I wanted to share this with you, it is a little long.
I believe I finally have our Nitro Z-19 well sorted as far as batteries and chargers are concerned. I replaced Interstate Group 31 AGM that came with the boat with an Odyssey Group 31 AGM. The original Interstate wet cell group 31 trolling batteries were getting tired after 3 plus years and 250+ cycles. I have a 24v Minnkota Ultrex. I decded to bite the bullet and got two 50Ah Ionic Lithium batteries. The cost was not that much more than AGMs and the long life seemed like a good value. Bonus is they only weigh 12 pounds each and take up half the space. I love the blue tooth connection to monitor their state of charge. I have 2 chargers. The previous generation NOCO Genius 3 bank 30 amp charger that came on the boat and a Stealth 1 DC Charger. I have two banks of the NOCO going to my cranking battery for 20 amps of full and fast charging. The 3rd bank is unused and taped off. The Stealth 1 charger is a DC charger powered by the cranking battery. It charges my two Ionic Lithium trolling motor batteries. It charges the batteries via the starting battery whether I have the NOCO plugged in or via the gas motor alternator when I am driving down the lake. It only charges if the cranking battery has sufficient charge. This combination is awesome. I just got back from a 4 day fishing trip where I fished from 6 to 10 hours per day. I never plugged my NOCO charger in to charge the batteries and just relied on the Stealth 1. When I got home, I checked the batteries state of charge. Trolling motor battery #1 had 86% charge and #2 had 84%. That is after four days of fishing! I ran the Mercury 200 4 stroke around the lake enough to burn 18 gallons of gas. With a set up like this, I never have to worry about where I will be able to plug in on a trip. And if I do ever run the batteries down in the wind or current, I can fire up the gas motor and run around the lake some to give them a charge. When the Odyssey gives up, I will probably go back to Ionic for their 125 Ah cranking battery.