Major balance issue with SoK 206Ah * 2

Dumbyellowdog · Tuesday at 2:41 PM

Hi all, I was seeing what I thought was big degradation on two non-BT SoK 206Ah 12V batteries that I have been running for 2.5 years now in a travel trailer with Victron Multiplus 3000 and a Victron 100/30 MPPT. Both were set to SoK recommended settings (14.6 absorb / 13.8 float).

It turns out the batteries drifted badly out of balance:

Battery 1:
Rundown Ah: 166Ah
Cell voltages:
3.49
3.52
3.32
3.32

Battery 2:
Rundown Ah: 172Ah
3.51
3.50
3.25
3.51

Here's my Q: I was unable to get them back in balance by following SoK's recommendation: Absorb/float them at 14.6 for 2-3 days. I added a couple of active balancers to them. Is anyone else having this experience using LFP batteries after a few years? Are people "top balancing" them at 14.6 every few months to keep them from drifting?

Suijkerbuijk · Tuesday at 2:59 PM

I set my float on 13.8 volts and leave it.
This way my battery always are balance on the top side.

You use lose cells .
So i will set alle cells on parallel so i have big 3.65 volt battery
Charge it and leave the battery for a time.
If you can set your systeem off line do this

If not than i will discharge the cells that are high with a light to pull it down.

740GLE · Tuesday at 4:08 PM

Odd that cells 1 and 2 in both units are running high.

What active balancer did you add?

With a delta of .25v, 250mv a 5a active balancer would still take a while to bring these back into check.

time2roll · Tuesday at 4:32 PM

At 14.60 there will be a cell (or more) that go over 3.650 with that out of balance condition.
Consider reducing the float so the high cell is 3.500 to 3.650 and let the active balancers work. Adjusting the voltage higher as things line up.
Probably take a week+. Please give updates.

Dumbyellowdog · Tuesday at 4:51 PM

I am using this one, 5A but I haven’t seen any more than 1A on any individual lead, yet.

https://a.co/d/bmQN7rY

Anyone been running SoK for 2.5 years who has seen any balance issues?

time2roll · Tuesday at 5:34 PM

Dumbyellowdog said:
I am using this one, 5A but I haven’t seen any more than 1A on any individual lead, yet.

1 amp would indicate close to 100 mV spread. Could take close to 500 mV spread to get the full 5 amps. Yes the spec is a bit misleading.
Although I see listed above 200 and 250 mV I would have expected more. Anyway give it time as the progression will slow as they get closer.

740GLE · Tuesday at 6:54 PM

Time is all you need to bring those back.

Dumbyellowdog · Tuesday at 7:45 PM

Time and the active balancers, but here’s my concern: if I relied on the internal BMS only, would I be able to recover such an imbalance?

The reason I ask is I’m building a DIY solar small boat soon, and was considering the sealed marine grade SoK or similar. But I wouldn’t be able to crack open the case so easily and add an active balance lead…

Alkaline · Tuesday at 9:29 PM

Dumbyellowdog said:
Hi all, I was seeing what I thought was big degradation on two non-BT SoK 206Ah 12V batteries that I have been running for 2.5 years now in a travel trailer with Victron Multiplus 3000 and a Victron 100/30 MPPT. Both were set to SoK recommended settings (14.6 absorb / 13.8 float).

It turns out the batteries drifted badly out of balance:

Battery 1:
Rundown Ah: 166Ah
Cell voltages:
3.49
3.52
3.32
3.32

Battery 2:
Rundown Ah: 172Ah
3.51
3.50
3.25
3.51

Here's my Q: I was unable to get them back in balance by following SoK's recommendation: Absorb/float them at 14.6 for 2-3 days. I added a couple of active balancers to them. Is anyone else having this experience using LFP batteries after a few years? Are people "top balancing" them at 14.6 every few months to keep them from drifting?

https://www.amazon.com/Heltecbms-Lifepo4-Balancer-Equalizer-Capacitor/dp/B0D46SP1XY/

then get a small switch like this https://www.amazon.com/TWTADE-Solder-Rocker-Switch-KCD1-X-F/dp/B07XD8J2PL so you can turn it on/off as needed.

After a few cycles they will balance back, what you are seeing happens and it happens even worse on budget batteries like chins. Be happy you can at least open the sok to fix it.

Bananaman321 · Tuesday at 9:43 PM

Dumbyellowdog said:
Hi all, I was seeing what I thought was big degradation on two non-BT SoK 206Ah 12V batteries that I have been running for 2.5 years now in a travel trailer with Victron Multiplus 3000 and a Victron 100/30 MPPT. Both were set to SoK recommended settings (14.6 absorb / 13.8 float).

It turns out the batteries drifted badly out of balance:

Battery 1:
Rundown Ah: 166Ah
Cell voltages:
3.49
3.52
3.32
3.32

Battery 2:
Rundown Ah: 172Ah
3.51
3.50
3.25
3.51

Here's my Q: I was unable to get them back in balance by following SoK's recommendation: Absorb/float them at 14.6 for 2-3 days. I added a couple of active balancers to them. Is anyone else having this experience using LFP batteries after a few years? Are people "top balancing" them at 14.6 every few months to keep them from drifting?

Dumbyellowdog · Tuesday at 9:45 PM

Alkaline said:
https://www.amazon.com/Heltecbms-Lifepo4-Balancer-Equalizer-Capacitor/dp/B0D46SP1XY/

then get a small switch like this https://www.amazon.com/TWTADE-Solder-Rocker-Switch-KCD1-X-F/dp/B07XD8J2PL so you can turn it on/off as needed.

