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[Sticky] Tell us about your Solar (PV) setup

Bob@Lochinver · 2021-03-05T17:13:42Z

I have just installed a new solar array on my south facing roof on the 29th Jan 2021 so all very new for me but my setup is as follows: 12 x JASolar 455w Panels (5.46kWp south facing array) Enphase Microinverters IQ7+, Lux AC ESS 3.6kW Inverter, 2 x 2.4kwh = 4.8kWh Aoboet Battery storage, and while I am on the Octopus standard tariff at the moment I am awaiting an install of a smart meter to take advantage of the better rates for charging my batteries outside of the solar charge day and to export my excess back to the grid. Based in Lochinver far North, west coast of Scotland My first month of solar production was from my Enphase system for February was 294kWh which I guess is okay :)

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Solar Photovoltaic (PV)

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bobflux

(@bobflux)

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Joined: 3 weeks ago

Posts: 37

04/03/2026 8:43 am

@mk4 Charge to 100%, discharge down to 10%.

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MK4

(@mk4)

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Joined: 2 months ago

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05/03/2026 9:24 am

Posted by: @bobflux

↑

@mk4 Charge to 100%, discharge down to 10%.

Since you seem to quite thoroughly investigate every step you take, how did you choose these levels? I am trying to understand what are the optimal levels to preserve battery health and lifespan.
Sungrow (our battery) documentation suggests a 10%-90% range. We are able to fully charge our 9.6kwh almost every day and now that we have the ASHP, we can also easily drain it on a daily basis. Thank you.

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bobflux

(@bobflux)

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Joined: 3 weeks ago

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05/03/2026 12:40 pm

Pylontech US5000 stores about 4.3 kWh accounting for inverter losses and costs 1000€. Over 3000 cycles this means one kWh going through the battery costs 7.7c ; half that for 6000 cycles. Much cheaper than drawing from the grid (about 0.20€/kWh) even if I run them into the ground they will pay for themselves nicely. And the more I use them, the more they pay for themselves.

I did some research, but unlike NMC which are special delicate snowflakes, LFPs just don't seem to care about anything except heat (the most important), the usual overcharge/discharge (which the BMS should prevent) and cycling near full charge.

There's this study which says "Cycling near the top of charge (75%–100% SOC) is detrimental to LFP/graphite cells." However, charging the battery instead of using the energy directly is also detrimental to the bottom line because the inverters have 10-15% losses on the roundtrip... So using the energy in real time is both more efficient and saves wear on batteries. In other words, priority to the EV charger and other stuff, battery charging comes last.

There seems to be a linear relationship between total energy cycled and aging, no matter the SOC span of the cycles, except the point mentioned above. So with half-cycles, they will last twice as many cycles... but if I only use half the capacity, then I need to buy 2x as many batteries, so why bother?

They report losing 1% SOH per year which is in line with manufacturer specs. With lots of care and cuddling, the cells will probably last longer than the BMS lol.

Pylontech says do not go below 5% SOC so I set it to 10% to be safe. I will probably add 1-2 more and set it to 30% to have some juice in case of blackout.

I set max SOC to 100% so the BMS can do its balancing. They do age faster at 100% but they don't stay there for long...

I put them in the cellar, the internal sensor reports temperatures around 20°C idle to 30°C at end of charge.

Max charge power is about 10kW so 0.5C, but this only occurs if nothing else wants power. If the car is plugged in, or there are other loads running, home batteries will of course charge slower or just wait for their turn.

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