JK BMS poor quality and alternative?

[Buu Tran]

I'm living in Hanoi, Vietnam. Currently I use 3 JK BMS. Until recently I thought that JK BMS rocks, however now I'm in doubt and searching for better alternative.
1. The first bms I use it in 4-cell configuration to assist my EV lead-acid battery. It used to work perfectly for few months, then suddenly I can no longer scan it using Bluetooth. I was thinking it' dead, but not completely dead, I turn it off, turn on again and everything works again.
2. I used 2 JK BMS for solar storage. Those used to work for few months perfectly. Now very often one of them causes trouble, when bms turn off discharge due to cell under voltage protection, battery pack voltage drops to very low level, something like 10v. In the app I see that all cell around 3v and my 15 cells gives around 45v, what is normal, but measurement shows that voltage drop in B- P- circuit is very big, about 35v (sometime 25-30v). Due to battery pack low voltage, my Deye inverter show "No battery" error. Only rebooting jk bms helps, so it's clearly bms problem.
Do some of you have same problem? What is better alternative?
Thank you
P.S. First bms is 40A 8p, 2 others 150A 24p

 

[Alkaline]

JK seem to have a higher than usual failure rate... I keep reading these types of post. Would be sad to put in them in the same group as Daly.

 

[Buu Tran]

JK seem to have a higher than usual failure rate... I keep reading these types of post. Would be sad to put in them in the same group as Daly.

It's seems like firmware bugs, not hardware failure, but you're right, JK quality is not convincing. All my three jk bms are buggy.

 

[LydMekk]

Well, my 200A versions are rock solid.

 

[Buu Tran]

I've found workaround, let me update it for other people may facing same problem. I increase cutoff voltage in the inverter a bit, so bms never triggers under-voltage protection. It looks ugly but it works.

 

[dmsims]

I've found workaround, let me update it for other people may facing same problem. I increase cutoff voltage in the inverter a bit, so bms never triggers under-voltage protection. It looks ugly but it works.

I would consider this normal best practice. The BMS is the last line of defense

 

[lunatik96]

I'm living in Hanoi, Vietnam. Currently I use 3 JK BMS. Until recently I thought that JK BMS rocks, however now I'm in doubt and searching for better alternative.
1. The first bms I use it in 4-cell configuration to assist my EV lead-acid battery. It used to work perfectly for few months, then suddenly I can no longer scan it using Bluetooth. I was thinking it' dead, but not completely dead, I turn it off, turn on again and everything works again.
2. I used 2 JK BMS for solar storage. Those used to work for few months perfectly. Now very often one of them causes trouble, when bms turn off discharge due to cell under voltage protection, battery pack voltage drops to very low level, something like 10v. In the app I see that all cell around 3v and my 15 cells gives around 45v, what is normal, but measurement shows that voltage drop in B- P- circuit is very big, about 35v (sometime 25-30v). Due to battery pack low voltage, my Deye inverter show "No battery" error. Only rebooting jk bms helps, so it's clearly bms problem.
Do some of you have same problem? What is better alternative?
Thank you
P.S. First bms is 40A 8p, 2 others 150A 24p

You may want to consider an active balancer. The built in balance current is negligible for the 280A batteries.
I was able to turn an unusable battery bank into very functional by adding an active balancer.
They recommend 5A for every 200A-hr of battery. I have a 8S2P config and 1-10A does OK.
You can disable the built in balance or have it kick in when 3 V.
The active balance circuit runs all the time.

 

[lunatik96]

Well, my 200A versions are rock solid.

Mine too - so far.

 

[SolarPirate]

Well, my 200A versions are rock solid.

Give it a week lol

 

[TimE]

50 cycles on mine so far with faultless performance

 

[LydMekk]

Give it a week lol

After a year still going perfect, both of them.
But, I knew what I was doing installing them correctly.

 

[Scoob]

My 200 amp 12v has been rock solid in my camper for a year now.

 

[Skypower]

I’ve got four JK’s in service and they are going strong. Thought I had a problem with state of charge but I figured it out. The manual could be much better written. It’s probably the most common bms sold now, so with that many out there, there’s going to be some failures, probably half of which are user related. All my Daly’s were 100% failures within 6 months.
Overkill BMS is still going strong however it needed an active balancer to maintain the service.

 

[mkimid]

Unfortunately, super capacitor in the active balancer has the limited cycle life. If operating the battery pack in top-up position (most full status), balancer will cycle the capacitor too many cycles, and practically, can standing 2~3 years for 1A, 3~5 years for 2A. the super capacitor is not expensive, and can buy from Aliexpress, and can replace it.

 

[OffgridSystems]

Do you have a Manufacturers part number or link to that part? Is a super cap really necessary? How many cycles are super caps rated for?

it would be interesting to do the math to see how much energy we are talking. If the energy in a cap is = 1/2CV^2, and the cap is say 2F (I have no idea what they are), and the time to charge the cap is 10msec at 4V, we have 1/2*2*4^2=16 joules. The power that cap can deliver is P = U/t or 16J divided by say 10msec is 16/.010 or 1600 watts. So can ceramic caps store that much energy? I'll have to go look at some data sheets.