Ugggh. Broke my JBD-AP20S003SV1.2 BMS.

[justgary]

I am trying to finalize my battery installation with 16S2P 230Ah cells. I bought two 7-20S BMSs, but they both came with only 4 gauge wire on them. I decided to change the wires to 2/0 gauge to help keep heat down under heavy loads. I discovered that they use red loctite on the threads for the studs that hold the cables on. I used a bit of solvent and managed to soften the loctite, but as I removed the B- nut I let the wrench slip and it damaged both of the little 0805 chip capacitors on the bottom of the board near where the B- cable bonds to the shunt via the stud.

I have the second BMS with good caps on it, but no decent way to measure them without removing them. It appears that their only function is to decouple the lid so that it is not DC connected to the B-. I'm trying to figure out what voltage and capacitance to replace them with. I have 0805 50V 0.1uf caps here, so I'm considering trying them.

I did send a request to JBD, but I figured you guys would like to help by laughing at my mistake while I wait for an answer. Photos to follow in the next post.

 

[justgary]

The good one:

 

[justgary]

OK, so I was able to measure the ones on the good board. They are ~9.6nf, which is close enough to 0.01uf for me. I can get them in 200V 10% for about $5 per 100 plus shipping from Mouser.

 

[400bird]

Excellent, should be a straightforward repair.
I'm surprised there aren't identifying markings on those capacitors.

 

[justgary]

Excellent, should be a straightforward repair.
I'm surprised there aren't identifying markings on those capacitors.

For some reason, chip caps rarely have any markings at all. This would have been much harder if I didn't have two of the same model.

It does drive me crazy that I need to change the cable.

 

[400bird]

Yeah, I've never understood why BMS manufacturers think they can call it a 200 amp BMS and included cables that are good for something like 60 amps. ?

 

[justgary]

Yeah, I've never understood why BMS manufacturers think they can call it a 200 amp BMS and included cables that are good for something like 60 amps. ?

It surprised me to see a 4 gauge cable on it. Another member here posted a photo of an earlier model that had two 4 gauge cables on each lug.

The rest of the BMS looks like it could handle 200A. The shunt on it is a 500A/50mV model, so it is probably the weakest part for continuous current. I'll be really happy with 100A continuous.

 

[justgary]

Well, it figures that as soon as I completed the order for new capacitors that I would go out and find the stick of them that I used to make sure the originals were 0805 size. I didn't check it after I found out that I needed 10nf and went rooting through my supply of them. Of course they are 10nf (0.01uf).

They are 50v, and I ordered 200v, but these are only to keep the lid from being DC grounded. I don't think they will ever be used if I can manage to not drop a power cable on the lid. Anyway, I put them in but have not tested the BMS yet.

Flux is always your friend when soldering.