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Old 05-25-2023, 03:11 AM   #1
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Default SOK 206AH battery installation

I replaced two 100AH Battleborn batteries with two SOK 206AH batteries. The footprint is not the same and they are a little taller but I had the room.

The Battleborns arrived fully charged 6 years ago. The SOK batteries arrived depleted. It takes a long time to charge 412AH from a generator. SOK would like the charge rate to be 40 amps per battery. I charged at 90 amps total for almost four hours by generator to a charged voltage of 14.3 volts.

The Battleborn weight was 28lbs each. The SOK spec is 48lbs each.

I paralleled them with two remaining healthy 100AH Battle born batteries. Each bank has it’s own battery monitor so I will let you know how that works. If it does not work I can separate them but I expect it to work. I’m expecting a total charge rate of 150 amps. Will let you know what it turns out to be when I get back on the road in July.

The second battery compartment cannot handle two SOK 206AH batteries.

The next job is to install the Velit high altitude furnace. I’ll test it at 10,000 ft in August. The Webasto works so very well below 5000ft I hate to take it out. It won’t last a week at 10,000ft.
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Old 05-25-2023, 12:05 PM   #2
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We hope to install our VeLit when we get home from the current trip in June.
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Old 05-25-2023, 12:34 PM   #3
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Originally Posted by hbn7hj View Post
I replaced two 100AH Battleborn batteries with two SOK 206AH batteries. The footprint is not the same and they are a little taller but I had the room.

The Battleborns arrived fully charged 6 years ago. The SOK batteries arrived depleted. It takes a long time to charge 412AH from a generator. SOK would like the charge rate to be 40 amps per battery. I charged at 90 amps total for almost four hours by generator to a charged voltage of 14.3 volts.

The Battleborn weight was 28lbs each. The SOK spec is 48lbs each.

I paralleled them with two remaining healthy 100AH Battle born batteries. Each bank has itís own battery monitor so I will let you know how that works. If it does not work I can separate them but I expect it to work. Iím expecting a total charge rate of 150 amps. Will let you know what it turns out to be when I get back on the road in July.

The second battery compartment cannot handle two SOK 206AH batteries.

The next job is to install the Velit high altitude furnace. Iíll test it at 10,000 ft in August. The Webasto works so very well below 5000ft I hate to take it out. It wonít last a week at 10,000ft.

Yep, that should be interesting. The SOK look to be very good batteries but with really low charge rates for being 206ah. It appears to be because SOK uses the same BMS in the 100 and 206ah batteries so the BMS is undersized in the larger battery.


There is currently a bit of confusion on Current Connection site related to charge rates when comparing to the SOK site. All the batteries used to 40 recommended and 50 max charge rate, but now the 206ah batteries, some anyway, say they are 70 max charge rate on the SOK site. The pix on site show 50 on the batteries however. On the Current Connection site they have a pic of the alleged new Bluetooth BMS for the 100ah battery and it says 70 max on it. My guess it the Bluetooth BMS is 70 amps and the non Bluetooth one is still 50 amps.


If you got the steel cased batteries, you can open them up and see the BMS and it will say how much the ratings are. The 206ah battery cells should certainly handle 70 max if the the 100ah can handle 50.


The non bottom basement brands of batteries seem to be going to lower charge rates very quickly so the advantage of high rate charging is going away. .4 to .5C rates are getting to be the norm and good AGMs can be charged at .4C pretty easily. The advantage now with lithium charging is getting to be only in the top 15-20% of charging where AGM acceptance drops quickly.
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Old 06-01-2023, 06:50 PM   #4
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You parallel connected two 100Ah batteries with two 206AH batteries? I always thought that was bad juju.
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Old 06-01-2023, 07:34 PM   #5
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We will see. Each bank has it’s own battery monitor. I’ll let you know how or if it works.

I expect it to work but if it doesn’t I can pop a circuit breaker and use each bank separately.
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Old 06-01-2023, 07:40 PM   #6
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My guess is you'll get 400Ah out of the combined four batteries. The combined pair of 100AH batteries will produce 200Ah and the combined pair of 206Ah batteries will also produce 200Ah (vice 412Ah) due to being limited by the lower-capacity pair of the paralleled 100Ah batteries. I'm eager to see your results.
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Old 06-01-2023, 07:43 PM   #7
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You parallel connected two 100Ah batteries with two 206AH batteries? I always thought that was bad juju.

I think the connection of multiple lithium batteries is more related to them being in series, not parallel. Several have started recommending add on battery balancers for series use, like are used with lead acid batteries.



IIRC it has something to do with the ability of the auto cell balancing to work correctly.
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Old 06-01-2023, 07:47 PM   #8
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I think the connection of multiple lithium batteries is more related to them being in series, not parallel. Several have started recommending add on battery balancers for series use, like are used with lead acid batteries.

IIRC it has something to do with the ability of the auto cell balancing to work correctly.
I don't claim to be correct, but I suggest that the auto cell balancing ability of LiFeP04 cells is exactly what will cause the pair of 206Ah batteries to limit their output to a combined 200Ah if paralleled with the pair of 100Ah batteries. Looking forward to the OP's observations.
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Old 06-01-2023, 07:58 PM   #9
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I’ll let you know next month. Fully charged there is no difference. What each bank looks like after withdrawing 100AH is what will be interesting. Also how they charge.

I have the instrumentation to observe. Can you withdraw 500AH with them combined? I don’t know but I expect so.
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Old 06-25-2023, 11:22 PM   #10
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This is the first data on dissimilar battery banks in size, brand, and age wired in parallel. I think it is partly a fluke for them both to be at 84% but does appear it will work

The 84 is percent charge of each bank after a bit of TV and Starlink.

