JK 4S 200A BMS

[Nami]

Wow… so, in essence, you can only use this BMS in a single battery configuration.

So, if more Ah is needed, you have to connect them all through the single BMS.

If more amp output is needed, you need to choose a different BMS system.

Actually you can imagine the batteries of electric motorcycles, many of which use 16S10P LI-ION batteries.
These batteries use one BMS,
Using one electrical load,
So when the customer's parallel batteries increase the battery capacity, in order to prevent the loss caused by the customer's misoperation,
We recommend that customers connect batteries in parallel
Then Connect to one BMS,

 

[rhino]

So when the customer's parallel batteries increase the battery capacity, in order to prevent the loss caused by the customer's misoperation,
We recommend that customers connect batteries in parallel
Then Connect to one BMS,

You can not parallel any of the JK BMS's even the 48V version ones?

Just want to make sure what is being stated is that even if you have 3 separate 16S battery banks all connected to a common busbar (like Andy has in his garage) you can not use 3 separate JK BMS's to control each of the three?

Sometimes when people refer to something in parallel they are talking about putting it in parallel on the same battery bank (like to increase amount of current it can support), but that is not what we are talking about so I want to make sure something isn't being incorrectly stated.

 

[Nami]

You can not parallel any of the JK BMS's even the 48V version ones?

Just want to make sure what is being stated is that even if you have 3 separate 16S battery banks all connected to a common busbar (like Andy has in his garage) you can not use 3 separate JK BMS's to control each of the three?

Sometimes when people refer to something in parallel they are talking about putting it in parallel on the same battery bank (like to increase amount of current it can support), but that is not what we are talking about so I want to make sure something isn't being incorrectly stated.

I've already made it clear
Because the battery discharge rate for energy storage customers is slow,
So the voltage difference between different battery packs is not very big.
But many customers use boats or electric motorcycles.
These devices have a very high starting power.
If the consistency of batteries is not good, the voltage of batteries will show a big difference when used in parallel. Parallel connection is not good for batteries and BMS.
So in order to prevent the misoperation of customers,
We do not recommend customer parallelism

 

[rhino]

I've already made it clear
Because the battery discharge rate for energy storage customers is slow,
So the voltage difference between different battery packs is not very big.
But many customers use boats or electric motorcycles.
These devices have a very high starting power.
If the consistency of batteries is not good, the voltage of batteries will show a big difference when used in parallel. Parallel connection is not good for batteries and BMS.
So in order to prevent the misoperation of customers,
We do not recommend customer parallelism

Something does not make sense since we have people using 5+ server rack batteries all in parallel and all with their own BMS and sometimes even with different BMSs.

I could potentially see an issue if you have multiple battery banks in parallel and a single one of those battery banks could not handle very high starting power, is that what you are saying? Otherwise if any one of the battery banks could handle the load all by itself I am having trouble understanding why multiple JK BMS's on each battery could not work with multiple battery banks in parallel.

 

[Nami]

Something does not make sense since we have people using 5+ server rack batteries all in parallel and all with their own BMS and sometimes even with different BMSs.

I could potentially see an issue if you have multiple battery banks in parallel and a single one of those battery banks could not handle very high starting power, is that what you are saying? Otherwise if any one of the battery banks could handle the load all by itself I am having trouble understanding why multiple JK BMS's on each battery could not work with multiple battery banks in parallel.

First of all, not everyone's battery pack is of the same quality.
Some customers may use 4S GRAND A batteries.
Then 4S GRAND B batteries are parallel with the 4S GRAND A batteries.
If the battery quality of the battery pack is not the same, the battery consistency of the two packs will be different and the discharge rate will be different when they link a load.
As I've already said, the battery discharge rate for energy storage users is slower and generally does not generate too much pulsed current, but not all loads are the same.
Use in different situations will produce different results.
So for the sake of insurance, we do not recommend parallel use.
Thank you

 

[hwse]

@ Nami If this is correct it will take the JK BMS from my #1 choice to not being in consideration. I find it hard to believe that this is correct. Anyway, my order that I was going to make tomorrow is now on hold. This would be a truly sever limitations that even Daly and JBD can handle with ease. I would really like to get the JK engineering's take on the issue because other than this I REALLY like the JK BMS.

 

[Nami]

@ Nami If this is correct it will take the JK BMS from my #1 choice to not being in consideration. I find it hard to believe that this is correct. Anyway, my order that I was going to make tomorrow is now on hold. This would be a truly sever limitations that even Daly and JBD can handle with ease. I would really like to get the JK engineering's take on the issue because other than this I REALLY like the JK BMS.

Currently only one SP04S028A for JBD can support concatenation.
For daly, only the new Configuration Parallel Module supports the use of Parallel PACK.
I know these products very well.
For the sake of battery safety for all users, we do not recommend parallel use. Thank you.
We are considering adding discharge diodes, which may work

 

[740GLE]

Sounds like lawyer talk to save us from ourselves.

IMO if a user has a 12v system of all the same brand size quality of cells, is only using this 12v pack for solar storage and inverter usage, you’ll be fine running in parallel.

Sounds like they are more concerned with people using these with motor starting applications and mixing quality cells.

