Trolling battery question

Guys,
I’m going to dig into this a bit more later today or tomorrow, but figured I’d pick your brains quick.

Took my Dad fishing Sunday and toward end of about a 6-hour outing had barely any ‘juice’ left, which is unusual.

Set-up:
24-volt Terrova about 2 years old.
2 Group 31 deep cycle batteries, each about 2 years old.

What I saw: Barely any power – and no lights on Terrova indicating any charge at all.

After we got back, we looked around a bit and one of the connections on one of the batteries appeared pretty loose (but still connected) so we tightened it. I hooked up charger again and have charged it. My Dad also suggests we load test each battery today/tomorrow. Any other things to check out you can think of? I’m hoping it was just the loose connection, but who knows.

Thanks in advance.

Check the acid levels in the batteries and the output on the charger wires.

A load test will not always show a weak battery.
Charge batteries unhook cables let sit for a day or two and check voltage if below 12.5 they are on there way out, or if you have a hydrometer..