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Question Enough Batteries or Incorrect Setup

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General Troubleshooting

Last Post by IN-OffGrid-Greenhouse 9 hours ago

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IN-OffGrid-Greenhouse

Topic starter

January 16, 2025 2:36 pm

(@in-offgrid-greenhouse)

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I'm OK at math but still learning electricity

Have an off-grid greenhouse in southern Indiana with the following setup
- EG4 3kW Off-Grid Inverter (1511025)
- 10 Rich Solar Mega 200 Watt 24 Volt Solar Panels
- 1 EG4-LL Lithium Battery (V2) | 48V 100AH (1511066)
- 2 EG4 LL-S Lithium Batteries | 48V 100AH (1511082)
- Batteries are installed in an EG4 Enclosed Battery Rack | 3 Slot (1511229)

As a general rule of thumb, I equate 100AH batteries to roughly 5kW of stored electricity, per EG4s product specs.
I have three 100AH batteries, so roughly 15kW stored.
My load is less than 0.5kW. So if my math is right, I should have a little less than 30 hours of available battery power to my loads. I don't appear to be getting anything close to that.

I get that temperature has an effect on battery life and it has been quite cold recently here in southern Indiana.

Yesterday (January 15), according to the monitoring SmartESS app, I had 70% battery at 5:00pm, which should be around 20ish hours. I only got around 12 hours.

Inverter Settings:
01 - Utility First
Do I have enough batteries to last at least 24 hours for my constant 0.5kW load?
Is my math way off?
Is there a setting in the inverter I've missed or configured wrong?

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Joel Brodeur

January 16, 2025 2:54 pm

(@joel-brodeur)

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Don't forget loss do to idle consumption (15W-70W 15 is standby so you are looking at closer to 70) and loss due to efficiency - (94% efficient battery to inverter- I generally call it 10% loss).

So, your .5kw load then become something more like .6+kw More like 25 hours of capacity at that load.

Doesn't explain it all so there may be other losses elsewhere and that was just quick math so....

See if anyone else chimes in here.

Sometimes the easiest solution is the best solution.
Sometimes not.

Posts: 204

Joel Brodeur

January 16, 2025 3:42 pm

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After looking at the spec a little more, I think the self-consumption of the inverter (while active) might be higher than the 15-70 mentioned before. The spec sheet says that is 15W standby and doesn't indicate what the 70W is full load active or what. So, I am guessing that it is higher, but I don't see in the spec's what it actually is.

Sometimes the easiest solution is the best solution.
Sometimes not.

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JLankford

January 16, 2025 4:14 pm

(@jlankford)

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@joel-brodeur

I keep seeing 60W as typical idle/standby consumption for the 3000EHV.

@in-offgrid-greenhouse

You need to understand a behavior called "SOC drift." Is your load a constant 500W, i.e. you have a constant current load of about 10 amps? Or is this an average quantity for the daily consumption? What is the lowest sustained load current on your system (not including the inverter standby current)?

Also, how often does your system get charged to a true, full 100% SOC based on voltage values?

Answer those questions and then I'll explain SOC drift...

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IN-OffGrid-Greenhouse

(@in-offgrid-greenhouse)

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January 16, 2025 5:06 pm

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JLankford

@jlankford Load varies between 300W to 500W for some low power heaters in a chicken coop. 1 heating unit stays on all the time, the other unit comes on periodically to keep their water from freezing.

JLankford

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January 16, 2025 5:18 pm

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IN-OffGrid-Greenhouse

@in-offgrid-greenhouse

OK, then I don't think you have a SOC drift problem - your baseline discharge current of ~6A is high enough to avoid it.

FYI, if you have discharge current at or below about 1.5A in your system, then the battery BMS will ignore that current in its SOC calculations. Over time, your actual SOC can be much lower than the calculated SOC reported by the battery, and this only gets reset upon full charge. If you add more batteries to your system the chance of SOC drift increases, because the load current gets spread across more units. The individual battery measurement threshold is 0.5A for these EG4 batteries (a common value for other brands too).

You still need to get a good full charge periodically in order to be able to trust your SOC value.

This post was modified 1 day ago 2 times by JLankford

Joel Brodeur

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January 16, 2025 5:25 pm

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IN-OffGrid-Greenhouse

@in-offgrid-greenhouse

On that graph, or someplace else in the app, can you identify a point in time (or a few) and let us know what your actual battery draws vs your load is at that same time?

ie. at 10:00 your battery draw was 700watts and your load was 500 watts?

Thanks,

Sometimes the easiest solution is the best solution.
Sometimes not.

IN-OffGrid-Greenhouse

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January 16, 2025 5:49 pm

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Joel Brodeur

@joel-brodeur Hopefully this helps. Appreciate your time.

Joel Brodeur

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January 16, 2025 6:00 pm

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IN-OffGrid-Greenhouse

@in-offgrid-greenhouse Hmmm, that is a head scratcher. Based on that you are only "Self-Consuming" around 20Watts. Offhand the only thing I can think of is perhaps the SOC reading is off and is showing 100% when it is actually lower. How old is the system?

