Maintaining your LiFePO4 batteries

[Neal]

I had a little correspondence with Solar Energy Systems (SES) Nappanee last week pinning down how often I should be discharging my LiFePO4 batteries for good health. The answer provided was monthly. As my coach is in storage I was able to do this via VRM which can control my two Victron Multiplex inverters changing them from "ON" to "INVERTER" so they are no longer charging. It took about 4 days to discharge to about 30%, I stopped just above as AGS is programmed to come on at 30% and handle the charge. A good way to exercise the GEN but don't need that right now. It took about 5 hours at a constant set 90A charge rate to bring the 1320 AH bank back to 100%. Things are looking good and dialed in with the new install. Love it!

 

[Ddmo]

Neal. Glad you are dialing it in and are able to control remotely. That is sweet.

Looks like you are purposely limiting current to 90amps. I’m assuming that there is no reason to push things since it is in storage, gentler on batteries and equipment. More curious about why 90 and not lower and slower. Was that recommended by SES?

Also wondering what you think about being 30% (396ah left, so consuming 924 ah) and only adding 450ah to be at 100%.

I had this issue with my setup in my old rig and never could quite dial it in. I was kind of hoping this was resolved with the newer inverter/chargers.

DDMO

 

[Neal]

SES set the 90A and I think that was the same as I had with the Magnum setup. I don't know that slower or faster makes any difference, you can throw a whole lot more at the LiFePO4's as you know and I think that's perfectly fine. What SES wants and setup mine to do is an 8 hour absorption for cell balancing. So it keeps voltage high for 8 hours to ensure all cells are balanced, maybe that was something that could have helped in the past?

30% does seem high. I thought it may be for protecting the 10.0V bottom end. I'll have to research if Victron has guidance on min voltage just like they surprised me with 41F min for charging. I know my GEN is programmed to come on at 30%. I may need to adjust these numbers as I get more comfortable with this setup. Looks like 15 or 20 percent may be better targets but don't go below values. I think 12.0V is the do not go below number? I thought it was 10 but now looking at charts it may be 12.

 

[Ddmo]

Thanks Neal. Balancing cells on the old one was something I had to do regularly, like every 6 months. I like the idea of just holding absorb higher for 8 hours.

But if I understand correctly. You consumed 924 ah over 4 days but only added 450ah to get back to 100%.

 

[Neal]

But if I understand correctly. You consumed 924 ah over 4 days but only added 450ah to get back to 100%

I discharged to 34% SOC from 100 and then turned the charger back on.

 

[Chuggs]

Four days... [drool]

Wish I could go four days...

 

[Neal]

Well, I should have let it go another day or two