The other picture shows the charge rate in amps. 400AH at the top, 200AH bank at the bottom. They didn’t charge in parallel. The old Battleborns absorbed 47 amps rather than 37 amps but slowed down nearing full charge as defined by 14.3 volts. Battleborns reached 100% when the SOKs were at 97%. Reducing the charge rate brought them both to 100%.

Total charge rate was 112 amps, far short of my goal of 200 amps but better than the 80-90 amps I was seeing with the failing Battleborns.

We will keep working with it. Right now it appears to work but if it doesn’t I’ll let you know.
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Old 06-27-2023, 12:23 AM   #11
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Today’s readings:
400AH Bank 82% SOC
200AH Bank 79% SOC

The Battleborn batteries tend to provide a little more current than they should compared to the SOK batteries. They also charge a little bit better. I suppose that means they have a little less internal resistance.

Will not charge this evening and see what tomorrow shows. Loads are Starlink 24/7, furnace, and lights with 200 watts tree shaded solar.

Solar today was breakeven with sunrise SOC the same as sunset SOC.
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Old 06-27-2023, 02:21 PM   #12
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This mornings readings:
400AH 69% SOC
200AH 67% SOC
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Old 06-28-2023, 02:50 AM   #13
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Tuesday evening;
400AH 66% SOC
200AH 65% SOC

We will take a last reading tomorrow. Looks to me like all is well to run the batteries this way.
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Old 06-28-2023, 04:00 PM   #14
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Wednesday morning:
400AH 54% SOC
200AH 53% SOC

Good enough. No need to separate the two battery banks.
Now to charge them with 300AH. That will take a while.
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Old 06-29-2023, 02:42 PM   #15
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This is an interesting set of data.

I've seen other installations with multiple battery brands/BMS brands that seem to behave like yours.
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Old 06-29-2023, 03:09 PM   #16
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It didn’t do as well on the charging cycle. After 2 1/2 hours of charging:
400AH 86%
200AH 99%

The Battleborn batteries accept charge better, Total charge rate was 115 amps. I didn’t continue but it did not reach my 14.3 volt cut off. The higher state of charge battery slowed it’s charging rate so it might level itself out. Anyhow, I’ll keep them combined.
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Old 06-29-2023, 03:33 PM   #17
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It didnít do as well on the charging cycle. After 2 1/2 hours of charging:
400AH 86%
200AH 99%

The Battleborn batteries accept charge better, Total charge rate was 115 amps. I didnít continue but it did not reach my 14.3 volt cut off. The higher state of charge battery slowed itís charging rate so it might level itself out. Anyhow, Iíll keep them combined.

There is one thing that hasn't been mentioned, that has made a lot of this kind of stuff harder recently.


Many of the brands seem to be going to automatic top balancing, some like SOK want it on every recharge cycle if possible. The auto balancing is not initiated until the charged voltage hits 14.4v in many cases like SOK and maybe Battleborn also.


I have not been able to get much of an answer on just how far off the voltages of the individual cells can be before it is an issue as it would make sense to stop the charging at the lower voltages than 14.4-14.6v that the balancing takes. We have plenty about how going all the way to 14.6 even can shorten battery life lately and that 13.8-14.0 v is a good place to charge to. But it is not mentioned about balancing in those lower voltage recommendations.


I have a set of the SOK batteries in the 206ah size here currently and have been testing to see how the auto balancing works and how much it changes the cell imbalance. SOK says to charge the 14.6v every time and hold for 15 minutes at the 14.6v.


SOK sets the high cutoff limit at 14.7v and if any cell gets to that voltage the charging is cut off. All they are doing to balance is charging until one cell gets that high and it shuts down charging. The cells then appear to separate from each other and individually connect to the highest cell or cells(?) so they can put a bit of charge on the others. When the voltage of the high cell gets below about 3.570v the charging starts again and all charge together for only a few seconds until the high cell again causes a shutdown. Rinse/repeat until the full 14.6v charging is discontinued. It can drive a smart charger nuts as it will see no battery reference for the shutdown time and it will restart most times in float because of the high voltage. I don't know how the smart lithium chargers do it, though, but they do mention that only a few chargers like Victron and Progressive Dynamics will start charging to wake up a shut down battery so those would probably be fine. My bench charger where I am testing is Blue Sea 40 amp unit and it works most of the time but will eventually just stop reconnecting. I expect our Magnum will not be able to handle it unless I put it two stage/rebulk mode which is claimed gets rid of the voltage requirement check but might still not like no battery reference times and lock out.


Are there any plans in place to balance any or all of your batteries?
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Old 06-29-2023, 04:21 PM   #18
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Are there any plans in place to balance any or all of your batteries?
Iíll get them all to 100% at 14.3 volts with another charge cycle but nothing beyond that. I can get to 14.6 volts but donít do it anymore.
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Old 06-29-2023, 04:34 PM   #19
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Iíll get them all to 100% at 14.3 volts with another charge cycle but nothing beyond that. I can get to 14.6 volts but donít do it anymore.

Do any of your batteries have the ability to show you the individual cell voltages?
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Old 06-29-2023, 08:43 PM   #20
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Do any of your batteries have the ability to show you the individual cell voltages?
No.

I thought BMS’s keyed off voltages but the 200AH bank stopped charging at 13.8 volts. I left the two banks combined and let the 400AH bank continue to 98%. Never did reach 14.3 volts. Next charge I’ll take it to 14.3 volts and set both banks to 100%
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