I have an ultrex 24V trolling motor. I can tell the deep cycle batteries are starting to get weak, I’m guessing there are 3-4 years old. they were in my first used boat, I put them in my new boat when I bought it. I’m just wondering what is the best to replace them with. I don’t know much about batteries, but I keep hearing about AGM and Gel batteries. What would be the recommended batteries for my 24V system? Also, is there a way to test my current batteries, or do they test either good or bad, or can you tell if they’re going bad and or weak?