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Capacity charging/discharging issue, only getting half. EG4-LL Lithium Battery | 48V 100AH

offgriddave

Solar Enthusiast
Joined
Feb 14, 2020
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I'm having weird capacity issues with the Signature Solar EG4-LL 48V. I've had it since Januray, daily use. I pull about 100-180w per hour 12-14 hours a day and charge it with a generator.

Yesterday my phoenix Victron 375VA cut off at 49.1v (where I have it set to turn off) but it surprised me because it was fully charged 8 hours before.
When it shut off, the battery was reading 49.1v and __30%__ charge. That's not right. There's a possibility it had a sharp voltage drop and I didn't catch it until after the victron tripped. But 49.1v is not 30% capacity! That's an issue

So when I got this battery I would charge it every 3 days. Then I noticed every 2 days. I figured I'm just using more power. Now it's every day.

If I do a back of the napkin calculation (inaccurate) I was only able to pull 2.5kwh from the 5.1kwh battery yesterday.

The performance is degrading.

When I charge it, I turn the charger off after 5 minutes after the BMS reads 100%. This is usually 54.4v to 56v. The cells all read equal. I don't know what the balancing algorithm starts or end. Is it possible because I am not pushing "100%" to 58v I am not balancing the internal batteries cells and causing me to get half capacity?

Also the first month I got it I caught the battery cells not equal -- some spiking way up. However I haven't seen that in a few months. I think that issue is gone. But I was concerned this might have damaged the cells. I was told that is normal?

Why is the BMS display saying 30% charge at 49.1V?
WHy does it appear I'm only getting half capacity?
How do I tell if its me or the battery?

Today I am going to charge it to 100% and then keep charging it to 58v... See if that fixes it. Any other ideas?
Signature solar offered a refund but I don't want to go through the logistics. I need a battery to work. I would have to order another one and have it hear first, then replace it.
Also I don't run windows so if I need to install the software and buy a cable, I'd have to run it in VMWare linux or something... but I don't know if that would help.
 
How are you charging the batteries? I would try getting them to 56.5 for at least 30 minutes and then capacity test. If i had to guess, it sounds like they have been consistently undercharged.

I too wish we knew more about the parameters of the cell balancing. Ive got several cells that are way low and they don't seem to be correcting over time (4 months)
 
I am charging with 2x 800w chargers but it usually puts out about 1400w-1600w. 31 amp at 54 right now

OK, so some other strangeness. I have never actually turned the battery "off" (the on/off switch, not the breaker). I just did. And charging. I am charging at 1400 watts currently.

It read at 82% capacity at 54.1v. and currently reads 98% at 54.4v. Now that ain't right

Maybe there might be a bug in the BMS software that if it's left on for months and months, the readings get way off?

Are BMS know to be lazy after a few months and give run-a-away bad readings?

I'm going to put this % capacity vs voltage chart here, below, as an attachment, from footprint to show what's I should expect vs what I am getting

The % on the display is totally off

It's at 100% capacity and 54.4v, (which is now correct according to this chart) pulling 31 amps. Not sure what it is doing at this point.

I'm going to push it to the "second" 100% 58.4v and see if this fixes my problem.
 

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I charged it to 58.5v basically as far as I felt safe to go (CC/CV kicked in and it was still providing 2 amps, but whatever). Disconnecting the charger the battery immediately went to 56.4v a few seconds later. 10 minutes later (now) it's at 53.4v and I'm pulling 3.3amp

From the screen most of the cells were 3.6 or 3.7v. However cell #5 was between upper 3.3v and 3.4000v. cell #1 was at 3.5v. They would not move, in fact, cell #5 actually went down while charging (?)

Do I have a bad cell #5 causing my problem? Or does the BMS "%" just completely inaccurate and I need to charge from 54.4v@100% to 58.4v@"100%"?

The problem again is that the battery voltage completely drops below "30%" reading on the display.
Let's see if pushing it up to 58.5v fixes it.

Is it possible I just need to cycle to 58 volts to get #5 to wake up? This kind of sucks after only 4-5 months of use.


