EG4 Lifepower4/Sol-Ark settings

[b.shaw]

My system is new and I'm in the process of optimizing the settings. I have some questions and am hoping I can get some advice on settings from you guys.

Question 1: Does the Sol-Ark low battery cut-off at 20% make sense given that each battery has a BMS protecting it from over-draining the battery? Or to put in a different way, Should I set the Sol-Ark's low battery cut-off to 0% or 1%?.

Question 2: Given that there are 6 BMSs in the batteries, are the Sol-Ark battery settings critical? Should I 'widen' the battery charge (and possibly discharge) parameter so that the Sol-Ark doesn't try to limit charge and discharge currents, letting the batteries BMSs control the charge and discharge cycle?

Given that the Sol-Arks are controlling charge & discharge (which I'm not convinced of), am I using the optimum settings? I see others posting slightly different battery settings than I have.


Float V: 56.3
Absorption V: 56.3
Equalization V: 56.3
30 Days, 0 Hours
Shutdown: 20% (46v)
Low Batt: 30% (47.5V)
Restart: 40% (52V)
Batt Empty V: 47
Batt Resistance: 8mOhms
Batt Charge Efficiency: 99%
Batt Capacity: 600Ah for 6 batteries
Max A Charge: 185A (maxed out & low for 6 batteries, IMHO)
Max A Discharge: 185A

More questions to come as I try to use the system to its full potential.

 

[BentleyJ]

The BMS in the batteries is a "last-resort" safety device for the batteries, it is NOT intended to be a control device. It Opens the connection between the batteries and the inverter to prevent permanent damage to the cells due to out of range Voltage, Current or Temperature. Under normal circumstances the BMS should never have to intervene. The Inverter settings control the system. Even when there is closed loop BMS communications with the inverter it's still the inverter controlling everything using some of the BMS info that is passed over to it.

Question 1) No, 10% to 20% Low Batt Cut Out is good.

Question 2) BMS does not control anything, its a switch its either On or Off. Charging and Discharging currents are set based on "C rates. Usually 0.2 to 0.3C for charging and up to 1C for discharging. It also depends on the wiring and bus bars etc. Amperage should never exceed the lowest rated component in the DC circuit. For a 600Ah battery bank a 0.3C Charge rate is 185A so its not low at all. Unless there is some particular reason for your situation where the batteries need to be charged fast I would consider lowering the Charge Amperage to 150A or even 120A (0.2C) and allowing a longer recharge absorption time.

Max Discharge?? With dual 12K Sol-Ark's I believe that's 9kW of output per inverter so discharge current could reach 200A when losses are figured in. 185A Discharge setting may slightly limit the inverter output unless increased but with 2 inverters can your wiring support a total of 400Amps? 400Amps would be 0.67 C discharge rate.

 

[BentleyJ]

Additional comments. LiFePO4 batteries do not need float. Would recommend turning it off most of the time and lowering the float voltage to 54.0 to 54.4V if you do use that feature for example to top balance the cells over a few days.

Absorption voltage is OK as is.

 

[b.shaw]

Thanks for your input BentleyJ, that's very interesting. I would have thought the battery manufacturer would would want to control the charge/discharge cycle and parameters over the inverter manufacturer.

 

[DougfromdaUP]

There is a lot of good information on charging your batteries. Keep in mind that everyone has different goals - maximum service life, maximum output, etc. Here's a thread to start with:

https://diysolarforum.com/threads/b...-stress-5-000-10-000-cycles.34813/post-435243

Also, with two 12Ks your charge and discharge current will approach 380 amps at peaks.

 

[DougfromdaUP]

By the way, I've been running a SolArk 12K and EG4 LiFePower4 batteries since may, so I've suffered through a lot of learning.

 

[b.shaw]

Very helpful... should be on the must read list!

 

[629658]

One other tidbit if the Sol Ark sees grid power it limits DOD to 40% regardless of your discharge settings. In off grid or no grid then your discharge limits apply.

 

[DougfromdaUP]

One other tidbit if the Sol Ark sees grid power it limits DOD to 40% regardless of your discharge settings. In off grid or no grid then your discharge limits apply.

This doesn't happen with my system. In good weather I routinely discharge to 20%, and I've left the grid connected since early november (since I live in Michigan.) If a storm is coming I change to 35%, which will last me many hours.

 

[629658]

That’s how my 15k operates and confirmed with Sol Ark. I like that feature too. It’s easy on my batteries 99% of the time and we can draw down to 20% on the rare occasion we lose grid. So I’m working my batteries in a 40-100% range which should give me many years of battery life.

