I may never run these batteries down. I am 64 and don't tournament fish so I don't tire batteries as much as I used to.

I bought a couple batteries that came out of a Honda FIT(bought used on ebay). The batteries are Toshiba SCIB cells assembled in series to make a 68 volt battery. 24 20ah cells in each battery. I am using two of these to make batteries for my boat. Two for a 28 volt trolling setup and one for a 14 volt starter battery.
They are very long lasting with some good specs compared to anything on the market.
Lithium marine battery's that are out on the market are LifePo4's. They are good for about 2000 cycles. Mine are good for ten times that and the specs I've read are that after 15000 cycles they still retain more than 80 percent of their capacity. I should never need another battery. The trolling batteries should be around 55ah and the starter should be 37ah.

They cost 390 per car battery so 780 plus the cutting and wiring plus putting them in a waterproof box will put them well under 900 dollars finished.
A big plus? All together they weigh around 75 pounds.

They will be the best if I never need another battery. Not so much if they go down but you roll the dice.

Did the recycler you bought them from say that would work? I was going to go the same way and was told by the large ebay seller that they would not work as I thought.

I'll let you know how they perform as soon as I get some experience with them.
A friend who bought 4 of the same batteries and wired them up replaced his 8 battery setup (4 31agm and 4 24agm) in his offshore boat. He has a big stereo for sand bar fun and said the new batteries hold up better than his big Sears batteries. The voltage drop on the batteries with his agm's were in the low 11 volts at the end of the day while his new battery bank dropped to 12.9 volts. Saved 400 pounds of weight. They are still new to him.
They use these in GEM and golf Carts so I'm guessing they are capable although their designed purpose was for long term storage for large computer systems and solar banks. They are designed specifically to be discharged fully and maintain their capacity.

"Maintenance free" is the same thing as lead acid. The water caps are a little harder to remove ....that's all.

He said "best". Not "bang for the buck".

Optima blue top group 31. The best I've ever had.

Walmart......yep! It's a battery for folks that don't know batteries.

Don't confuse "Marine" or Dual Purpose" with deep cycle. The plates are a little bit larger than auto batteries and will suffice for running lights and a stereo, but won't hold up to the deep discharges of a trolling motor If it doesn't say Deep Cycle on the case it's not. Walmart batteries are not deep cycle.

The Best? In my opinion, the best would be either Northstar or Odyssey. Both are $$$ AGM batteries, but have lasting power and long life. My last set of Northstar batteries were 6 years old and still running strong when I traded my boat. New boat has 3 group 27m Northstar, so I really believe in them. I have heard a lot of good things about the Duracell 31 AGM (made by Deka) sold by Sam's for about $180, but don't have any personal experience.