JBD 4S 200A BMS

[MisterSandals]

I have not noticed any differences.
I “think” the Overkill full function is free while Xiaoxiang full featured was ~$6.

 

[HRTKD]

I have two sealed 12v x 480Ah packs that have this 200A JBD BMS and they seem to be completely unable to balance the pack. They are in a sealed case so I cannot open them to do anything to help the balance by charging or discharging individual cells. I have tried charge balance on and off but the low cell never seems to make any gains. If I try to charge them at anything greater than 14.1v I hit OVP with one cell at 3.65 and the low cell still at 3.37.

Any ideas on how to get this pack to balance?

It may not be the BMS. It could be a less than healthy cell.

With the battery voltage down from the 14.1 volts that is tripping you up, charge with fewer amps. That may allow the high cell more time before it hits 3.65, which will allow the low cell to come up further. Balancing usually doesn't happen until 14.2 volts, but that threshold is a parameter in the BMS that can be changed. You could try lowering, but only to get past the initial balance.

Do you have the two batteries in parallel or series? (since you said 14.1 v charge, you probably have them in parallel) If it's series then that is part of your problem. Disconnect the batteries and charge them individually.

 

[John Frum]

Agreed, but both JBD and Overkill have an app. Is there a problem with either one?

Since they are the same BMS I presume the app is the same.
Possibly just different revisions of the same code base.

 

[John Frum]

I have two sealed 12v x 480Ah packs that have this 200A JBD BMS and they seem to be completely unable to balance the pack. They are in a sealed case so I cannot open them to do anything to help the balance by charging or discharging individual cells. I have tried charge balance on and off but the low cell never seems to make any gains. If I try to charge them at anything greater than 14.1v I hit OVP with one cell at 3.65 and the low cell still at 3.37.

Any ideas on how to get this pack to balance?

As long as the delta is trending down with repeated cycles the battery is becoming more balanced.
To help that along set the BMS to balance regardless whether it is charging or not.
The make the absorption timer longer.
So set balance to activate at ~3.4 volts per.
Make sure your float voltage is <3.4 volts per.
Set the absorption duration longer to get the passive balancer longer to work while the cells are held in the high knee.
Its a bit more stress on the cells but its all you can really do.
If you start getting cell over-voltages you will have to lower the charge voltage even more.

 

[hwse]

As long as the delta is trending down with repeated cycles the battery is becoming more balanced.
To help that along set the BMS to balance regardless whether it is charging or not.
The make the absorption timer longer.
So set balance to activate at ~3.4 volts per.
Make sure your float voltage is <3.4 volts per.
Set the absorption duration longer to get the passive balancer longer to work while the cells are held in the high knee.
Its a bit more stress on the cells but its all you can really do.
If you start getting cell over-voltages you will have to lower the charge voltage even more.

Here are my settings.

• I have balance turning on at 3.34v
• Charge balance off (static balancing)
• I have charge to 14.1v and then turned off both charging and discharge so that the cells are static except for the balance current.
• after 25-minutes, the low cell has dropped 11mv and the high cell has dropped 82mv and the delta has gone from 211mv to 140mv. So maybe it is working. I will let it run until the delta quits dropping and then charge it back up ot OVP and see if the next cycle is better.

 

[hwse]

It may not be the BMS. It could be a less than healthy cell.

With the battery voltage down from the 14.1 volts that is tripping you up, charge with fewer amps. That may allow the high cell more time before it hits 3.65, which will allow the low cell to come up further. Balancing usually doesn't happen until 14.2 volts, but that threshold is a parameter in the BMS that can be changed. You could try lowering, but only to get past the initial balance.

Do you have the two batteries in parallel or series? (since you said 14.1 v charge, you probably have them in parallel) If it's series then that is part of your problem. Disconnect the batteries and charge them individually.

• I concidered the cell heath. One thing that tends to show that to not be the case is that I get very simulur delta voltage at the OVP and the UVP. If the cell was weaker, I would expect the delta to be much greater at one end or the other. Most cases of mis-matched cells I have seen will have much greater delta voltage at one end or the other but not the same at both.
• It does not seem to matter how long I hold the voltage at 14.1v, cell #1 never seems to go any higher. I typically turn on charge balance until the pack gets to the absorption voltage and then I turn off charge balance after that so that it will continue to balance in the static mode.
• The two packs are in parallel, but I am currently working at balancing the pack with the greater imbalance with both charge and discharge FETs turned off to isolate that one.