And have you tried a series of deep discharge/charge cycles?

PS I am going to have to give this one some thought.

Sometimes the easiest solution is the best solution.
Sometimes not.

IN-OffGrid-Greenhouse

(@in-offgrid-greenhouse)

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Posts: 12

January 16, 2025 6:08 pm

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Joel Brodeur

@joel-brodeur The solar panels, inverter, & 1 EG4-LL Lithium Battery (V2) | 48V 100AH (1511066) were all purchased in May 2023, they were tested but not permanently installed. Purchased the 2 EG4 LL-S Lithium Batteries | 48V 100AH (1511082) and EG4 battery rack in November 2024. Installed everything in their permanent locations in early December 2024.

THANKS!

IN-OffGrid-Greenhouse

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January 16, 2025 6:17 pm

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Joel Brodeur

@joel-brodeur I have not tried the series of discharge/charge cycles. I'm trying to avoid that because it takes my 8kW generator about 6 hours to fully charge the three batteries from 0% to 100%. That's a lot of gasoline or propane I really don't want to afford.

JLankford

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January 16, 2025 6:26 pm

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IN-OffGrid-Greenhouse

@in-offgrid-greenhouse

Rather than numerous cycles, can you get one good full charge on the system to reset the SOC 100% reference point? How log has it been since the batteries were fully charged (not just showing 100%, but 100% and 56V)?

IN-OffGrid-Greenhouse

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January 16, 2025 6:36 pm

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JLankford

@jlankford I didn't know about the 56V thing so I don't know the last time they were 100% with 56V. I do know it will happen today as my batteries were at 0% this morning and have been charging since 8:00am eastern.

Rabbit Hole - Does it matter which of the batteries is battery 1, battery 2 or battery 3 in the stack?
I currently have the EG4-LL Lithium Battery (V2) | 48V 100AH (1511066) as battery 1.

JLankford

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January 16, 2025 6:45 pm

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IN-OffGrid-Greenhouse

@in-offgrid-greenhouse

Are you charging with the inverter? If so, are you using SOC set points or Voltage set points?

My experience with inverter charging using SOC, the charging cycle will stop immediately upon reaching 100%, even if the battery has along way to go before actually full. This is part of the SOC drift problem - unless the battery hits a true full it can't reset it's SOC 100% reference point.

As far as battery order, my understanding is that for communications the newest battery model (LL-S) needs to be the master battery. But that's for the large hybrid inverters, I don't know about the 3000.

IN-OffGrid-Greenhouse

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January 17, 2025 5:08 pm

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JLankford

@jlankford Yes, I am charging through the inverter. My complete inverter settings, including the undocumented magical mystical setting number 38, are in one of my replies to the original topic post.

It was sunny all day and I ran my generator for 12+ hours yesterday to try and get from 0% to 100% and 56V. Got to 95% in about 5 hours, got to 99% in around 7 hours, never got to 100% or 56V. Got stuck on 99% and 55.6V for 5 hours of generator run time.

Joel Brodeur

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January 16, 2025 6:08 pm

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IN-OffGrid-Greenhouse

@in-offgrid-greenhouse

You might have a look at the following thread:

https://forum.eg4electronics.com/community/postid/12131/

@signaturesolarjess

Discussing how to "Reset" SOC"

Sometimes the easiest solution is the best solution.
Sometimes not.

JLankford

(@jlankford)

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January 16, 2025 7:00 pm

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Joel Brodeur

@joel-brodeur

I just started re-reading that thread from SS on recalibrating SOC. So many things wrong with these instructions. In what world is 46.0V equal to 20% SOC? In what world does LFP chemistry have the same memory effect problem as Ni-Cad? The errors make it difficult to trust anything about that post.

This post was modified 1 day ago by JLankford

Joel Brodeur

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January 17, 2025 2:15 pm

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JLankford

@jlankford

FWIW

I agree that the Numbers and "reasoning" are not right for LFP batteries.

I think a better way to explain would be that when batteries are short cycled frequently the BMS will tend to adjust the SOC downward.

I have a challenge using suggesting specific numbers to anyone when using voltage for anything simply because every end use case is different. Voltages will vary depending on how much load is on the battery.

I have found that on MY system 20% is right around 51.6 when under my typical loads. However, depending on what I am doing that can and has been different.

I have seen mentions of another way to reset batteries, but I am hesitant to do it with direct confirmation from EG4 and preferably even a TSB on the EXACT process.

But the idea is to set your charging to above 100% and allow the BMS to shut the battery down in an over charge alarm and do the same thing at the low end. Supposedly this will reset the high and low SOC readings.

Like I said though, I will not and do not recommend this as forcing a fault is not my idea of proper maintenance, and without explicit direction from the Manufacturer with a TSB I will not do it even though it makes more sense to me than trying to guess appropriate voltages for each situation.

I still love this stuff though. 🙂

Sometimes the easiest solution is the best solution.
Sometimes not.

Posts: 59

Ron

January 16, 2025 4:26 pm

(@ron)

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Joined: 3 months ago

About 11500-12000 watts of useable battery which is still 20 hours

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