When Not To Let Your AIO Communicate With The Batteries

[Kornbread]

A conundrum was brought forth when I asked the forum what might cause a Growatt spfxxxxt to fail starting pv production in the early morning sun. One of several replies; @Zwy posted it could be a possible issue with bulk/float settings, which in a roundabout way, brought us to pre-programmed charge settings when allowing an AIO and battery to determine their own state of affairs.

To be upfront, the ability of the Growatt AIO and eg4 batteries to communicate was one of the features I felt added value to the package. Plug and play. Everybody is talking with each other and happy. Then I posted some charts from Solar Assistant, like the small zoomed clip below. The battery is hoovering around an indicated 99%-100% charge. Yippie, full charge, right, well ... see the voltage?





At first I thought this was the funky bms doing its balancing act that some have posted about, but after some discussion @robby reasons it is the AIO charging up to the very limit of the battery's ability, the bms halting charge, the battery settling, and the process repeating. Keep in mind, when selecting the Li setting in the Growatt AIO and letting the AIO and eg4 batteries do their communication thing, the charge settings are not adjustable. These are factory settings and 57+v is pretty far up the LiFePo4 knees.

So ...

I assume these settings are approved by both Growatt and eg4. Are they?

Why are these charge settings so high? Doesn't this stress the cells possibly shortening their life?

Like me, how many people out there have these components communicating, doing their own thing, expecting the advertised 7000 cycles since everything is 'factory', when in reality we are pushing the upper edge, and possibly shortening the life of our expensive components?

Thoughts ...

 

[timselectric]

I started out with communications. Until I understood the charging profiles of these batteries. Then I switched to manual settings. And improved my storage capacity. I believe that the BMS is being too modest. Much happier now. Myself and (I believe) the battery.

 

[toms]

Manual settings and BMS - Inverter/Charger communications aren’t mutually exclusive.

The charger doesn’t accurately know the SOC or temperature of the cells. The BMS is best placed to know what charging current is suitable.

With manual settings unless you can limit charge current as full SOC is achieved, limit charge current when passive balancing, and limit current when temperature limits are reached - you will be shortening the cell life.

With BMS - Inverter/Charger communications, these situations can be easily configured.

If you use the wrong settings, it will cause issues with or without comms.

 

[Zwy]

Manual settings and BMS - Inverter/Charger communications aren’t mutually exclusive.

The charger doesn’t accurately know the SOC or temperature of the cells. The BMS is best placed to know what charging current is suitable.

With manual settings unless you can limit charge current as full SOC is achieved, limit charge current when passive balancing, and limit current when temperature limits are reached - you will be shortening the cell life.

Does one really need that last 2%? I agree with Robby, that top 2 or 3 or 4% really isn't needed. For that reason, having the BMS control charging to 100% SOC with the current situation causes more damage than charging to the lower knee area. That is what @Kornbread wants to discuss, and others have noticed this is a problem.

With BMS - Inverter/Charger communications, these situations can be easily configured.

No, if the EG4 and GW do not allow changes to the charging profile, nothing can be configured.

The only solution is to switch to manual configuration with no BMS/ Inverter communication.

If you use the wrong settings, it will cause issues with or without comms.

If the current settings in the EG4 BMS or the inverter/charger with comms between the two are configured incorrectly, then it causes issues both short term and long term.

The ideal situation would be the ability to adjust the charging profile with user input and have both the BMS and inverter/charger communicating.

 

[Kornbread]

The ideal situation would be the ability to adjust the charging profile with user input and have both the BMS and inverter/charger communicating.

I feel this would be ideal. The manufacturers could provide a narrow band of adjustment if they were concerned about user error in regards to proper settings.

The Growatt manual specifically states some parameters are not user accessible when in Li charge mode, which is the mode that must be used for inverter/battery communication.

 

[robby]

The Long Version and sorry for the Length.

I have both high end and mid priced server rack batteries and with the high end eFlex batteries they offer firmware updates about once every month. These updates will have tweaked parameters for the charging voltages. When I first got the batteries I think they used 55V and then in later updates it went to 54.6 and now it's 54.4V.
I inquired as to why they had changed the values and John the head engineer at Fortress told me that they have dozens of batteries being cycled several times per day in their Lab and they have noticed no decrease in capacity going down to 54.4V and they expect it will bring a lot of extra cycles to the Batteries lifespan. I can personally attest that I have seen no decrease in capacity as the Sol-Ark Records the Charging and Discharging capacity for everyday.

I use to use closed loop and I wish I could go back to using closed loop but I need the RS485 port on the Inverter to run Solar Assistant so that I can see realtime data remotely. I am really pissed that Sol-Ark will not turn on the second RS485 port but there is nothing I can do about that.

The Problem with the EG4 battery IMHO is not as simple as appears to be. What they should be doing is simply updating the Firmware in the battery so that it uses a more realistic Voltage level but I suspect the main reason why they have set it so high to begin with is because of mismatch in the quality of cells in the packs.
I have three cells in my EG4LL that are definitely not on the same level as the other thirteen.

On good solar days this is not an issue as they will discharge and charge up fairly evenly from 20% to 100% SOC using 54.5V The extra 0.1V is for line losses. All the cells in the EG4LL remain matched and are fine.

The problem occurs when I get two consecutive days of overcast skies and only reach between 40-75% SOC on both of the days. Then those three cells show up their defects on the first Sunny day when I can get up to 100% SOC by 12:30pm and still have plenty of PV power available until 5pm.

When I hook up the laptop to the eFlex batteries all the Cells are perfectly in balance at around 3.40V and the pack reads 54.4V then I look at the EG4LL and it is reading 54.4V but some of the Cells are at 3.56V and some are at 3.4x volts but those three cells are stuck at approx 3.31V and will not budge. The SOC status on the LCD says 94% and will not budge as the pack is in "standby mode". The Sol-Ark is of course saying 100% SOC because it is seeing 54.4V which is what it is expecting based on my settings.

