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

SolarPrep

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GXMnow: I had thought about pulling one cell out of each of these, and going with 7s, even if the intent is to end up in series at 14s. It is a better voltage range for the majority of inverters out there. These are bolted together Samsungs, so a cell will just pop out.
 

TRP-racing

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Hello,

I am newbie in this forum so be patient with me.
I have an issue with Heltec active balancer (8S/200A/2A). I recently update my mobile phone and now I cannot log in. Issue is that I change PIN to my own and I forgotten it :(.

Does anyone known how to reset it without bluetooth connection? I tried to disconnect all wires, let it be for couple off hours and connect back but seems that new PIN is written to memory which does not need any power (eeprom or similar).

Below I added picture of the system to just get Your attention :). I added protection there before I connect it to system. Someone may pick up that there is risk of short circuit if something drop there. Battery pack is made from Nissan Leaf's modules.

Thanks in advance

20211216_183821.jpg
 

Mark81

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Hello everyone!

Need your advice.
Main issue I'm trying to solve is the spark in the switch when connecting battery to the inverter. It literally melts/welds metal parts inside.
I'm using fuse holder as a switch between battery and inverter:

1.jpg 2.jpg


I know some one uses resistors to precharge capacitors in inverter. But I thought about neater solution: turn off bms -> close the fuse holder -> turn on bms.

S11226-21582026.png

And I've come across strange bms behavior.
I thought those "Charge" and "Discharge" switches on "Control" tab will cut off the bms entirely. But they don't. Why?
More over when "Charge" and "Discharge" are OFF, bms starts to show incorrect current and power values (while current clamp meter and inverter show no changes).
I tried different app versions including the latest from this site: https://www.pgyer.com/Cfq3
Also enjpower-bms from Play store. Nothing worked as expected.

Real values:
4.jpg inv.jpg


"Charge" and "Discharge" are OFF:
3.jpg


So what would you suggest for spark issue?
And what do you think about real meaning of those "Discharge" option in the app?
 

Sanwizard

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Feb 2, 2021
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Hello everyone!

Need your advice.
Main issue I'm trying to solve is the spark in the switch when connecting battery to the inverter. It literally melts/welds metal parts inside.
I'm using fuse holder as a switch between battery and inverter:

View attachment 77278 View attachment 77281


I know some one uses resistors to precharge capacitors in inverter. But I thought about neater solution: turn off bms -> close the fuse holder -> turn on bms.

View attachment 77280

And I've come across strange bms behavior.
I thought those "Charge" and "Discharge" switches on "Control" tab will cut off the bms entirely. But they don't. Why?
More over when "Charge" and "Discharge" are OFF, bms starts to show incorrect current and power values (while current clamp meter and inverter show no changes).
I tried different app versions including the latest from this site: https://www.pgyer.com/Cfq3
Also enjpower-bms from Play store. Nothing worked as expected.

Real values:
View attachment 77283 View attachment 77285


"Charge" and "Discharge" are OFF:
View attachment 77282


So what would you suggest for spark issue?
And what do you think about real meaning of those "Discharge" option in the app?
For spark, use a pre-charge resistor in parallel to your on/off switch, and use a momentary switch to trickle current to the caps in the inverter before turning the switch on.
 

upnorthandpersonal

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I know some one uses resistors to precharge capacitors in inverter. But I thought about neater solution: turn off bms -> close the fuse holder -> turn on bms.

This will still cause an inrush current and might turn off the BMS (overcurrent). A precharge resistor is the way to go.

I thought those "Charge" and "Discharge" switches on "Control" tab will cut off the bms entirely. But they don't. Why?

Check this post:

Although, if both are off, it should be so. Did you blow up a MOSFET accidentally by not having a pre-charge resistor? Is the clamp meter showing 0A in the case when both are off?

I've not tried the latest version of the software yet, will do when I have some time.
 
Last edited:

Mark81

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@Sanwizard @upnorthandpersonal

Thanks for your replies.
Resistors work, yes... but how can I explain to some one why would they need to have two switches and special order for them?
It sounds a bit amateur-ish...
Are there industrial solutions to make such precharge as a part of single movement of a switch handle? Like two stage switch, I don't know...
 

upnorthandpersonal

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Resistors work, yes... but how can I explain to some one why would they need to have two switches and special order for them?
It sounds a bit amateur-ish...

