Probably a dumb question so bear with me, I'm no electrical guru by any stretch and I'm amazed how significant minor things can be sometimes. I put all new batteries (Wally World Everstarts) in my boat three years ago. Well my on board charger just started not bringing my two trolling motor batteries up to full charge. They are both 27DC Everstarts. I checked the voltage on both of them after I took them off charge and one checks almost 13 volts but the other checks 11.3 volts. I'm assuming that the 11.3 means the battery is toast, right. I wanted to make sure it wasn't my on board charger so I used a standalone charger and just charged the weak battery for 6 hours. When it was charging it reads 13+ volts but right after taking the charger off it is back to 11.3 or so. My question is, I have a size 29 deep cycle Interstate that holds a charge pretty good. I'm pretty sure it will fit into the size 27 battery tray. Will there be any issues with just swapping the size 27DC for the size 29? Will the batteries not being identical cause any issues for my onboard charger. I think it is a guess but I'm not sure. I do know that it doesn't have separate status lights for both charging circuits. It has a red light when fully charging and then it goes to red and green when the batteries are charged and then to just green when it is in trickle / maintenance mode. What made me even check was that usually after a day of fishing I could plug the charger in and within 4 hours or so the green light only would be on. Now it won't go to just the green light but both red and green. Thanks for any advice.