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Heltec BMS' (up to 350A) with Active Balancing & Independent Active Balancers

For my iPhone, I just went to the App Store and searched "JK BMS" and got it from there. It comes up "Ji Kong" on the boot page.
I purchased the BMS through "Flower Dog Store" on Ali Express. I know, go ahead and laugh, they had the best price and free shipping.
I just opened my "About" page.

Vendor ID: JK-B2A24S20P
Hardware Ver: 3.0
Software Ver: 4.1.4
Manuf. Date: 200619 I assume that is June 20, 2019
Version: 2.8.4

I powered it up 18 times and it has now been on for 145 days straight since I wired up my battery bank.

My balance threshold will also go down to 0.003 volts, I have it at 0.008 right now. The quoted accuracy is 0.005 volts, but I think that is absolute drift. Mine was off a bit more than 5 mv when I got it. But it seems to as all of the cells read about the same amount high. So from cell to cell it is likely more accurate than the absolute reading. After I did a calibrate, each cell reads within 2 mv of what my Fluke reads. To Calibrate, just measure the actual voltage right at the BMS at a very low load current, and then enter that value. It then calculates the correction for each cell so the total of all cells equals what you enter. I just randomly measure 4 cells for a quick check. Hmmm. All four cells measured a bit higher than the BMS was reporting. I had calibrated it when it was about 95 F out, and today it is just 50 F in my garage. So the temp compensation may not be the best. The total pack voltage was still within 0.13 volts, so it is certainly not a gross error. And the Schneider is reporting the voltage as even a little higher. It just finished charging an shows 57.0 volts, but I am measuring 56.6 volts. That error is 0.028 volts per cell in my 14S setup. I decided to calibrate the BMS to the actual terminal voltage measured with my Fluke at 56.60 volts. And now the 4 cells I measured are reporting within 0.002 of the reading on my Fluke. I feel the BMS is the protection and it needs to be accurate to what the cells measure. I can fudge the numbers in the Schneider to get the cells to the desired voltage. Having the battery actually lower than the inverter thins is fine, as long as I set the shut off voltage a bit higher to compensate.
 
Heltec has a pretty good Black Friday sale going on do I went forward with a ‘dumb’ 300A 8S BMS for $54 and an 8S 5A Active Balancer for $22.

The Active Balance BMS they had cost $100 and lacked any programability/flexibility while the ‘Smart’ 300A BMS they had also cost $100 but was limited to 50A charge current which won’t cut if for my 80A charger.

This conbo will cost me less and offers the flexibility of connecting or disconnecting the Active Balancer. And balancing 280Ah cells at 5A sounds a lot more practical than balancing at 1.2 or 1.5A.

I figure I can monitor my cells ~monthly and charge them well up into the knee with the Active Balancer connected whenever I am unhappy with the post-charge balance I see.

Alternatively, if my cells stay within 100mV of each other all the way down to 2.9V, I can leave the Balancer connected all the time since it will only ever be active late in a charge cycle when cells are above 3.4V.

Eventually, Heltec will hopefully offer Smart BMS w/ Active Balance with higher charge currents but until then, this rig will hopefully give me the performance and flexibility I need...

Thanks to everyone who has helped me on my quest on this thread. I’ll post feedback in ~2-3 months when I get everything put together and tested.
 
fafrd said:
Heltec has a pretty good Black Friday sale going on do I went forward with a ‘dumb’ 300A 8S BMS for $54 and an 8S 5A Active Balancer for $22.

This conbo will cost me less and offers the flexibility of connecting or disconnecting the Active Balancer. And balancing 280Ah cells at 5A sounds a lot more practical than balancing at 1.2 or 1.5A.

I figure I can monitor my cells ~monthly and charge them well up into the knee with the Active Balancer connected whenever I am unhappy with the post-charge balance I see.

Alternatively, if my cells stay within 100mV of each other all the way down to 2.9V, I can leave the Balancer connected all the time since it will only ever be active late in a charge cycle when cells are above 3.4V.
Click to expand...
Sounds like you got a good combo, and a reasonable plan on how to use it

fafrd said:
The Active Balance BMS they had cost $100 and lacked any programability/flexibility while the ‘Smart’ 300A BMS they had also cost $100 but was limited to 50A charge current which won’t cut if for my 80A charger.
Click to expand...
fafrd said:
Eventually, Heltec will hopefully offer Smart BMS w/ Active Balance with higher charge currents but until then, this rig will hopefully give me the performance and flexibility I need...
Click to expand...
The Active balancing Smart BMS does already exist (can't get 5A though, choices are: 0.6, 1A, 2A or 3A). A handful of folks purchased this one. Not sure about the max charge current.
 
