Re: [A/S] Batteries For 1979 31' Soverign

[Charlie/Betty Burke <cbburke@xxxxxxxxxxxxx>]

Deep cycle batteries are best rated by a standard called Reserve Capacity 
Minutes. RCM is a test standard used across brand to provide an EPA mileage 
type rating in uniform use test. The test like an EPA rating rarely relates 
to reality but applied across brand it gives a basis for comparison. The RCM 
test is with a discharge rate of 25A at an ambient temperature of 80 deg 
starting with a fully charged new battery. The rating is given in minutes. 
To apply reality simply divide the 25A discharge by a rate more typical of 
your use and multiply that number times the rating. (25A/5=5x160=800
minutes or 13.3 hours of continuous use at a rate of 5A per hour.
When the Costco in our area started selling deep cycle batteries we check 
them out, same with Walmart. In both cases, while the batteries are made by 
major manufacturers the RCM rating of them was lower that a name brand 
battery. By example: Costco's Group 27 which is made by the same company 
that makes Interstate had a RCM of 130 minutes. The same size battery from 
Interstate has an RCM of 160 minutes. The price at the time was directly 
proportional to the RCM. One case of you get what you pay for.
The Ultima batteries have a ton of advantages for RV except for one. Their 
RCM is pretty short, at 105 minutes.

Charlie