I thought that was re-inforced tape, but it could be the ribbon cable. Maybe that's the BMS on top, with all kinds of black goop on it.

I believe you have four fiberboard panels forming the sides of the battery compartment under the shrink wrap. I carely removed the end and found my BMS.

fish4.jpg
 

harryS

Well-Known Member
My first thought was it was re-inforced strapping tape, You can see a small strip of tape on the side of the BMS in my picture. but if you see wires, don't cut. There's only one ribbon in a battery and it's the balance wires, Here are two representativeBMS circuit boards, They often have metal plates that serve as heat sinks. And it's not really a ribbon cable. More like 13 or 14 loose wires.

P1620645.JPG
 

harryS

Well-Known Member
Abd it could still be a charger issue. I only have one charger that requires a load before it supplies voltage, but some chargers work like that, Just be careful and don't tear things apart til you must.
 

harryS

Well-Known Member
With those voltages, there is no reason why the battery should be inhibited from charging. Suggest the BMS is at fault.

Available on amazon and ebay. If you're super lucky, they use the same balance connector with the wires in the same order. but that rarely happens. Expect to splice in the new balance wires.

13S BMS for 48V battery, 54.6 V max. 4.2 max cell voltage. You want one that is more or less the same size. Should have balance ciruitry. If they don't show a balance current of 40ma - 50ma in the specs , then it doesn't have them, Some vendors will say balance BMS when they don't balance,,
 

tomjasz

Well-Known Member
Consider using grounding devices when working with a BMS. The biggest reason EM3ev and others stopped selling BMS was due to DIY fellas killing the BMS with poorly understood electronic repair techniques. Static electricity can smoke a BMS.

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