Dzl said:
Sounds like you got a good combo, and a reasonable plan on how to use it



The Active balancing Smart BMS does already exist (can't get 5A though, choices are: 0.6, 1A, 2A or 3A). A handful of folks purchased this one. Not sure about the max charge current.
Click to expand...
Yeah, that sounds like the one I was considering, but they were all limited to 50A charge current which won’t work for me.

I got this rig inexpensively enough that if it doesn’t cut the mustard (or proves incapable of keeping up with cells that begin to degrade/mismatch), it’s only a matter of time before Heltec or others begin offering higher-current smart BMSs with Active Balance.

My only real concern is Balancing to a weak cell low in the cycle will cause that weak cell to hit the overcharge protection cut off before the other cells are charged.

Charging will pause while the weak cell is balanced down within 30mV of the stronger cells at which point charging should resume, but losing that efficiency every charge cycle seems like a worthwhile problem to avoid if possible.

I like the way Passive Balamce is typically only active high in the knee above 3.55V (typical) and in my point of view, it’s a pity they fixed Active Balance being effective all the way down to 2.9V.
 
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fafrd said:
Yeah, that sounds like the one I was considering, but they were all limited to 50A charge current which won’t work for me.

I got this rig inexpensively enough that if it doesn’t cut the mustard (or proves incapable of keeping up with cells that begin to degrade/mismatch), it’s only a matter of time before Heltec or others begin offering higher-current smart BMSs with Active Balance.

My only real concern is Balancing to a weak cell low in the cycle will cause that weak cell to hit the overcharge protection cut off before the other cells are charged.

Charging will pause while the weak cell is balanced down within 30mV of the stronger cells at which point charging should resume, but losing that efficiency every charge cycle seems like a worthwhile problem to avoid if possible.

I like the way Passive Balamce is typically only active high in the knee above 3.55V (typical) and in my point of view, it’s a pity they fixed Active Balance being effective all the way down to 2.9V.
Click to expand...
Ahh okay, now I understand, I misinterpreted what you were saying earlier.

The datasheet I saw did not specify a lower charge current for that BMS (it doesn't specify charge current at all from what I can tell).
 
upnorthandpersonal said:
No, they go higher. The 100A version for instance is 100A charge and discharge.
Click to expand...
Figuring out specs from Heltec’s documentation/website is a nightmare.

Communicating directly with the company, I confirmed that they offer no ‘Smart’ BMSs supporting a minimum of 100A Maximum Charge Current.

If you believe they offer an 8S Smart BMS supporting 100A Maximum Charge Current, I’d appreciate a link.
 
The official spec sheet on my JK (Heltec) says 14S to 24S but if you use an external power supply or a DC step up converter to get the 40 volts, it even worked properly at just 4S. It is also rated for 200 amps in both charge and discharge, with a 300 amp peak rating. It goes for about $200 US though.
 
GXMnow said:
The official spec sheet on my JK (Heltec) says 14S to 24S but if you use an external power supply or a DC step up converter to get the 40 volts, it even worked properly at just 4S. It is also rated for 200 amps in both charge and discharge, with a 300 amp peak rating. It goes for about $200 US though.
Click to expand...
Yeah, using a step-up converter would be a way to get an 8S BMS from a product intended for higher voltage, but what a pain.

Also, I wanted 300A maximum discharge and 600-1000A Peak.

In actual use, I’ll probably never exceed 180A sustained or 500A peak, but my sense is that these Chinese budget BMSs cut corners when it comes to current ratings, so I always like to spec for 150% if not 200.%...
 
I have been trying to get information about the CAN bus connector and how to get a mate to connect to it and Michelle Duan finally told me today that they sent me a BMS that doesn't have CAN bus capability. ?
Now I have to figure out how to do a return unless someone is interested in a 200A 14S-24S BMS. I haven't powered it on or anything. I spent a month waiting for my cells, and now I learn that I have to get another BMS, or send this one for an upgrade.
PM me if you are interested. This is what I have.

This product is no longer available.

