Off-grid system is showing unexpected idle charging and sudden battery SOC jumps

[moh001 (Mats)]

Hi

On the cottage I hava an off-grid PV system consisting of: Multiplus II 24/3000, Smartshunt (connected with VE.Direct to Multiplus) and SmartSolar charger 100/20 (connected to Multiplus with VE.Direct USB cabel). The system includes 3 x 350W PV panels connected to the Multiplus, and to catch the morning sun, I have a 440W PV panel on the sauna building (named Bastu in the pics below) connected to the 100/20 SmartSolar charger. The battery bank consists of 4 x 220Ah AGM batteries.

Everything works well overall, but I’ve noticed two issues:

Even though the “Bastu” PV panel provides around 340W, the status still shows Idle or even Discharging.

The battery charge level jumps from 80% to 100% suddenly.

I suspect it’s a settings issue — but I’m not sure where to start.

Thanks - Mats

[pwfarnell]

You sound like you have 2 problems with your SmartShunt.

1. The wiring is not correct on your Bastu PV and the negative goes to the battery, not the shunt.
2. The SmartShunt settings are wrong.

See the FAQs below.

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[moh001 (Mats)]

Thanks @pwfarnell . You are absolutely correct. Negative goes directly to battery, not to the shunt. I did also read your post about the settings and I changed them accordingly. I will re-wire the negative next time I visit the cottage. Thank you one more time!!