Bulk verses Absorption verses Float, - State of Charge - Confusion

Q&A and troubleshooting
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Long Time reader, First Time Poster….. Call me confused

My current configuration (In an RV)

Multiplus II 12/3000/120-50 2x120V

SmartShunt IP65 500V/50mV

Two 330AH 12V LiFePO4 Deep Cycle Batteries (In parallel for 660AH Total)

Battery Specs (From Mfgr)

Absorption Charging Rate: 14.5V

Float Charging Rate: 13.6V

Inverter CutOff: 10.7V

Recommended Low Voltage Disconnect:10.4V

Current Smart Shunt - Battery settings

Battery Capacity: 628AH

Charged voltage: 14.3

Discharge Floor: 20%

Tail Current: 4.00%

Peukert exponent: 1.05

Charge efficiency factor: 99%

Current threshold: 0.10A

My current Conditions

I am plugged in to a 120V/15A shore power grid feed. According to my VRM portal information, It is showing approximately 124V, 6.3A, 725W coming in from the feed. I am also showing 680W of an AC Load, primarily powering my refrigerator and 120W of DC Loads. The DC Loads are lighting, Furnace fan, Refridge, tank monitoring.

My current state of charge shows 76% on my Victron Connect App with the battery(ies) showing Float Charge level. This SOC percentage has been slowing dropping over the last several days as loads have changed for one reason or another. Furnace coming on as temperature drops, etc

I also have a Bluetooth app for my batteries. This app shows the batteries with a SOC of 100% and a voltage of 13.8 for Battery One and 13.77 for Battery Two.

I don’t know why I am seeing two different states of charge depending on the two apps. I was also lead to believe that the battery(ies) would be charged to nearly 100% as a result of the 15A shore power feed. The Float would suggest a near 100% State of charge condition if I understand it correctly. With the Victron SOC showing 76% SOC, why isn’t the charger now in Absorption mode?

What am I missing or not understanding

I look forward to and appreciate your thoughts

2

The SOC is only a reported parameter, it does not control the charging. Charging is based on battery voltage. Absorption only restarts if the voltage falls below float, about 0.1V below for lithium from memory.

Also, have you adjusted the Multiplus settings to the battery voltages recommend by the manufacturer as the default voltages for lithium are based on Victron batteries and are lower.

Your shunt settings are fine which is one common cause of poor accuracy. The other is incorrect wiring on the shunt. See the attached FAQ. If not wired right, especially the chassis ground in a vehicle you can get odd results.

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Many, Many Thanks pwfarnell for your reply

I will take a look at the settings in the Multiplus II and a much closer look at my wiring

Again, Thank You very much

4

Redid some ground wiring per PWFarnell’s recomendations. Everything is now in order.

If PWFarnell gives advice, Listen

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