What’s your daily SOC range?

[Skypower]

I recently just added a third battery to the bank and the result was something I hadn’t given much thought to. A reduced depth of discharge which means a higher average state of charge. As you may know, that keeping a higher state of charge is detrimental for the long term for Lifepo4. Looking back on Solar Assistant data, I can see my new average daily range is now 100%(55.2 volts) to 70% (52.8volts) or 30% depth of discharge. About three out of four days it gets to 100%SOC. Opinions and what’s your range?

 

[Q-Dog]

You are fine as long as the batteries are cycling and not being held at 100% for days at a time.

 

[JRH]

I recently just added a third battery to the bank and the result was something I hadn’t given much thought to. A reduced depth of discharge which means a higher average state of charge. As you may know, that keeping a higher state of charge is detrimental for the long term for Lifepo4. Looking back on Solar Assistant data, I can see my new average daily range is now 100%(55.2 volts) to 70% (52.8volts) or 30% depth of discharge. About three out of four days it gets to 100%SOC. Opinions and what’s your range?

I’m cycling mine from about 35/ 40 %low to about 90/100 % high everyday according to the 712 shunt Usage numbers .All numbers make sence when looking at does it make sence… or does it add up…
im charging and discharging using about a rate of 15 to 20 % per hour …of bank total ..

im not sure what else to do as that’s the power I need to draw from a 400amp bank at 24 v to run what I run at this point…and what the panels and gear puts back in…at this point in good sunshine..
I do see that that a lower discharge rate gives better total amperage output…

Mine are never sitting long at a high SOC as I go out and use some power if I’m gonna leave them sit awhile…especially if the temp is up outside…Maybe down to about about 65% SOC if I’m Gona be gone.
that’s my layman’s plan at this point…they just seem to work and don’t give me any grief…
I guess their happy..!
J.

 

[OffGridForGood]

If you build an ESS that can get you through four days of autonomy, kinda by definition your depth of discharge will be super low. At least during good solar summer weather.
I just set the max charge voltage down a bit, and encourage the Official Solar Tester to go ahead and run the dryer or something...or I weld up something ...
Edit: this time of year nearly every day ends with 100% SOC,
Overnight brings this down to 85% ish maybe 80% if we run some late in the day loads.
Back up again the next day. it is summer.

 

[sunshine_eggo]

One thing to remember when having concerns about elevated SoC and LFP... temperature plays a huge role:

Insights for understanding multiscale degradation of LiFePO4 cathodes

Lithium-ion batteries (LIBs) based on olivine LiFePO4 (LFP) offer long cycle/calendar life and good safety, making them one of the dominant batteries …

www.sciencedirect.com

I have a 40°C alarm set for my batteries - It's triggering daily now. I only charge the NMC to 75% anyway, but I've lowered it to about 65% now since DoD while we're away is only about 9%.

 

[timselectric]

Currently 15% to 18% DOD for me.

 

[OffGridForGood]

Currently 15% to 18% DOD for me.

Thats only because you got that nice big battery rack up and running,...but didn't have time to expand the loads and add inverters yet!!!

 

[timselectric]

Thats only because you got that nice big battery rack up and running,...but didn't have time to expand the loads and add inverters yet!!!

It's coming.
But also more battery. lol

 

[Skypower]

If you build an ESS that can get you through four days of autonomy, kinda by definition your depth of discharge will be super low. At least during good solar summer weather.
I just set the max charge voltage down a bit, and encourage the Official Solar Tester to go ahead and run the dryer or something...or I weld up something ...
Edit: this time of year nearly every day ends with 100% SOC,
Overnight brings this down to 85% ish maybe 80% if we run some late in the day loads.
Back up again the next day. it is summer.

I’m using Solar Assistant’s “Maintain battery state of charge” and I had it dialed in pretty good for two batteries but now it’s a little out of wack. When it’s working it does a pretty decent job of supplementing grid on cloudy days or high demand hot days. It also only draws from grid when rates are low. My lowest SOC is around midnight. If I see excess and there was a miscalculation, I’ll dump power by doing a load of clothes, dishes or cool the house down to almost chilly.

 

[Brett V]

I’m usually around 60% capacity or 40% DOD in the morning before production goes in to the green. Hit 100% SOC almost every afternoon. I’m only charging to 55.2 volts though.

 

[Skypower]

One thing to remember when having concerns about elevated SoC and LFP... temperature plays a huge role:

Insights for understanding multiscale degradation of LiFePO4 cathodes

Lithium-ion batteries (LIBs) based on olivine LiFePO4 (LFP) offer long cycle/calendar life and good safety, making them one of the dominant batteries …

www.sciencedirect.com

I have a 40°C alarm set for my batteries - It's triggering daily now. I only charge the NMC to 75% anyway, but I've lowered it to about 65% now since DoD while we're away is only about 9%.

I don’t know if it cools down there at night. I have fans that blow air over the batteries from 2AM to 10AM when it’s cool but not when the air gets hot. Cooling them down gives them just that much more time to heat up. If you have rack batteries I don’t know. Best of course is climate control. The flat spot in the middle is when I took everything off line and to grid so I could spend quality time balancing the new baby.

