Off-grid EasySolar-II SOC dropping

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the-doon asked Dec 8, '21

Off-grid EasySolar-II SOC dropping

Hi, I have an off-grid system using an EasySolar-II 3kVA paralleled with a MultiPlus-II 3kVA. Connected to 4 of 48V 50Ah Dyness lithiums and 4000W of solar panels. Everything is working perfectly except the SOC shown on the EasySolar is dropping a little day by day. It’s down to 86% today when it hit the full battery voltage of 52.0V which is set by the battery via CAN-bus. I’ve seen the threads saying to set the MPPT slightly higher to trigger the reset of the SOC but my MPPT says it’s under ”External Control” so nothing I change raises the charge voltages etc. Is there a way to force the SOC to 100% at a certain voltage eg. 52.0V? It’s never shown 100% but it used to be pretty common to see 97 or 98% but now it just seems to be dropping a little day by day.

EasySolar All-in-One

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Answer 1 · 2021-12-19T16:00:52Z

kevgermany answered · Dec 19, 2021 at 04:00 PM

Do you have a smart shunt or BMV in the system, or is the Easysolar generating the SOC values?

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Answer 2 · 2022-01-16T22:46:01Z

the-doon answered · Jan 16, 2022 at 10:46 PM

Nothing added, just using the EasySolar for SOC. Another thing to add is that we are away and the SOC has gone back up to 98% again. So the problem only seems to happen when we are there using the system full time.

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Answer 3 · 2022-01-17T00:21:55Z

ejrossouw answered · Jan 17, 2022 at 12:21 AM

Did you try setting the batteries as battery monitor as you mention it is working with cabus?

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the-doon commented · Jan 17, 2022 at 10:48 AM

Thanks ej, I’ll have a look next time I’m there.

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the-doon commented · Jan 17, 2022 at 10:59 AM

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Answer 4 · 2022-01-17T06:04:25Z

bbmz answered · Jan 17, 2022 at 06:04 AM

Is there a connection between the battery / BMS and the victron system? Which lithium chemistry are you talking about?

At the moment it seems to me, that your Victron system is guessing the SOC only by battery-voltage. Especially on LiFePo this can be quite hard …

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ejrossouw commented · Jan 17, 2022 at 07:15 AM

B86BC165-9242-4B5E-9BCF-E333C524E1D3.jpeg"... battery voltage of 52.0V which is set by the battery via CAN-bus." This suggests he can use the battery's own SOC which will be the most accurate as is done with the LG battery in the image.

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b86bc165-9242-4b5e-9bcf-e333c524e1d3.jpeg (243.1 KiB)

Answer 5 · 2022-01-17T06:34:01Z

kevgermany answered · Jan 17, 2022 at 06:34 AM

The units inside the Easysolar cannot measure current through the battery. Net result is the SOC is the best it can do, but is not especially accurate. If there's a battery monitor (BMV) there's a direct measurement of battery current and a much more accurate SOC reading. In this case the SOC calculation in the Easysolar is/should be turned off and the BMV values used.

With lithium batteries, if the electronics in them are able to output SOC, it is as accurate as you can get. No point in adding a BMV, it's built in.

So, just go by the battery values.

Sometimes they can feed their SOC to the Victron equipment. You'd need to check with the battery supplier or the Victron compatible batteries list.

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