if you want to check the voltage on your batter, you can do it in two ways:
1) on the console, press and hold the mode and chrono buttons until the 4 zeros show at the bottom. put in the code 3772 (i think that's it) then on the bottom left side, it should tell you the voltage of your battery.

or if you have a volt meter at home, take your batter, and put the positive into port 4 and the negative on port 2 on your charge port, and that should give you a correct reading as well.

as well, sometimes plugging in your battery to the external charger until it is fully charged, then disconnecting it, letting it sit for an hour, sometimes helps to reset it.