 

[Skypower]

I’m usually around 60% capacity or 40% DOD in the morning before production goes in to the green. Hit 100% SOC almost every afternoon. I’m only charging to 55.2 volts though.

Seems like a lot of people are liking 55.2 V

 

[timselectric]

Not me, I charge my batteries all the way up. lol

 

[EastTexCowboy]

I'm hitting 60% DOD most days now, lower if it's cloudy. That will change when I add more batteries. In a little cooler weather it was 30%. I usually hit 100% each day or close. Collier weather I'm at 100% by noon. Today it made a little over 80kwh and barely made it to 100%. Winter will be interesting.

 

[EastTexCowboy]

Seems like a lot of people are liking 55.2 V

I have mine at 57v. Seems to be the only way I can get the batteries to balance. @timselectric told me to drive it like I stole it.

 

[ksmithaz1]

I'm running a rather inefficient block home. At the present time I have 30KWH, and I shutdown at 7%, this generally occurs after 2200hrs. TOU is 1300-2000, and my usage/production generally flips around 1700, so I need at least 3 hours, it has lasted until 0100. If I don't charge my car and get good sun, I'm at 100% by 1230. My control computer only allows charging from 1130-1500 @4400KW, but if solar output dips during that time the batteries kick in a little from time to time to make up the difference and I may not get to 100%. So far so good. I may pick up the low cutoff, another point but I am deep cycling. I started by trying cutoff at 10%, then dropped it to 5 before tweaking it up to 7. My inverter will not kick back on until it's at 5% above the cutoff, so it's a bit of a game, that's generally before 0715. I'm just trying to maximize $ savings. Everyone has the "do this to save your batteries", but if I have '30' KWH, I want to be able to use close to that amount as needed. One of the things you have to consider is arguments like "I get twice as many cycles if I only use my batteries between 25% and 75%". Well yes, but you pushed the same number of watts in and out of the unit until it died, so that is a bit of a game as well. At some point I will be getting another 30KWH, but it will probably take 60 and 8 more panels to run overnight.

I have noted that the batteries struggle a bit more to provide output when below 10%. the 5-7 jump was pretty significant when my A/C cuts on. I'm staring at a Micro-Air, which I hope will improve things even more.

 

[Brett V]

@timselectric told me to drive it like I stole it.

Sage advise.

 

[EastTexCowboy]

One thing to remember when having concerns about elevated SoC and LFP... temperature plays a huge role:

That's one of the reasons I sprung for the mini split in the garage. Mine stay around 25-26C day and night. Internal temps on the inverters top out at about 58-59C. Better for everything. Including me, when I'm out there.

 

[OffGridForGood]

I'm running a rather inefficient block home. At the present time I have 30KWH, and I shutdown at 7%, this generally occurs after 2200hrs. TOU is 1300-2000, and my usage/production generally flips around 1700, so I need at least 3 hours, it has lasted until 0100. If I don't charge my car and get good sun, I'm at 100% by 1230. My control computer only allows charging from 1130-1500 @4400KW, but if solar output dips during that time the batteries kick in a little from time to time to make up the difference and I may not get to 100%. So far so good. I may pick up the low cutoff, another point but I am deep cycling. I started by trying cutoff at 10%, then dropped it to 5 before tweaking it up to 7. My inverter will not kick back on until it's at 5% above the cutoff, so it's a bit of a game, that's generally before 0715. I'm just trying to maximize $ savings. Everyone has the "do this to save your batteries", but if I have '30' KWH, I want to be able to use close to that amount as needed. One of the things you have to consider is arguments like "I get twice as many cycles if I only use my batteries between 25% and 75%". Well yes, but you pushed the same number of watts in and out of the unit until it died, so that is a bit of a game as well. At some point I will be getting another 30KWH, but it will probably take 60 and 8 more panels to run overnight.

I have noted that the batteries struggle a bit more to provide output when below 10%. the 5-7 jump was pretty significant when my A/C cuts on. I'm staring at a Micro-Air, which I hope will improve things even more.

In winter months, I use TOU to charge every night at low cost, during Nov - Jan when overcast skys make the solar charging potential Suck. I don't often drive the SOC very low, as I always want some capacity for the original purpose of this set up - utility outages.
If I let the SOC drop like a rock, and the utility drops out, then I am on (expensive) gen set charging at over a dollar per kWh. Since utility outages are rather common occurance, I like to keep SOC above 50% as a general rule, until the utitlty is down.

 

[ksmithaz1]

That's one of the reasons I sprung for the mini split in the garage. Mine stay around 25-26C day and night. Internal temps on the inverters top out at about 58-59C. Better for everything. Including me, when I'm out there.

It's really hot here. 112ish today. I'm not cooling my utility room, just a vent fan, inverters are rated to 140C, and the batteries claim 131F. I do have a big fan on them. The cars (both EV) are generally charged setting out in the middle of the sun, so we will see.