How are you planning on recharging them?
I didn't peruse the Deka, but are they not limited to no more than 30 amps per 100 amp hours?
Northstar is a little more vague on minimum bulk charge amperages, I've been using Odyssey's Specs, because they make many of the same claims.
Odyssey says their group 31, rated at 100 AH, when cycled deeply, absolutely requires 40 amps minimum until 14.7v is attained, then 14.7v is to be held for 4 hours. Get three of these and you need 120 amps and a charger capable of 14.7.
Odyssey® Battery Technical Manual – Seventh EditionSears Die hard platinum are rebadged odyssey. Their group 31 goes on sale every so often for 230ish$
I have a Northstar. They say that 12.1v is 50%. last time I took 55 A/H from it( 90 amp hours total) it was still reading 12.2v under a 4.5 amp load. Fully charged resting open circuit voltage on my group 27 is 13.06v.
I think the NorthStar is under rated capacity wise, and when I use it to start my engine, it cranks it faster than two group 27 marine batteries did previously.
I've not had a deka AGM, but I am impressed with the Northstar, but I don't think it would be a good low and slow recharge solar battery.
The NS has responded well to high amp charge currents of 35+ amps. Much better than 25 amps, and way better than the ~12 amps my solar can do.
I'd still pad their bases if they are going to be beat up mid boat.
Batteries plus re-badges a Northstar as X2 Power and adds a year to the warranty.
Lifeline AGM is likely still top dog AGM
