EQ4800-L9 capacity mismatch: 41.9 kWh capacity but measured ~37 kWh

[TheRoseManCanberra]

I'm in Canberra and this worries me, i wish i'd known about this before i bought a L9 in January, i would have gone elsewhere.

[QLDuser]

Do you guys realise that it is battery preservation issue? Best practice recommends that lithium batteries are cycled within certain limits to preserve better lifespan. Cycling from 10-100% gives it a certain lifespan which I think is what FoxESS estimates, ie 6000 cycles before dropping to 70% efficiency. Of course many other factors impact upon its lifespan such as temperature and how fast the battery is charged or discharged etc. Dropping to 0% battery will bring on faster deterioration. Ideal recommendation is actually to cycle between 20-80%.

For good explanation on FoxESS see https://www.solarwind.net.au/extending- ... -warranty/

[Beno62]

Do you guys realise that it is battery preservation issue? Best practice recommends that lithium batteries are cycled within certain limits to preserve better lifespan. Cycling from 10-100% gives it a certain lifespan which I think is what FoxESS estimates, ie 6000 cycles before dropping to 70% efficiency. Of course many other factors impact upon its lifespan such as temperature and how fast the battery is charged or discharged etc. Dropping to 0% battery will bring on faster deterioration. Ideal recommendation is actually to cycle between 20-80%.

For good explanation on FoxESS see https://www.solarwind.net.au/extending- ... -warranty/

Not very relevant to the thread.

[QLDuser]

I was suggesting that you can only access 90% of capacity because the last 10% is to protect health of battery.

[welsouki]

So in either case, there is either something wrong with the app figures, and in both cases, we aren't able to access the full battery as specified. At best we are missing 10% capacity, and at worse we are missing 20% capacity.

All can be reproduced using Fox Cloud stats, home assistant is just a handy way of graphing and logging that data at a good higher interval. So I definitely don't think it is a home assistant issue.

But as you suggested will write to Fox and see what they say.

StarryTissue, did you end up hearing back from Fox ? I just realised I have the same issue.
e.g. charging yesterday from 20% to 85% at constant 9.87kW took 140 minutes, so ~23kWh charge for 65% SoC increase, which equates to a 100% SoC of 35.4kWh.
Doing the above check for few different days in the last few months, the number fluctuates between 35-37 kWh.

Have we ruled out one of the battery modules not working but it's not being reported by the system ?
The EQ4800 has 9 modules of 4.66kwH, so an inoperable module will also have the effect of losing the ~10% capacity we are seeing.
But I see no faults on the app or inverter.

I am going to submit a ticket to Fox. let's see what they say.