At work we use O.S. Walker magnets to pickup coils (up to 2000#).
The magnets have marine deep cycle group 27 batteries in them. Magnets are used 8 hours a day 5 days a week. In the past i have used Diehards, Interstates & others. Would spend $$ trying to get the best batteries. In the end I have found that the Exides that i can get at Menards for $71 work as well & last longer. Go figure.