In purchasing replacement AGM batteries I encountered two constraints. The first is shipping. Unless you purchase locally and pick them up the cost for shipping two batteries is usually $100. A second criteria was the number of cycles with the battery discharging to 50%
I started my search by calling local battery distributors to find what brand and model they carry. I was looking for the GC size, a pair of six volt that are used for golf carts or better yet, industrial equipment. It seems floor sweepers are a common piece of equipment using such batteries. Ignore the term deep cycle, it has has no meaning. I did not trust the distributor to provide the information on number of cycles, but using their information on make and model searched for the information on the web.
Most AGM batteries are rated at 300 cycles to 50% DOD. Translated this means you can take the battery to a 50% discharge rate 300 times. However the scale is linear, my approximation would be you could take it to 60% 360 times and 70% 420 times etc... I was uncomfortable with a rating of 300 cycles. I tend to work my batteries very hard, with my new AGM's it is not unusual to take them to 75% in one day.
A search for batteries meeting the higher 1,000 cycles to 50% DOD gave some surprising results. I could not find models from Interstate or Trojan that fit the criteria. Names like Deka, Concorde, Lifeline were some I found that fit the 1,000 cycle mark. The last two are premium priced batteries
With help of PerryB I found a source for Crown batteries that fit the criteria. Since their warehouse was in Chicago they would also do free delivery. 6CRV220 was the model at a cost of $231 each. Perry had some personal experience with Crown that gave him much confidence in the company. These are made in Ohio. Crown does some big batteries, their website features a photo of a locomotive.
After two weeks of very heavy use while boondocking I was quite pleased. I did invest in a larger portable panel due to limited sunlite. By the way, the propane detector has stopped alarming during solar recharging.
Paul and Janet Braun
2003 Toyota 4Runner V8 now 2012 Toyota Sequoia V8
Escape 19' 2010 now 2014 Escape 21'