*Update again, replaced* EG4 Wall Mount battery cell not reaching absorb voltage.

[On_The_Road]

Very slowly, but they don't need a lot. (Almost) every day I'm at 100% for a few hours, and my batteries balance for some random time:
EG4_PP_BatteryBalanceMinutes (Backwards from last night):
[0, 74, 150, 63, 75, 69]
[0, 59, 100, 33, 36, 77]
[0, 0, 33, 0, 0, 22]
[0, 0, 0, 0, 0, 0] <--- Didn't hit 100%
[0, 22, 27, 67, 13, 29]
[0, 27, 16, 14, 5, 87]

Ignore the zeros on the first battery, it's using the Secret Battery One Protocol, but I imagine it's somewhere in the range of the others..

So sometimes just a few minutes, sometimes a couple of hours, but they always seem to be under 40mv Delta pretty quickly.
View attachment 311631
40mv is the balance threshold, so I'd guess I'm OK.

At what total voltage or voltage per cell are you holding at?

 

[wpns]

At what total voltage or voltage per cell are you holding at?

 

[On_The_Road]

Fair enough that is a pretty impressive Delta considering passive balancers and being at 3.5.

 

[fnnwizard]

So, before doing anything too major on my own I reached out again to Signature Solar as the issue is slowly getting worse, and actually got them to talk to their “advanced tech”, and they want me to force the batteries into “over-volt” by setting the absorb on my charge controllers to 58v.

The BMS should then be triggered into top balancing. They state it won’t cause harm and the BMS should recognize and halt charging for protection. So, we’ll see. They couldn’t give me a defined time to set absorb, sounds like just long enough for the “over-volt” to be triggered.

Thoughts?

What inverter do you have/ Here's the prob with that suggestion. As soon as the packs hits that OVP, it's likely one of your cells will be above 3.65V. It will stop the charging as expected, the inverter will run off the pack so now is in a discharge phase = no balancing, unless you set the bms parameters to balance while in discharge mode.

I will write it 100x if I have too so @EG4TechSolutionsTeam ends up getting it right. Whoever the ess top tech is at EG4, (s)he doesn't have a good grasp on LFP / BMS operations.

EG4 ships BMSs with passive balancers. How is a 100ma or less balancer supposed to take care of a pack that has 280,000mah of capacity?

By charging at a rate mo more than 100mA = could take a hundred hours if off by 10Ah, <5% for the 280 pack.
That bms, it's actually closer to 150mA balancing. But yeah, will still tak 67hr of continuous balancing, lol. Usually better to take cover off and icharge low cells and or discharge hi cells.

 

[fnnwizard]

What inverter do you have/ Here's the prob with that suggestion. As soon as the packs hits that OVP, it's likely one of your cells will be above 3.65V. It will stop the charging as expected, the inverter will run off the pack so now is in a discharge phase = no balancing, unless you set the bms parameters to balance while in discharge mode.

I will write it 100x if I have too so @EG4TechSolutionsTeam ends up getting it right. Whoever the ess top tech is at EG4, (s)he doesn't have a good grasp on LFP / BMS operations.


By charging at a rate mo more than 100mA = could take a hundred hours if off by 10Ah, <5% for the 280 pack.
That bms, it's actually closer to 150mA balancing. But yeah, will still tak 67hr of continuous balancing, lol. Usually better to take cover off and icharge low cells and or discharge hi cells.

Here's a good visual of proper charge/balancing as pack is put into use.





Parameters: BMS balance 3.41V balance, diff = 10mV.
Charger set to 3.525V/cell (56.4V)

 

[IAm_Not_Lost]

What inverter do you have/ Here's the prob with that suggestion. As soon as the packs hits that OVP, it's likely one of your cells will be above 3.65V. It will stop the charging as expected, the inverter will run off the pack so now is in a discharge phase = no balancing, unless you set the bms parameters to balance while in discharge mode.

I will write it 100x if I have too so @EG4TechSolutionsTeam ends up getting it right. Whoever the ess top tech is at EG4, (s)he doesn't have a good grasp on LFP / BMS operations.


