EG4 BMS Charge Limit Settings

[JBoffgrid2022]

Hello All,
I am having a little bit of a conundrum with my solar input/bms charge limit settings. Here's what I've gathered so far. I have three EG4 6000XP's wired in parallel. I have three EG4 wallmount batteries that are connected to these inverters directly as well as connected in parallel. I have three separate strings of 400W bifacial panels coming in and wired into each inverter.

Total output of my panels should range from 19,200-24,000 watts depending on the sun exposure. But I have not seen this input once since I've installed the system. I did notice that the rated charge limit per unit is only 125A which should equal 375A total PV input limit. It seems I am not harnessing anywhere near the total potential energy I am getting from array, am I wrong here??

If so, any thoughts on how I could change or alter my setup to harness all of this power?

My Setup:
-3 EG4 6000Xp (Wired in parallel)
-3 EG4 Wallmounted batteries (Wired in parallel and in series)
-48 Aptos 400-500W bifacial panels (Wired 2S8P x 3)

 

[fnnwizard]

Hello All,
I am having a little bit of a conundrum with my solar input/bms charge limit settings. Here's what I've gathered so far. I have three EG4 6000XP's wired in parallel. I have three EG4 wallmount batteries that are connected to these inverters directly as well as connected in parallel. I have three separate strings of 400W bifacial panels coming in and wired into each inverter.

Total output of my panels should range from 19,200-24,000 watts depending on the sun exposure. But I have not seen this input once since I've installed the system. I did notice that the rated charge limit per unit is only 125A which should equal 375A total PV input limit. It seems I am not harnessing anywhere near the total potential energy I am getting from array, am I wrong here??

If so, any thoughts on how I could change or alter my setup to harness all of this power?

My Setup:
-3 EG4 6000Xp (Wired in parallel)
-3 EG4 Wallmounted batteries (Wired in parallel and in series)
-48 Aptos 400-500W bifacial panels (Wired 2S8P x 3)

3x wall mounts ALL in parallel right? no series. Then each 6kxp connects to each pack? A pic of inverter and batt install would help.
48 modules - I think you mean 8s2p or 2p8s ? - NOT 2S

The nitty gritty in order of most importance:

1. each MPPT can convert 4kW pv = should be 6 individual strings, = each PV input of each 6kxp gets an 8S - likely this to fix

2. Enable sharing of batteries in the settings

3. Are you running closed loop ( coms) under soc? If so, inverter can slow down charging from the various coeds programed in inverter... what are batts reporting for soc?

 

[JBoffgrid2022]

3x wall mounts ALL in parallel right? no series. Then each 6kxp connects to each pack? A pic of inverter and batt install would help.
48 modules - I think you mean 8s2p or 2p8s ? - NOT 2S

The nitty gritty in order of most importance:

1. each MPPT can convert 4kW pv = should be 6 individual strings into each PV input of each 6kxp - likely this

2. Enable sharing of batteries in the settings

3. Are you running closed loop ( coms) under soc? If so, inverter can slow down charging from the various hard coeds programed in inverter... wht is batts soc reporting?

Each inverter has the following: 2 strings / 8 panels. There are three inverters with the same setup. I have no idea how to write that out, my apologies!

1. Correct, each inverter has two strings entering them, so six strings total.
2. Yes, I have shared battery on.
3. Yes, closed loop coms are set to SOC, not voltage. Battery SOC has been 100% when the sun is out and is charging fast.

Could my issue be that there is not enough demand on the inverter/PV array to actually see higher that 15kw PV input? I will show some graphs below to help explain my issues. Thank you!

 

[JBoffgrid2022]

I'm looking at the graph again and it looks like the up tick of the PV input is being cut off once the SOC reaches the 90% mark +/-. What do you think?

Regardless, I want to make sure my BMS charge limit settings are correct.

 

[TM48]

I'm looking at the graph again and it looks like the up tick of the PV input is being cut off once the SOC reaches the 90% mark +/-. What do you think?

Regardless, I want to make sure my BMS charge limit settings are correct.

I have two 6000xp's and three wall mounts with 12300 watts of PV. I have my charge settings set at 200 amps. The max I've seen was 204 amps or about 67 amps per battery. That's about .24C which is all I want to charge at for battery longevity. That peak was on a December 25f day when the SOC started at 19%. Fully charged before 1 pm and made a record of 60 Kwhr.

 

[fnnwizard]

I'm looking at the graph again and it looks like the up tick of the PV input is being cut off once the SOC reaches the 90% mark +/-. What do you think?

Regardless, I want to make sure my BMS charge limit settings are correct.

I think the 90%soc mark does derate the charging. Cant remember. Should be in the manual of battery. I would change the settings to run under V to make sure the batteries are getting to 100% soc = 3.55V per cell initially if cells don't show that.

