I have a Everstart group 27 battery that I use for my cranking and all accessory(hds9,7and lmc5 and all my pumps and things. I have had it for about 3 years and I just added the voltage on my hds screen read out like 11.3 volts this is right after I got done charging the batteries overnight so I plugged the charger back in and the volts slowly climber back up to 12.4 how can I test the battery and tell if its going bad and if so what kind of battery would you guys suggest also I have notice my front fish finder shutting off on its own while I have been fishing lately