[takomaned]

Hi Al. When I got my 31 S/W the battery was beyond usable. I checked out both types (wet cell and spiral cell). I found that the Optima had more cold cranking amps and had a better warranty than the Interstate. Google search found the best price and I paid $109, before a discount coupon from Optima.
Joe K's idea of using a clock timer is what I also do, and it works well with a standard battery charger. I've heard of battery tenders going bad and "cooking" batterys. With the timer, it's only powered up for the aamount of time you have it come on for. My Optima is only 3 yrs old so I can't provide any info about lifespan.