Edit:

test #1
Ran it for 1 hour at 3.5 amp 53v.. something like 180wh, from the top 5120wh. The battery showed 94%. I turned off everything, including the battery and waited 5 minutes. Turning it back on showed it at 96% which is consistent performance for the battery, matches my calculation of where it should be. I'll do some more testing

5120 - 185.5
4934.5
4934 / 5120
.963671875
 
Last edited:
So after more tests... there's a bug in the BMS and display.

After 30-60 days the % indicator starts lagging. Up to 30%, for me. This could mean it damages the battery.

Fixing the bug:
After 30-60 days usage, or a week, fully charging the unit to 100% or "53.8v" (due to the bug) , and then continuing for another _hour_ or 1.5kwh more, to 100% to 58v, then unplugging everything, and turning off everything, with the most important step to turn the battery switch 'off' to remove power to the BMS circuit, it will reset the BMS % to normal at the top.

Before I was using the Victron on/off bluetooth everynight, and breaker switch once and a while for extended days. Never using the On/Off switch.

After this, the percentage will correctly correspond to the battery voltage and charge.

I believe this bug could damage the battery, because it was showing 30% charge at 49.1v. Luckily my victron shut off.

Eventually the % will get so out of wack, without power cycling the BMS circuit, the BMS will destroy the battery.

If you have your battery or inverter set to 20-80% to get the 7000 cycles, it will eventually start to leak 10,20,30% and destroy your battery --- you'll be running your battery between -10% and 50% (if it's even possible, or you haven't noticed you only have 50% capacity).

this means you can't just setup this battery somewhere like a server rack and leave for a year, you'll need to be there to turn it off and on at the top every once and a while.

I don't know if its required to be at the top charge of the battery to reset it or not. I think it is required.

Edit: after doing this the cell voltages are all over the place and unablanced. Turned off charging, no charge no pull, 3.3v for #5 and 3.5v for a couple at the far end. Basically the EG4 BMS is total fucking garbage.
 
This is being reviewed, I believe the science and mathematical basis of lithium charge is more complicated to understand but we now have an active internal programming team as well as my hyper-cycled battery bank from 3 years ago in the shop to see if there are any more things that could be done.

one of the things about the cells used are that they are 108AH, so the real soc% is different than what you expect it is. I see an opportunity to improve the balance logic and achieve better self-calibration though
 
I'm going to take a crazy wild guess what's going on inside the BMS logic and probably reveal massive lack of knowledge at the same time.

I imagine the BMS boots up, it looks at the battery. There's probably some kind of look up table. Then, there appears to be some calculation of a coefficient, or fudge factor. It calculates this coefficient and stores it into whatever functions as the BMS's RAM. Then it uses this in another calculation to show the % charge.

For whatever reason after weeks or months this coefficient starts to lag behind the actual state of the battery. Either the ingress power measurement or egress measurement of this coefficient isn't balanced that causes it to lag behind or run away from reality, eventually giving out a bogus % charge. Like 100% at 53v or 30% at 49.1v..

Cycling the power of the BMS appears to reset whatever this broken calculation is. So that shows it could be a firmware upgrade fix, which is basically what you hinted at in your comment.
 
From the screen most of the cells were 3.6 or 3.7v. However cell #5 was between upper 3.3v and 3.4000v. cell #1 was at 3.5v. They would not move, in fact, cell #5 actually went down while charging (?)

Sound like it's out of balance, which is not uncommon after a while of use.

I have seen cells like your #5 take forever to catch up to the rest, also I've seen them go down in voltage while charging.
This could mean your #5 cell is just that much out of balance with the rest, a likely case. It can also mean it's gone bad, less likely but not out of the question.

I would keep trying to get it topped up, and balanced to where every cell has hit 3.6v. If you cant get that to happen after days of trying you might have a dud. If you finally get it to top off each cell, and it quickly goes unbalanced again after a few cycles you might have a dud.
 
yeah that's probably the issue

if you read my post carefully, or maybe I didn't explain that I resolved it very well:

after running the charger a half dozen time in the 100% area for a few hours each charge, and letting the CC/CV do it's thing. #5 is normal and I don't have the issue.


