bad battery or what??

[b] i have an 08 700 rhino now there is no telling how long the battery was on the shelf before they put it into my rhino but here is my problem when i used to ride the volt meter was always reading 14 volts or over but today i went to pull my next door neighbor's forklift off a trailer and the battery was dead well i jumped it off but afetr riding it around all day i haven't been able to get it to read 14 volts it will go to 14 every so oflten but it mainly stays at 13.9 0r 13.6 could this be a dead cell?? i know it can't bee the charging system because if i rev up the motor the volts go up so i know thats workin any ideas???

As technical as they are. i am not going to venture a guess. But its possible

someone on another forum said don't worrie about the .4 volts but the thing is she was up to 14.2 before and then i went to crank her over and she wouldn't start . i jumped her off and now she's barely reaching 14v she's mainly hovering around 13.6/13.8 after yesterdays ride . i might just run a second battery for a backup like i had on my hpx with a cutoff switch it came in handy a few times because of a dead battery.[b]