Float Voltage during sun hours 0.2V higher

[Skipper]

In my ESS system, during the time pv delivers the power to the gel batteries I’ve noticed that the V is exactly 0.2V higher.

When the Multiplus is taking care of the Float charging (at night), the V is as I’ve set it in the settings of the Multiplus. When the MPPT is providing the power for the float charging it’s 0.2 V higher.

I’ve changed the settings in the Multiplus twice, but during the day the 0.2V still happens. I’ve got the ‘keep batteries charged’ mode selected in ESS.

Is this a feature?

[lxonline (LX)]

For solar to provide loads there has to be a bit of potential to make power flow in the right direction. (Or at all)

Is there voltage drop over the cable from the mppt to the battery bank?
Is the battery being overcharged?

[Skipper]

There is no Voltage drop as the MPPT shows the same voltage as the Smartshunt (at least within 0.02 V accuracy). I’ve tried different charge levels on the MultiPlus. From 27.2 (27.4 during the day) and 27.4 (27.6 daytime) and 27.6 (27.8 daytime). Every time the difference is 0.2V.

[lxonline (LX)]

@Skipper

daytime

To make power flow, one has to have a higher voltage than the other otherwise power does not move.
So to make solar go to loads, the mppt has to slightly raise its voltage to move power in the right direction.

If the mppt battery terminal= battery terminal, there would be no movement of power from your panels.

[Skipper]

Thanks for the explanation.