Extra batteries added - Weird charging/discharging stats

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Milanu
Posts: 2
Joined: Wed Sep 11, 2024 1:22 pm

Hi, definite novice here seeking some reassurance please.

I had a 5.53kwp PV array installed a couple of years ago with 2 * FoxESS Cube batteries i.e. 2*2.88kwh, the inverter is model H1-5.0-E.

Just had two further batteries added to the system, again FoxESS Cube 2.88kwh. So now have a total battery stack of 11.52kwh.

It’s only the first week since batteries added and I am noticing so very odd charging and discharging patterns with the SOC% value leaping up/down in big steps.

Example of what I saw according to foxes web stats/graph.

SoC is at at 100%. System starts discharging from batteries at a steady discharge rate around the 2.8kwh for around 39 minutes at which point SoC reported to be 20% (my min SoC) and then it’s all grid consumption kicked in. That seems way too fast to dump the entire (-20%) stored power.

My simple calculation is that 80% of my new usable battery capacity (11.52kwh) is 9.2kwh which at a discharge rate of circa 2.8kwh should last a little over 3 hours, not 39 minutes.

First week so I am guessing there is some battery management balancing to happen but performance in the first week with double battery capacity appears worse than before the extra batteries were added. Is this weirdness normal ?

As an aside, is there a way to see more battery stats in the phone app or the web app? I cannot even find any recognition of the total battery capacity available to my system. Can you see individual battery stats i.e. Capacity, Charge levels either in % or stored kwh? To my mind SoC 100% could mean one battery is working and full and the other 3 are dead? How would I know? Presumably these batteries lose max storage capacity over the years, or do they not deteriorate over time like phone batteries? I did download and try a different phone app "Energy Stats" which does not give better battery stats as far as I can see. I would love to see what each battery is doing is more detail.
Dave Foster
Posts: 1298
Joined: Thu Oct 13, 2022 7:21 pm

When you added the extra batteries, did you ensure that the existing stack was at 50% SoC ?

Have you updated the battery firmware so that all versions are the same ?

If either of those haven't been done the batteries will perform exactly as you say, badly, and depending on the state of charge of your stack was when you added them - balancing can take anywhere up to 4 weeks, slightly quicker if you charge to 100% and drop to 10% every day.

The website show you the battery volts (which confirms how many batteries are fitted), it will also list all the battery serial numbers and display the nominal capacity which also confirms what batteries you have installed.

Depending which app you have, you will get similar or slightly fewer stats - V2 being the best.
Milanu
Posts: 2
Joined: Wed Sep 11, 2024 1:22 pm

No idea what SoC of stack was when installed as I did not do the install, so I guess that could be a contributory factor. Firmware is all the same version. Thanks for the voltage tip. I'll have another look as I did not spot that. Cheers!
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