Battery charging (maintaining a good life expectancy)

[Grumps]

Hi,
I'm not sure why I can't find topics about this already, as I'm sure it's a popular question.

I have a recent solar-battery installation, and now my SEG is active (export tariff). The export tariff is greater than the off-peak rate.
From what most people say regarding lithium batteries, a rule of thumb is to keep the charge between 20% to 85%. This obviously reduces usable battery capacity to 65%.

What I'm doing at present is to fully charge the battery during nighttime off-peak electricity rates, then power the house during the 18 peak hours from the battery. To maximize revenue, the power generated by solar is exported.
If I do this, then the battery goes from 100% to about 40% before it is charged again. Sometimes lower if heavy loads are used during the day (that can't be scheduled for off-peak times).

Is this a popular scenario, or is there anything better to maintain battery life?

[MaterialBarracuda48]

I have had my EP11 for a year now, and still reports 100% SoH (State of Health)
My min SoC is 10% and max 100%, it will sit at 100% for a few hours each night, until discharge is allowed from 05:30.

All I do is allow it to discharge during the daytime to feed my house usage, and it does not charge up until 23:30 (though I get a few random charges from IOG slots, but they aren't often)

Once a month, I will discharge it all the way down to 10% so that the BMS can keep calibrated and know the end points of the cell Voltages.


That works for me, others will chime in give their opinions shortly.

[evilbunny]

I have had my EP11 for a year now, and still reports 100% SoH (State of Health)

The specs for the Fox ESS batteries we had installed last month state they will have 80% capacity after 3,000 charge cycles.

Although some LFP battery chemistries can do 6,000 before the max capacity drops to 80%.

So I'd be extremely concerned at this point if you did notice anything, considering you're only 1/10th of the way there.

[MaterialBarracuda48]

Here is a thread about SoH being discussed here, viewtopic.php?p=11640#p11640 where Kosymodo has their EP11 heated installed 5 months after mine, and reporting 96% SoH.

I would just use the 90% DoD (Depth of Discharge) available to you, and not worry too much about keeping the SoC between 20% to 85% max

I have only just done 243 Cycles of the battery after 1 year, some are higher than me (example Kosymodo) in the above thread.

You are doing the same as me, charging at night, using battery for 18hrs and exporting max solar. Unless you did something extremely mad with your battery, it is hard to break it, or wear it out doing what you are doing.

[UK_KH_User123]

I think charging to 100% is not a problem with our batteries and I think discharging to 10% could be done quarterly (or even less often) for 'cell maintenance'. Another way to be nice to your battery is to keep charge and discharge rates as low as you can to achieve your goals. For example, if you have six hours to go from 30% to 100% you can probably do that at 4kW charge rate. Take as much time as you have available to charge up.

[evilbunny]

Another way to be nice to your battery is to keep charge and discharge rates as low as you can to achieve your goals.

Another consideration when buying is that having a big battery stack would charge slower on the same sized inverter than a small battery stack.