2 - EG4 indoor Wallmounts.
I am kinda new to the Lithium world and I am curious about my new system.
There has always been a minor discrepancy between the two batteries but nothing significant.
However, I have been having plenty of sun and the battery bank never got below around 85% before charging back up to full. Now we are losing sun and the bank is getting lower and the discrpency is growing.
Is this normal with a Lithium bank?
If not are there things I should check?
Thank,
JB
This is fairly typical and not something to immediately raise concern. Ideally, to promote long-term cell health and maintain accurate SOC readings, you should cycle the battery bank monthly discharging it fully from 100% down to around 20% to achieve an 80% depth of discharge. This practice helps balance the cells and recalibrate SOC readings. With the voltages aligning closely, I don’t see any immediate cause for concern.
@jared I was told never use SOC but voltage only and that 80% depth of charge was from 56v to 47v. Is this correct?
@pawnee When I used FLA I too was told to never use SOC. However, with my old system I found that with proper bi-annual maintenance (re-torquing all lugs, cleaning connectors, and swapping first and last batteries in array) that SOC appeared to be just as effective as Volts. For my old system I also always used return amps to determine a full battery.
Since each inverter/charger manufacturer could determine SOC in a different way (amps in vs amps out, battery voltage with some black magic compensation for loads, etc.) I can completely agree that Volts vs SOC would tend to be better. However, the best overall method I found that works is to trust in the manufacturer recommendations. I spent years tweaking my old system just to finally discover that the best settings for system were the ones recommended by the manufacturers of those systems.
That being said, it appears EG4 is recommending to base charge and discharge on SOC. How they calculate SOC, I am not certain and would love to know but until then I personally will run based on what they tell me until I see evidence to the contrary.
Just my opinion on the matter, not telling anyone else what they should do.
Best regards,
JB
@joel-brodeur thanks. I’m going to contact Tec support and double check. I’ll make a post and see what EG4 says. I’d love to she a SOC vs Volts chart for the Lifepower 4 V2’s
@pawnee I generally prefer using SOC for BMS communication with our batteries. I'd only switch to voltage to recalibrate SOC unless you find it performs better for your use case in voltage mode. A range of about 56.2V to 46-47V roughly aligns with an 80% depth of discharge. This chart provides a helpful reference for voltage-to-SOC percentages.
@jared thanks. The Tec guys at Signature solar discouraged me from using SOC so now I’m not sure what to do
@pawnee Interesting, why is that? Both options generally work well, but I prefer BMS communication as it allows the battery to communicate directly with the inverter for error reporting and to manage charging and discharging parameters.
The closed loop vs open loop white paper on our website might be worth a read as well.
@jared my Lifepower4 V1’s and V2’s do communicate with the 18k but the SOC on all 6 shows 0% at 47 volts. Is this right? I’m just doing what the Tec guys told me. Start AC charge at 47 volts end at 56 volts. Thanks
@pawnee Which firmware version is installed on the LifePower4 V2? In my opinion, 0% would not be 47v. However, it would be very close.
@jared the V1’s are the newest firmware. The V2’s were bought last month. I’m assuming the latest it I can try loading the BMS test for them and make sure. Thanks
Good to know, Thank you.
JB
A follow up on this. My generator ran today and seemed to have charged everything in the expected manner.
However, the generator shutdown as soon as 1 battery reached 100% no overrun to balance the batteries (the other battery was at 98%.
After a few minutes both batteries did say 100% SOC but then after just an unexpectedly short time they dropped to 98% almost like the batteries decided to balance after one of them reach 100%
Is this expected behavior, I would have thought a 10 to 20 minute overrun with the inverter kinda going into bypass while the batteries stabilized to get them both up to 100%?
I have attached my logs for the day but please be aware that they may look a little jacked up due to DST time change. I changed the clock sometime around 2:15
@joel-brodeur This is the expected behavior. However, I’ll forward this to our R&D team to explore potential improvements in the charging logic when connected to a generator. Currently, the system is designed to shut off as soon as the BMS reports 100% to the inverter to conserve fuel, but allowing a bit of overhead to continue cell balancing during generator charging could be beneficial.
@jared Thinking about this, I can see how some folks would want to conserve fuel, and some would want to "top-off" batteries.
When the developers look it over perhaps, they would want to make it adjustable with a recommended setting in miutes say from 0 to 20?
Just a suggestion.
Thanks again for all the help and patience,
JB
It looks like the discrepancy in SOC is growing with every cycle.
Any suggestion. My fear is that one battery gets so low that it goes into protection while the other keeps running?
Looks like the cell voltages are fine just the SOC is out of alignment. 🙁
Any ideas?
Thanks,
JB
@joel-brodeur would you mind sending me the SN for the inverter through a DM? I would like to take a look at the data.
After working with Jared it looks like we have my system squared away.
Battery Type = 2-Lithium
Lithium Type from EG4 to Lithium type1 (for indoor wall mount)
The drift appears to have settled out after just a single gen charge cycle.
Thanks Jared, you rock sir.
JB
