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EG4 batteries not charging to 100%

C

ChuckHomeLab

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Apr 20, 2022
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My batteries SOC seem to be getting more and more out of sync. The voltages amongst the batteries appears to be the same. But the SOC is different between all of them. How can I get the SOC reading to be more accurate. I would think all the batteries should be within 1% of each other on the SOC.
Can the SOC rating be based off the battery voltage? With current settings, the battery is stopped charging at these SOC%.
1712009015199.png
Do I need to adjust any of these settings? Should my float charge be higher?
1712011424498.png
 
Floating at 54v (3.375v pc) isn't going to get you a full charge.
Unless you can float for a few days. And, that will only get you to maybe 98%.
Not to mention that you aren't getting any useful cell balancing. Except for the short time that absorption is maxed out.
I would set float to at least 55.2v , if you can float for several hours each day.
Higher, if not.
 
ChuckHomeLab said:
My batteries SOC seem to be getting more and more out of sync. The voltages amongst the batteries appears to be the same. But the SOC is different between all of them. How can I get the SOC reading to be more accurate. I would think all the batteries should be within 1% of each other on the SOC.
Can the SOC rating be based off the battery voltage?
Click to expand...
You have multiple batteries in a pack. The SOC needs to be reset by charging the entire pack until they all reset to 100%. The SOC is based off a coulomb counter and obviously there is some drift. Since each battery is in parallel with each other, I would expect the voltages to be the same. Clearly within batteries the cells in series do have differences and more time at CV (Absorb) may correct that.
 
The SOC reported by each of the batteries - never seems very accurate.
They are relying on the BMS to calculate the SOC but the BMS doesn't measure low currents well, (or at all) and it seems the BMS SOC is only accurate once it triggers full 100%,
I had similar experience, and nearly lost my mind trying to get all the packs to 'agree' - got a Victron Smart Shunt.
The shunt accurately reports overall SOC, and I don't dwell on what each pack "thinks" the SOC is, they are all the same voltage and the BMS's keep the cells all in line, I call it good.
 
Ampster said:
You have multiple batteries in a pack. The SOC needs to be reset by charging the entire pack until they all reset to 100%. The SOC is based off a coulomb counter and obviously there is some drift. Since each battery is in parallel with each other, I would expect the voltages to be the same. Clearly within batteries the cells in series do have differences and more time at CV (Absorb) may correct that.
Click to expand...
How do I get them to 100%? It appears maybe the bms is cutting off the charging because it thinks they're charged?? I have 3 batteries. Do I need to turn 2 of them off and charge them 1 at a time? Raise the float voltage?
 
ChuckHomeLab said:
It appears maybe the bms is cutting off the charging because it thinks they're charged??
Click to expand...
If that is the case the one with the lower SOC would be getting the charge and resetting to 100%. If raising the Absorb voltage doesn't do it then maybe the approach of @OffGridForGood is best. Either ignore the differences or buy a shunt with a good coulomb counter.
 
Last edited:
Roughly the same here. 3.55V charge and 3.45V float per cell.
Works very well.
Btw. the only time your SOC will be correct is every time your batteries are really full/100% and the SOC resets itself ^^.
I just look at the voltage of each cell and just ignore the listed SOC...3 different BMSs and they all list the SOC different. After a while you will have these numbers memorized LOL

Table:

VoltvsSOC.jpeg
 
LydMekk said:
After a while you will have these numbers memorized
Click to expand...
The only thing I would add to that chart is that once you have charged to whatever voltage per cell you choose, they will settle at 3.33-3.34 volts per cell and retain the percentage charge which they were charged to. The difference between charging voltage and the voltage thye settle at is just surface charge and does not represent self discharge or lost capacity.
 
Last edited:
Yup
Voltage versus SOC is different. Depending on whether charging, discharging, or resting.
Think of the battery as a wagon. Being pulled in either direction by a stretchy rope.
The surface Voltage is represented by you pulling the rope. And the actual SOC of the battery is the wagon following behind of the stretched rope.
 
So batteries have charged and this is what I see now.
1712088210241.png
Is this good? I noticed pack #3 voltage is different.
 
ChuckHomeLab said:
So batteries have charged and this is what I see now.
View attachment 206592
Is this good? I noticed pack #3 voltage is different.
Click to expand...

If you're dealing with LifePower4 batteries, I would recommend they're updated to firmware version v3.37. Given the significant voltage differential, isolating that particular battery to attempt charging it to within 0.5v of the other two. Additionally, verifying with a multimeter that the voltage matches the reported value.
 
ok, Ill look into the firmware update. I think pack #3 reached full capacity first, so it had shut off charging and was settling down to its resting value. Pack #1 and 2, had just shut off charging when I took that screen shot, so they were showing surface charge. Now that they have been sitting a few minutes the voltage is coming down on pack 1 and 2.
1712088801064.png
 
Last edited:
Looking at the charts.
I saw the battery SOC jumped from 93% to 102% in 10 seconds.
The voltage went from 55 to 58 in about 7 minutes.
1712090237417.png
 
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