What's weird is I've had seen cell voltage go down while charging as well a few times. Complete mystery to me. I guess it's balancing.
 
yeah that's probably the issue

if you read my post carefully, or maybe I didn't explain that I resolved it very well:

after running the charger a half dozen time in the 100% area for a few hours each charge, and letting the CC/CV do it's thing. #5 is normal and I don't have the issue.

Excellent, yeah that half dozen top offs allowed the BMS time to balance the high cells down while #5 played catch up.

What's weird is I've had seen cell voltage go down while charging as well a few times. Complete mystery to me. I guess it's balancing.

Yeah I've had stubborn cells like that, more than a few times with different packs that do that voltage dropping while charging. You'll see them rise into the upper 3.4ish area, and then fight back down. It's the cells, not anything balancing causing that. I think what's happening is the other cells surrounding it begin to top off, then some dynamic changes in the pack, probably internal resistance since that changes at different SOC.
 
I'm having a similar problem I just noticed. I've got 4 EG4-LL (1 v1 and 3 v2). All seemed well for months but now they are all only charging to about 53.5V total (all cells showing ~3333) so none appear out of balance...

I'm running off grid with sol-ark 12k and charge parameter has been set to 56.5...

I have power cycled the batteries but not at top charge as it doesn't seem like BMS is allowing them to go to that range anymore but I'll need to check the data logs and monitor...

So, seems to be a BMS issue.

Any help appreciated.
 
Screenshot_20230630-194648.pngLooking at the data chart for today, it looks like an extreme battery voltage drop from 56.5V down to 52.8V with load only around 1kW...bad battery pack/cells somewhere, correct?
 
I'm having a similar problem I just noticed. I've got 4 EG4-LL (1 v1 and 3 v2). All seemed well for months but now they are all only charging to about 53.5V total (all cells showing ~3333) so none appear out of balance...

I'm running off grid with sol-ark 12k and charge parameter has been set to 56.5...

I have power cycled the batteries but not at top charge as it doesn't seem like BMS is allowing them to go to that range anymore but I'll need to check the data logs and monitor...

So, seems to be a BMS issue.

Any help appreciated.
Have you ever updated the firmware on the batteries?
 
I can walk you through this. Or i can have one of my guys reach out to you and send you a cable. this is the first time ive heard of the LLs having any issues
I went through the YouTube video from about 8 months ago...this is the cable that was sent to me. I have 2 of them and also made one myself. I can't remember the exact error I ran into but essentially software would communicate fully. I'm pretty tech adept with a strong MS Windows background, so I'm more than familiar with COMM ports and such...

Are you thinking the voltage drop off would have something to do with firmware? Why all the sudden?

Thanks!
 

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I went through the YouTube video from about 8 months ago...this is the cable that was sent to me. I have 2 of them and also made one myself. I can't remember the exact error I ran into but essentially software would communicate fully. I'm pretty tech adept with a strong MS Windows background, so I'm more than familiar with COMM ports and such...

Are you thinking the voltage drop off would have something to do with firmware? Why all the sudden?

Thanks!
I had the guys reach out to you and ship you the correct cable.
 
I had the guys reach out to you and ship you the correct cable.
Thank you. I received the cable and just finished updating the v1 firmware...I don't see an update available for v2 on the website.

Also, the V2 batteries don't have the menu to select the comm protocol as shown in the video

Batteries are plummeting every day within hours of PV dropping (early evening) from ~56V to ~53V in less than an hour with ~1.5-2kW load...
 
Thank you. I received the cable and just finished updating the v1 firmware...I don't see an update available for v2 on the website.

Also, the V2 batteries don't have the menu to select the comm protocol as shown in the video

Batteries are plummeting every day within hours of PV dropping (early evening) from ~56V to ~53V in less than an hour with ~1.5-2kW load...
Someone will contact you soon. I’m sure there’s a easy fix for this
 
Someone will contact you soon. I’m sure there’s a easy fix for this
Thank you. I've successfully updated the v1 firmware and selected Sol ark for communication. However, the Sol ark isn't seeing the batteries (I've triple checked ID's and everything). Is there a particular network cable pin out required? In using a standard RJ45 patch.

Also, I successfully connected to BMS tools and there were no errors.

I am trying to connect with Sol ark support to see if they can help as well.

Thank you.
 
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