Batteries will not hold charge

[Beaudinj]

I have a 2019 Lund rebel it was set up for 12 volt system. I put a 24v trolling motor on it and ran a second battery in series. The onboard charger is a two bank 5 amps each. Last season i could run about 4 hours before dead batteries. I upgraded the batteries to Blue top Optimum Batteries, thinking they would last longer ,no luck still get 4 hour out of them trolling. The trolling motor is Minn Kota power drive 70lbs thrust. All electronic and electrical down riggers run of the starting battery. the front battery is used to make the 24 v connection . the question is "why are the batteries only lasting 4 hours and takes to days to charge?"

 

[alldodge]

Welcome
Your charger isn't much if Bats are low. Charging 5 Amps to a dead Bat will take some time.

Your Minn Kota 70 list max current draw is 42 Amps

Blue top Optima Group 31 list 155 Amps @ 25 Amps, 75 Ahr. So the 2 Bats in series = 50 Amps. The 155 minutes / 60 = 2.6 hours at max. Your getting 4 hours because you run/stop, run/stop.

Could go with Lithium type but will need to get a special charger just for it. Bat's cost $700 plus each.

Either that or get 2 more AGM's and put them in parallel with your other 2

 

[dingbat]

I have a 2019 Lund rebel it was set up for 12 volt system. I put a 24v trolling motor on it and ran a second battery in series. The onboard charger is a two bank 5 amps each. Last season i could run about 4 hours before dead batteries. I upgraded the batteries to Blue top Optimum Batteries, thinking they would last longer ,no luck still get 4 hour out of them trolling. The trolling motor is Minn Kota power drive 70lbs thrust. All electronic and electrical down riggers run of the starting battery. the front battery is used to make the 24 v connection . the question is "why are the batteries only lasting 4 hours and takes to days to charge?"

Amp hours are amp hours.....
You need more of them to run longer.

The bluetop is a hybrid starting battery. You really need a true deep cycle battery for that application

 

[dingbat]

Double