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

GXMnow

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If you are lucky and only 1 or 2 FETs (mosfets) shorted, you may be able to use it by just removing the bad ones. With the case off, just pull a little current across the heavy blue and black wires and feel which FET starts getting hot first. Since it is a shorted FET, you do not even need to power up the board.

If it works like that at reduced current, then you can try sourcing a few new FETs to repair it back to full power. The soldered down FET's will take a lot of heat to get off the board. Be careful not to damage any other parts around them. I repaired a few old school brush motor RC car speed controllers. Same basic problem. One FET (mosfet) would short out and the motor would be stuck at full speed, but all the current through just the one bad FET. The FET would get crazy hot, especially if you then hit the brakes. I needed a heavy 100 watt iron to get the FET's off the board.
 

Martijn

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Finally able to use my JK, 8S, 2A balancing. Figured I had to assemble the 24V battery first, for a quick charge before I did the top balance. But assembled it, charge it slowly using a 10A power supply and when there was a cell over-voltage, let it rest for a while, charge slower, did that a couple of times and the balancing worked perfectly. In the end, all cells were topped :)
 

Nami

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Jan 13, 2022
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125
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.
From March to mid April 2022. Jikong will update and produce a BMS that supports 4S configuration and active balance function,
 

Nami

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Jan 13, 2022
Messages
125
If you have any questions, please contact me directly. Thank you. We are the person in charge of hankzor store and can solve the BMS problems of friends Daly, JBD, Jikong and ant,
I am very concerned about the needs of customers, so I will watch the forum from time to time and improve it in time according to the correct feedback from customers,
 

Martijn

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Joined
May 6, 2021
Messages
187
If you have any questions, please contact me directly. Thank you. We are the person in charge of hankzor store and can solve the BMS problems of friends Daly, JBD, Jikong and ant,
Nami,

I'm using the 8S 24V, 2A balancing version. I noticed that when the inverter is connected and charging or discharging, the amperage reading in the Android app is fluctuating. I noticed the same with a Daly BMS.

What causes this ( I read something about interference? ) and how can it be solved?
 

Nami

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Joined
Jan 13, 2022
Messages
125
The current detection frequency of BMS is twice per second. Since the inverter is generally a sine wave inverter, the current fluctuation is relatively frequent, so the BMS current display will fluctuate greatly. We are preparing to reduce the current acquisition frequency of BMS, which will reduce the fluctuation. The current fluctuation will not affect the balance and protection function of BMS

Nami,

I'm using the 8S 24V, 2A balancing version. I noticed that when the inverter is connected and charging or discharging, the amperage reading in the Android app is fluctuating. I noticed the same with a Daly BMS.

What causes this ( I read something about interference? ) and how can it be solved?
 

Martijn

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Joined
May 6, 2021
Messages
187
The current detection frequency of BMS is twice per second. Since the inverter is generally a sine wave inverter, the current fluctuation is relatively frequent, so the BMS current display will fluctuate greatly. We are preparing to reduce the current acquisition frequency of BMS, which will reduce the fluctuation. The current fluctuation will not affect the balance and protection function of BMS
Sorry, I don't understand.

As far as I can see, the inverter/charger is pulling or pushing a (fairly) steady current. In my test, I was pulling about 1200W 230V AC continually, which was about a 56A pull from the battery (24V DC).

Here's the graph.

Yet, the app was fluctuating wildly, to well above the 56A pull. The JK at least has a delay before shutting down because of an over-current situation, so no problem there are the moment, but I wonder what happens if I pull a higher current and if the current reading will go above the limit (for too long) with the incorrect reading.

1642079237563.png1642079642456.png
 

Nami

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Joined
Jan 13, 2022
Messages
125
I understand your concern. You want to confirm whether BMS will be protected due to current fluctuation, which requires more professional knowledge. I see you use victron inverter. Due to the characteristics of the inverter, the current displayed by the inverter is processed by sine wave, and the BMS collects instantaneous current, so the current collected by the BMS is not completely consistent with the current displayed by the inverter. We have received many similar problems, so we are trying to reduce the acquisition frequency. Thank you

Sorry, I don't understand.

As far as I can see, the inverter/charger is pulling or pushing a (fairly) steady current. In my test, I was pulling about 1200W 230V AC continually, which was about a 56A pull from the battery (24V DC).

Here's the graph.

Yet, the app was fluctuating wildly, to well above the 56A pull. The JK at least has a delay before shutting down because of an over-current situation, so no problem there are the moment, but I wonder what happens if I pull a higher current and if the current reading will go above the limit (for too long) with the incorrect reading.

View attachment 79471View attachment 79472
 

Martijn

Solar Enthusiast
Joined
May 6, 2021
Messages
187
I understand your concern. You want to confirm whether BMS will be protected due to current fluctuation, which requires more professional knowledge. I see you use victron inverter. Due to the characteristics of the inverter, the current displayed by the inverter is processed by sine wave, and the BMS collects instantaneous current, so the current collected by the BMS is not completely consistent with the current displayed by the inverter. We have received many similar problems, so we are trying to reduce the acquisition frequency. Thank you
So there will be a firmware update for the BMS?
 