At 24V/48V, these things are just normal for now, especially in DIY. I think those new 48V server rack batteries have them built in and they work automatically. I've thought about building an automatic version myself, but it's just not something I've had time for, as a simple push button does the job.
 

curiouscarbon

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@Sanwizard @upnorthandpersonal

Thanks for your replies.
Resistors work, yes... but how can I explain to some one why would they need to have two switches and special order for them?
It sounds a bit amateur-ish...
Are there industrial solutions to make such precharge as a part of single movement of a switch handle? Like two stage switch, I don't know...
to address the two switch issue i decided to have only one switch.

the one switch actually physically disconnects the positive connector of the battery pack, but it only connects it to the heavy duty contactor.

after the switch is turned on, a microcontroller will read the voltage on the output.

if the voltage is in correct range then it will pre charge the bus, and only when the bus is pre charged, connect the main contactor.

this will be done by firmware on arduino. can share more details if interested.

i too refuse to have two switches, but its not necessary technically

battery positive -> fuse -> manual disconnect -> contactor -> inverter

the manual disconnect will feed the contactor but the contactor wont close until the precharge is complete.
 

curiouscarbon

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the switch controlled by human

it signals need to turn on

precharge controlled by computer

contactor controlled by computer
 

Mark81

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@curiouscarbon

Ideally yes - this is how it should be.
But I have to use what I have. I know that bms can act as a solid state switch (for cell undervoltage protection it worked well). The only problem is that I don't know how to control it manually.
Anyway thanks for your suggestion.
 

Biasjo

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I am starting a thread specific to he Heltec 200A Smart BMS with 2A Active Balance. 200A max charge. 350A max discharge
I have 4 of them and I bought them from the Alibaba Heltec store here - https://www.alibaba.com/product-detail/14-24S-200A-Smart-BMS-with_62544207027.html

edit: I forgot to mention this BMS is the same as JK brand. In fact the JK site has more up to date software that can be downloaded from play store or Apple. Check here for more info - https://www.jkbms.com/

Someone asked me to do a review of this BMS. I am not really ready to do a full review because I am new to DIY batteries and it takes me a long time to test these BMSs thoroughly. I actually have only used one so far. I am just getting ready to set up a second one.
And, I just wanted to start a place specific to this BMS so I can add my thoughts as I learn new information.
Of course I also want to hear from others using this BMS

My highest discharge current so far has only been about 70A and that was for a short time. My highest charge current was about 100A.
I hope to test a sustained discharge rate of at least 100A someday. My planned system would need changes for me to test higher than that and it could be years before I come to the conclusion that I need more amps. I don't expect that day to come but as I said I am new to this so I may change my mind someday.

I am very satisfied with this BMS so far.

The software is great.

The active balance is really cool. I had heard that 2A wouldn't be enough but my findings are that 2A is extremely useful and for my purposes I doubt 5A or 10A would be any better.
2A takes a long time but it keeps cells balanced perfectly. I can use 80% of battery capacity and be confident it will stay balanced. But, a passive balancer could probably do that too.

I love how it balances the cells perfectly whenever charging stops. It does even better when ever I am floating above the balance trigger.
Sometimes it can't completely keep up when charging / discharging high amps.
Sometimes it can't keep up in the knees. But so far it can always keep up enough so I am balanced if I only use 80% capacity and stay out of the knees.
I use their active balancers on a 16s 280ah battery and they work great.
 

curiouscarbon

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@curiouscarbon

Ideally yes - this is how it should be.
But I have to use what I have. I know that bms can act as a solid state switch (for cell undervoltage protection it worked well). The only problem is that I don't know how to control it manually.
Anyway thanks for your suggestion.
good point.

it is indeed a lot of effort on my part required and various parts. still muddling through.

good luck with yer system🙂👍🔋
 

GXMnow

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Hello,

I am newbie in this forum so be patient with me.
I have an issue with Heltec active balancer (8S/200A/2A). I recently update my mobile phone and now I cannot log in. Issue is that I change PIN to my own and I forgotten it :(.

Does anyone known how to reset it without bluetooth connection? I tried to disconnect all wires, let it be for couple off hours and connect back but seems that new PIN is written to memory which does not need any power (eeprom or similar).

Below I added picture of the system to just get Your attention :). I added protection there before I connect it to system. Someone may pick up that there is risk of short circuit if something drop there. Battery pack is made from Nissan Leaf's modules.