By charging at a rate mo more than 100mA = could take a hundred hours if off by 10Ah, <5% for the 280 pack.
That bms, it's actually closer to 150mA balancing. But yeah, will still tak 67hr of continuous balancing, lol. Usually better to take cover off and icharge low cells and or discharge hi cells.

I have SMA Sunny Island inverters. Classic 250 charge controllers.

The low cell is off by about 100-120mV at it’s worst during absorb phase. Once charging stops and float occurs, it settles into being about 30mV off and then that narrows as the cells discharge down to around 3.3 volts.

Per what the tech seemed to be saying, it sounds like just getting a cell to reach an over voltage state will cause the BMS to evaluate and begin top balancing.

Edited due to putting mA instead of mV.

 

[fnnwizard]

I have SMA Sunny Island inverters. Classic 250 charge controllers.

The low cell is off by about 100-120mA at it’s worst during absorb phase. Once charging stops and float occurs, it settles into being about 30mA off and then that narrows as the cells discharge down to around 3.3 volts.

Per what the tech seemed to be saying, it sounds like just getting a cell to reach an over voltage state will cause the BMS to evaluate and begin top balancing.

The perfect scenario to balancing is charging the pack at a low enough current so that the low cell continuously gets charged while the hi cell continuously gets discharged and staying under 3.65V ( preferably lower).

You want (your goal) the lowest cell to be at least 3.450V if current is <5A to be close to 100% charged.

 

[IAm_Not_Lost]

The perfect scenario to balancing is charging the pack at a low enough current so that the low cell continuously gets charged while the hi cell continuously gets discharged and staying under 3.65V ( preferably lower).

You want (your goal) the lowest cell to be at least 3.450V if current is <5A to be close to 100% charged.

Well, today I put the absorb at 58v like I was told. No alarms or other notifications occurred on the batteries, and a couple cells got to around 3.675 and then the battery stopped allowing it to progress upwards. Maybe about 10 minutes charge at around that higher level.

Not sure what’s supposed to happen next. The tech said to put the absorb voltage back to normal after doing that one absorb charge at 58v.

 

[fnnwizard]

Well, today I put the absorb at 58v like I was told. No alarms or other notifications occurred on the batteries, and a couple cells got to around 3.675 and then the battery stopped allowing it to progress upwards. Maybe about 10 minutes charge at around that higher level.

Not sure what’s supposed to happen next. The tech said to put the absorb voltage back to normal after doing that one absorb charge at 58v.

Yep, as expected per post #29. Normally, you don't want to go over 3.65V at a .05C ( 14A for 280Ah cells) charge termination. You went to 3.675 at what is likely to be in the 2A or less range.

The fact that the BMS doesn't give any warnings til you hit 3.700V is a very false indicator that nothing is "wrong". Going to 58V right off the batt to try and get cells to balance is counter productive, but EG4 keeps preaching that .

I've written everything needed to get the packs in line, in a safe, LiFePO4 friendly manner. I'm not EG4 support, but I began using LiFePO4 before there were chargers availble to the gen public. We modified available chrgrs and sometimes we were, the carbon based BMS .

Maybe the post below, referencing a very old post of mine in some defunct diy ev forum might shed some light into my experience with LFP... note the posting date of those postings .

F

Post in thread '[SOLVED] Ruined 2 12.8V LFP batteries by charging to 100% & leaving in garage'

Oct 10, 2024

The voltage increase is about 0.005-0.010V/cell, so on a 4S, you're looking at a total 12.8V battery voltage change of 0.02-0.04V. It is highly unlikely that this slight change in voltage will in any way affect the real-world capacity, charge response, or BMS behavior unless one is charging to 3.40V or lower, which is very uncommon.

https://www.tytlabs.co.jp/en/review/issue/files/453_057sasaki.pdf

I've always thought that Lifepo4 "memory" was non existence. Ever since from my initial testing of the A123 26650 from developer packs and Dewalt 36V packs back around 2007 to...