This product is no longer available.
m.alibaba.com
 
fafrd said:
Yeah, using a step-up converter would be a way to get an 8S BMS from a product intended for higher voltage, but what a pain.

Also, I wanted 300A maximum discharge and 600-1000A Peak.

In actual use, I’ll probably never exceed 180A sustained or 500A peak, but my sense is that these Chinese budget BMSs cut corners when it comes to current ratings, so I always like to spec for 150% if not 200.%...
Click to expand...
There is a 300A version of the Heltec Smart BMS with active balance that has higher peak.
But I wouldn't try pushing even 200A through one of those. They are expensive too.
There are people reporting problems with these BMSs when using high amps.
I only plan to use a max of 100A on my 200A BMS.
 
Haugen said:
I have been trying to get information about the CAN bus connector and how to get a mate to connect to it and Michelle Duan finally told me today that they sent me a BMS that doesn't have CAN bus capability. ?
Now I have to figure out how to do a return unless someone is interested in a 200A 14S-24S BMS. I haven't powered it on or anything. I spent a month waiting for my cells, and now I learn that I have to get another BMS, or send this one for an upgrade.
PM me if you are interested. This is what I have.

This product is no longer available.

This product is no longer available.
m.alibaba.com
Click to expand...
That's too bad. I wasn't planning to use CAN.
But I am about to order 3 more BMSs so I will have to think about adding CAN in case I decide to use it.
It's a winding road
 
ArthurEld said:
There is a 300A version of the Heltec Smart BMS with active balance that has higher peak.
But I wouldn't try pushing even 200A through one of those. They are expensive too.
There are people reporting problems with these BMSs when using high amps.
I only plan to use a max of 100A on my 200A BMS.
Click to expand...
Please can you share links of this complaint?
 
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I just looked at that thread. It looks like it lost the balance leads for cell 15 and 16. That is a very odd failure. The voltages on the cells that were still there all look fine. I don't see how it damaged any cells. When it saw the voltage error it did shut down. And a few posts after his failure, he reports all the cells balanced fine. I am inclined to believe he had a wiring problem. Maybe a bad connector at the BMS or something like that. I am not saying the BMS could not have failed, but this is a very odd failure. The MOS switch didn't fail, it just stopped seeing voltage above cell 14. Very strange.

Mine has been up and running about 150 days, but running under 50 amps for now. His failure sure is not an over current fail. I would have certainly done some more testing to see what went wrong. He returned it and swapped it for a DALY. It is also interesting that up to cell 14 is on the first connector. He lost the cells on the second connector. I am not using any on the second connector, just the last lead which is the power to the BMS.

The short BlueTooth range is an issue. Drilling out the holes in the case helped, I get about 30 feet now. Basically anywhere in my garage works fine, won't make it through the wall into the house though. And the instructions really need to detail the startup procedure. It took me 2 days to get it to power up after an e-mail back from the seller about needing over 5 volts above the battery voltage. I was close to thinking it was a dead board.

One other note. If you experiment with the board on different packs, make sure to do the factory reset and then set the new pack parameters. At first, I just changed the number of cells and it acted very odd. It seems to just do the balance wire test on the power up after a reset. When the cell count changed, it kept reporting errors until I did a reset and it did the balance wire test again.

I will keep reporting if I have any issue with it, but so far it has been rock solid. It would have been nice to get the version info off his failed one. Mine is hardware version 3 and I have seen others report version 4 now.
 
ArthurEld said:
There is a 300A version of the Heltec Smart BMS with active balance that has higher peak.
But I wouldn't try pushing even 200A through one of those. They are expensive too.
There are people reporting problems with these BMSs when using high amps.
I only plan to use a max of 100A on my 200A BMS.
Click to expand...
Yes, I know, but that model was limited to 50A max charge current, which is insufficient for my needs.

And in general, I overspec by at least 50% if not 100% on continuous discharge current precisely because I’m concerned about these Chinese BMSs being underbuilt.

My 4kW inverter will pretty much never be maxed out and will draw 160A when it is.

My solar charger, on the other hand, will be pushing a full 80A continuously through the 2-3 hours surrounding peak sun, so I need a BMS that can sustainably handle that level of charge current.

For single-port designs, I have to admit I’m somewhat mystified why charge and discharge specs are not identical - isn’t it just the same switch controlling the same current path but with current flowing in opposite directions?
 
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