Heltec (JK) 200A Smart BMS with 2A Active Balance

Diesel Pro

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Jul 21, 2021
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I found the same android 12 issue but app version 3.7.5 does work.

As for fluctuating current reading it also does this when charging, maybe a bit less. I really like this BMS. It would be nice to have this aspect fixed.
 

Nami

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Jan 13, 2022
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Can anyone share the PDF version of victron's CANBUS protocol? I need more detailed documents. Thank you,
 

upnorthandpersonal

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It's on this site in resources, and on the github page in at least two locations:


 

Dacflyer

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Jun 5, 2020
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Hello!
Finalizing my repair story.

My previous posts:

Summary:
1) My BMS and inverter had survived all the tortures and now work fine
2) Precharching resistor is the only way to go by now

1) Repair.
Luckily there was only one burnt transistor: D-S, G-S - everything was 0 Ohm in it. Gate 100 Ohm resistor saved the driver I guess.
After soldering it out now "Discharge" and "Charge" switches work as designed: cut off current to zero amps.

View attachment 79602

2) Experiment
I agree that next experiment is quite stupid and unnecessary.
But!
Imagine the following situations:
a) You turned off a BMS with "Discharge" switch and now want to turn it back on again using "Discharge" switch in app
b) There was some fault situation in a battery, BMS turned it off, now it waits for some timeout or fault has gone for some reason, and then BMS turns the battery back on again.

The result:
- current is extreme (500-1000 A or even higher)
- BMS goes into "Short circuit" error mode and waits for timeout (60s)
- after timeout everything repeats.

View attachment 79604

Case 2:
- you switched off battery with "Discharge" option
- if you switch it on again with "Discharge" option you'll get "Short circuit" and... see above.

Case 3:
- problem in balancing wire
- BMS doesn't see that cell and goes into fault mode (battery off)
- for some reason balancing wire begins work fine again -> BMS turns on battery -> "Short circuit" and see above.

Case 4:
- cell undervoltage protection occured
- ....sorry I don't remember and didn't try it now. Can anyone remind please will BMS wait (in off state) until charging starts? Or it will turn on after the cell voltage rose over Cell-Undervoltage-Release value?

Here's current measurement. I didn't set correct range but judging from skyrocketing curve slope I assume it was ... maybe around 1000A.

View attachment 79603


I have repaired tons of car amps, and some inverters and most all use MOSFETS etc. In all my cases if 1 or a few were damaged, you can bet that the others were damaged or stressed.. I tried to just replace the bad ones and hoped that the others were ok,, but they eventually failed. Now if i ever change any out, I replace them all.. They aren't that expensive.. Just thought i'd share..
 

Dacflyer

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Ahhh, ok,, didn't know if it was updatable..
I almost have the 2nd half of the system working..
I need to find some more jumper cables to go between batteries.. The heavy orange ones, i have some, but they are too short to use.
 

upnorthandpersonal

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Ahhh, ok,, didn't know if it was updatable..

There is a nice programming header on the BMS PCB and it's a normal STM32 (or a clone depending on the version), so if they release the source code it's straight forward to program and make modifications. You could even add a firmware updated over the RS485 port or something; possibly even USB.
 

GXMnow

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I have repaired tons of car amps, and some inverters and most all use MOSFETS etc. In all my cases if 1 or a few were damaged, you can bet that the others were damaged or stressed.. I tried to just replace the bad ones and hoped that the others were ok,, but they eventually failed. Now if i ever change any out, I replace them all.. They aren't that expensive.. Just thought i'd share..
I totally agree. My point of removing the one shorted FET was to be able to test operation and ensure the rest actually does work. If you ever want it to be reliable again, I would also change all of the FETs that are in parallel. Sometimes you just have to work with what you have.

I have a rather long story, I will try to shorten.
Had a virtually new (ran 20 hours) 7,000 watt switching power supply for a xenon lamp system. The FET's shorted out and it popped the DC rail fuse. The manufacturer sent us another one. It ran just 8 hours, shorted FET, blown rail fuse. I pulled them both apart, each one only had 2 or 3 bad FETs, so I took all the good ones and put them in the same unit that had no other damage. Installed it and it ran 3 weeks while the manufacturer was stress testing us a third unit. My pieced together unit was still working just fine, logged about 250 hours with no issues. We get the new fully stress tested unit, they want the blown ones back for inspection. The new one failed in under 12 hours.

It turns out that the lamp igniter unit, which sparks 20,000 volts across the bulb was installed on the positive leg of the lamp. This was an oddball lamp, most of them have the igniter on the negative side. The power supply had extra filters on the negative side to handle any noise coming back from the igniter. They didn't bother with a filter on the positive side. The FETs that survived were able to handle the noise. When I used those seriously stress tested FETs, they all lived. It was the one totally wrong case were the survivors were over spec. New FETs would have most likely kept failing. Of course, the proper fix was to rewire the lamp and move the igniter to the negative side. This lamp was originally shipped with an old school 400 pound transformer power supply, but that beast failed. The transformer windings looked like black slinkies dangling around the cores. The equipment owner went ahead and sourced another old school power supply. The shipping was almost as much as the new switcher supplies cost.
 
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