I've notice mine will fluctuate a little bit like you describe. My last ruck had a variable rate alternator in it, just to save maybe a very small thimble of gas. They will vary a little depending on the over all charge and condition of the battery. Mine will sit for 3 or 4 days at a time fairly often. When it does and I start it up it will charge at a solid 14.8 volts for awhile. Yesterday I left it on a 2 amp trickle charger for the day while I was gone, green light full charge when I got home at the end of the day. Since I am coming down the home stretch on the original battery I checked it with the battery tester coming right off the charger. Physical battery temp about 35 to 40 degrees, 12.8 resting voltage 656 CCA. Battery is rated at 730 CCA. Checked it again this morning after resting all night, 12.7 resting voltage and still 656 CCA. I have kept the garage heated to around 40 degrees + or - during the last couple of weeks of zero and below zero temps. Started right up and the digital readout in the dash bounced between 14.4 and 14.5 volts. I prefer to check my own batteries with my own tester (Foxwell) than one from a place that sells batteries . . . . . . . . . .