Thanks in advance

View attachment 77276
Here is the best online manual I can find for the JK-BMS with active balance
I have looked over it again, and I can't find any mention of a factory reset to get rid of password changes. Do you have any common passwords and pins you may have used? This may be a problem. You could try sending an e-mail to one of the bigger vendors who sell these and see if they have any idea on how to reset it.
 

Mark81

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Jan 19, 2021
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Hello!

Reading the manual from the GXMnow's link above it says:
" Discharge ... when it displays "off", it means the current protection board discharge MOS is off and the battery is not allowed to discharge."

So can I ask you guys to try this option in your bms?
Because as I mentioned earlier setting Discharge to OFF didn't switch off the load in my case (only app started show wrong values).
I have suspicion that my board can be faulty and doesn't do its protection job.
I would be much appreciated if you check this for me.

Discharge OFF.png
 

fatfash

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Most likely your BMS is faulty. The power output should be zero, I have switched off several times the charge and discharge of my (JKBMS) without issues when replacing cables to my inverter. I once had issues with the Heltec BMS (with 1A active balancer) I bought that didn't last a week but had to replace them with JKBMS (with 2A active balancer) and they have been perfect for 3 weeks now. Which do you have installed JKBMS or Heltec BMS ?
 

upnorthandpersonal

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So can I ask you guys to try this option in your bms?
Because as I mentioned earlier setting Discharge to OFF didn't switch off the load in my case (only app started show wrong values).
I have suspicion that my board can be faulty and doesn't do its protection job.
I would be much appreciated if you check this for me.

Yes, this should turn off the discharge as I mentioned. Could it be you might have destroyed a FET due to inrush current on your inverter? O, I remember, you measured with a clamp meter or something and the actual current is 0A?
If so, maybe something is wrong in version 4 of the app (still no time to test here...).
 

GXMnow

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Mark81 I agree it sounds like you may have damaged the mosfets in your BMS with the inrush current. Mosfets can fail in the shorted mode. That will prevent them from turning off. Turning off discharge on mine does drop the current to zero. It will still charge at low current with some voltage drop. I never tried pushing high current charge with discharge off. Turning off charge also does drop charge current to zero. I never really tried pulling any current out while charge was off. I was just happy to see it stop charging, so I knew it would protect from an overcharge condition.

At one point in the past, I had a balance lead wire fail, that shut down both charge and discharge and the battery bank reported as open from my XW-Pro inverter. Once I repaired the balance lead, it all started working fine again. I have not had a problem with it since.

Right now my system is charging at 20.8 amps from the XW-Pro. The JK-BMS in the old battery bank is reporting about 10 amps, but it does bounce around about +/- 1 amp due to the 120 Hz ripple current from the power factor corrected charging. Using my Fluke Clamp meter, it shows just under 10 amps on the old bank. The new bank is just over 10 amps. The 2 strings in the new bank are just over 5 amps each. My new bank is using dumb Daly BMS units, so I can't monitor them on my phone.

I really like having 2 banks now, I can shut off either one and run on the other. Even a battery fault in one of the banks won't shut down my system. My only concern is if one bank does shut down. I could end up with a similar issue where it might try to reconnect when the two banks are at a different state of charge. That could cause a vey high current to flow. But unlike connecting the an inverter where it is just a short surge, this could result in very high current for a long time as it might try to discharge the higher bank into the lower bank through 2/0 cables. For this reason, all 4 strings of cells are fused a just 100 amps each. But that could still subject the JK-BMS to 200 amps for quite a while if it happens when I am not here. I was quite nervous about this potential issue when I first added the second battery bank. It took me 2 days to get the new bank discharged down to where I full charge my old battery bank. I am only charging to 4.05 volts per cell (Li MNC cells) and the new cells were at 4.15 when I got them. I used my adjustable buck converter power supply to pull 5 amps from the new battery and push it into the old battery. Once I got the old battery down to under 4.05 per cell, I waited until the old bank charged up to match it, and then closed the switches. At only 0.05 volts difference, there was still 5 amps of current flowing from the new bank into the old bank, but it tapered down quickly. They have been running in parallel now for 6 months. The new bank has longer cables, and I expected it to run a little less current, but it actually pulls a little more current. I think the combination of 2 100 amp BMS's and the newer cells just has a tiny bit less internal resistance than the old bank with the single 200 amp rated JK-BMS.
 