 

[Nami]

Sounds like lawyer talk to save us from ourselves.

IMO if a user has a 12v system of all the same brand size quality of cells, is only using this 12v pack for solar storage and inverter usage, you’ll be fine running in parallel.

Sounds like they are more concerned with people using these with motor starting applications and mixing quality cells.

Because China is the largest exporter of batteries,
I know about Chinese batteries. I also have many batteries.
I come into contact with more battery brands and types,
Not all batteries are good batteries,
There are many GRAND B or GRAND C batteries on the market. Not everyone will buy expensive GRAND A grade batteries.
If the customer purchases a GRAND A battery that is very consistent, then the battery does not need a balancer at all.
We have our own lab and I want our customers to follow our advice.

 

[Vi s]

@Nami
I guess you have tested parallel usage in your lab, what issues did occur, what was the worst thing that happened?

 

[Nami]

@Nami
I guess you have tested parallel usage in your lab, what issues did occur, what was the worst thing that happened?

Depending on the quality of the battery, the failure does not occur at the beginning. But it happens during use, no matter what brand of BMS (currently all but those with lithium parallelism support parallelism).
I can't advise customers to spend a lot of money on the best quality batteries, only not in parallel.
This is a problem that needs time to solve, and of course, technology. We will create better products to meet the needs of the market

 

[rhino]

To be clear, this is what is being said CAN NOT be done?

 

[Vi s]

Depending on the quality of the battery, the failure does not occur at the beginning. But it happens during use, no matter what brand of BMS (currently all but those with lithium parallelism support parallelism).
I can't advise customers to spend a lot of money on the best quality batteries, only not in parallel.
This is a problem that needs time to solve, and of course, technology. We will create better products to meet the needs of the market

Thank you.
What kind of failure are you talking about? Do you mean the BMS shuts down or breaks down?

 

[Vi s]

To be clear, this is what is being said CAN NOT be done?
View attachment 95538

?? Nice effort and nice drawing!
Looks like the setup from Andy.
Which app did you use if i may ask?

 

[Nami]

To be clear, this is what is being said CAN NOT be done?
View attachment 95538

NOT RECOMMEND

 

[hwse]

NOT RECOMMEND

Wow. From what you are saying, every single drop-in battery can only be used as a single battery and never connected to another in either series to increase voltage or parallel to increase amp capacity. Battle Born allows up to 4s (48v) and no limit on parallel.

• I know of boats using their batteries in 8P (800A @ 12v and others with 4p4s (400A @ 48v) that were designed by Battle Born.
• Andy has three banks of 280A - 304A batteries each with a different brand of MBS (JK, JBD, Heltec)
• Will Prowse has I do not know how many large batteries in parallel.

Almost all DIY batteries are used for energy storage so parallel connections is a vital issue. I am afraid that this thread is going to really hurt your sales.

 

[740GLE]

Imagine all those server rack battery owners finding this out ?

I think something is getting lost in translation.

Remember “not recommended” doesn’t mean failure is 100% guaranteed. Just too many unknowns of the end user, the manufacturer can use this as a scapegoat to blame the user.

 

[Nami]

Imagine all those server rack battery owners finding this out ?

I think something is getting lost in translation.

Remember “not recommended” doesn’t mean failure is 100% guaranteed. Just too many unknowns of the end user, the manufacturer can use this as a scapegoat to blame the user.

If parallel battery packs are required, the same voltage can reduce the chance of failure,
But it's hard to achieve,
Or add a discharge diode in each battery pack, which is the way we are currently considering

 

[Vi s]

If parallel battery packs are required, the same voltage can reduce the chance of failure,
But it's hard to achieve,
Or add a discharge diode in each battery pack, which is the way we are currently considering

Another solution could be to add something like an intelligent (which knows true capacity of each battery and decides how the energy should be distributed) "active balancer" in-between the batteries to balance them!?
The active balancer could be just an intelligent DC to DC charger (since you charge the battery as a whole) or discharge Diode if that works to balance the voltage of each battery in parallel (+ keeping actual capacity in mind).

For example:
As we know 40% and 60% SOC is at exactly the same voltage.
So battery 1 is at 40%,
battery 2 at 60% and
battery 3 at 70 or 80%.
Now let battery 3 charge first battery 2 instead of battery 1 because even though they are at the same voltage they don't have the same capacity!
Hope you understand why knowing the actual capacity of each battery is important.

But anyway there should be no problem to have batteries in parallel because the BMS of each battery protects them.
For example even in the very unlikely case that battery 1 is at 48v and battery 2 at 57v, the BMS of battery 2 will limit or shut off the current which flows to battery 1 (because of the voltage difference) so there should be no issue. Also the BMS of battery 1 will shut down in case of too high charge current. So maybe just add a current discharge and charge limiter in your BMS and everything should be safe or!?
Same with charging and discharging, let all BMS's communicate with each other and limit charge and discharge current accord to their individual capacity.
Test it in your lab. How much current does actually flow from 57v battery to a 48v battery!?
You could also add a fuse in between each battery bank for protection against very unlikely cases.
Or recommend if parallel usage then you must add fuses in between each battery.

 

[hwse]

Food for thought
The setup.

The torture test.