Can't charge over 27v with EG4 LLv2 batteries

[GreenMtnScout]

Hey Everyone,
Newbie here, thanks in advance for any help you can provide.

I recently installed 6 EG4 LLv2 batteries(coming from lead acid and still running a 24v system). I have a Trace SW4024 inverter that's worked great for over 20 years. I never had any issue charging the lead acid batteries up to 30 volts on an equalization run. With these new batteries, I'm not charging over 27 volts, on generator or solar. The automatic generator start is working, but it almost immediately goes into float mode and then shuts down 20 minutes later(at the most). Manually running the generator will bring the voltage up to 27 or 27.1, and it'll stay at that voltage for the remainder of the time it's running. I'll have around 120 amps coming in, so each battery is getting around 20 amps for charging. Even after an eight or nine hour run, the batteries won't be fully charged. I've ordered two of these chargers(https://signaturesolar.com/eg4-battery-charger-24v-35a-1/) to plug into the system and will use them to supplement the generator(which is a 12kw kohler wired for 120).

I've talked to signature solar and have received conflicting information. The last tech I talked to said this was normal behavior. Previous techs wanted me to set the charge voltage to 30 to try to reset the BMS, but since I can't get past 27 volts, that wasn't going to happen.

I feel like the batteries are somehow the limiting factor in the charging process, but I'm not sure how to correct it. I can get into the BMS and things seem to be normal there(no errors are being flagged).

I have the bulk charge setting at 28.1 with no absorption time. I have tried adding some time to the absorption, but since I'm not getting to 28.1, it's not doing anything. Float voltage is set to 27.1. That's also set to 0 hours but has been changed to 2 hours(I'm concerned with overcharging them) with no effect. I've set that as high as 28.1, and they still won't charge past the 27.1.

Here are my charge settings:
Bulk/absorption - 28.1 volts for 0 hours
Float - 27.2 volts for 0 hours
Equalization - 27.2 for 0 hours(this is set only because I have to some type of setting)

Any advice/insights will be appreciated.

Thanks.
Justin

 

[sunshine_eggo]

Link #2 in my signature.

When you are observing 27.0-27.1V, what current is flowing?

Have you checked for a voltage discrepancy between the battery AT the terminals and the battery cable connection AT the inverter vs. what the inverter is reporting?

Assuming you have no communication between the batteries and the Trace, the only way the batteries can prevent charging is if there's BMS charge protection engaged. This will force the batteries to accept 0A charge.

 

[GreenMtnScout]

Hey sunshine_eggo,
The generator will be putting out a consistent 120 amps, but the voltage won't go above 27. When looking at the voltage, I'm looking at the batteries themselves, a victron smart shunt(which is running solar assistant), and a trimetric that's been in place since the original installation. I also have the two outback charge controllers that show the voltage. All of these devices are within a couple hundreths of each other and all 6 batteries match each other in volts and SoC.

I've put a voltmeter on each battery and isolated each battery to make sure they're reading accurately. There is no communication between the inverter and the batteries.

Thanks.
Justin

 

[sunshine_eggo]

That current has to go somewhere. When new batteries are received, they must legally be at no more than 30% SoC, but most end up in the 30-50% range. That means you have at least 600Ah to input into those batteries.

LFP charging takes on almost all of its charge below 27.6V (3.45V/cell), so...

1. If you are showing 120A, and you're confident in that number AND
2. voltage is under 28.8V AND
3. batteries/connections aren't getting warm...

Keep charging.

This is a very common "symptom" with folks transitioning from lead to LFP... you're used to spending hours at absorption where with LFP, it's rare you spend more than about 15-30 minutes AND most of the charge is taken on below 3.45V/cell (27.6V).

 

[Partimewages]

Don't be tempted to turn the voltage up.
Bad things happen when you're not watching!

 

[GreenMtnScout]

That current has to go somewhere. When new batteries are received, they must legally be at no more than 30% SoC, but most end up in the 30-50% range. That means you have at least 600Ah to input into those batteries.

LFP charging takes on almost all of its charge below 27.6V (3.45V/cell), so...

1. If you are showing 120A, and you're confident in that number AND
2. voltage is under 28.8V AND
3. batteries/connections aren't getting warm...

Keep charging.

This is a very common "symptom" with folks transitioning from lead to LFP... you're used to spending hours at absorption where with LFP, it's rare you spend more than about 15-30 minutes AND most of the charge is taken on below 3.45V/cell (27.6V).

Hey sunshine_eggo,
Thanks for the response. Do you see an issue with adding those two 35 amp chargers to the mix and running them with the generator? It would put me up to between 30 and 35 amps per battery. EG4 says they can take up to 50 amps apiece.

You're saying that if I'm able to keep charging, I'll push past that 27 volts and get up into the 28.1 range before backing down to the 27.1 float range?

Thanks.
Justin

 

[GreenMtnScout]

Don't be tempted to turn the voltage up.
Bad things happen when you're not watching!

Hey Parttimewages,
Are you thinking I shouldn't expect to see 28.1 volts?

Thanks.
Justin

 

[Tomthumb62]

You're saying that if I'm able to keep charging, I'll push past that 27 volts and get up into the 28.1 range

Also keep in mind that most of the charge/discharge curve is extremely flat for these lifepo4 batteries. During charging It will stay “stuck” for a very long time and it’s not until the last little bit that the voltage starts climbing very quickly. Unlike lead acid which steadily (more or less) climbs throughout the bulk charge phase.

 

[Partimewages]

No reason to really go above 3.45 volts per cell.

 

[sunshine_eggo]

Hey sunshine_eggo,
Thanks for the response. Do you see an issue with adding those two 35 amp chargers to the mix and running them with the generator? It would put me up to between 30 and 35 amps per battery. EG4 says they can take up to 50 amps apiece.

As long as you don't exceed the charge spec for any individual battery, should be fine.

You're saying that if I'm able to keep charging, I'll push past that 27 volts and get up into the 28.1 range before backing down to the 27.1 float range?

Yes, but if the batteries are imbalanced, the BMS may cut off before you get to 28.1. I would try 27.6V first and see how that goes.

 

[GreenMtnScout]

Thanks for the help everyone. I appreciate it.