• fnnwizard

• 

 

[IAm_Not_Lost]

Yep, as expected per post #29. Normally, you don't want to go over 3.65V at a .05C ( 14A for 280Ah cells) charge termination. You went to 3.675 at what is likely to be in the 2A or less range.

The fact that the BMS doesn't give any warnings til you hit 3.700V is a very false indicator that nothing is "wrong". Going to 58V right off the batt to try and get cells to balance is counter productive, but EG4 keeps preaching that .

I've written everything needed to get the packs in line, in a safe, LiFePO4 friendly manner. I'm not EG4 support, but I began using LiFePO4 before there were chargers availble to the gen public. We modified available chrgrs and sometimes we were, the carbon based BMS .

Maybe the post below, referencing a very old post of mine in some defunct diy ev forum might shed some light into my experience with LFP... note the posting date of those postings .

F

Post in thread '[SOLVED] Ruined 2 12.8V LFP batteries by charging to 100% & leaving in garage'

Oct 10, 2024

The voltage increase is about 0.005-0.010V/cell, so on a 4S, you're looking at a total 12.8V battery voltage change of 0.02-0.04V. It is highly unlikely that this slight change in voltage will in any way affect the real-world capacity, charge response, or BMS behavior unless one is charging to 3.40V or lower, which is very uncommon.

https://www.tytlabs.co.jp/en/review/issue/files/453_057sasaki.pdf

I've always thought that Lifepo4 "memory" was non existence. Ever since from my initial testing of the A123 26650 from developer packs and Dewalt 36V packs back around 2007 to...

• fnnwizard

• 

Ok, appreciate your help. The cells never hit 3.7v, nor did any alarm ever start. I think around 3.675 or maybe 3.69 was about the highest before dropping.

Yes, amps were fairly low. 2-4 amps I think to the battery.

 

[fnnwizard]

Ok, appreciate your help. The cells never hit 3.7v, nor did any alarm ever start. I think around 3.675 or maybe 3.69 was about the highest before dropping.

Yes, amps were fairly low. 2-4 amps I think to the battery.

Yep, thats how I read it. going to 3.69V is prob the worst since it won't give alarms = makes one think every thingg is ok when it's not.

I forgot to ask, what was the low cell(s) at when the charge finished with hi cells at 3.675+?

What you want to do is get 1 cell to 3.55V, note the Amps, pack V, and lowest cell V and report back. From there, I can provide better advice on what you need to do and still be able to continue to use the batteries.

 

[IAm_Not_Lost]

Alright, been a minute, I know.

So, I have exchanged lots of emails with the EG4 reps, and apparently, per them, the only way to get the BMS to do a top balance is to set off the over voltage alarm, which, is 3.8v per cell. Or 60v for the battery. They said doing that briefly is fine and won’t harm the batteries. I believe only about 6 amps was going to the each battery at the time.

They had initially told me 3.7v per cell, but apparently were using outdated information. I had even told them it says in my basic manual that the over voltage alarm was listed at 3.8v.

So, I did that at their explicit instruction and got all three of my batteries to get to that event, although only one has the cell that is slowly falling out.

So, we’ll see if that causes it to slowly correct the cell that isn’t charging all the way.

 

[wpns]

Alright, been a minute, I know.

Eh, three weeks, I've gotten distracted for way longer than that.

So, I have exchanged lots of emails with the EG4 reps, and apparently, per them, the only way to get the BMS to do a top balance is to set off the over voltage alarm, which, is 3.8v per cell. Or 60v for the battery. They said doing that briefly is fine and won’t harm the batteries. I believe only about 6 amps was going to the each battery at the time.

That's the strangest recommendation I can remember hearing, did they have a reasoning behind it, or are they just guessing at something that'll keep you busy and not bother them for a while?

So, we’ll see if that causes it to slowly correct the cell that isn’t charging all the way.

