MPPT controller only powers battery, not loads until SoC high

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valerion asked Sep 23, '22

MPPT controller only powers battery, not loads until SoC high

With all the loadshedding right now in South Africa right now, I have set my batteries to "Optimized with Battery Life" at a 100% SoC. Grid feed-in is disabled with grid setpoint of 50W and DVCC enabled using ESS.

I have a MultiPlus 5000 with 12 lead carbon batteries (replacing an older AGM bank), a single MPPT controller, CCGX, a BMV 702 and a ET112 grid meter.

What I see is that if the battery SoC is below the SoC setpoint, only the battery is charged from the PV array, while loads are powered from the grid. The PV output is throttled to whatever the battery needs, and no higher.

If I then lower the target SoC to below the current SoC, the PV array powers both the loads and the battery.

These two images were taken very close together, to eliminate any shading issues.

The problem that I have is that this severely limits the production in the morning, until the batteries have had a chance to charge, lowering my overall production for the day. Is there a way to get my PV array to also power loads at the same time it charges the battery? It might be an incorrect setting somewhere.

ESS

screenshot-20220923-104625.png (186.9 KiB)

screenshot-20220923-104905.png (188.0 KiB)

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Answer 1 · 2022-09-23T15:15:42Z

ponzoa answered · Sep 23, 2022 at 03:15 PM

Have you tried changing your "Optimized with Battery Life" at a 100% SoC" to say 85%? If you don't allow feed into the grid, your MPPT is correct to power down at fully charged baterías.

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valerion commented · Sep 23, 2022 at 03:53 PM

Let me test that. However, it is still as charged in the second screenshot and it's not throttling the MPPT charger. The only difference between the two is the SoC value I set and whether it's above or below that.

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ponzoa valerion commented · Sep 23, 2022 at 04:00 PM

Let us know how you go. I believe the behaviour is correct as effectually you're asking the system to keep the batteries charged so the MPPT should throttle down when full. By dropping this to 80% or so, you'll let the system use the battery and hence the MPPT(s) also.

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Answer 2 · 2022-09-27T07:47:47Z

valerion answered · Sep 27, 2022 at 07:47 AM

After some days of testing ...

Any form of Optimized tracks the battery charge ONLY. If the battery is in bulk charge, it draws quite a bit from the PV. Loads are always powered by the grid, until the battery is completely full, then solar powers loads. But this only occurs after solar noon, so I get very little solar production.

Keep Batteries Charged mode uses both the grid and solar to charge the batteries, but it runs the solar production at the total of battery and load usage. This way I get 1.5kW of power generated at 10am, instead of 200W. So even though the batteries will charge from the grid, this will still work out cheaper for me.

It seems that with lead acid and ESS you can't store energy from solar for later consumption, which I assumed to be the case from the way the documentation is written.

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Answer 3 · 2022-09-27T08:36:48Z

nickdb answered · Sep 27, 2022 at 08:36 AM

Is your SOC accurate? How have you set the shunt?

At lower charge levels the battery should pull plenty of power and only throttle at higher states of charge, which should be well above your minimum set.

So either you are setting your minimum too high, or batterylife is doing it (turn it off) or the SOC reported is wrong.

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