You probably need to reset the AH to zero once the batteries are as full as you can get them and start over with the Trimetric.
The percent full only works when the AH count is right. To get that right, you need to enter a capacity number for the battery bank. That was 520 when they were new (four 260s in series parallel) but is now say 75-80 percent of that when full) They will still show almost proper voltages (12.6 instead of 12.7 say for full. Hydrometer will also be closer to 1.26 for as high as it will go.
All of those inverters etc have to go through the shunt as well as the battery to frame neg wire now goes to the shunt from the frame to get a proper AH count too.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.