JK 1A or 2A?

[Bleedingblue]

Looking to replace my 6 overkill 100A BMS's with some JK's. The top balance is way out of balance on 5 of my 6 battery banks.
Those 6 banks are all 280AH cells
I also have 4 305AH banks that are JK 150A with the 2A active balancers.

Since I have 10 total banks in all and it spreads out the charge current among the 10 you think it would be OK to just go with the 1 amp active balancers?

I have 6 of the voltage detection controllers and 6 Heltec 5 amp balancers I have not hooked up yet. Just thinking about doing all that makes my head hurt. So that is why I'm thinking about just switching up the BMS's to the JK's

 

[LakeHouse]

I guess it depends on how much of a rush you're in to get the five out-of-balance banks balanced... If it's no rush and they aren't limiting your ability to operate your system, go ahead and save some money with the 1A balancers. As long as you're regularly getting pack voltage high enough to balance, the 1A JK's will absolutely get those packs balanced, it'll just take twice as long as the 2A version.
Once they're balanced for the first time, you likely will see no difference between the 1A and 2A versions. 1A should be lots enough to maintain balance.
You could also purchase the 1A's and install them on 4 305AH banks (presumably currently balanced) and switch the existing 2A's over to the unbalanced packs. This may be as easy as unplugging wiring harnesses, but I'm not 100% sure if the 1A and 2A harnesses are interchangeable.

 

[Pi Curio]

Rule of thumb, 1A per 100Ah cell capacity.

I'd go with the BMS that has a 2A active balancer. You can always lower it to 1A later in the settings if you want.

 

[LakeHouse]

Rule of thumb, 1A per 100Ah cell capacity.

I'd go with the BMS that has a 2A active balancer. You can always lower it to 1A later in the settings if you want.

A 2A active balancer would be undersized for 280Ah cells per your rule of thumb. Also, this is the first I've heard of any such rule.
I run 230Ah cells in a 16S configuration with a 2A JK active balancer, and it balances for maybe 3 minutes a day. A 1A balancer would increase that to 6 minutes a day. And my cells are used cells from Aliexpress (yes, I know, lesson learned on buying cells there), so they're far from what people on the forum would consider 'Grade A'.

 

[Pi Curio]

A 2A active balancer would be undersized for 280Ah cells per your rule of thumb.

If I have to specify, " at a minimum", well...

Besides, he already said he has JK 150A 2A BMS on the 305's. Having the same BMS make and model for all of the cell packs is a good thing.

Also, this is the first I've heard of any such rule.

It's a good guideline.

 

[LakeHouse]

Why complicate things, he won't be saving any money by having 4x JK 150A 2A sitting collecting dust.

That's not what I was suggesting. I meant to repurpose the existing 2A's to balance the unbalanced packs, and install the new 1A's on the packs that are currently already balanced.

Wouldn't it be simpler and a better use of investment to replace the other BMSs with JK 150A 2A ones instead?

How so? If a 1A active balancer is sufficient, there's no upside to a 2A.
And don't forget, the original question was:

you think it would be OK to just go with the 1 amp active balancers?

In my opinion, the answer is yes.
I see no downside to having multiple JK BMS's with different active balance capabilities.

 

[Steve_S]

Keeping It Sweet & Simple.
Active Balancing MOVES power from Hi to Lo. The 1A vs 2A is the ability to move that energy from Hi to Lo.
There is NO LOSS if you have either, Active doesn't waste power, only moves it. How Fast & How Much it can move does make a difference, especially when cells are above 3.390Vpc +/-.

Having 1 pack with a 1A balancer in Parallel with those that have 2A makes ZERO DIFFERENCE... It is all internal to the specific battery pack, the others don't know or care at all. This will also not be any sort of issue with the new Inverter Edition BMS', either.

 

[Pi Curio]

That's not what I was suggesting. I meant to repurpose the existing 2A's to balance the unbalanced packs, and install the new 1A's on the packs that are currently already balanced.

You are correct, I've misinterpreted what you were saying, that's on me.

How so? If a 1A active balancer is sufficient, there's no upside to a 2A.
And don't forget, the original question was:

Initially, my impression was that you were suggesting taking the JK BMSs off and replacing these with the Overkill on 305's. Again, my bad.

In my opinion, the answer is yes.
I see no downside to having multiple JK BMS's with different active balance capabilities.

Still, when making such an investment I'd try to minimize things that might not work out and wouldn't risk having a difference in hardware between 1A and 2A BMSs.

If necessary, I'd swap the BMSs on those 6 batteries gradually with emphasis on the same make and model.

 

[Pi Curio]

Having 1 pack with a 1A balancer in Parallel with those that have 2A makes ZERO DIFFERENCE... It is all internal to the specific battery pack, the others don't know or care at all. This will also not be any sort of issue with the new Inverter Edition BMS', either.

I wasn't completely sure about the 1A - 2A part, good to know. Thanks

 

[Steve_S]

I always suggest 1A Active per 100AH capacity. Unfortunately the JKBMS at present only do up to 2A. They do have specific balancers that do more but not BMS integrated. Now we are seeing 300AH more commonly and Q1-2024 the 510s & 560s will be available to consumers... There is going to have to be some catchup there at some point. JK is still the only one with built-in Active Balancing as far as I know. I have heard chatter in the backgroud that others are working on adding that +.

