FOUND THE TROUBLE MAKER.
The Victron BM-712 had a aux battery voltage circuit 100ma FUSE that measured 69 ohm of resistance. This was messing all the BM voltage indications up. Has been doing this for some time. Now the voltage at the BM is identical to the voltage on the battery measured with a DVM at the battery end. This is a great relief for me, to find and fix this problem.
Original message:
"Installed the Renogy DCC50S battery charger. Input is from two 180 w Grape solar 12v panels in parallel. Alt input is from vehicle alt/batt (usually switched off). Charges three BB LiFePO4 100AH 12v batteries wired in parallel.
The BCDC50S charges the batteries up to 14.4 v, 100% SOC as monitored by a victron 712 monitor. Then it maintains a charge voltage of 14.15 v dc, 0 amps, 0 watts. Normally the camper it lives in draws about 0.2 A dc to keep the smoke/carbon monoxide monitors going and the refer and heater control devices active (not on, just ready). I call this the camper burden. So it appears to be supplying the parasite load, maintaining 14.15v on the battery but not charging it (no need, its at 100 % SOC). I looked at the Tech Spec page of the installation & operation manual. It stated for battery type Li Boost charge voltage is 14.4 v, float charge voltage is listed as --, Equalize voltage is listed as --, Boost Return voltage is listed as 13.2v.
Is the Renogy DCC50S battery charger performing IAW the specs ?"
Because of the incorrect voltage readings at the BM device, the voltages noted above were not accurate. In reality the DCC50S goes thru Bulk charge mode and enters Boost charge mode, as indicated by the slow flashing solar charge indicator red light. It just stays in that mode with 0.00 A charge to battery. If I use a clamp-on meter, I see that it is still charging 0.005 A to battery. There is a burden load (parasite load) on the battery caused by an under voltage device that must pull some current at all times. If I turn on the dc power to the inverter/charger there is a 2A burden (parasitic load) caused by the inverter, even if it is not charging or inverting. So I think the DCC50S is staying in boost charge mode (about 14.3v) to supply power to the parasitic loads and finish up a full charge on the Li battery (very slowly).
I think its working per specs.