Equalizing bank of eg4 batteries

[Texican]

I have been using a bank of 6 eg4 lifepower batts for about 50 days now and have had the equalization settings on the lv6548 inverters in the default setting which is disabled for all equalization.

the charging for today is done and the SOC s are varied from 93.4 up to 100.4 percent SOC across the 6 batteries

my charge settings are bulk 56.0 and floating 55.0v

should I enable equalization ? and if so, what settings would be best ? would that likely fix the issue ?

thanks

 

[BentleyJ]

Battery equilzation is for Lead Acid Chemistry ONLY. It helps de-suphate the plates and has nothing to do with parallel batteries being a different States of Charge. It sounds like you may need to increase your Absorption time. As long as the voltage stays constant the full batteries will not overcharge but the under charged ones will have time to catch up.

 

[Texican]

thanks, I dont hink my lv6548 have an absortion time setting, I will have to check

 

[wayne530]

@Texican I've noticed something similar in my bank of 6 EG4 LiFePower4 batteries, though not quite as extreme as what you're seeing. Over time, I find that one pack (maybe 2) will show a significantly different SoC % at the same voltage level. I found that disconnecting the pack and top balancing it with the EG4 charger, then reconnecting it to the bank when its voltage equalizes with the bank voltage will correct the issue. It's tedious and I'm told by SS/EG4 that it's normal and "won't affect the performance of the pack/bank."

Just curious if you've perhaps found a different way to address the SoC % differences across your bank?

 

[jberger]

Can you show us your wiring for those batteries?
I've had 3 of them connected for months, but I'm not seeing that kind of drift.

I'd suspect the wiring or connections are causing resistance differences and discharging them at different rates.

 

[wayne530]

Can you show us your wiring for those batteries?
I've had 3 of them connected for months, but I'm not seeing that kind of drift.

I'd suspect the wiring or connections are causing resistance differences and discharging them at different rates.

I'm not sure about @Texican but I'm using the EG4 cabinet which has two copper bus bars running the height of the cabinet. Batteries are all connected using the same length (~12") of #4 copper welding cable and torqued according to the spec for the bus bar and the battery terminals. Inverters (2x) are directly connected to the cabinet bus bars in a diagonal configuration. There is a 200A class T fuse between the positive bus bar and positive battery terminal on both inverters. I initially had troubles with pack #2, but now it's in pack #6:


Pack #2 started out with a small difference in SoC % as well, but over time it will continue to drift. When I pulled pack #2 to top balance it, it was showing 92% SoC at the same voltage level as all other packs, which were showing 100% SoC. Since top balancing it, it hasn't had an issue. Pack #1 is at the top of the cabinet and Pack #6 is at the bottom.

 

[Koldsimer]

Do not do an equalization.

Increase bulk/absorb to 57v. I'd keep float at 57 until the soc is consistent.

Set absorb for an hour and see if the cells don't eventually balance out. Watch out for runaway cells, but i don't think 57v will be problematic.

IMO, 56v is not enough to top balance cells properly and that would explain your soc differences from pack to pack.

My eg4's did the same thing at 56.5. At 57v, everything is peachy and my packs are always within 1% of each other.

 

[wayne530]

Do not do an equalization.

Increase bulk/absorb to 57v. I'd keep float at 57 until the soc is consistent.

Set absorb for an hour and see if the cells don't eventually balance out. Watch out for runaway cells, but i don't think 57v will be problematic.

IMO, 56v is not enough to top balance cells properly and that would explain your soc differences from pack to pack.

My eg4's did the same thing at 56.5. At 57v, everything is peachy and my packs are always within 1% of each other.

Sure, I will give it a try. I'm conducting another experiment at the moment to try and better understand why Solar Assistant is reporting that battery charged is more than 2.5x battery discharged at bulk 56.4v, float 55v. I'm using LV6548 inverters and I don't believe there is an absorb function, but I could be wrong about that.

 

[Texican]

Do not do an equalization.

Increase bulk/absorb to 57v. I'd keep float at 57 until the soc is consistent.

Set absorb for an hour and see if the cells don't eventually balance out. Watch out for runaway cells, but i don't think 57v will be problematic.

IMO, 56v is not enough to top balance cells properly and that would explain your soc differences from pack to pack.

My eg4's did the same thing at 56.5. At 57v, everything is peachy and my packs are always within 1% of each other.

my number 6 battery was showing soc 85 when all others were 100 at same voltage
set charge to 57 and it fixed to 100 soc in about 1 minute...thanks
set it back to 55/56 after that. will see if it stays good for a while

 

[wayne530]

my number 6 battery was showing soc 85 when all others were 100 at same voltage
set charge to 57 and it fixed to 100 soc in about 1 minute...thanks
set it back to 55/56 after that. will see if it stays good for a while

I've noticed the same thing and once/month will set it to 57V for one day, then back to 55V.

 

[Texican]

I've noticed the same thing and once/month will set it to 57V for one day, then back to 55V.

did you just have 1 battery showing low soc at normal voltage?