Nami

Solar Enthusiast
Joined
Jan 13, 2022
Messages
125
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
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 think one thing I have to remind you is, https://www.jkbms.com/ It is not the official website of Jikong. You can clearly see that the logo of Jikong is different from that on the website. My factory has contacted the person in charge of the website, but there is no result. Thank you for your support

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.
 

Martijn

Solar Enthusiast
Joined
May 6, 2021
Messages
187
We will update the acquisition chip of BMS
Use a less sensitive current acquisition chip to reduce the acquisition frequency,
Oh darn, no firmware update :-(

But, what I don't understand: picking up the current less often, won't correct the 'misreadings', right? It will still possibly read '15A' when it's actually 150A, but now it won't read a new value as frequently? What use is that?

Wouldn't it be more useful if you average a few readings instead, so that both readings that are less than the actual value and readings that are above the actual value are somewhat flattened?
 

Nami

Solar Enthusiast
Joined
Jan 13, 2022
Messages
125
We are studying this matter with engineers because we have received many similar problems. The current solution is to reduce the acquisition frequency. Of course, we will also consider the average value you said. Because it is approaching the Chinese new year, we will get the latest upgrade results from February to March,
 

Martijn

Solar Enthusiast
Joined
May 6, 2021
Messages
187
We are studying this matter with engineers because we have received many similar problems. The current solution is to reduce the acquisition frequency. Of course, we will also consider the average value you said. Because it is approaching the Chinese new year, we will get the latest upgrade results from February to March,
Thank you for your time and answers and good luck solving the issues.
 

hwse

Solar Addict
Joined
Jan 2, 2021
Messages
304
From March to mid April 2022. Jikong will update and produce a BMS that supports 4S configuration and active balance function,
Do you have any more specific info on when a 4S version will be available?
 

GXMnow

Photon Sorcerer
Joined
Jul 17, 2020
Messages
1,900
I'm using the 8S 24V, 2A balancing version. I noticed that when the inverter is connected and charging or discharging, the amperage reading in the Android app is fluctuating. I noticed the same with a Daly BMS.

What causes this ( I read something about interference? ) and how can it be solved?
I have a JK-BMS on my battery bank, and I know exactly what you are talking about. Let me see if I can explain it a little better.

A pure sine wave inverter does not draw a constant current. The current from the battery follows a sine wave shape. It ramps from zero current up to peak current in 1/4 of a cycle. The peak current is actually about 40% more than the average current. Then the current will ramp back down to zero at the 1/2 cycle time. At this point, the inverter reverses polarity, and ramps the current back up again, hitting the peak at the 3/4 cycle time. The battery current is positive again, and the inversion happens in the inverter circuit. The the current ramps down back to zero again at the end of the cycle. The process them repeats for every cycle.

If you measure with an averaging meter, you will just see a fairly steady current that should be close to the true RMS current. I use a True RMS Fluke meter, and it is able to give a vey accurate reading on this odd waveform. The current reading in the BMS just measures the voltage across a shunt resistor. This reading is only taken periodically, and it is not synced the the changing current from the inverter. It might take a reading at zero current, or at the peak current, but most likely, it will fall somewhere in between. Due to the shape of the wave, the reading tends to bounce a bit above and below the true RMS current. It is not perfect, but over the long term, it is "good enough" for the BMS to calculate the amp hours charged in or discharged out of the battery. This works because if you average the readings over a full hour, the high and low readings will average out.

There is not a simple fix for the short term reading fluctuations. Ideally, reading it much faster and doing a running RMS type average would be best, but that takes more memory and computation. That is basically how my Fluke meter does it. An easier and cheaper way to do it is to just put an analog low pass filter on the signal from the current shunt. This will not be perfectly accurate, but by putting in an average to RMS correction factor for a sine wave, it will be very close, as long as the current wave follows a sine wave shape. Many AC voltage and current meters do this. When you measure 120 volts AC, it is actually averaging the sine wave and doing a small correction. It is accurate for a clean sine wave, but if it is a square wave, or triangle wav etc., then the reading will be a little off. A true rms meter is still accurate, no matter the wave shape.

In the case of the BMS random reads, it is actually very accurate over the long term because it is adding up the amp hours of each reading on the waveform. If you just watch the reading for a few seconds, you can get a pretty good idea of what the average reading is. If you need more accurate, use a clamp on amp meter or install an external shunt with averaging or true rms reading.
 

weeman

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Joined
Sep 23, 2019
Messages
10
Is anyone having issues with the JK Android App on Android v12? I've just updated my phone to v12 and now the JK app instantly crashes as soon as it is opened. I've tried clearing the app data / cache and have the latest v4.0.0 build 33 of the app.
 
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