curiouscarbon

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I really like having 2 banks now, I can shut off either one and run on the other. Even a battery fault in one of the banks won't shut down my system.
😎👍🔋🔋
My only concern is if one bank does shut down. I could end up with a similar issue where it might try to reconnect when the two banks are at a different state of charge. That could cause a vey high current to flow.
good point

multiple battery pack reconnect high difference state of charge condition feels very important to me to address robustly

manual control and care of course natural inexpensive option
But unlike connecting the an inverter where it is just a short surge, this could result in very high current for a long time as it might try to discharge the higher bank into the lower bank through 2/0 cables. For this reason, all 4 strings of cells are fused a just 100 amps each.
📝
But that could still subject the JK-BMS to 200 amps for quite a while if it happens when I am not here. I was quite nervous about this potential issue when I first added the second battery bank. It took me 2 days to get the new bank discharged down to where I full charge my old battery bank. I am only charging to 4.05 volts per cell (Li MNC cells) and the new cells were at 4.15 when I got them. I used my adjustable buck converter power supply to pull 5 amps from the new battery and push it into the old battery.
cool! active balance 😎🔋⚡🔋
Once I got the old battery down to under 4.05 per cell, I waited until the old bank charged up to match it, and then closed the switches.
*eating popcorn accelerates*
*slight sweating*
At only 0.05 volts difference, there was still 5 amps of current flowing from the new bank into the old bank, but it tapered down quickly.
50 millivolts delta and 5000 milliamps, interesting!
They have been running in parallel now for 6 months.
🥳🎉 rad!
The new bank has longer cables, and I expected it to run a little less current, but it actually pulls a little more current. I think the combination of 2 100 amp BMS's and the newer cells just has a tiny bit less internal resistance than the old bank with the single 200 amp rated JK-BMS.
interesting insight!

if the cable is good copper and the crimps or connectors are similar resistance, the longer run serving more amperes could be explained by the lower internal resistance of the newer cells.

thank you for this information and experience about parallel operating more than one battery pack together, i really appreciate it.

each pack having a "smart precharge" circuit is desirable to me and i'm trying to build it.

basically, each pack has MOSFET BMS and a Resistor Precharge.

when "connect request", the precharge circuit measures voltage on Bus Side ("other battery") and compares it to Battery Side ("this battery").

it connect resistor first and measure amperes flow through e.g. 20ohm 100W resistor

if it's many amperes, then connect is CANCELED and BMS is controlled to not connect

the precharge circuit would be connected directly to the battery, so that precharge may occur while mosfet bms is in disconnect state

rambling over 😊
 

Mark81

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Jan 19, 2021
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Hello.

Update.
TLDR:
1) BMS is faulty
2) Precharging resistor works

BMS.
Clearly a defect:

v2.jpg

If I turn off charging and discharging the board gets hot really quickly:

S20108-14104504.png

I've found at least one dead MOSFET. Its gate is short circuited to the Source. There may be more (up to 8) around it, but it could be just the dead one heats up them all around itself - hard to say, I haven't soldered it out yet.

All MOSFETs are of N-Channel type G035N10:

Full-resolution pictures board gallery: https://imgbox.com/g/fe7q9BVvhM

P20108-144203.jpgP20108-144129.jpgP20108-143347.jpgP20108-143729.jpgP20108-162128.jpgP20108-144348.jpgP20108-144316.jpgP20108-144217.jpg

Precharging resistor
I used 5.6 Ohm and it took like 5 sec for precharging current to drop from ~1A to 0A (voltage difference was about 3-4 volts).
Still it doesn't feel like a neat solution.

So as I hadn't burnt the board completely yet this means my repair story continues)
I'll try to solder out shorted transistor and see whether this will solve the issue.
 
Last edited:

upnorthandpersonal

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Should be a pretty easy repair.

If I turn off charging and discharging the board gets hot really quickly
Probably because all the current is going through the body diodes of the MOSFETS. More info for those who want to know.

Pre-charge circuits are just a fact of life at this moment. Some people want to have it included with the battery/bms but as we've seen in another thread, this causes issues with some inverters out there when used with those new EG4 batteries (which include a pre-charge circuit). Personally, I think it should be something that's part of the inverter.
 
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