 

[wayne530]

did you just have 1 battery showing low soc at normal voltage?

I have 2 of 6 that consistently go into this state--given the same pack voltage, it's reported SoC is lower than the other packs, all of which report 100%. After some back and forth with Signature Solar, I am told this is "normal" and could be related to the specific production batch of cells. Since the workaround is easy (although tedious with my LV6548s), I haven't really investigated it further. I have also noticed that some of my EG4 BMS's will stop reporting data and require a power cycle to reset the BMS. Signature Solar was investigating this with the vendor but never got back to me. If you get any additional details on this, please let me know. I set the bulk a little lower because I don't want to use a ton of power (whether from solar or utility) to do that extra bit of charging, given the high resistance of the packs when at a high SoC.

 

[DougfromdaUP]

The LiFePOwer4 BMS is wrong. They diverge after days of not being fully charged. If your bus bar is ok, the batteries are really at a very similar SOC regardless what their BMS says. It appears that any current under two amps in or out isn't counted. I've had them since May, and at first was worried, but have since learned to just ignore their bms. Watch the current into each battery the next time you charge and you'll see.

 

[wayne530]

Yeah, I also suspect the BMS, especially given the other issue I've experienced with the temps and other values getting stuck and no longer reporting actual values, but the last value read. It's not a big deal--it just messes up the Solar Assistant graphs and I'm a little OCD about it. As you said, there has been no observable impact.

 

[Texican]

using solar assistant it takes about 10 seconds to change the charging voltage to 57, and it fixed the wrong soc immediately. I figured the bad pack reading was wrong so I let it go a couple months.
had a bigger issue a week or so ago for couple days where solar assistant for some reason repeatably became unconnected from the whole battery bank and was jumping back and forth from batts to utility. that was weird, but has not happened since

 

[CoryF]

Hi all, I've spent the a while reading through these threads as I've been building my system, and had a similar question to the OP.

I realize that battery equalization is a feature for lead acid batteries, but couldn't you set the equalization voltage to the same value as the bulk charging voltage (setting 26 [bulk] = setting 31 [equalization]) and then enable equalization (setting 30 = EEN)? According to the manual, assuming the other equalization settings were left at their default, this would set the charger in CC until the equalization voltage is met, then remain in CV for for minimum of 60 minutes every 30 days. It goes on to say that if the equalization voltage is never met (unlikely with LiFePo4) it will extend the time to the equalized timeout (120min default). Once complete it returns back to the programmed float voltage.

This seems like the perfect way to automatically force a top balance every 0-90 days... This is only required because these inverters don't allow you to set the absorption time. According to the manual's charging curve absorption can be anywhere between 10min and 8hr, but there are no specifics on which parameters determine the absorption time.

From the EG4 6500EX manual:

In Equalize stage, the controller will supply power to charge the battery as much as possible until battery voltage raises to the battery equalization voltage. Then, a constant-voltage regulation is applied to maintain battery voltage at the required equalization voltage. The battery will remain in the Equalize stage until the battery equalize time setting has arrived.

If the battery equalization time has expired while in the equalize stage, and battery voltage does not rise to the required equalization voltage point, the charge controller will extend the battery equalization time until battery voltage achieves battery equalization voltage. If battery voltage is still lower than battery equalization voltage when battery equalization timeout setting is over, the charge controller will stop equalization and return to float stage.

 

[TurbineTester]

using solar assistant it takes about 10 seconds to change the charging voltage to 57, and it fixed the wrong soc immediately. I figured the bad pack reading was wrong so I let it go a couple months.
had a bigger issue a week or so ago for couple days where solar assistant for some reason repeatably became unconnected from the whole battery bank and was jumping back and forth from batts to utility. that was weird, but has not happened since

How did you set Solar Assistant to change the battery charging voltage?

 

[offgridfarmgineer]

Hi all, I've spent the a while reading through these threads as I've been building my system, and had a similar question to the OP.

I realize that battery equalization is a feature for lead acid batteries, but couldn't you set the equalization voltage to the same value as the bulk charging voltage (setting 26 [bulk] = setting 31 [equalization]) and then enable equalization (setting 30 = EEN)? According to the manual, assuming the other equalization settings were left at their default, this would set the charger in CC until the equalization voltage is met, then remain in CV for for minimum of 60 minutes every 30 days. It goes on to say that if the equalization voltage is never met (unlikely with LiFePo4) it will extend the time to the equalized timeout (120min default). Once complete it returns back to the programmed float voltage.

This seems like the perfect way to automatically force a top balance every 0-90 days... This is only required because these inverters don't allow you to set the absorption time. According to the manual's charging curve absorption can be anywhere between 10min and 8hr, but there are no specifics on which parameters determine the absorption time.

From the EG4 6500EX manual:

Hi, having same issue where a bunch of my are around 82-85 Ah max capacity. Did you try this or find out more about it?