SOC keeps decreasing and remains at 0%

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justinp asked Dec 8, '20

SOC keeps decreasing and remains at 0%

Hello everybody,

My experimental installation is composed of :

1x SmartSolar charge controller MPPT 150-60
1x 60Ah 12.8V Battery from Victron energy
1x Venus GX
1x BMV 712 Smart

I have an issue with the SOC that keep decreasing and now remains at 0%, even if the charge controller is in “bulk” mode. In facts, I tried to let the battery charging for a long time and I synchronized the SOC at 100% but it decreased just after slowly to 0%. I also checked that my shunt was correctly wired and there are no other wires than the battery on the “only battery” side of the shunt. So I guess that the shunt is not the problem.

Does anyone know how could I keep the SOC synchronized? I tried to modify the Tail current, Peukert exponent and the charge time detection as followed :

Do you think that I have to re-adjust those parmaters ?

Here is the SOC remains at 0% :

Thanks a lot for your help !

Have a good day !

Justin

BMV Battery Monitor SOC

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Answer 1 · 2020-12-08T14:58:41Z

jwfrary answered · Dec 08, 2020 at 02:58 PM

Hi.

I know you have, but double check your shunt wiring! And direction of current flow.

secondly. Have you calibrated the shunt to zero amps? - you need to do this with absolutely nothing flowing in our out. Preferably the loads are disconnected.

I would also reset to factory defaults to start off a fresh.

Had this on an install when a customer fiddled and then his SOC ran to zero. But batt was full!

let us know how you get on

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Answer 2 · 2020-12-09T09:36:18Z

justinp answered · Dec 09, 2020 at 09:36 AM

Hello jwfrary,

Thank you very much for your answer.

The SOC finally increased yesterday to 20% and the MPPT state turned to the “absorption” mode. So, as you said I think that the battery is in fact nearly full.

I will try to disconnect the loads and calibrate the shunt to 0 amps like you advised me. I also asked to my Victron supplier that told me to keep adjusting the BMV parameters (tail current, charged voltage..) so it could keep synchronized.

I'll let you know if I manage to get the SOC synchronized with my real battery level of charge.

Have a good day,

Justin

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jwfrary commented · Dec 09, 2020 at 03:21 PM

@JustinP I have found that really the default values work pretty well out of the box unless it’s a pretty big bank say 600 ah upwards or out of the ordinary batts like the huge 2v and 6v one.

It’s always interesting to know the solution so please do post it when you get there. Or come back with more info!

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