I can review manuals later tonight to be sure if u don't find out by then.

 

[Zapper77]

3x6000XP with Shared Battery enabled, max charge and discharge should be the combined total of all three. (125x3=375 amps)

 

[Recovering EE]

Off-grid systems will only produce whatever power is necessary to satisfy the current loads.

After the Sun comes up, the system will put out enough power to charge the batteries and provide for the other (household?) loads. Once the batteries are charged to 100% SOC, the system will throttle back to only putting out enough power to satisfy the household needs.

If there's nowhere for excess energy to go, the system won't produce beyond current requirements, plus a little overhead that the system itself uses.

 

[Quattrohead]

Could my issue be that there is not enough demand on the inverter/PV array to actually see higher that 15kw PV input?

Exactly.

 

[JBoffgrid2022]

Thank you all! I'll look over the manual tomorrow to see what it recommends for the voltage vs. SOC.

 

[fnnwizard]

Each inverter has the following: 2 strings / 8 panels. There are three inverters with the same setup. I have no idea how to write that out, my apologies!

1. Correct, each inverter has two strings entering them, so six strings total.
2. Yes, I have shared battery on.
3. Yes, closed loop coms are set to SOC, not voltage. Battery SOC has been 100% when the sun is out and is charging fast.

Could my issue be that there is not enough demand on the inverter/PV array to actually see higher that 15kw PV input? I will show some graphs below to help explain my issues. Thank you!

Yeah, your battery pack shows 50% soc = ~ 21kWh and you charged that much from about 7:30 to 10:00AM. Total output is close to 15.6kW and its not even 10:00AM yet .

If batteries were much more depleted to extend charging into the noon hours, I'm sure you will see close to PV power expectations dependent on module mounting positions.

One thing to look at, if you are over paneled, is to manually reduce max charging current (settings menu) and aim for a ~.20-.25C max charge rate if typical weather and usage allows. You should still be able to fully charge and 2 things will really benefit you.

1. The lower Crate charging will be easier on the cells and electronics (bms and charger).
2. reduce the time the cells stay at high soc.

You'll have to adjust again over the winter months, but it'll be well worth it.

 

[Quattrohead]

Or just get more batteries and tell the power company to take a hike.

 

[Madcodger]

Or just get more batteries and tell the power company to take a hike.

This!

 

[fnnwizard]

Or just get more batteries and tell the power company to take a hike.

Haha, I wish it was this simple.
But sometimes trying to tell Poco this, ends up shooting self in foot more.

Need to know:
Usage patterns
Weather patterns
Grid reliability
Grid costs.

But let's throw some numbers to get some idea...
Assume his needs are met currently.
USA grid on avg is very reliable = < 44hrs down time in year
Let's assume all that happens during nonPv hrs.

Say OP uses high amounts, 2kW during this time. So 88kWh.

Assume costs is on high side at $.20/kWh.
This yearly costs from grid < $20.

Powerpro indoor great deal at 3300 with tax. Looking at 165yrs to break even.
So either line the Pocos pockets, or EG4s.

 

[TM48]

Your logic only gives credit for having batteries during a grid down event? My batteries are used 24 x 7. 100% at night and during any solar variation during the day.

 

[wpns]

"MOAR BATTEREIS!" is always the solution, except when more panels, more inverters, or (to close the loop) more load is the solution.

However, the OP has SOC getting down to the 50% range on (I assume) a typical night, so that's a pretty good balance. Run it for a while and see how it does, after a year see how much you've paid the PoCo, and see how that affects the amortization of more batteries. Batteries are the most expensive part of the system, I'd give the market and tariffs and the economy a year to settle out anyway.

 

[wpns]

I'd leave it in SOC mode, each camp has it's followers, and I'm not going to open the SOC versus Voltage can of worms, but I'd stick with SOC if you aren't having any problems.

 

[fnnwizard]

Your logic only gives credit for having batteries during a grid down event? My batteries are used 24 x 7. 100% at night and during any solar variation during the day.

Yes, assuming his energy needs are currently met with the existing batteries, with the rest of the qualifiers as written, additional storage is just (unneeded expensive) “insurance”.

I'd leave it in SOC mode, each camp has it's followers, and I'm not going to open the SOC versus Voltage can of worms, but I'd stick with SOC if you aren't having any problems.

Agreed it's personal re soc vs la/V.

Here's some data though. For the 18kPv, I've tested extensively with coms/SOC, coms/V, LA/V.
I had thought coms/V was the best of both worlds until recently. Because of the unusually unfavorable weather lately, I had to put batteries in standby overnight with the lowest AC charge to avoid export (100W).

This of course, charges the batteries at a "phantom" rate = bms doesn't account for = SOC ends up being under-reported.
For the 18kpv, in any coms mode, if BMS registers <10% SOC, it will AC charge batts until BMS registers 13% to go into standby, but won't allow discharge until 15%.

