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paul-martin asked

MultiPlus-II 12/3000/120-50 120/240V SOC when in float

I recently completed installation on my Victron MultiPlus-II 12/3000/120-50 120/240V Charger/Inverter along with a SmartShunt 500A and 300AH of 12 LiPO batteries and Cerbo GX in my RV. I have not gotten a chance to install the PV system yet. Everything works great, but I am trying to tweak my settings. What I am noticing is that when I am in Bulk and Absorption, my batteries charge to 100% SOC. Once it goes to float, the parasitic drain of the 12v system (approx 23w) slowly drains the battery SOC down.. I haven't see how low, but I was wondering is this normal? Shouldn't the charger keep the battery at near 100%? Is it possible I didn't correctly configure my SOC correctly on the shunt? If so what is the typical conditions to zero out the SOC? Is this maybe how the system protects the longevity of the batteries? Sorry for the rookie questions, just in all my research I haven't seen anything about this. I just want my system to be charged to 100% when in use so that if we lose or need power I'm not starting at 80% SOC. Any suggestion would be appreciated.

Absorption Set at 14.2v

Float set to 13.6v

Smart shunt set to 14.1V

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1645714516091.png

Multiplus-IISmartShuntSOCfloat
1645714293525.png (44.1 KiB)
1645714516091.png (23.7 KiB)
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2 Answers
Alexandra avatar image
Alexandra answered ·

@Paul Martin

Do you have DVCC enabled?

There is also rebulk offset if you have lithium programmed in. But that is 0.2v under float, so it should be rebulking.

If you have a DC system it is better to use a shunt for accurate SOC.

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paul-martin answered ·

I figured it out and it’s entirely my fault! It was the VE. Bus Smart dongle. As soon as I unplugged the dongle it went into bulk charge. I think it’s because I took a shortcut and attached the positive and negative terminals of the dongle directly to the open bolts on the DC terminals on the multiplus instead of to the battery or bus bar and either it was reading the voltage that it was sending to maintain the coach DC system, or not taking into account resistance of path to the batteries. Anyway, it’s now floating at 100% correctly. I thought I had it set to read it’s settings from the smart shunt, but apparently it wasn’t or was overriding. Thanks for all the help!

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