overvolt Trolling motor

aaronski

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Jul 9, 2009
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San Francisco,ca
Hi guys,

Anyone know if it's possible to overvolt an el-cheapo minn kota trolling motor? there are 12v ones out there for ~$100, but I'd like to use my 48v or 36v lipo with the motor, and it would suck to just fry it...
 
I have heard of people running 24 volts on the motor rated for 12. I'm not sure how far you can push these though. I'm looking at getting a few for an electric sailboat one day:D
 
You need to watch just upping the voltage, because the current that the motor will draw will rise massively as the prop rpm increases (it's a cube law relationship, so doubling the voltage, doubles the potential prop rpm but the power goes up by 8 times).

You might be able to get away with using a brushed ebike controller as a speed controller and voltage reducer, by limiting the throttle travel to restrict the maximum motor rpm. This would let you run the motor at normal power and act as a voltage to current transformer, with some current limiting protection built in. You'd draw less current from the battery pack, too, in proportion to the ratio of the voltage drop.

The cheap Minkota motors don't have PWM speed controllers, just a couple of resistors in the motor housing to switch speeds (they call them 'speed coils'). There's an interesting thread on the Boat Design forum where a chap has experimented with making one of these cheap Minkotas more efficient; he used a brushed motor controller. See here: http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-15.html#post302305 and also his final pictures, here: http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996-28.html#post381261 for some ideas that might help.

Jeremy
 
I ran one using a little curtis brushed 24v controller on the 12v trolling motor. The curtis must have had a lower current limit than the motor was accustomed with direct connection, because it actually reduced the thrust. It ran just fine, as least until a drop of seawater got to the controller's pcb.

I don't understand how the voltage limit works with brushed motors, so I'd be leary of 36V, but at least with a trolling motor cooling shouldn't be much of an issue. You might look for a 24V trolling motor instead.
 
I posted this exact question on another forum and also called Minn Kota service dept. to find out what voltage range the Riptide saltwater trolling motors could handle....they were zero help :(

I have a Riptide 12V motor and wanted to build a lithium battery for it, but was not sure if 4s hot off the charger would be too much (say 16.8 volts or so). The riptide series is expensive ($500) so I didn't want to blow it right away.

Would be interested to hear your results and the model number of your trolling motor if you attempt to overvolt one.
 
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