what size battery for a 45 thrust? and, Minn Kota or Motor Guide?

[jaredmede]

I have a Sea Eagle 9 (11' inflatable boat). I have a Die Hard Deep Cycle group size 24M battery. I plan on getting either a Minn Kota 45 transom SW or a Motor Guide 45 transom SW (suggestions on that decision appreciated as well). Is this battery good enough for that size motor? Approximately how long will a 45 thrust motor last on half speed and at full speed? The battery says "Amp Hours at 20 Hour Rate: 80" and the RC is 135 mins. Any thoughts on this or Min Kota vs. Motor Guide would be great. Thanks in advance.

 

[jtexas]

Re: what size battery for a 45 thrust? and, Minn Kota or Motor Guide?

80 amp hours at a 20 hour rate means that a constant 4 amps for 20 hours will drain the battery to 10.5 volts, giving it a rating of 80 AH (20 x 4).

12V trolling motors usually run with a 40- or 50-amp fuse, so assuming your steady-state current draw is half that, or 20 to 25 amps, you might expect to get around 3 1/2 to 4 hours. That will decline as the battery ages.

But, because a battery provides less power when you drain it more quickly (google "peukert effect"), you'd get more like 2 1/2 to 3 hours of continuous run time until the battery was completely and utterly dead.

By the time the battery gets to about a 80% state of charge, it'll be going noticeably slower, and will be effectively useless for powering a T/M before it hits 50%, so bottom line, expect at most an hour and a half of continuous run time.

Of course you'll get more time if you're using it intermittently. You should get a good half-day fishing out of it, at least.

135 RC means 135 minutes reserve capacity...means it takes 135 minutes for a 20 amp load to drain the battery to 10.5 volts.

Remember, draining a battery to 10.5 volts can cause permanent damage.

Always recharge soon as possible after each use -- storage at less than full charge is a leading cause of premature battery failure.