question

does nobody have a solution? Not even the Victron technicians? Surely it must be possible to find out where this value comes from? This value entered itself automatically.

These are my settings, charger is off. I only want to save energy with solar. 

these are the Mppt settings

I too had 30.40V for a nominal 24V multiplus II/Mppt/lifepo4 ess enabled. This is precisely 2V above my multiplus setting of 28.4V absorption for the multiplus ii charger page in remote VE configure3.

Prior to enabling ESS, I manually set Mppt chargers individually /150/60 and 100/20 at an offset +0.4V, as suggested for a DC coupled AC grid backup for high W surge loads But on average targeting solar consumption With battery storage and shoulder usage.

in ESS this manually setting a higher voltage in each MPPT is advised and marketed as being beneficial in terms of ease of use. With this olde method of manual offset, I usually got max voltage of around my setting of absorption V. But if I was commissioning and testing the system I sometimes got a momentary spike up to 30V Upon battery connect in the daily history but upon actual monitoring this never sent more than a second or two of higher voltage and current to batteries.

So in my ESS, hopping to circumvent the Networked operation page Solar charge controller ( viz MPPT ) 2V offset which in Victron literature is the preset variable offset for non Keep Battery Full options, I lowered the Multiplus absorption voltage to 27.6V which led to Networked Operation page for each of the two MPPT reflecting 29.6V. That is still above the 3.65V per cell (29.2V) that I would manually target, but a daily history shows that the charge really disn’t stay above 30.4V (when I had previously set multi to 28.4V absorption ). I also switched ESS from Optimised with BatteryLife to Optimised without BatteryLife, which someone suggested was ok for lifepo4, and immediately was able to use battery below 50% SOC charge as the BatteryLife algorithm was disabled (it probably stayed above 50% during the first few days of commissioning as it learnt the daily load pattern).

I have tried to search again and again for an answer as to how the variable 2V is programmed to adapt as the battery nears absorption voltage. A clue is that keep battery charged setting is set by Victron to only 0.4V which is perhaps because a full battery is always going to operate close to the tail high voltage ramp up of the lifepo4 battery so needs to be kept smaller. Yet perhaps I got this backwards as lifepo4 has a flat charge curve in the middle and thus 0.4V might reflect the middle flat part of the curve whereas 2V might reflect the need to accept spikes in voltage whenever DC loads suddenly change and the MPpT responds to the change in loads? Victron really needs a representative to provide details as to how the solar charge variable offset affects actual battery cell voltage. for example, the daily history never has shown sustained voltage of above the 28.4V I set, except say 0.05V variations, and yet the max battery voltage is sometimes recording as 30.3V, which occurs once absorption is reached and the MPPT rapidly switches the solar array down and off.

In addition, I can’t follow the logic of this prose:

• A fixed solar offset of 0.4V is used instead of a variable 2V. (values for 48V systems, divide by 4 for 12V). Note that this solar offset is only applied when ESS-mode is set to Optimized in combination with the Feed-in excess solar charger power-setting enabled, or when ESS-mode is set to Keep batteries charged.

My question is, does “this Solar offset” refer to the 0.4V fixed, or, the 2V variable? Or both?

I am not feeding any power into the grid and am operating in ESS mode 2, set at 70W power taken from grid.

Also, the recent ESS setup seems to have included many DVCC features, so I’m not sure of the need for DVCC to be turned on, which I have now kept off. eg the multiplus has taken internal control of the MPPT which say external control now.