I think I am figuring things ok with my assumptions... This is gonna be just like the LEDs replacemnts we all did a couple or more years back. I bet - After I spend all the money I dont have to spend I'll have to pull out what I just bought and spend it all over again hehe...
This is all part of my pre-planning to setup for two separate battery banks with one in the bed of the truck and the other one the tongue of my trailer. I started accumlating parts last fall for this project. Pure cost is gonna drive me to the COSTCO/SAMs GC2 6V batteries in the end... $97 for a GC2 is gonna be hard to beat... I would rather find some 150AH 12VDC batteries but they will cost aorund $200 each I am seeing. I'm gonna need four of them as my 5 year old GP24 85AH batteries are just now starting to fail. Maybe the battery bunny will smile on me... I will be real lucky if my remaining two GP24's will last this spring/summer camping season. Lost one so far...
* This post was
edited 05/05/12 01:12pm by RoyB *
My Posts are IMHO based on my experiences - PM me Roy and Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS
From reserve capacity, you can determine the AH rating based on a 25A discharge rate. For example, furnace and lights on in the trailer and watching tv.
From the AH rating for the common 20Hr rate, you know the AH based on a discharge rate that is usually lower. For example a T-125 240AH battery, the 240AH rating is based on a discharge rate of 240A/20hr or about 12A
Take the 25A reserve capacity and calculate AH = 25Ax Reserve capacity in Hrs = the AH rating with a 25A discharge
And then calcuate the AH based on the trojan 75A reserve capacity.
As an example suppose the battery has a 20Hr rating of 240AH
the 25A reserve rating may be about 9 hours so the 25A AH rating would be 225AH
The 75A reserve rating may be about 2.5Hrs or 185AH
what you'll find is that the higher current will give lower AH ratings. Knowing your typical discharge current, pick the rating (20Hr, 25A, 75A) that best matches your use and the battery with the largest number for that rate is what I'd go with. for me, the GC 20Hr rate is actually a higher current drain than we typically have. Usually we are in the 5-8A range with LED lights, furnace adds another 6A.
More than likely you'll find that the highest 20hr AH rating will give you the longest 25A reserve time and the longest 75A reserve time. they are all related. For a given battery, once you get above a few amps draw, the higher the current draw the lower the AH rating will be.
* This post was
edited 05/06/12 09:22am by ktmrfs *
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2004.5 Silverado 4x4 CC/SB Duramax/Allison
Good thread, people. Like pianotuna's puekertism. and ktmrfs emphasis amplification of matching whatever battery's specification to a very particular type of usage. Folks that use 1.1 amperes of LED lighting over a very long period of time have a much different perspective than some weekend warriors that will consume 800 ampere hours using the microwave and 26" flat panel television watching the playoffs on a satellite TV.
Let's simplify this all. Here is what I'd recommend.
Stuff in as much capacity as possible without exceeding the weight rating for the compartment. If you are solar charging keep at or above 60 watts per 100 amp-hours of storage. Balance the demands on the bank to match its size. If you do those three things plus minor routine maintenance battery life will be long and rving will be fun. Miss on any of them and expect short battery bank life time.
Don (still lusting after six 800 amp-hour 2 volt cells)