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JBD smart BMS displays wrong cell voltage

sunrise

sunrise

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Joined
Jul 16, 2020
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206
Hello,
A while ago I watched Will's youtube video on JBD Smart BMS and it looked nice so I purchase 2 of them (12v 4s 120A) from aliexpress
https://www.aliexpress.com/item/4000425316662.html?spm=a2g0s.9042311.0.0.27424c4dTRne5e
for 2 LiFePo4 banks.
After the prep work (crimping, top balancing, etc), One BMS works well but I found the other one shows wrong voltage for cell 3 and 4, as shown in the screenshot. I also observed that the shown voltages for cell 3 and 4 fluctuates very quickly(~ +-0.01v) compared to the other battery bank, which fluctuates way slower. I have done the following for diagnose -
- Checked all connectors made sure they are properly tightened.
- Use multimeter and measured voltage, readings are correct, which is different from BMS reading (delta are ~ 0.002 between cells), note I took readings from battery's metal connector directly, the top of the screws and balance wire ring connectors just to make sure I don't have connector issues.
- I swapped cell 3 and 4, same result - any cell in position 3 are showing higher voltage than the cell in position 4.
- I swapped balance cable from the other BMS that worked properly. same wrong result.

At this point I think the BMS is faulty. I suspect the balance circuit might have contact issues.

Wondering if there is anything else I can do to diagnose this. I have contacted the seller but they are not being very helpful yet :(

50421198671_d7eba5b0e3_k.jpg
 
HRTKD said:
Can you provide a link? I'm running 1015. The Play store is still showing 1014. OverKillSolar's website has only 1015 also.
Click to expand...
Seems like just a minor build number bump, I'd avoid posting APK links as it's pretty risky, I'd use the Playstore one to be on the safe side. The only reason I use it is I have an old android phone which does not have much personal data, no cell service. If you really want it I can PM you.
 
I'm tempted, but version 1015 does what I need. Having the cells on the main page would be nice though. 1015 does have its quirks. It's disappointing that they aren't posting newer releases on the Play store. That's always a concern.

1014 was not an acceptable build however.
 
I to have the app off over kills sight and it does not have the on off buttons for charge and discharge. If I need the turn the discharge I have to use my ipad.

Greg
 
@LanduytG @HRTKD The cost to upload/publish an APK to Playstore is minimal for a company. You'd be wondering why they would not want to do that, most likely they felt it's just too much hassle to follow these processes, but it's the same mentality that gets their website compromised and a malware version uploaded and we are all screwed.
 
I think I have looked at everything concerning the app and the latest I've found 1013

Greg
 
sunrise said:
@LanduytG @HRTKD The cost to upload/publish an APK to Playstore is minimal for a company. You'd be wondering why they would not want to do that, most likely they felt it's just too much hassle to follow these processes, but it's the same mentality that gets their website compromised and a malware version uploaded and we are all screwed.
Click to expand...

I certainly had to think twice before going the APK direct route. The other barrier to submitting to the Play store is that your code gets scanned by Google. Any exception will disqualify it. And, like you said, perhaps they are just too lazy to fix their code.

I thought about buying a cast-off iPhone just for configuring/viewing the BMS. It sounds like that is their primary platform for deployment. However, my understanding is that the Apple store has more stringent requirements. If XiaoXiang can satisfy Apple, surely they can satisfy Google. But on the Apple side they charge for the app. The app in the Google Play Store is free for full functionality.
 
HRTKD said:
I certainly had to think twice before going the APK direct route. The other barrier to submitting to the Play store is that your code gets scanned by Google. Any exception will disqualify it. And, like you said, perhaps they are just too lazy to fix their code.

I thought about buying a cast-off iPhone just for configuring/viewing the BMS. It sounds like that is their primary platform for deployment. However, my understanding is that the Apple store has more stringent requirements. If XiaoXiang can satisfy Apple, surely they can satisfy Google. But on the Apple side they charge for the app. The app in the Google Play Store is free for full functionality.
Click to expand...
"The other barrier to submitting to the Play store is that your code gets scanned by Google. Any exception will disqualify it. And, like you said, perhaps they are just too lazy to fix their code."

That's exactly why I only want to install apps from Playstore, to scan the binary and see what API the app is invoking, it doesn't make sense for a BMS monitoring app to scan file system, open photo albums, listening on SMS, reading clipboard etc.

I notice the apk I use often ask permission to restart the whole bluetooth stack (as a way to fix connection issue), I grant it one off permission, but who knows, with that permission the app probably gained system level access to bluetooth stack, it might be able to read all bluetooth traffic on that phone. I would never allow this if the phone I use it on isn't a controlled environment.
 
sunrise said:
Hello,
A while ago I watched Will's youtube video on JBD Smart BMS and it looked nice so I purchase 2 of them (12v 4s 120A) from aliexpress
https://www.aliexpress.com/item/4000425316662.html?spm=a2g0s.9042311.0.0.27424c4dTRne5e
for 2 LiFePo4 banks.
After the prep work (crimping, top balancing, etc), One BMS works well but I found the other one shows wrong voltage for cell 3 and 4, as shown in the screenshot. I also observed that the shown voltages for cell 3 and 4 fluctuates very quickly(~ +-0.01v) compared to the other battery bank, which fluctuates way slower. I have done the following for diagnose -
- Checked all connectors made sure they are properly tightened.
- Use multimeter and measured voltage, readings are correct, which is different from BMS reading (delta are ~ 0.002 between cells), note I took readings from battery's metal connector directly, the top of the screws and balance wire ring connectors just to make sure I don't have connector issues.
- I swapped cell 3 and 4, same result - any cell in position 3 are showing higher voltage than the cell in position 4.
- I swapped balance cable from the other BMS that worked properly. same wrong result.

At this point I think the BMS is faulty. I suspect the balance circuit might have contact issues.

Wondering if there is anything else I can do to diagnose this. I have contacted the seller but they are not being very helpful yet :(

View attachment 24409
Click to expand...
Hello, i arealize this is an older post but wanted to as how did you resolve this problem? I am having the same as you describe.
 
EcoRV said:
Hello, i arealize this is an older post but wanted to as how did you resolve this problem? I am having the same as you describe.
Click to expand...
It was a defective unit, but the aliexpress seller used all tricks one can image to not be responsible. After 2 weeks of back and forth, he finally admitted it was bad unit and the solution he offered was for me to send the unit back to him at my cost, I checked it took about $40 plus time. so I just ordered one from a different seller on alibaba.
 
Try calibrating voltage if you haven't already.calibration.jpg

Cell voltages, current and temperature can all be checked for accuracy and calibrated.
 
I'm having the same issue with a JBD BMS I picked up. Multimeter reads 3.36, BMS reads 3.371. Where do I get the JBDTools and how do I connect to my BMS to calibrate?
 
JBD Tools v2.5 here: https://diysolarforum.com/threads/jbdtools-v2-4.23053/#post-280081

You need to be confident in the accuracy of your multimeter. The BMS voltages shown could be more accurate than your multimeter if the meter is old and hasn't been subsequently calibrated or perhaps just wasn't very accurate to begin with ........

You need the JBD UART communication box, USB cable and Windows PC to use JBD Tools. The UART box looks like this. https://www.amazon.com/Lithium-Protection-Overcharge-Communication-Interface/dp/B08514CXLF Probably many places to get it, that's just one example.
 
Thanks WingNut - I wondered about the Multimeter, so I bought a 2nd. One is a mid-level Fluke the other a Kleine and they both have the same voltage difference over the BMS. The difference isn't really that great so I might just leave it be unless it worsens over time
 
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