These batteries are in my motorhome in which I am currently living so I need to leave one on at all times but can switch the other off for C/D in the app to isolate it.

 

[John Frum]

Here are my settings.

• I have balance turning on at 3.34v

That is pointlessly low.
What is your float voltage?

• Charge balance off (static balancing)

good.

• I have charge to 14.1v and then turned off both charging and discharge so that the cells are static except for the balance current.

Why are you disabling the current paths?

• after 25-minutes, the low cell has dropped 11mv and the high cell has dropped 82mv and the delta has gone from 211mv to 140mv. So maybe it is working. I will let it run until the delta quits dropping and then charge it back up ot OVP and see if the next cycle is better.

You want to use absorption voltage to hold the cells in the high knee so that the balancer can actually perform a top balance.

 

[hwse]

That is pointlessly low.
What is your float voltage?

good.

Why are you disabling the current paths?

You want to use absorption voltage to hold the cells in the high knee so that the balancer can actually perform a top balance.

3.34v was what I needed to go to in order to keep the static balancing going when the float voltage was set at 13.5v

I am closing both paths to freeze the power that is in the battery (no in or out) while the static passive balancing pulls down the highest cells. This method seems to let me continue to passive balance at a higher voltage without a high float voltage. I charge up to 14.1 and lock both FETs and let it cook. Here is where I am after several more hours and the delta is down to 110mv. Once it drops down to around 50mv I will charge it back up to 14.1 and see if I have made any gains.

 

[hwse]

Here is where I was after balancing all night for about 17 hours. The delta had dropped to 66mv.



I then recharged it to 14.1v again and this time the delta is 175mv with the highest cell down to 3.581v from the previous 3.619v so it is coming into better balance. I will repeat this cycle this coming week to see if I can get it balanced to where I can bulk it up to 14.4v with a delta of less than 200mv which would be a very big improvement.

 

[hwse]

Here is today's results.
Here is where I was after balancing all night for about 24 hours. The delta had dropped to 59mv.



I then recharged it to 14.1v again and this time the delta is 182mv with the lowest cell up to 3.421v from the previous 3.375v & the highest cell down to 3.603v from the previous 3.581v This is the first time I have seen the low cell over 3.4v.

 

[pretzel]

Here is today's results.
Here is where I was after balancing all night for about 24 hours. The delta had dropped to 59mv.

View attachment 130311

I then recharged it to 14.1v again and this time the delta is 182mv with the lowest cell up to 3.421v from the previous 3.375v & the highest cell down to 3.603v from the previous 3.581v This is the first time I have seen the low cell over 3.4v.

View attachment 130312

Seems like you are on track for success. The balancing on a JBD is super slow, so it will take days and weeks of eeking it along like that.
Frustrating, too, when hitting the 3.65 cutoff voltage.

I had the same issue, but have access to the cells, so just attached a capacitive active balancer and it was done plenty fast.

 

[hwse]

Seems like you are on track for success. The active balancing on a JBD is super slow, so it will take days and weeks of eeking it along like that.
Frustrating, too, when hitting the 3.65 cutoff voltage.

I had the same issue, but have access to the cells, so just attached a capacitive active balancer and it was done plenty fast.

Especially true given that my other battery has a JK BMS and the active balancer in that BMS top balanced all 4 pairs of cells with 560Ah total capacity to perfect 3.65v in one charge. Huge difference between +2A active and .15A max (and usually much less) passive balancing.

 

[hwse]

After making several more rounds of charging to cell #3 OVP and then static balancing for 24 hours, I am starting to see some significant progress.

This time I was able to recharge to 14.26v. This is the first time I have been able to get the pack voltage above 14.1v. The delta is 192mv with the lowest cell up to 3.466v up from the previous 3.42v. I now have two cells that are able to above 3.60v instead of just cell #3.

progress.

 

[hwse]

One more step and now I can get up to 14.37v.

 

[pretzel]

One more step and now I can get up to 14.37v.

View attachment 130891

Hey - I think I figured out a way to automate this top balancing process using only the built in balancing.

First, make sure you are set to only balance when not charging.

Then, under Parameter View, top two values:
- set the overvoltage to 3.55v
- set the overvoltage release to 3.45v

The BMS will charge up until whatever cell hits 3.55v, then charging will be turned off and active balancing kicks in.

