Which battery do you need?
The first question you want to ask before buying the battery is what it will be used for. If you are only camping at CG's with shore power there is no reason for a group 27 battery, or a DEEP CYCLE battery, the BASIC group 24 that comes with the TT is all you need, as it sole purpose is for emergency breaking (TT's electric break away switch activated) and will absorb any spikes that may be produced by the TT's battery charge controller (from a shore power spike). The new TT battery control centers suppress the spikes now. With proper maintenance, the standard RV/Marine battery that is standard on TT's will last for years.
If you are looking at a lot of dry-camping then the recommendation would be TRUE DEEP CYCLE batteries (not RV/Marine batteries which have CCA ratings). 12 Volt DEEP CYCLE batteries have less Ah ratings than (2) 6VDC batteries in series, so you may want to look at (2) 6VDC batteries in series. IE.. my (2) 6 volt batteries are rated at 260Ah rating, of which I can only use 130Ah of the 260Ah (12VDC minimum voltage level - 50%)
As for Flooded batteries vs AGM there is plenty of debate as to whether the extra money is worth it for the AGM. If your batteries are in an enclosed area, than AGM would be a good choice.
There are plenty of manufactures out there that have both flooded and AGM product lines.
Interstate (not sure about True DEEP Cycle Batteries, did not see any listed)
and many more....
Space is a driving factor on TT's as they have limited room to place your batteries. If you are looking for a true DEEP CYCLE battery, it should NOT have a CCA rating in the specifications. That is the easiest method for IDing non TRUE deep cycle batteries.
These are only a few thoughts regarding type of battery, I am sure that others will add to the list.
AGM battery charging (per the battery university):
AGM batteries are sensitive to overcharging. These sealed batteries can be charged to 2.40V/cell (and higher) without problem; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages).
Just my thoughts,
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