We recently changed our old LA batteries for AGM deep cycle. We have a 24v system so have two 12v connected in series. Old batteries were 140ah new ones are 125ah. Didn’t initially adjust the bmv settings for the new ah (rookie error) but have done since. The BMV SOC is reading as low percentage despite voltage being ok. I think I need to adjust the tail current and or the peukert but not sure what to use if I do - I know someone had previously posted and suggested changing peukert to 1.15 and tail current to 2% but I would appreciate your input. The batteries are charging off either generator and battery charger or the engine ( have solar too but not much this time of year)
Victron uses a general AGM Peukert of 1.25, but AGM batteries can have a Peukert varying between 1.05-1.15, so you could change this to see if it’s works. Otherwise you could check the batterie’s specifications, if the exact Peukert value is mentioned on the label, or online. Or maybe your dealer can tell you.
If you exchange batteries and you change the capacity in the app, still the shunt needs to do a full charge cylcle to reset it self to 100% SOC. If the batteries are 100% charged, and the charger is in float, then you can always do a manual “SOC to 100% reset” in the Victron app settings.
With my Victron AGMs I used a Peukert of 1.12, I found a charge efficiency factor of 98% was closer to the truth as they did not often get cycled below 80% and a tail current of 1%. If you charge your batteries with solar increasing the charged voltage to 0.2 to 0.4V below your absorption voltage may avoid spurious synchronisations and reading too high, but from the sound of it this is not the problem you are having, rather the opposite
