First of all, save yourself some money in the long run and get a marine rated battery. Car batteries will have a considerably shorter life and do not appreciate being drained down and recharged very often. They will eventually give out.
Next, find out the amperage rating on your trolling motor 20 amps, 30 amps, 40 amps etc. Multiply that by 5 and you will come up with a battery rating that will just last the 5 hours that you desire.
Example: 40 amps x 5hrs = 200 amp hours
80 amps x 5hrs = 400 amp hours
If by chance you would like to have some extra juice and not try to limit yourself, then add another 20% to that figure and that should give you a safe enough buffer. If the math seems too confusing, then just multiply the aformetions sum by 7 instead of 5.
Remember that the Marine rated battery is a deep cycle battery. It will handle almost complete discharge and come back to life much better after charging.
Marine batteries cost a "Few" dollars more but are worth it in the long run. You could expect to pay @90 bucks for a decent marine battery. An equivelantly rated car or truck battery may cost about half of that but you could go through 4 or 5 car batteries to every 1 marine battery.
Please feel free to ask any questions that you may have. We are all here to share with one another.[cool]
From your friendly Moderator.[

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