Proposrt 20 on 2 group31's and a group 27
 

Im upgrading my battery system this weekend and wanted to see what you guys think about adding the promariner 20, dual bank onboard for a group 27 deep cycle battery on one side of the perko and 2 group31 agm's on the other. Is the prosport barely big enough? In the description it says good for up to 125amp hours per battery, but I dont know if thats for the bank or for each within the bank. I have 3 blue tops that I have been running for a few years and they are toast at this point.

It's not entirely a clean equation based solely on your battery amp/hour capacity. Other issues come into play like the battery switching system used whether a basic manual switch or an ACR/VSR, your alternator size and how far you routinely discharge your batteries. A ProSport 20 is bare minimum for the collective amp/hours of the three batteries mentioned. Using Optimas and if your stereo bank is never cycled below 12 volts I'd say you are just okay. Using Deka AGMs in that size I would move up to a 30 amp charger.

David
Earmark Marine

Manual perko switch, and looking at the Dekas from westmarine or Die Hard Platinum from sears. Length of charge time is not really an issue as I am out for a day at a time only. I have pounded the optimas over the years and now they are giving me issues from a voltage standpoint and being able to hold a charge. I think I will be happy going from a 24 to 31 in group size and pure reserve capacity. Ive seen the 30amp charger on your store and am interested, but at twice the price I just wanted to see if the 20 would work:banghead:

I never factor re-charge time unless you are a tournament fisherman. I only consider the charger amperage capacity and its ability to completely rebound from sulfation in order to extend the lifespan of the batteries and maintain the highest percentage of the original reserves during the lifespan. Past a point, it is particularly hard on your alternator to push the use of old batteries. An owner of an alternator shop said that if everyone replaced their batteries at the appropriate time he would be out of business.

David
Earmark Marine