Can you watch the balance process? I have a process that makes time-lapse movies of the balancing on each of my batteries every day:

http://dotnetdotcom.net/20250719_Batt6.mp4

Cyan outline is cells that are balancing. Blue is the low cell, red would be a high cell.
The defaults for these batteries (EG4PPOFWM) is cells above 3.4 volts and delta greater than 40mv, IIRC
You can see it's trying to bring the other cells down to meet cell 10:

but of course it doesn't really spend a lot of time on it, as 40mv is easy to achieve.
Here's a typical day, it takes maybe an hour to get most of them under 40mv delta:

And the one holdout (Yellow) is still connected, so it's buffering the HV busses.
All this under automatic 'closed loop' control from the 18Kpv inverters.

 

[wpns]

The low cell is off by about 100-120mA at it’s worst during absorb phase. Once charging stops and float occurs, it settles into being about 30mA off and then that narrows as the cells discharge down to around 3.3 volts.

Just going thru this thread again, do you mean milliVOLTS above instead of mA?

 

[IAm_Not_Lost]

Just going thru this thread again, do you mean milliVOLTS above instead of mA?

Yes, mistype, sorry.

 

[wpns]

Hmm, I just read the thread over again, I wonder if you've ever done any balancing at all. You need to get at least one cell over 3.4 volts, with a delta(*) of 40mv for balancing to start, and you need to let it balance until the delta is under 40mV.

But if your pack is perfect except for one low cell, then you need a charge voltage of (SWAG) 54.6V to start bringing the other cells down to meet the one low cell, and you probably want to work your way up to 57-58 volts to get everything balanced out and fully charged (under 3.65V/cell, but somewhere in that range) and then back off to 56.5-ish volts for normal operation.

And don't worry about absorb time and absorb versus float voltage, they'll turn off their charge FETs when they've had enough.

That's what mine want in closed loop with 18Kpv, so you probably want to be in that range.

(*) EG4 never responded to my query about whether that was one cell 40mV different from any other, or 40mV delta from the average, or something different, but it's possible they can't get the OEM to tell them, so whatever...

 

[IAm_Not_Lost]

Hmm, I just read the thread over again, I wonder if you've ever done any balancing at all. You need to get at least one cell over 3.4 volts, with a delta(*) of 40mv for balancing to start, and you need to let it balance until the delta is under 40mV.

But if your pack is perfect except for one low cell, then you need a charge voltage of (SWAG) 54.6V to start bringing the other cells down to meet the one low cell, and you probably want to work your way up to 57-58 volts to get everything balanced out and fully charged (under 3.65V/cell, but somewhere in that range) and then back off to 56.5-ish volts for normal operation.

And don't worry about absorb time and absorb versus float voltage, they'll turn off their charge FETs when they've had enough.

That's what mine want in closed loop with 18Kpv, so you probably want to be in that range.

(*) EG4 never responded to my query about whether that was one cell 40mV different from any other, or 40mV delta from the average, or something different, but it's possible they can't get the OEM to tell them, so whatever...

I’ll see if this over voltage alarm triggers the BMS to start…doing it’s thing, and if not I’ll look at sitting there and playing with lower charge voltages and slowly trying to bring it up. I just work during the day and the kids always have stuff on the weekends. I might have one weekend day every two weeks I can sit there and monitor it while it’s actually getting to full charge.

 

[wpns]

I’ll see if this over voltage alarm triggers the BMS to start…doing it’s thing, and if not I’ll look at sitting there and playing with lower charge voltages and slowly trying to bring it up. I just work during the day and the kids always have stuff on the weekends. I might have one weekend day every two weeks I can sit there and monitor it while it’s actually getting to full charge.

You don't have Solar Assistant or anything like that, do you? It'll talk to your batteries with RS485 and log stuff, though I dunno how detailed it'll get...

 

[TM48]

Alright, been a minute, I know.

So, I have exchanged lots of emails with the EG4 reps, and apparently, per them, the only way to get the BMS to do a top balance is to set off the over voltage alarm, which, is 3.8v per cell. Or 60v for the battery. They said doing that briefly is fine and won’t harm the batteries. I believe only about 6 amps was going to the each battery at the time.

They had initially told me 3.7v per cell, but apparently were using outdated information. I had even told them it says in my basic manual that the over voltage alarm was listed at 3.8v.

