Look at interstate SRM-4D this is what we use in our house bank. They are true deep cycle, with heavy plates. (I have seen a blown up one) Cost is about $200 each, and are rated as 200AH, thou I suspect 160AH is more likely at a shorter 20 hour rate.
Sadly this is is called "marketing mumbo jumbo" or really "misleading marketing" IMHO... the SRM-4D is a "dual purpose" battery or what they call "deep cycle/cranking".. Everyone else with this battery is more straight forward and simply refers to it as a dual purpose battery
The Interstate SRM-4D is made by Johnson Controls/JCI for Interstate. Their U series golf cart batteries (GC-2's), which are deep cycle are also made by JCI. Their larger batteries in the deep cycle line (L16's etc) are still made by US Battery.
The old U2200 6V, that was manufactured by US Battery was an excellent high quality high cycling GC2 battery. Now that it is made by JCI I really have no idea of what the quality is, at least in terms of cycles. JCI/Interstate will not publish, nor do they test for, lab rated cycle life data
. The bottom line is the SRM 24, 27, 31 and 4D could have about
half the cycle life of the U2200 GC-2 golf car battery (source Roy H. & Joe S. @ IB). They are simply not a true "deep cycle" battery they are a dual purpose
A number of years ago I actually called interstate to try and find out the Ah rating, plate thickness and Peukerts constant of the SRM-4D for a customer who had already purchased them.. What a debacle it was.
Even their tech support had no real clue about these batteries. I got three different answers, from three different levels of tech support/engineering, when I asked about the 20 hour Ah rating, Peukert, plate thickness and lab rated cycle compared to their "U" series batteries...
I finally got in touch with Roy H. and Joe S. who were able to get me Peukerts constants but JCI does not test those batteries for a true 20 hour rate. A 20 hour rate has to be backward engineered. Roy H. and Joe S. were excellent guys to finally get in touch with but they still lacked data because JCI does not provide it.
If you have or use a battery monitor you really need to know the precise 20 hour Ah rating & Peukerts, at a bare minimum, or it will not work correctly. Interstate/JCI simply don't publish a 20 hour rate, which is what we use for deep cycle
batteries. They publish Reserve Minutes, 5 Hour, 15 Hour and 25 Hour but not
a 20 hour...?
If the manufacturer does not publish a 20 hour Ah rating the battery is usually
not a true deep cycle battery
but then again Interstate does not market this as a true deep cycle battery, they market it as a deep cycle/cranking battery. In other words, dual purpose.
The cycle life will be and is reflective of this in a deep cycling application.
You can ask them for the cycle life
of the 4D compared to their GC-2 "U" series battery. Unless things have changed dramatically, you will be met with dead silence, as I was. They can, and do, have cycle life data on their true deep cycle products made by USB but not the stuff made by JCI..
Early on I never did get a an accurate
20 hour rate even after speaking with multiple people over about a week. Even after talking with Roy H. I still had to physically measure the battery by doing a 20 hour load test. I guessed it was 8A, based on the 25 hour and 15 hour rates, but an 8A load at 80F only resulted in 138 Ah's out of the SRM 4D battery.
The problem with capacity testing flooded batteries is they take a long time to cycle up
to capacity. GEL and AGM will deliver rated capacity in 2-10 cycles but flooded batteries can take 50+. So even with accurate capacity testing I still had no way to know what the actual 20 hour rate was until the batteries were broken in
? Very frustrating...
Anyone who tests a lot of batteries, like I do, can tell pretty quickly by by simply looking at the CCA of that battery that it is not a true deep cycle
flooded cell battery. A deep cycling
battery would have a lower CCA value in a flooded deep cycle cell or not even be rated in cranking amps.
Interstate labels it as "deep cycle/cranking" these are hybrid batteries that attempt to do both but almost always miss the mark when put into a true deep cycling application like on a cruising boat. The bottom line is to always question the marketing mumbo jumbo
As I mentioned above one of the only true 4D flooded deep cycle batteries I know if is the Dyno 4Dd (the small "d" designates deep cycle). This is not to be confused with the Dyno 4D which is for starting. This battery has an Ah rating of 180 Ah's and cost $268.00 and like many true deep cycle, thick plate batteries, they do not publish a CCA value.
My best guess is the SRM 4D is a 150-160 Ah battery at the 20 hour rate but it is not going to give the cycles
of a true deep cycle
When buying batteries we don't just pay for Ah's
we also pay for cycle life