Hi Phil, there are a few things here ..... And I am not fully sure what you are questioning, so going to cover all bases ...
The actual
battery capacity depends on how hard you pull a current from them when it comes to Lead batteries. The lower the current, the greater the capacity. It is a thing called the Peukert factor or effect or component (you see all terms used).
The
Victron BMVs have a setting in them to set the Peukert value to tell it now much the batteries are affected by this. What this means is that if the
battery draw has been very light, the State of Charge percentage is bigger than you think it should be for the amount of AHs draw.
Ignoring Peukert, the SOC of your batteries would be 94%, not 96%, but overnight the current draw would be pretty low in terms of the
battery bank size which is why it is ended up larger than you might have calculated.
You may be questioning the SOC with reference to the setting you have for the discharge floor? The discharge floor setting on the
BMV is a bit of a weird setting. It does NOT make any difference whatsoever to the State of Charge reading or calculation. It seems to have three possible purposes.
1) it is what is used to display the "Time to Go" value. This is the amount of time the batteries have, based on the usage over a period of time (think it is the last 5 minutes?) until the
battery SOC drops to the discharge floor value.
2) there is a SOC setting option for the relay in the
BMV which activates and deactivates the relay. It uses the discharge floor value as a starting point for this. The idea here is that someone may have a auto-start generator and when the discharge floor is reached, the relay is activated and a signal sent to the generator to turn on.
3) You can have a warning buzzer activated when the discharge floor is reached.
What people do with the setting depends on their needs. Personally, I have tended to use it to turn things on when the batteries are high, not low, so end up with a "discharge" floor of 85% or 90%!
If you were thinking the displayed SOC value is the AVAILABLE usable capacity based on the discharge floor setting, nope, it does not work that way - it is the batteries ACTUAL capacity where 100% is full, and 0% is dead as a dodo.
Were you maybe surprised how much current was drawn overnight when everything "off" maybe? I wish I was only using 13.5Ah overnight
Now few other things....
The
Victron BMV battery monitor expects the
battery bank capacity to be at the C20 rating for accurate measurements. Your batteries are 110Ah at C100 but they are 100Ah at C20, so you should have the capacity set at 200 and not at 220 (this difference will not be why there is an apparent mismatch of AHs drawn and SOC value.). When you make that change, IRRC the
BMV will change the SOC reading dynamically.
Why did you chose 60% as the discharge floor? TBH it doesn't really matter what it is set at for most people, but if it is a "don't want to drop below that
battery SOC" thing, your new batteries are perfectly ok below 60% or 50% for that matter.
There is a good
Victron video (on YouTube) on how to setup the
BMV depending on if you have lead or lithium, and if you have
solar or not.
It is worthwhile watching that, especially the
solar part, as if the
BMV is not setup right, what can happen is it can prematurely reset the SOC back to 100% if certain things coincide, which is possible with
solar charging when the
BMV is not setup expecting
solar. (It is about current levels at certain voltages, but the video explains it so no point in repeating it here).