a battery question

[MH Hawker]

as most of you all know I should have a job testing battery's till destruction

, my present one is one of the sealed delco voyagers, this is the first one I have had over the least 7 years that has made it past the warranty period and is well into season 2, I normally get 1 year out of one, ok so I brought the boat home to do several small projects, including a new digital volt meter and when I got it in a ran across 2 problems, I had installed a new FF that shows voltage, the new one and the new VM showed a slightly different voltage, both meters read from different sources the FF reads from the accessory system and the panel meter reads from the instrument system the difference was .2 a DVM showed 12.4 the FF was 12.3 and the panel meter was 12.2, so the its connection cleaning time so, I went over all of then under the console and the motor and that cured it, this was over several hours with all most all is no load, but the voltage dropped off to 12.0

so I thought its time to run the battery down and give it a hot charge I normally use a marine grade 10 amp charger but it would only charge for about 30 minutes then drop off and shut down so I broke out my old school one a plain 2/10 amp one, it went to a full 10 amp charge and stayed there for 2 hours then started to drop off, net morning it was down the 4 amps or so came back a few hours and it was off and showed full charged, the volts showed 13.0 and I am sure that as a surface charge 2 hours later it was down to a nice 12.6, as the day went along I looked at it ever few hours and it started to rise at the end of the day it was up to 12.9 and this morning its back to 12.6

the question is why did it rise to 12.9

 

[dingbat]

It's strange battery behavior week....fished last Friday. Left the dock with both at 12.8v. Ran 20 miles up Bay. Trolled for 6 hours using a full compliment of electronics.

About 5 hours in sonar shutdown for no reason. Came right back up and shutdown again.

Turned side scan off and it stayed working. Assuming the house voltage was low, checked to see if ACR was enabled. Nothing..... ACR go bad???

All three sources of battery voltage (sonar, chart plotter and helm meter) all showed good voltage.
Turns out the sonar shut downs where software related. Update resolved issue.

Both batteries at 12.8 the next morning. Maybe ACR lamp burned up

Can't answer why it rose but the spec on those batteries at full charge is 12.9 volts. your normal 12.6 is a bit under charged.

 

[MH Hawker]

its on its the 22 mouth on a 18 mouth warranty, first time i had a battery last longer than warranty, my conditions kill them in a year and the delco is the only one that has more than a 12 mouth warranty so i am happy with 12.6, i may get the rest of the season out of it