How often to cycle for maintenance

[karamazov]

Just got my DIY build online (that will be another post) but I'm looking for some recommended maintenance best practices for battery longevity.

I have a ~29kWh bank I built myself (thanks to what I learned from this forum and Will's videos), the primary purpose of which is an emergency grid-down backup.

My power coop charges a flat rate, so I'm not going to save any money by selling back from the batteries during "peak" hours. Therefore cycling them daily seems like a waste. So I was thinking of how best to set the batteries up on a schedule. Would programming the inverter to basically cycle them once a week to maintain them in a healthy state? Can I get away with longer than that? Or would it be bad to let them sit at "100%" (roughly 3.4v per cell) for a long time?

 

[OzSolar]

Or would it be bad to let them sit at "100%" (roughly 3.4v per cell) for a long time?

The oft repeated advice is 50%. Below is a thread that digs into it. What I don't know is does leaving them at 100% all of the time vs. 50% most of the time turn a 15 year stationery life (just my guess) into a 7 year or 12 year?? EG: Is perfect the enemy of good enough?

The obvious problem is that your backup power system will sit there at 50% most of the time so you would have to figure out how to get them charged back up just before the big ice storm etc.

What is considered "storage"

Read a lot of threads that said to store your lifopo4 battery at 50%-60% SOC. What is considered storage? 1 month of no use but still hooked up in the RV or is it 6+ months unhooked and sitting in your garage? My LifePo4 batteries will be used as the house batteries on my RV. The RV will sit...

diysolarforum.com

 

[zorlig]

For emergency grid down backup float them at 3.4. it's the most cost effective solution, it's what all the telcoms do etc. There is no need to cycle or do anything else at all.

 

[Bud Martin]

@OP.
How often does your grid go down, and for how long?

 

[karamazov]

For emergency grid down backup float them at 3.4. it's the most cost effective solution, it's what all the telcoms do etc. There is no need to cycle or do anything else at all.

Hmm, interesting, a lot of the other places I was reading said that you had to cycle lofepo4 batteries every few months or so. But if it's good enough for utilities then I guess it should work for me.

@OP.
How often does your grid go down, and for how long?

Our power has actually been pretty reliable since we've moved here a year and a half ago or so, so it's not a regular occurrence. The one time it did happen was for a few hours at night.

 

[zorlig]

Hmm, interesting, a lot of the other places I was reading said that you had to cycle lofepo4 batteries every few months or so. But if it's good enough for utilities then I guess it should work for me.

Our power has actually been pretty reliable since we've moved here a year and a half ago or so, so it's not a regular occurrence. The one time it did happen was for a few hours at night.

Just make sure your BMS balances at 3.4. I think the only reason to cycle would be to get them to a high enough voltage to balance.

 

[SeaGal]

How often to cycle for maintenance?

I try and get out on my bike once a week for a few miles in summer ?‍. Not sure that keeps up with degradation through overuse and ageing though!!