OK, so this may be a strange request, but perhaps my usage case is a bit different…
My usage load on the LifePO4 battery is pretty low lately, relative to the output from my solar panel. So basically, my LifePO4 is staying above 80% charge pretty much all the time. It runs down to the low (usually around 85% SOC) at night, then is quickly charged up to full again the next day. So it seems exaggerated to go through full absorption and float phases every single day, for only a little bit of capacity used. And the battery’s SOC is spending quite a lot of it’s life above 14V, which I worry to be bad for the battery long term.
Would it not be better for the battery to just disable absorption and float and just let the charger charge up to say 13.8 or so and then just stop charging? Then the battery would spend more of it’s life in a ‘healthier’ SOC (80% or so)?
If this is a SmartSolar then you should be able to change the settings using the VictronConnect app. Reduce absorption voltage to 13.7V and still get a reasonable charge. You should also be able to set a maximum absorption time of say 15 mins if you leave it at 14.0 or 14.2V. If it is a bluesolar get a VE Direct Bluetooth dongle to program it via VictronConnect.
Similar with mine however I’m not worried by it as IMO the do not charge above 80% is a hangover from old technology lithium batteries.
I only have half hour absorption and although it gets to 100% the MPPT then switches off until the battery voltage drops to 13.5v and after that only supplies the load and nothing to the battery unless the load is greater than the MPPT can supply then it part comes from the battery.
Most of the time although it’s sitting at 98% and 13.5v the current is 0A so I can’t see how it’s doing any harm to the batteries.
I do on occasions, if it’s going to be really sunny as now, turn the MPPT off for a few days more because I can than for any other reason.
@jrmartin505 an add on thought, if you reduce the absorption voltage then your BMS may not balance the cells, you would still need to get them up to 14.2V or whatever your battery manufacturer recommends every few weeks or so. My lithium batteries normally cycle down to 80% and get a daily absorption with 15 mins max then spend the rest of the day at 13.5V on float.
Yes, it seems that what I really need to do, upon further consideration of these ideas is to limit the absorption time. That way the battery spends less time up in the 14+ volts range, but still gets there to do balancing. I’ll try 15 minutes. I do have one cell that’s slowly balancing up to the others so it will be interesting to keep an eye on.
And I guess I’ll leave the float alone at 13.5. BTW, how long is your float set for?
As it’s solar only ( I have no shore power) float is only on until the sun sets. I don’t believe there is a setting to limit float duration but the sun does a pretty good job.
My charger has the same settings as the MPPT, it also has a Sonoff WiFi switch on it so I could set the on/off times to mimic sunrise and sunset.
Full setup here is 130w solar panel, 70/10 MPPT controller, IP22 charger. Controlled by Venus OS on an RPi3b. There are several Sonoff switches enabling me to switch on and off various parts of the system. A TP link MiFi connecting it to the VRM portal. All done very much on the cheap as is my wont.
Same answer as above, stays at 13.5V covering loads until the sun sets then goes down to circa 80% overnight. Then gets charged either by engine alternator or solar.
