EG4 LL V2 screen SOC accuracy

[bakada]

I bought the two EG4 6500EX and six EG4 LL V2 batteries in the kit offered by Signature Solar in order to get closed communication but despite having read through all of the threads on here and upgrading to the latest firmware for the inverters, I am still getting error 61. I switched setting 5 on the inverters to USE and have been using manual settings to let the inverters manage the batteries that way.

This lead me down a path of figuring out what is the best way to monitor the SOC without having the read the display on the inverters or the battery screens. I found and installed SolarAssistant and it has been working well so far using emulated BMS because I am still unable to connect directly to the batteries (neither on a Windows PC using BMS_Tools (v2.20) or on a Raspberry Pi using SolarAssistant. That is until one day when I decided to check the actual SOC on the battery screens themselves and, to my shock, realized I had actually drained the batteries down to 4% when SolarAssistant was showing around 50% using the emulated BMS. I realize emulated BMS is not very accurate, but I did not expect it to be so vastly different. I am now paying attention to the voltage of the batteries instead.

I have switched SolarAssistant to Use Inverter Settings for battery monitoring. Should I pay more attention to the SOC on the battery screens or is this generally regarded by the community as pretty inaccurate and voltage is what really matters?

 

[DIYPV]

I recently got my SA connected and found the BMS display SOC to be the accurate.
Prior to connecting SA to the battery, I tried to use SA Emulated values, but noticed they were way off.

EG4 Battery/Inverter Comm to SA worked accurately, but there was a lag in data (3-5min delay) so the SA dashboard data was not real-time. When I finally connected the BMS to SA all worked as expected.

 

[mountkay]

I DMed OP with some suggestions. Sounds like they got comms working. Im just gonna post my suggestions here in case anyone else needs them.

1st suggestions is classic - make sure Setting #5 is: 2p1 is set EG4 while 2p2 is set to USE.

2nd suggestion is check the pins on the communication cable. Mine have the pins in different spots for each end of the cable.
The side I have plugged into my 2p1 Inverter has the wires/pins in spots 3&5.
The side of the cable that plugs into my master battery has the wires/pins in spots 1&2.

Not sure which suggestion seemed to make comms work. Idk if the pin locations on the comms cable really matter, but I figured it was worth checking as its an easy thing to do.

 

[bakada]

Many thanks again @mountkay. Your suggestions really stirred me in the right direction and refreshed my memory of all the posts that I read through.

I just wanted to add that aside from the suggestions you mentioned, in case anyone else is facing the same issues, I also used a torque wrench/screwdriver to tighten the batteries to the rack. Those screws were definitely on the looser side. After making sure that is done and double checking the pins (the white placement in the battery manual is where the pin should be set to. i.e. for address 1: pin 1 off, pin 2 on, pin 3 on, pin 4 on, pin 5 on, pin 6 on), I changed the 2p1 to EG4, kept 2p2 on USE, reset everything and error 61 no longer shows up.

The only question I have now is the accuracy of the BMS in terms of SOC. For example, the voltage right now is 51.8V and the battery SOC is 14%. Does that sound about right?

 

[mountkay]

Should I pay more attention to the SOC on the battery screens or is this generally regarded by the community as pretty inaccurate and voltage is what really matters?

It is tough to measure the SOC using voltage for LFP batteries because they have such a flat discharge curve. You can use voltage to try and measure, but that is just the same metric that the battery / inverter SOC estimation is using. I dont use Solar Assistant but I believe it also just uses battery voltage for SOC.

The best way to measure SOC is with a Smart Shunt.

Below is a general guide to Voltage-SOC estimates.
But I imagine each specific battery will be a bit different.
For instance, EG4 says for the LL V2: Bulk charging is 56.2. Float charging is 54.0.
I think these correlate to the below charts 100%(charging) and 100%(resting).

After making sure that is done and double checking the pins (the white placement in the battery manual is where the pin should be set to. i.e. for address 1: pin 1 off, pin 2 on, pin 3 on, pin 4 on, pin 5 on, pin 6 on),

yes, as per the EG4 LL V2 battery manual - http://eg4electronics.com/wp-content/uploads/2023/03/EG4-LL-48V-24V-Manual-1.2.1.pdf

Master battery should be set to ID:1 as you described, (1: off) (2-6: on).
Each other battery should have a different and unique ID address.

 

[DIYPV]

The only question I have now is the accuracy of the BMS in terms of SOC. For example, the voltage right now is 51.8V and the battery SOC is 14%. Does that sound about right?

As mentioned above, it’s hard to really determine SOC based on voltage, but for what it’s worth my EG4 (v2) batteries show similar as yours. Typically around 51.8V SOC is 14-18%.

 

[novaleaf]

It is tough to measure the SOC using voltage for LFP batteries because they have such a flat discharge curve. You can use voltage to try and measure, but that is just the same metric that the battery / inverter SOC estimation is using. I dont use Solar Assistant but I believe it also just uses battery voltage for SOC.

The best way to measure SOC is with a Smart Shunt.

Below is a general guide to Voltage-SOC estimates.
But I imagine each specific battery will be a bit different.
For instance, EG4 says for the LL V2: Bulk charging is 56.2. Float charging is 54.0.
I think these correlate to the below charts 100%(charging) and 100%(resting).

View attachment 146512

fyi that voltage chart image does not seem accurate for the EG4 48v v2 100ah. For example, using the Chargeverter I charge up to 63% @ 53.5v.