The only way I can get those three cells to go back to 3.40V and get the other cells that are high to all balance out is to turn OFF the four eFlex batteries and set the CC voltage to 57V and then the EG4LL starts to pull in 14Amps for Approx 30 seconds and then discharge back 10Amps to the Inverter for 30 seconds. This back and forth of passive balancing goes on for Approx 2 hours until all the cells are now at 3.56V and then the SOC Jumps up to 100% on the LCD display.

As soon as I set the Inverter charging voltages back to 54.5V the EG4LL starts discharging but it discharge the cells evenly and settles at 3.40V and Surprisingly the SOC on the LCD stays at 100% even though it Discharged for about a minute at Approx 14 Amps and the pack voltage dropped from around 57V to 54.4V
At this point I turn back on the eFlex batteries and this pain in the rear ordeal is over with for now.

BTW I should add that even though all the batteries are at 54.4V and 100% SOC they will slowly settle down to 53.4V over the next hour or two but the SOC will stay at 100% on the Sol-Ark and also on the EG4LL LCD display.
IMHO 53.4V is the natural point where most 48V LiFePo4 packs chemistry settles down.

So my conclusion based on all of this is that the manufacturer of the EG4 battery realizes that if they lowered the Voltage setting sent to the Inverter in closed loop mode. It would result in them getting a ton of complaints that the batteries are not charging above 94% SOC. So they opted to go with a 58V setting that guarantees you will never see the problem, but they must have also realize that this setting will have a serious impact on the packs lifespan.

My recommendation is to get it out of closed loop mode because the EG4 BMS settings are not implementing properly, instead of it being a benefit it becomes a detriment to the batteries cycle life.

 

[toms]

No, if the EG4 and GW do not allow changes to the charging profile, nothing can be configured.

The only solution is to switch to manual configuration with no BMS/ Inverter communication.

My solution would be to change one or both of the EG4 / GW.

This isn’t an issue with BMS - AIO communication, it is an issue with cheap hardware that doesn’t do what it should.

 

[Quattrohead]

I use to use closed loop and I wish I could go back to using closed loop but I need the RS485 port on the Inverter to run Solar Assistant so that I can see realtime data remotely. I am really pissed that Sol-Ark will not turn on the second RS485 port but there is nothing I can do about that.

RS485 is simple 2 wire serial connection, just use a break out box or tap the wires directly. You may need to terminate the end device with 120 ohm resistor.

 

[robby]

RS485 is simple 2 wire serial connection, just use a break out box or tap the wires directly. You may need to terminate the end device with 120 ohm resistor.

One usable port and two devices that need a port. Lots of So-Ark owners have been down this road, it's either the Battery Cable or the Pi board for Solar Assistant. I could use the RS232 port but then I would loose the WiFi Dongle.

 

[Kornbread]

My solution would be to change one or both of the EG4 / GW.

This isn’t an issue with BMS - AIO communication, it is an issue with cheap hardware that doesn’t do what it should.

Change, as in replace the Growatt with another brand, or the eg4 batteries with another brand? Which component controls the charge settings? IMO, the cheap hardware is doing exactly what it is programed. It is the programming, as in the charge settings, that need relaxed.

 

[robby]

Change, as in replace the Growatt with another brand, or the eg4 batteries with another brand? Which component controls the charge settings? IMO, the cheap hardware is doing exactly what it is programed. It is the programming, as in the charge settings, that need relaxed.

Yes it is the Firmware in the batteries that has all the wrong settings. It is programming the Inverter with overly high values!
I doubt they are ever going to get the password to get into the advanced menu since signature solar could not get it to change the Pre-Charge Timing. The only hope is an update that has proper default settings.

 

[Kornbread]

Someone needs to hack these dam# batteries.

 

[Zwy]

My solution would be to change one or both of the EG4 / GW.

This isn’t an issue with BMS - AIO communication, it is an issue with cheap hardware that doesn’t do what it should.

Not a hardware issue, that appears to be working as programmed.

It's a software/programming issue.

 

[Kornbread]

Isn't it mentioned elsewhere that calendar aging will be an issue before actual cycling, so does running the cells up high into the knees actually hurt longevity?

 

[Zwy]

Isn't it mentioned elsewhere that calendar aging will be an issue before actual cycling,

It could. Fully cycling the battery, meaning running it from your set SOC to your set lower SOC cutoff, would not cause shortened cycle life as fast as calendar aging.

so does running the cells up high into the knees actually hurt longevity?

Yes, the data sheets from the manufacturers showed this to shorten cycle life.

 

[Kornbread]

Yes, the data sheets from the manufacturers showed this to shorten cycle life.

Why did the manufacturer run the voltage up so high?

 

[bones1]

I started out with communications. Until I understood the charging profiles of these batteries. Then I switched to manual settings. And improved my storage capacity. I believe that the BMS is being too modest. Much happier now. Myself and (I believe) the battery.

Can you share your manual settings, I have eg4 48 v batteries. Thank You.

 

[timselectric]

My settings are aggressive. But, I'm trying to get full capacity. You could back off a bit, with no detectable difference on a small to medium battery bank.

 

[bones1]

My settings are aggressive. But, I'm trying to get full capacity. You could back off a bit, with no dedtectable difference on a small to medium battery bank. View attachment 106469

Thank You. I see you have a Growatt inverter, I have EG4 inverters will this still apply? Sorry, I should have mentioned that.

 

[timselectric]

Which inverter does not make any difference. As long as you have the ability to manually change the settings.