May be semantics/pedantic, but I see a lot of people referring to various deep-cycle marine batteries as "SLA" or "sealed lead acid." Some may refer to AGM as SLA, but SLA batteries are different. Think UPS, scooter, emergency exit lighting in buildings, etc. Those are SLA. For vehicle use the common options are:
- FLA (Flooded lead acid) deep cycle - Not maintenance-free, have caps with vents and the electrolyte level needs to be checked regularly.
- AGM (Absorbent Glass Mat) deep cycle - Maintenance free, various types of AGM exist (Optima spiral cell, standard AGM plates, etc). Some may refer to these as SLA, and while they are technically sealed and are lead acid chemistry they are not defined as "SLA", they are AGM.
- Lithium/LiFePO4 - Best power/energy density per lb, best able to handle deep discharge compared to AGM, able to handle higher continuous amp draw, but are sensitive to freezing.
To your question, I'll say that, in/for the US, there are only a handful of FLA and AGM battery manufacturers. East Penn (makes Deka batteries), Clarios (Formerly Johnson Controls), EnerSys (makes Odyssey), and Exide.
The Deka Marine Master Group 24 battery is not an AGM ("SLA") battery, it's a standard flooded-cell (FLA) battery. An Interstate (made by either Clarios or Exide), such as
https://www.interstatebatteries.com/products/srm-24?productline=marine, is comparable to the Deka. Interstate has a good dealer network as well and I think you should have good luck being able to locate them in-stock.
You may be able to locate Exide or rebranded-Exide (Duracell, EverStart, etc) Deep Cycle batteries at various retailers, but they also only have a 12-month warranty.
I'm on the fence about Odyssey batteries, a lot of people swear by them but they are also a lot more expensive. I've used a couple of Odyssey batteries in the past and I wasn't able to get any better use or life out of them than cheaper alternatives that had similar or better warranties so I'm hesitant to recommend them.
Hope this helps!
