best deep cycle battery for trolling motor

snuffy45

Seaman Apprentice
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Jul 25, 2008
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I have been looking at sears web site and they list 3 deep cycle batteries. 24m,27,29m. question is example 29m specs- 200 minute reserve- 115 amp hr at20 hour rate. what does that mean, how long can I expect battery to operate trolling motor. others, 27m- 180 reserve-105 hr at 20 hour rate. 24m- 135 reserve-80 hr at 20 hr rate. I know it has to do with time it will stay charged but not sure how to figure it. help please??
 

Silvertip

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Sep 22, 2003
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28,758
Re: best deep cycle battery for trolling motor

Group 24, 27, and 29 are the physical sizes of the battery. 24 is the smallest and 29 is the largest. Reserve capacity is the amount of time the battery can power a 20 amp load. Obviously the bigger battery has the most capacity but not all group 29 batteries for example will have the same numbers so watch for that. Without knowing how big your trolling motor is we can't tell you how much current it draws but I can give some relative numbers. If your motor is in 40 - 50# thrust range it will draw "about" 42 - 46 amps when set on the fastest setting. Therefore, if your motor is set to fast, and it draws 40 amps (roughly) and you have a group 29 battery with 200 minutes reserve time, you would discharge the battery in about an hour and a half. At half speed (20 amps) it would run about 3 hours. The story in all of this is that when it comes to trolling motor batteries, buy the largest capacity deep cycle you can afford and have room for and charge that battery immediately after every use (not the next day, or next week, -- immediately!!!!).
 

mthieme

Captain
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Oct 6, 2007
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3,270
Re: best deep cycle battery for trolling motor

The higher the amp hours, the longer you can run.
 

snuffy45

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Jul 25, 2008
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Re: best deep cycle battery for trolling motor

OK, I am starting to see the light. don't know why I didn't tell you what trolling motor I had. it's a OMC Cobra model# OBFL2TA. I searched that model # and read it was a 1995 36" shaft with 23 lb. of thrust. It is a 3 speed. don't know the amps used though. but should be less than the one in previous post. found a 31M at auto parts store with price the same as the smallest one at sears but it didn't give any info on reserve minutes on web site, going to call them to check. thanks for the info at least I know what to look for.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
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28,758
Re: best deep cycle battery for trolling motor

On the fastest setting, your 23# thrust motor will draw about 20 amps give or take a little. My suggestion is that with that motor you don't need a group 31 but it certainly would be nice if you have the room. These are very heavy so it you have to lug it to the cabin or house to charge, that's an issue. Regardless, a battery with 200 reserve minutes would run a little over 3 hours (theoretically). Since most trollers are not running continuously at wide open setting, run time would be a fair amount longer.
 

snuffy45

Seaman Apprentice
Joined
Jul 25, 2008
Messages
41
Re: best deep cycle battery for trolling motor

thanks alot for the info. that helps me alot. I am going to check the mwanurements for the 31 to see if it will fit battery box and if it will I think I will go that way just for a little more power. the charging isn't a problem since I trailer the pontoon and can charge it on the boat where I park it. if it's to big I'll go with the 29, I'm sure it will be enough but a little more won't hurt. we mostly use it on medium just to keep it in straight line as we mroll along the bluffs fishing, we have learned to use the wind to help push us along just need a little nudge to keep the front headed the right way. thanks again, very useful info.
 

Irv964

Petty Officer 1st Class
Joined
May 3, 2008
Messages
315
Re: best deep cycle battery for trolling motor

Group 24, 27, and 29 are the physical sizes of the battery. 24 is the smallest and 29 is the largest. Reserve capacity is the amount of time the battery can power a 20 amp load. Obviously the bigger battery has the most capacity but not all group 29 batteries for example will have the same numbers so watch for that. Without knowing how big your trolling motor is we can't tell you how much current it draws but I can give some relative numbers. If your motor is in 40 - 50# thrust range it will draw "about" 42 - 46 amps when set on the fastest setting. Therefore, if your motor is set to fast, and it draws 40 amps (roughly) and you have a group 29 battery with 200 minutes reserve time, you would discharge the battery in about an hour and a half. At half speed (20 amps) it would run about 3 hours. The story in all of this is that when it comes to trolling motor batteries, buy the largest capacity deep cycle you can afford and have room for and charge that battery immediately after every use (not the next day, or next week, -- immediately!!!!).

Silvertip, I thought a battery had to cool some before re-charging? I have never heard of the immediately after use theory before.........Irv964
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: best deep cycle battery for trolling motor

Not an issue. And immediately after use means within a reasonable time after you hit the dock. Leaving a battery discharged for a day or more begins the failure process. Mine gets plugged in the minute I hit the dock. The battery in your car for example gets far hotter than your troller battery ever will and it is under charge constantly.
 
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