So, I did that at their explicit instruction and got all three of my batteries to get to that event, although only one has the cell that is slowly falling out.

So, we’ll see if that causes it to slowly correct the cell that isn’t charging all the way.

I wouldn't take that to the bank. EG4 has a document that claims 100% charge is indicated when the highest cell reaches 3.7 volts. Direct observation shows that false. I have witnessed the four I have reaching 100% when the highest cell reaches just over 3.5 volts. Apparently it looks for some tail current value before indicating 100%. Typically the hi cell hits something like 3.511 and then one to two minutes later it changes from 99 to 100%. 3.8v is way too high.

 

[IAm_Not_Lost]

I wouldn't take that to the bank. EG4 has a document that claims 100% charge is indicated when the highest cell reaches 3.7 volts. Direct observation shows that false. I have witnessed the four I have reaching 100% when the highest cell reaches just over 3.5 volts. Apparently it looks for some tail current value before indicating 100%. Typically the hi cell hits something like 3.511 and then one to two minutes later it changes from 99 to 100%. 3.8v is way too high.

I agree that 3.8v is too high in any common use. The tech said that just doing that one time to create an over voltage protection event would trigger top balancing from the BMS.

 

[SunDave]

If you are ever looking for a replacement, Pytes has been solid. I have had one time where they went to sleep apparently, but after a restart, they were good to go. Two years on them now. Balance to about 25-30mV and they just do the job. No drama.

 

[IAm_Not_Lost]

If you are ever looking for a replacement, Pytes has been solid. I have had one time where they went to sleep apparently, but after a restart, they were good to go. Two years on them now. Balance to about 25-30mV and they just do the job. No drama.

I haven’t actually had any issue with these batteries from a direct functioning standpoint, and maybe I’m being prematurely paranoid, I just noticed that this one cell seemed to be falling out from the others during charging.

Maybe I’m not giving it enough time, but it’s been at least a couple of months with it sometimes upwards of 100mV less than the other cells, maybe a little more, during absorb charge, then they all slowly match up again as the battery discharges in the evening.

 

[TM48]

This is what the OEM's manual states for charge parameters:
PowerGem Plus User Manual
19
Note:
1. Each pair of power cable, its limited continuous current is 200A, if the inverter Max. work
current is more than 200A, please add power cables according to the proportion.
2.After power cables connection is OK,you’d better turn on the breaker firstly before turning
on the batteries’ SW button,then the pre-charge function is effective.
3.2.2 Battery parameter settings on the inverter
Max Charging(Bulk) Voltage: 56.5V
Absorption Voltage: 56V
Float Voltage: 55.5V
Recommend Shut Down(cut off) Voltage: 49~50V
Recommend Shut Down(cut off) SOC: 20%
Recommend Restart Voltage: 52V
Recommend Max.Charge and discharge Current: 140A*battery QTY

 

[IAm_Not_Lost]

This is what the OEM's manual states for charge parameters:
PowerGem Plus User Manual
19
Note:
1. Each pair of power cable, its limited continuous current is 200A, if the inverter Max. work
current is more than 200A, please add power cables according to the proportion.
2.After power cables connection is OK,you’d better turn on the breaker firstly before turning
on the batteries’ SW button,then the pre-charge function is effective.
3.2.2 Battery parameter settings on the inverter
Max Charging(Bulk) Voltage: 56.5V
Absorption Voltage: 56V
Float Voltage: 55.5V
Recommend Shut Down(cut off) Voltage: 49~50V
Recommend Shut Down(cut off) SOC: 20%
Recommend Restart Voltage: 52V
Recommend Max.Charge and discharge Current: 140A*battery QTY

For my Indoor wall mounts my charge parameters are a little different in my manual. But yes, for normal charging I have followed the manuals recommended voltage explicitly using my charge controllers.

 

[TM48]

For my Indoor wall mounts my charge parameters are a little different in my manual. But yes, for normal charging I have followed the manuals recommended voltage explicitly using my charge controllers.

Those parameters are straight from the actual manufacturer. Not the importer.