I have a batch of new Inverter-BMS models coming to replace my current fleet of JK's along with steel cases for all of my packs, so they're identical. The "finalization" of my build over the past couple of years. It will be nice to have them all on CANbus and easily accisible & manageable

 

[Skypower]

2 amp for 270 to 320 ah. More amps means less time needed to balance at absorb voltage. Less time at absorb means less stress on the cells.

 

[LakeHouse]

I always suggest 1A Active per 100AH capacity.

I’m not trying to start an argument here, but I’m very interested as to why you suggest this.
My personal experience has been that a 2A active balancer is way more than is needed for my 230Ah cells. After initial install and a few months of operation, I purchased a backup JK BMS (it’s one of the few components I think I’d have trouble sourcing local in an emergency) and went with the 0.6A active balancer. From my monitoring, the 2A balancer just didn’t have much work to do. It would maybe balance for a few minutes (or less) per day.
Have others had different experiences? I.e., a case where an active balancer of less than 1A per 100Ah of capacity couldn’t maintain balance in a pack that started balanced?
I can understand higher balance current to balance a new pack.

 

[Steve_S]

I’m not trying to start an argument here, but I’m very interested as to why you suggest this.
My personal experience has been that a 2A active balancer is way more than is needed for my 230Ah cells. After initial install and a few months of operation, I purchased a backup JK BMS (it’s one of the few components I think I’d have trouble sourcing local in an emergency) and went with the 0.6A active balancer. From my monitoring, the 2A balancer just didn’t have much work to do. It would maybe balance for a few minutes (or less) per day.
Have others had different experiences? I.e., a case where an active balancer of less than 1A per 100Ah of capacity couldn’t maintain balance in a pack that started balanced?
I can understand higher balance current to balance a new pack.

You got lucky with a well matched/batched set of cells. This is often not the case for most people, unless they purchase from a Known Good Supplier that offers properly matched & batched cells. I run 6 Packs for my home and have built & delivered quite a few. A few years of experience at this has provided an education.

 

[time2roll]

Use what you have and install the Heltec. Get some extra harnesses and move them around monthly or just buy a few more and complete the set.

Get the 2 amp if you must buy new BMS.

 

[Bleedingblue]

I always suggest 1A Active per 100AH capacity. Unfortunately the JKBMS at present only do up to 2A. They do have specific balancers that do more but not BMS integrated. Now we are seeing 300AH more commonly and Q1-2024 the 510s & 560s will be available to consumers... There is going to have to be some catchup there at some point. JK is still the only one with built-in Active Balancing as far as I know. I have heard chatter in the backgroud that others are working on adding that +.

I have a batch of new Inverter-BMS models coming to replace my current fleet of JK's along with steel cases for all of my packs, so they're identical. The "finalization" of my build over the past couple of years. It will be nice to have them all on CANbus and easily accisible & manageable

Shouldn't it be rated by how many amps of current is going into the cells vs how large the cells are?
If you are charging with 80amps it needs a large balancer to distribute that current quickly. Right now I rarely see 20 amps and since it's winter it's even less

 

[Bleedingblue]

Use what you have and install the Heltec. Get some extra harnesses and move them around monthly or just buy a few more and complete the set.

Get the 2 amp if you must buy new BMS.

I have 6 heltecs and 6 controllers for them. I'm just thinking about the headache of messing with all the wires on em.

 

[grizzzman]

I always suggest 1A Active per 100AH capacity. Unfortunately the JKBMS at present only do up to 2A. They do have specific balancers that do more but not BMS integrated. Now we are seeing 300AH more commonly and Q1-2024 the 510s & 560s will be available to consumers... There is going to have to be some catchup there at some point. JK is still the only one with built-in Active Balancing as far as I know. I have heard chatter in the backgroud that others are working on adding that +.

I have a batch of new Inverter-BMS models coming to replace my current fleet of JK's along with steel cases for all of my packs, so they're identical. The "finalization" of my build over the past couple of years. It will be nice to have them all on CANbus and easily accisible & manageable

Dang Steve..... You should have a tool box of BMS's at your place.......

 

[Bleedingblue]

what is a bms inverter

 

[Bleedingblue]

I guess it depends on how much of a rush you're in to get the five out-of-balance banks balanced... If it's no rush and they aren't limiting your ability to operate your system, go ahead and save some money with the 1A balancers. As long as you're regularly getting pack voltage high enough to balance, the 1A JK's will absolutely get those packs balanced, it'll just take twice as long as the 2A version.
Once they're balanced for the first time, you likely will see no difference between the 1A and 2A versions. 1A should be lots enough to maintain balance.
You could also purchase the 1A's and install them on 4 305AH banks (presumably currently balanced) and switch the existing 2A's over to the unbalanced packs. This may be as easy as unplugging wiring harnesses, but I'm not 100% sure if the 1A and 2A harnesses are interchangeable.

Right now since it is winter and I'm only getting maybe 1 full day of sunshine per week I've yet to see my banks get above 60% most of the time they never get above 40% during the day. Lot of times I'm out of juice. My solar system is 19kw.

 

[time2roll]

Right now since it is winter and I'm only getting maybe 1 full day of sunshine per week I've yet to see my banks get above 60% most of the time they never get above 40% during the day. Lot of times I'm out of juice. My solar system is 19kw.

Conservation might be a better focus right now.