ulterra 80lb draining batteries

I have the MK3-DC on my boat. I love it. Just by using the battey condition meter on the 36v Terrova it is never goes below 3 of the lights. It is always on 4 or 3 lights. I have a 2008 Yamaha F250 for the DC charging. I start the motors, run all my electronics, pumps and accessories off a group 31 deep cycle AGM. This setup has never failed to start my big motors. I have never seen the voltage go below 12v. The starting battery seems to get to the requried 13.5 volts to start the charging with the MK3-DC very quickly. This is based on the voltage readout on my humminbirds. And the Humminbirds always read lower on the voltage than a good multimeter does at the battery. Another benifit of the DC charger is the less ‘depth of the discharge’ of the batteries the longer they will last. My new pure lead AGM batteries are rated at 900 cycles @ 80% discharge and 400 cycles @ 50% discharge. If you end the day with a nice run and start the next day with a nice run you should start the day with the Terrova meter on full. It’s not meant to fully charge the batteries but it will add hours to your capacity in a given day or like eyecatcher said fish for a week without recharging.

For reference the xi5 80# max amp load is 39 amps.
4 hrs certainly doesn’t seem to be enough. You should get significantly longer runtime with the 31s, but something doesn’t seem right.
Do you have anything else running off those batteries along with the trolling motor?

I ended up upgrading to the 31’s and they haven’t went dead on me in a day yet. Although I haven’t spent a full day on the river doing a lot of pulling upstream to really put them to the test. But so far I’m happy with the upgrade.