Deep cycle battery: RC vs Ahr??

Standard for deep cycle batteries is AH at 20 hr rate. Reserve Capacity is a measurement for starting and marine hybrid batteries.

If choosing a battery that has both ratings, select by weight. More lead = more goodness.

ReadThe 12 Volt Side of Life, maybe it will help.

Reserve capacity is number of minutes battery can supply 25 A. Amp Hours is the Amperage a battery can supply over its rated time (usually 20 hours). Batteries designed for deep cycle use are usually rated in AH, batteries rated for vehicle/dual use are usually rated in RC.

A battery rated 120 min RC would be providing 50 AH; but that would be at the 2 hour rate which is a pretty high draw. This battery would be able to provide more AH total at a lower draw.

A battery rated 200 AH (at the 20 hour rating) would be able to supply 10 Amps for 20 hours. This battery would probably be able to provide about 300 AH at a 100 hour rating.

I think batteries rated in AH are designed for true deep cycle use; batteries that have a starting Amperage rating and an RC rating are designed for dual use, and are not truly suited for deep cycle use.

Doug

I understand that I don't want CCA since I have no starting load but this stuff makes my head swim.

BTW: Trojan lists both RC and AH for the T105
http://www.trojanbattery.com/product/t-105/

johnm1 wrote:
I understand that I don't want CCA since I have no starting load but this stuff makes my head swim.

BTW: Trojan lists both RC and AH for the T105
http://www.trojanbattery.com/product/t-105/

Nothing wrong with a manufacturer listing both but like said, the 20 hour rate is normally used for comparing batteries for deep cycle use.

Confusing isn't it?

Forget batteries that list ONLY Reserve Capacity. It's done to deceive the customer.

The LOWER the ampere hour rating (20 hr rate) while having the GREATER battery weight in pounds (both are needed in this formula)the more cyclable the battery.

Think of battery power measurement as being equated to SPEED in a human being.

Think of battery longevity (cyclability) as being equated to ENDURANCE. Ever see a weight lifter running the 440 meter track? it's pathetic.

The greater the cold cranking amp rating the poorer the ability battery has to withstand repeated charges and discharges. Fast & Furious Failure.

With 2 deep cycle batteries coming from the same company, look for weight comparisons. Water is featherweight in comparison to battery acid or plastic case. Heavier is better.

You want a lot of Amp Hours.. Batteries rated with "Reserve Capacity" are most likely starting, not deep cycle, even if they say MARINE/deep cycle (Tose are Starting batteries first and foremost. Not even close to a GC (golf car) battery when it comes to DEEP CYCLE).

MEXICOWANDERER wrote:
Confusing isn't it?Think of battery longevity (cyclability) as being equated to ENDURANCE. Ever see a weight lifter running the 440 meter track? it's pathetic.

Gee, thanks ... it's going to be very hard to get that image out of my brain!! :E

However, I think it illustrates the thought perfectly to me to understand.

johnm1 wrote:
I need some of you "smarter than me" people to enlighten me ... please. I'm looking at batteries for my RV (travel trailer) to be able to boondock longer without running the genny or going solar (which I want to do anyways).

I see some batteries only have RC (reserve capacity) listed instead of Ahr listing. Which one is a "better" measure for true deep cycle batteries to be used in a RV?

Thanks,

If you post the data you are comparing you could get some actual direction.

There is no formula to convert RC to Ah