Was surprised when, at peak rates for us (>$.50/kWh), the 18K was pulling all energy for loads from grid, and charging the batts at 500W. Depending on the number of packs, 500W may not be enough for BMS to register the required 3% so the batts and loads will pull from grid until PV also kicks in to get soc to =>15%.
And, AC charge can not be turned off, unless manual grid breaker is switched off, I'd consider this a bug too.

I'm back to LA/V but using an "adjusted V" to go to grid if ever needed with Home Assistant.

Here' the current, way off SOC, and it's cloudy here today again so might not get enough charge for BMS to reset to 100% until next week.

 

[TM48]

I'd give the market and tariffs and the economy a year to settle out anyway.

Definitely

 

[JBoffgrid2022]

Or just get more batteries and tell the power company to take a hike.

I"ve already given my power company the shove, they wanted to charge us over $100k just to bring their power down to my house. Then I'm sure I'm monthly bill would be around $500-$600/month for the rest of my life... No Thanks. All in, I'm only around $56,000 for my solar setup after my rebate. I'd say that's a pretty good deal.

 

[JBoffgrid2022]

Haha, I wish it was this simple.
But sometimes trying to tell Poco this, ends up shooting self in foot more.

Need to know:
Usage patterns
Weather patterns
Grid reliability
Grid costs.

But let's throw some numbers to get some idea...
Assume his needs are met currently.
USA grid on avg is very reliable = < 44hrs down time in year
Let's assume all that happens during nonPv hrs.

Say OP uses high amounts, 2kW during this time. So 88kWh.

Assume costs is on high side at $.20/kWh.
This yearly costs from grid < $20.

Powerpro indoor great deal at 3300 with tax. Looking at 165yrs to break even.
So either line the Pocos pockets, or EG4s.

No grid power, sorry if I wasn't clear earlier.

 

[JBoffgrid2022]

"MOAR BATTEREIS!" is always the solution, except when more panels, more inverters, or (to close the loop) more load is the solution.

However, the OP has SOC getting down to the 50% range on (I assume) a typical night, so that's a pretty good balance. Run it for a while and see how it does, after a year see how much you've paid the PoCo, and see how that affects the amortization of more batteries. Batteries are the most expensive part of the system, I'd give the market and tariffs and the economy a year to settle out anyway.

I'm pretty sure my solution at this point is an additional battery bank connected to the master inverter/battery combo because I don't have any grid power to supplement the needed power on cloudy days/overnights. I may also end up installing a back up propane powered generator for those extended cloudy days during December/January.

 

[JBoffgrid2022]

Again, because I skipped using my utility company, I am under budget and I can afford to get the battery bank and back up generator and still be way ahead

 

[Madcodger]

Hi @JBoffgrid2022 . I had not read your earlier post too closely, but reading it again, here are my thoughts. We had a similar system as yours (three 6000XPs and three EG4 wall mount batteries) but have only 32 400W panels. We were getting to 100% SOC many days but dropping into the 20-30% SOC range more often than I wished for Maine winters. Once we added two more identical batteries to the system, we haven't dropped below 41% since Dec 22. I would therefore suggest that a couple of additional batteries will allow you to make use of all that PV capturing ability you have, which seems to be the root of the problem, as it appears from your chart that you are hitting 100% SOC and then just staying there until dusk, as expected.

The other thing to think about is the azimuth and tilt of those panels and the season of the year. I'll assume your azimuth is close to 180 degrees, so the more likely variable is tilt, which most people fail to fully consider. We have two 45-degree strings of 8, that do a pretty good job all year here in Maine. But in winter, our real stars are the 67-degree string of 10 panels, and the 90-degree string of 8. I'm amazed at their performance compared to the 45-degree strings, as I was previously skeptical of just how much tilt would affect performance. Each of those strings performs acceptably in summer and we get plenty of power because they're exposed to so many hours of sun, but when the days are short in winter, they're like energy vacuums, pulling in an amazing amount of power per hour.

Bottom line: I'd add a couple of batteries, but then if you find they're not hitting 100% SOC most days, I'd look at tilt even if it means separating some panels into additional strings (assuming azimuth near 180 degrees). Hope that helps.

 

[JBoffgrid2022]

Hello @Madcodger, thank you for this well thought out reply. I have been leaning towards this solution for a while, and now it seems I am not alone with my issues, thank you for helping me with this. I don't have the room on my walls to install anymore EG4 wallmounted batteries but I could easily fit a server rack that holds six Lifepower4 batteries. This would give me a total of 75kwh of backup power. I had my system installed last fall and I was able to track the solar input over December and January. Very low solar production during those two months but I did have a few days where it produced a good amount. I'll keep you all posted as I make my decisions on how I will move forward.