I’ve got my 18s5p spot welded up and ready for series connection!
These are am04/jp40 cells
Right now I’m looking at doubling up 10ga between the P groups.
Do you guys think this is sufficient?
I’ve got my 18s5p spot welded up and ready for series connection!
These are am04/jp40 cells
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I doubt you’ll be running any more than 10awg to each solo, so double 10awg seems perfect
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I love The 30 t from battery hook up, especially the price you can’t beat it I still have over 100 to use up… I can’t really tell much as far as voltage sag on a 14 S4P pack but I don’t have much to compare to. They also have 8S Lipo now to where you could make a 16s quick pack…
Hey kids.
I’m helping a buddy that is not on the forum.
He built a little 10S1P pack.
Buthe is having some issues with the LLT BMS reading.
Physically everything looka good.
Measuring 35 volts total.
An 3.5 per cell.
Seems it maybe an issue in the BMS.
Has anyone seen anything similar?
Can the BMS be reset in any way?
Edit:
Solved. He didn’t have the charge port connection on c- and b-.
All good now.
Looks clean, ive had issues with that style of header connector getting loose and dropping a reading before, try checking the voltage at the soldering on the bms VERY CAREFULLY. Easy to mash a probe into the wrong place and short it out - i put a little tape on the probes so only the very point is exposed.
If it is testing good there then it’s something internal to the bms and the bms took a shit for some reason. Best to replace it.
If the problem is intermittent at all i would check and re-solder the wires at the battery termination point - could be a broken wire in the insulation or at the solder - if it is this i would generously cover the joint and wire with some hotglue or silicone so any vibration can only occur well away from the solder joints.
GL
Edit: bms app screenshot shows total pack voltage is low - but the readings when you probed it didn’t total the same. The bms total voltage is done end to end afaik so this makes me think it is intermittent - could also be bad welds in 1&/or2. My intuition says the series connections between 1&2 or 2&3 Maybe give them a once over and flex test
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I have a similar problem to what @rafaelinmissouri had. However, my bms was being used in parallel with 2 other JBD BMS as a temporary little battery bank setup. It was workng fine for about 5 months till I checked on it today.
When I open the app, it shows a very unstable reading, and bounces between which cells are balancing. When I read the battery cells manually with a voltage meter, the cells vary between 3.65 to 4v per cell. I am glad I caught the issue before it got worse.
I have no clue why this has happened, but makes me concerned about using JBD BMSs with future projects. If anyone has seen something like this before lmk what you think is going on.
I tried using both apps, but the second app disconnects quickly with the 2 broken BMS.
Ive seen readings like this from that app and get a much better more reliable connection with the overkill solar app. Definitely worth a try. Both apps are not perfect but overkill is better imho. Both do better when connecting to multiple bms if you restart the app when switching between bms so try that if you haven’t yet to connect to the other bms.
As far as the balance issues - i have had some of the jbd act up like this and thankfully have caught them before anything got damaged or drained. For the 50 or so i have used i think there are 2 in my boneyard that were doa like this. I still think they are the least worst option available. None of the more expensive options have treated me better and there isn’t much cheaper to try. Imho i would swap that bms and see if it corrects and give the balance leads a once over - though this looks like something on the bms failed.
Ive had bms act like this after a short or miswire also which makes me think something on the ic died. Unfortunately reliability and fail safe circuit protection that protects the bms isn’t a part of the jbd design at this price point
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Thanks for the recommendation of that app. It works pretty nicely. Unfortunately it didn’t solve my problems though.
I guess it’s a hardware issue. Sad to see after such short time. I really expected there to be some sort of emergency shut down if it was malfunctioning, but I guess not. Kinda scary. It still lets me manually disable the discharge though 
The problem couldn’t have come from these BMSs being in parallel in a group of 3 packs, could it? I asked a seller once if you could put them in parallel, but who knows if they actually understood what I was asking.
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In parallel as in multiple bms managing the same cell levels? What’s the purpose of setting that up?
Uhh no not exactly. In parallel as in I have 3 separate 14s packs each which their own BMS connected in parallel. Sorry for the confusion
Just set up as a temporary little battery bank.
Looks clean! What did you use to cover each p group? Is that electrical tape?
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It’s 2inch heavy duty vinyl electrical tape 
I didn’t think out the plan with the heat shrink early enough. Plus I’m the only one that’ll be looking in the enclosure anyways.
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I didn’t even realize they made electrical tape that wide. Everything’s nicely spaced out so I’m sure you won’t have any problems. Great build!
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Thanks man!
There’s fish paper under the vinyl also.
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It sounds very much like a connection issue. Like one or more cells doesn’t have its balance wire connected.
Have you tried plugging your harness in properly?
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Thanks for the suggestion. Yeah I noticed that was crooked in the picture a little after I posted it. Unplugged and plugged the balance wires a few times and checked them with the voltage meter and it all seemed fine. But still voltages would bounce from .1v per cell to 5 volts per cell. I really want it to just be a bad connection but it doesn’t seem like it. Normally if a cell isn’t connected to the BMS it would just show wrong voltages in the app, but be stable, right?
Not necessarily, I’ve seen some pretty weird behaviour from poorly connected balance leads.
In my experience, 99 times out of 100 this type of behaviour is due to a poor connection somewhere.
It certainly could be the bms itself, but I’d be triple checking all the connections and continuity of the wires first.
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Hmm interesting. I’ll definitely give it a try. These packs were temporary as I was going to tear them down and salvage the cells anyway, so perhaps I didn’t make the best connections on the BMS leads.
I also have another identical pack that is working fine, so I might desolder this BMS and swap the 2 to see what exactly is going on.
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That’s a great troubleshoot 
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