Batteries out of balance in 48v system

[Tatertot51804]

First off please ignore the rats nest of an install I have going on. I've only been playing with solar for about a year and it's in preparation for moving and becoming off grid so I've been experimenting with stuff to see how it's going to work for me. This wall has been redone 10 times probably lol. Once I move I plan to have a nice electrical room with everything mounted neatly and all of my wires run through panduit.

I am currently living in a 5th wheel camper and have an eg4 3000ehv inverter connected to 16 230w solar panels and 180ah of batteries. I have 3 redodo 100ah,1 amperetime and 8 valance 40ah. Every battery was fully charged with a 12v solar controller and once each group of 4 had been fully charged they were wired in parallel and charged again. After that all of the batteries were wired into their series groups. (the ampere time is in the group due to the same issue I'm having with the ampere time now)

I am having issues with some batteries being off from the others. I kind of expect it from the valance batteries. I did not capacity test those to match them. However with the redodo batteries being brand new I would expect those to all be internally balanced. The highest bulk setting I can do is 55.5v. Any higher than that and I end up with 1 battery hitting high voltage disconnect. When they finally do go into float 3 of the redodo go to 13.3 but one sits at 14.2. I swapped in an ampere time, tried again, and got the same issue. It doesn't matter what order the batteries are in when wired in series, that same battery goes high. Ive had these charging and discharging for months and it's not resolving itself. I figured after a lot of cycling the cells would balance inside each battery. I'm doing series setups because I'm poor and this allows me to buy batteries as I can afford them rather than coming up with 1000-1500 at one time.

Has anyone else had issues like this with their batteries? I do not currently have pictures of the voltages in question because the batteries are not fully charged right now.

 

[sunshine_eggo]

dismantle one string of the bank.

parallel all 4 batteries and charge to 14.4V, hold for 4 hours.

Reinstall string, dismantle other string and repeat.

Consider 48V/12V balancers to maintain balance going forward:

HA02 Battery Equalizer

HA02 battery equalizer is an energy transfer equalizer that can compensate for batteries in both directions. This is manufactured by Heltec.

srikobatteries.com

You'd need one per string.

 

[Warpspeed]

Two possible ways to do this.

As above, parallel the batteries and charge up to 14.4v
Then discharge the parallel batteries down to about half, perhaps 12.4v and then recharge.
Do this several times.
It really takes several gentle charge/discharge cycles for the four parallel batteries to share the load and get really happy together.

Second method.
Charge up the series connected string to a safe voltage, where the highest voltage battery is not excessively high as you are now doing.

Connect a discharge resistor across the highest voltage battery to bleed off some of the excessive charge.
Do this very gradually with a relatively low current, and be patient.
Perhaps one amp of discharge ? (12 or 15 ohms) and discontinue when the battery terminal voltages become more equal.

When its safe to do so, increase the charging voltage of the whole series string back up to where it should be.

I prefer the second method as its less disruptive and less work.
If the resistor is fitted to clip leads, you can just attach it to whatever cell needs to be brought down a bit at full charge.
Don't be in too much of a hurry.
If the whole process is done very gradually, it should then stay that way for a long time.

 

[Tatertot51804]

dismantle one string of the bank.

parallel all 4 batteries and charge to 14.4V, hold for 4 hours.

Reinstall string, dismantle other string and repeat.

Consider 48V/12V balancers to maintain balance going forward:

HA02 Battery Equalizer

HA02 battery equalizer is an energy transfer equalizer that can compensate for batteries in both directions. This is manufactured by Heltec.

srikobatteries.com

You'd need one per string.

I had thought about that. When I started buying these 12v batteries I didn't think I'd have issues like this. But that's how we learn I guess. I just can't spend $1500 on a server rack battery and also have to pay freight when I can get four 12v batteries for 800 shipped. Since I only have a 3000w inverter and plan to get a 2nd one when I move I'm considering aolithium server rack batteries since they are $1100 with free shipping right now

 

[Tatertot51804]

Two possible ways to do this.

As above, parallel the batteries and charge up to 14.4v
Then discharge the parallel batteries down to about half, perhaps 12.4v and then recharge.
Do this several times.
It really takes several gentle charge/discharge cycles for the four parallel batteries to share the load and get really happy together.

Second method.
Charge up the series connected string to a safe voltage, where the highest voltage battery is not excessively high as you are now doing.

Connect a discharge resistor across the highest voltage battery to bleed off some of the excessive charge.
Do this very gradually with a relatively low current, and be patient.
Perhaps one amp of discharge ? (12 or 15 ohms) and discontinue when the battery terminal voltages become more equal.

When its safe to do so, increase the charging voltage of the whole series string back up to where it should be.

I prefer the second method as its less disruptive and less work.
If the resistor is fitted to clip leads, you can just attach it to whatever cell needs to be brought down a bit at full charge.
Don't be in too much of a hurry.
If the whole process is done very gradually, it should then stay that way for a long time.

I have actually used a load resister before to drain the batteries down. I've even connected a 12v inverter to one and run a box fan. I can get the voltages close but as soon as they charge back up they are out of whack again

 

[ksmithaz1]

I have an 80's mix tape of soft music. Maybe if you played it for the batteries. I could send it to you... ?

 

[Warpspeed]

I have actually used a load resister before to drain the batteries down. I've even connected a 12v inverter to one and run a box fan. I can get the voltages close but as soon as they charge back up they are out of whack again

If you do the discharge very slowly (at a very low rate) and maybe repeat the process several times it should eventually pull down the higher voltage battery sufficiently.
Its mostly about being very patient.