The balancing will continue until the voltage in the highest cell drops to 3.45v, then the process starts again.

You will need to choose your two values (above) to fit your particular needs. the 3.55 / 3.45v seems to be working for me.

Then increase the values up to as high as 3.65 / 3.50v. Personally, I'll stop at 3.55 / 3.45 or maybe 3.60 / 3.45, but no higher, as it's not really necessary.

I'm just testing this now so I'll update if things don't go well.

I top balanced this 4s 160ah pack about 6 months ago and so far it's still plenty close enough, so this is just fine tuning it.

 

[hwse]

Hey - I think I figured out a way to automate this top balancing process using only the built in balancing.

First, make sure you are set to only balance when not charging.

Then, under Parameter View, top two values:
- set the overvoltage to 3.55v
- set the overvoltage release to 3.45v

The BMS will charge up until whatever cell hits 3.55v, then charging will be turned off and active balancing kicks in.

The balancing will continue until the voltage in the highest cell drops to 3.45v, then the process starts again.

You will need to choose your two values (above) to fit your particular needs. the 3.55 / 3.45v seems to be working for me.

Then increase the values up to as high as 3.65 / 3.50v. Personally, I'll stop at 3.55 / 3.45 or maybe 3.60 / 3.45, but no higher, as it's not really necessary.

I'm just testing this now so I'll update if things don't go well.

I top balanced this 4s 160ah pack about 6 months ago and so far it's still plenty close enough, so this is just fine tuning it.

I had thought about doing the same and am sure that it will do the same balancing that I have done but I am just paranoid about requiring the BMS to shut down charging. I like it there but do not want to rely on it being there. Like a safety pressure relief valve that you never want to trip.

 

[MisterSandals]

I had thought about doing the same and am sure that it will do the same balancing that I have done but I am just paranoid about requiring the BMS to shut down charging.

Yea, I cringed when I saw pretzel using his BMS (last ditch battery safety device) as a charge controller.

The charge controller is called a charge controller because its specifically designed to control charging. The BMS is not. Pretzel, you should start a thread with what you are proposing and lets get to the root of your charging woes and fix it the right way.

 

[hwse]

I suspect that they reason that he is setting OVP low at 3.55v is that he has the charge controller set just high enough to trip when the high cell gets to 3.55 but if it did not trip, the charge controller would stop charging before the high cell hits 3.65v. This would still provide redundancy of protection, but I am more comfortable with manual control of the charging without hitting OVP so that I can better monitor the situation.

 

[pretzel]

Yea, I cringed when I saw pretzel using his BMS (last ditch battery safety device) as a charge controller.

The charge controller is called a charge controller because its specifically designed to control charging. The BMS is not. Pretzel, you should start a thread with what you are proposing and lets get to the root of your charging woes and fix it the right way.

Thanks for checking my work and watching out for well being
No charging or balancing woes here.

Yep, my power supply is an Iota DLS-30.
With the plug in it tops out at 14.2v, so that's still just 3.55v/cell, which I'm calling 100%

I initially top balanced it 6 months ago with a bench supply + a Heltec type active capacitive balancer.
Just checking it's still solid at the top, and indeed it's within about 0.035v/cell

So this thread is still JBD related - ideas on how to use it to top balance through settings using the built in functionality
I stated the process in my above post, but if anything seems unclear or off, please ask away, -thanks

 

[hwse]

Aww, thanks for checking my work and watching out for well being
No charging or balancing woes here.

Yep, my power supply is an Iota DLS-30.
With the plug in it tops out at 14.2v, so that's still just 3.55v/cell, which I'm calling 100%

I initially top balanced it 6 months ago with a bench supply + a Heltec type active capacitive balancer.
Just checking it's still solid at the top, and indeed it's within about 0.035v/cell

So this thread is still JBD related - ideas on how to use it to top balance through settings using the built in functionality
I stated the process in my above post, but if anything seems unclear or off, please ask away, -thanks

With 14.2v charge and the parameters that you describe I can concede that you still have redundant protection as long as your imbalance is not too great. With my pack,I could not charge to 13.9v without tripping my OVP at 3.65v. Like I said, I started with 300-mv imbalance. At that level, I lowered my float voltage to 13.9 and watched it as the voltages came up and turned off charging when cell #3 went above 3.64v