Reserve cap and Min SOC settings...

[Monkeypuzzle]

Hey all, I'm new here so a little info:

I'm UK based and I've been building off grid systems using Studer and Victron inverters powered by banks of Pylontech batteries for use in our work putting on small scale live events. These have powered band stages in parks, light trails, soundsystems on floats etc for about 6 years so I have a good idea of the technicalities and terminology used in solar. I've just had a FoxESS 5kw system with 5.2kwh of batteries put in my house with 2.6k of panels facing SE and 1kw of panels facing SW. I currently don't have any feed in arrangement as I don't have a smart meter (coming soon) so I've changed the charge time to just after I generally stop getting charge power from the sun. I assume this will make the most efficient use of my solar generated energy as as much as possible will go into charging the batteries? I know it would depend on the amount per kwh i can get for selling vs what i would pay to charge but with my set up would i actually be better off leaving it like this rather than going on a split cost tarrif and setting it to charge late at night?

Anyway, to my main question... With my mobile systems, I always overspec the batteries as much as I can for any job they go on. This means I rarely see a SOC of less than 50%. I know that this may seem like i'm carrying more batteries than I need but I want them to last as long as possible and having the reserve is always good on live events.... Consequently, I've changed the Reserve cap and Min SOC to 45% from the 20% the installer set it at. I know this will make them last longer but could I be squeezing more from the system If I dropped it back downwith any noticable reduction in battery life? Average daily load is about 8kwh and current power from the panels is about 10kwh (it has been pretty sunny since they were commisioned...) Also, whats the difference between Reserve Cap and Min SOC?

Many thanks, Matt

[Dave Foster]

LiFePo4 batteries are much more stable than Li-ion and have a wide range of use (depth of discharge), the Fox batteries are 90% DoD and it is better to use the entire depth of discharge rather than a reduced limit such as 50%. The BMS manages the individual cell balance of the batteries and it learns how each cell is performing as the batteries approach 10% and 100% respectively - although the 100% is the critical number to achieve from time to time as most pack/cell balancing occurs in the last 5% between 95-100%.

On the difference between minSoC and Battery Reserve - unless you have installed an EPS (emergency power supply) they should both be set to the same value (usually 10%), if you have EPS the difference between minSoC and battery reserve is effectively ‘reserver’ for when the gird fails and it is running on battery power only.

[Monkeypuzzle]

Thank you very much for this, its really helpfull. I've lowered the values so I'm making much better use of teh batteries. I'll have a chat with the chap from the electric company regarding which tarrif is best when they come to install teh smart meter on Thursday. Very happy with the system so far...

Matt