UPDATE #3:
i've had access to shore power the last few days, and have not been staying in the camper. so my usage has been at an absolute minimum... 0.9a fridge controls, a light occasionally for taking readings, no laptop use, no coffee maker, nothing. today is thursday. i fired up the pm 75amper tuesday evening, and let it do its usual thing... 15 minutes of boost followed by several hours of abs. i didn't take any readings throughout, just the initial battery voltage (-EDIT--12.61v--, which surprised me seeing as i hadn't been using anything?). at some time overnight it kicked down to float (i'm assuming, and i'll address that next) and continued there all day wednesday until about 8:30pm. at which time i decided to try out my other charger and try doing a 'top off' charge like many have suggested.
now, back to assuming it was in float mode all that time. the other day (updates #1 & #2) it sat at 0.3 to 0.4 amps for the longest time (about 6hrs was it?). but this time it sat at 1.1 to 1.2 amps, from the time i first checked it wednesday morning, 'til i turned it off wednesday evening. so, here's my dilemma:
the voltage was at about 13.67 the whole time. so, i wondered whether the charger had stayed in abs mode the whole time, or if the 13.67v reading was simply a result of the batteries holding onto a good surface charge while on continuous float??? ...of course, if the pm4b had a higher vabs setting this would not even be a concern.
back to the top-up charge. LANDYACHT mentioned the "shoe-maker" charger likes to blow by the mid 14's and jump up over 15v. this reminded me of the nautilus 15amper i got stuck buying when my pm4b 60amper blew up on its second run (that's another story). it too gets easily excited and i seemed to remember it jumping up over 15v on one occasion. so i hooked it up and turned it on, and here's what happened:
the batts were at 12.80 with the fridge on, 12.81 turned off. the charger kicked on at 15amps (its max setting and according to its readout), and over the next 10 minutes rose from about 13.6v? (charger readout) to 14.89v (actual meter reading). throughout the first 15 minutes of charging the amps dropped continually to 11.5 (readout), and then suddenly down to 10.0 amps in about 10 seconds. then they dropped very slowly from that point on. at some point i realized i hadn't thought to check the amp reading on the trimetric... well, while the charger showed 9.8a, the trimetric said 8.9! i figured it was either a faulty charger readout, line loss over the light gauge charge cables, or a rare case of charging dyslexia :). either way, i'm glad i installed the trimetric.
after some time, the readout still said 14.8v, so i took a meter reading and it was actually at 14.93 volts. so clearly the chargers readout is unreliable! at this time the amps were down to 8.8 (so a very slow drop).
over the next hour or so, the amps rose up and down, between 8.8 and 9.0 (trimetric), while the volts hovered around 14.93 - 14.92 respectively.
i decided to check on the batteries, and stuck my ear down next to the vent grill. and as usual they were sizzling, popping, burping, etc., and rather smelly. so, i turned the charger down to the 2amp mode and let them cruise there for a while at 1.2a and 13.91v.
by this time it was getting close to 11pm, so i unplugged it, and plugged in the pm4b. apparently it ran at 1.1 to 1.2 amps throughout the night, and the battery? / charge? volts were at 13.67, as before. i unplugged it around 8am this morning.
so that's it. i haven't had the chance to do sg readings yet, but will not be surprised if the batts are low on water... will know in a while.