After a few cycles they will balance back, what you are seeing happens and it happens even worse on budget batteries like chins. Be happy you can at least open the sok to fix it.

Yeah, I’ve basically done exactly that. But what if I want marine grade batteries in a boat? Sealed etc. Any good sealed batteries with active BMS?

Alkaline · Tuesday at 9:52 PM

sfk has a 300 with active balancer and a switch on the outside: https://www.sunfunkits.com/product/...r-dual-heating-lithium-iron-phosphate-battery
you can turn it on / off or have it only run when the battery is near charging. It is plastic so maybe good for marine.

Another company that has active balance is big beard battery:

Big Beard Battery 12-Volt 300AH 3600 Watt Lithium Battery | Big Beard Batteries

Experience a new era in energy storage with the Big Beard Battery featuring an Internal Battery Management System (BMS) equipped with cutting-edge Active Balancing technology. This powerhouse of a battery goes beyond the ordinary, delivering exceptional performance, reliability, and a host of...

www.bigbeardbatteries.com

but it is metal similar to the sok.

Sam Cho TX · Tuesday at 9:59 PM

This manual explains the switch sfk has:
https://diysolarforum.com/threads/major-balance-issue-with-sok-206ah-2.87787/#post-1156811 page 15 explains it.

So the issue with the balancer is that if stays on it can cause the battery to go out of balance so you want to only run it when you are charging and then turn it off when its done. This is why the sfk switch is nifty as it turns off after a certain voltage.

other option is once every 6 months turn it on just to balance and then you should be good to go.

Suijkerbuijk · Wednesday at 12:51 AM

Dumbyellowdog said:
Yeah, I’ve basically done exactly that. But what if I want marine grade batteries in a boat? Sealed etc. Any good sealed batteries with active BMS?

I use marine grade lifepo4.
Problem that even those can have unbalanced cells
Those battery are shipped not full charge and have to balance them to.

This problem will always be.

KITROBASKIN · Wednesday at 10:06 AM

We have a pair of 12V 100Ah marine (plastic case) and I can tell you it is not difficult to open them up. Furthermore, the BMS should be handling top balance. Don’t exceed 3.6 per cell. It is not needed and not good long term. Your BMS may not be working well.

Where did you purchase? Currentconnected is widely recommended here on diysolarforum. Co-owner is active here.

SOK video replacing BMS in marine case:

Dumbyellowdog · Wednesday at 10:06 AM

Will it “always be” though? If someone made a sealed marine grade battery with a JK-BMS, I’d be good to go and not have to deal with cracking open the battery, right?

12V LiFePO4 Battery Pack with JK BMS 2A Active Balance

12V 200Ah/280Ah LiFePO4 Battery Pack – a compact and efficient energy solution. Engineered with advanced lithium iron phosphate technology, this battery pack ensures reliable and long-lasting performance for your RV and EV. As a backup power storage system,experience the convenience of a robust...

eelbattery.myshopify.com

Dumbyellowdog · Wednesday at 10:13 AM

KITROBASKIN said:
We have a pair of 12V 100Ah marine (plastic case) and I can tell you it is not difficult to open them up. Furthermore, the BMS should be handling top balance. Don’t exceed 3.6 per cell. It is not needed and not good long term. Your BMS may not be working well.

Where did you purchase? Currentconnected is widely recommended here on diysolarforum. Co-owner is active here.

SOK video replacing BMS in marine case:

Oh, that’s awesome I didn’t realize the SoK marine grade were also user serviceable. That’s probably what I’ll get, then.

I got my non-BT SoK batteries direct from SoK in Dec 2021. I was looking for a better balancing solution because I wasn’t sure if anyone has success running LifePo4 for multiple years and not having balance drift issues. I imagine a JK BMS would solve it, but it doesn’t appear any of the major brands have anything like that in a turn key battery yet.

KITROBASKIN · Wednesday at 10:34 AM

There have been reports in the past of not the best communications with SOK, but have you communicated with them about this? A person named Min was who I traded emails, but it must be mentioned that Dexter, from Current Connected, was on my side and made it happen just with a couple, brief emails. Then I was very polite with Min, even after delays honoring a warranty issue.

Dumbyellowdog · Wednesday at 11:13 AM

KITROBASKIN said:
There have been reports in the past of not the best communications with SOK, but have you communicated with them about this? A person named Min was who I traded emails, but it must be mentioned that Dexter, from Current Connected, was on my side and made it happen just with a couple, brief emails. Then I was very polite with Min, even after delays honoring a warranty issue.

Yes, I talked to Min and others on the SoK battery group on FB. They suggested maxing out charge to 14.6 for a few days to solve, but that did not actually solve it. Before top balance it was 164Ah, after 3 days of 14.6 it was 172Ah. So my impression is: top balance does do something with the BMS I have, but extremely slowly. The active balancer perfectly balanced the second battery from 166Ah to 206Ah (rated capacity) in 36 hours.

So maybe the passive BMS has gotten dramatically faster in the last few years, but I haven’t heard anyone claiming that is so, yet.

740GLE · Wednesday at 12:17 PM

Dumbyellowdog said:
Yeah, I’ve basically done exactly that. But what if I want marine grade batteries in a boat? Sealed etc. Any good sealed batteries with active BMS?

I’d def want some sort of grommet preventing that steel case touching the balance leads.

KITROBASKIN · Thursday at 9:00 AM

Not sure I would classify SOK marine cases as ‘sealed’. Yes there is a gasket but it does not seem to be sealed as much as the EPOCH trolling batteries we have (which are fitted with a vent valve).

After replacing the SOK BMS, the cells were balanced sufficiently within a few days (this is what I remember).

Major balance issue with SoK 206Ah * 2

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