 

[DougfromdaUP]

That’s how my 15k operates and confirmed with Sol Ark. I like that feature too. It’s easy on my batteries 99% of the time and we can draw down to 20% on the rare occasion we lose grid. So I’m working my batteries in a 40-100% range which should give me many years of battery life.

From your first post it looks like you were inferring that all Sol-Arks would not discharge the battery below 40 percent if the grid was connected. Are you still maintaining that that is true? What did Sol Ark confirm with you? I certainly believe that your system operates in that fashion, since it's a user setting. But I'm concerned that you think that 40 percent is some kind of limit for the depth of discharge for all SolArk 12ks with the grid connected.

 

[629658]

Can’t speak for the 12k buy that is what the Sol Ark support guys told me. Could be my settings I suppose but either way that’s how mine is operating and I really like it. My battery manufacturer likes it too. They say we are treating our batteries well and to expect zero longevity issues with these settings.

 

[DougfromdaUP]

I try to be gentle to my batteries, too, but i figure only going to twenty percent is as gentle as I can afford to be. If there is good information on exactly how much the life would be affected by changing from 40 to 30 for DOD I'd like to see it. So many tables, charts, etc. have conflicting info. I hope they last a long time.
And I guess yours are going to last longer than mine!

 

[629658]

I try to be gentle to my batteries, too, but i figure only going to twenty percent is as gentle as I can afford to be. If there is good information on exactly how much the life would be affected by changing from 40 to 30 for DOD I'd like to see it. So many tables, charts, etc. have conflicting info. I hope they last a long time.
And I guess yours are going to last longer than mine!

This is from the Trophy battery website:
“Battery Cycle Life” is a term used to denote the number of times a battery may be charged and discharged, with the battery capacity remaining at 80% or higher. Note, after this number of cycles, the battery is still very useable.

But, please be very cautious when comparing Battery Cycle Life values you see in marketing materials.

Lithium Ferrous Phosphate batteries can have a long life and an exceptionally long life under the right conditions.

Here is an example. Over the life of a battery, if it was charged to 100%, deeply discharged, with high ambient temperatures, then the number of Battery Cycles will be low.

If a battery is charged to around 95%, then discharged to only 50% on most charge-discharge cycles, and kept at reasonable temperatures, the battery will last an extraordinary number of cycles.

Thus, to make an informed decision a claim of very high Battery Cycles, one needs to know the starting state of charge, the rate of charge, the depth of discharge, the rate of discharge, the ambient temperature of the tests, and the storage conditions of the battery before performing the tests.

Marketing Materials rarely provide all of these details.

A manufacturer’s battery specification may list only 2,500 to 3,500 under demanding conditions, then show charts showing alternative conditions where the “Battery Cycles” can reach 10,000 or more.

Note: A claim of 7,000 battery cycles may be perfectly valid, provided one uses standard practices to help ensure the long life of the battery. Under more demanding conditions, the number of cycles may be much lower.

So, the same battery, rated under differing conditions, may be rated at 3,000 to 10,000 cycles or more. Thus, please be cautious when you read claims of high battery cycles.

It is important to note that when using batteries in solar systems, the nature of the charge/discharge cycle typically results in a high number of battery cycles.

The same applies when using batteries in Uninterruptable Power System for one’s home or another facility. This battery application, proving power on-demand, also typically results in extended battery life.

Batteries stored at high temperatures, charged to 100%, then discharged to a low level every day will not last as long as the same battery used under more favorable conditions.

To ensure that your battery lasts a long time:

Keep the battery relatively cool. Temperatures in the 90s (F) are acceptable, room temperature is even better, but much over 100F diminishes the battery’s life.

Purchase enough battery capacity, measured in Amp-Hours (AH) or Watt-Hours, so that you are not deeply discharging your battery daily. You may purchase multiple batteries and connect them in parallel or purchase larger capacity batteries.

Ideally, charge your battery to only 98% or so and discharge your battery (generally) to only around 50%. Under these conditions, each charge-discharge cycle does not even count as a Battery Cycle.

Note: Most car manufacturers never discharge their batteries below a certain level in their battery-powered and hybrid vehicles. They are using the practice of lightly discharging the battery to extend the life of the batteries. This enables their batteries to be used every day for many years.

For emergencies, when the electrical grid is down, or you expect it to fail for some reason, it is perfectly acceptable to charge your battery to 100% and then discharge it to 20% during the outage. This technique will count as one “Battery Cycle” out of the many thousands of cycles available in the battery.