"Any: deep cycle will do what you want. The problem is for "how long" it will do what you want. Deep cycle batteries are specified by Group Size such as 24, 27, 31, etc. The larger the group size, the higher it's capacity. For a 55# trolling motor you will need a group size 27 and if you are a very serious fisherperson who is out for 1/2 day or more at a time, you should go even bigger. Within each group size there are some numbers you need to compare.when shopping. A group 27 may have a "Reserve" of 175 minutes and that would be specified with either a 25 or 23 amp draw. Those numbers mean the battery can operate at 23 (or 25) amps for 175 minutes. Consider that your 55# motor will draw in the neighborhood of 46 amps maximum so that's double the 23 amp specification for a deep cycle. So that 175 minute number now is 1/2 that or 87 minutes before the battery is depleted. Granted, you will not be operating the motor at 46 amps 100% of the time so run time will vary depending on how you use the motor. The key is that the Amp/Hr and Reserve numbers need to be compared when you shop. One group 27 battery may not have the same spec as the others you look at yet it costs more. That would not be a bargain. If you live in a relatively rural area, there is generally a farm store like Tractor Supply, Farm & Fleet or similar. My local farm store for example has a group 27 deep cycle for $75 on a daily basis. I've used them for years without issue. You can spend $200 for a battery that doesn't perform any better and may or may not last any longer.
