Victron SmartShunt

[chrisski]

For my caravan i have a switch on the earth and shut the complete system down when not in use. The bmv has self consumption that is not measured in soc% so gradually drains the battery.

That I have seen. After a couple of months of storage between the 5 mV the Victron Shunt uses and the normal battery drain, the batteries are at a lower SOC, but the meter still reads 100%.

[Bala]

I have the Victron shunt and my 712 BMV does not do this. I turn off the batteries with a blue sea switch a lot and the SOC remains accurate. If you’re talking removing the voltage sense wire, than perhaps that will do what you’re saying but i don’t understand why that wire would be disconnected.
[/QUOTE]

For my caravan i have a switch on the earth and shut the complete system down when not in use. The bmv has self consumption that is not measured in soc% so gradually drains the battery.

[chrisski]

I would not spend too much time worrying about three different readings within .1 volt of each other. Too much work would be required to calibrate the equipment and the cost would be a bit much. Just work with what you have. Sometimes its equipment not called. Could be normal voltage loss if measured at different places, and this depends on current and size of the wire when measuring different places.

I agree that the voltage is not a good way to measure battery SOC, but if you need a voltage to activate the transfer switch that tidbit does nothing to help you.

The only thing i would recommend looking into is the victron shunt has an option to power a relay based on SOC. If your transfer switch allows an electric input for on and off in addition to a voltage, this could work.

For the shunt to be calibrated you need to fully charge the batteries with the shunt connected. Anytime the shunt or battery is disconnected and reconnected the shunt will read 100%. You again need to do a full charge to calibrate.

I have the Victron shunt and my 712 BMV does not do this. I turn off the batteries with a blue sea switch a lot and the SOC remains accurate. If you’re talking removing the voltage sense wire, than perhaps that will do what you’re saying but i don’t understand why that wire would be disconnected.

[Bala]

The only way to get accurate v readings is to buy a quality meter like fluke and pay to have it calibrated. I don't bother for lead acid and drop in lithium.

[ShedPower]

Thats helpful, thanks. I think I am panicking about voltage too much.

[Bala]

Voltage is not a great indicator of Soc.
if you have any load on the battery it will bring the voltage down. This is where the shunt helps with its Soc %

For the shunt to be calibrated you need to fully charge the batteries with the shunt connected. Anytime the shunt or battery is disconnected and reconnected the shunt will read 100%. You again need to do a full charge to calibrate.

[ShedPower]

Thanks. I am confused though how the batteries can be 99% full and now be 12.4v. It doesn't seem possible, does it? The batteries were all fully charged when I installed the shunt. The batteries were brand new but they were quite cheap so I am a bit suspicious if they are really poor quality and not fit for purpose. I just don't know.

[Bala]

Use the victron shunt to find the dod you want to set the transfer at.

So if you decide its 75% state of charge on the victron see what the volt reading is on transfer switch and set it accordingly.

[ShedPower]

Hi

Ive just installed a Victron smart shunt and have some voltage discrepancies. The shunt is saying 12.5v a multimeter is saying 12.4, and I have a automatic transfer switch that says 12.3v. all connected directly to the batteries, which are 3 130am in parallel using two bus's to join the batteries together. It is perplexing and important as I have to set the transfer switch at the voltage that it will transfer to grid power. I usually have that set to 12.2v, If it transfers too soon it defeats the whole object, if it transfers too late it will harm the batteries.

Any advice appreciated. Thanks.