12 vs. 24V

[birdy3897]

I can't decide if I want a 12V 55lb or a 24V 65lb trolling motor for my boat. The ones I am looking at are MinnKota Power Drives. My boat is pretty heavy as it is an old 1978 Imperial 16ft with an inboard. I converted the bow to a bass style deck for fishing and am probably looking at the 54inch shaft because it is a tri-hull. Are 24V longer lasting as far as run time on the water, or will a 12 do just as well? Is it worth the extra battery the 24 requires? I will probably be using the trolling motor a lot of the time I am on the water as I like to cruise shorelines and not run the Inboard a lot. Never had neither so I have no idea. Price wise I am looking at about another 75 bucks and another battery for the 24volt. Is it worth it?? Any help would be appreciated!

 

[PAkev]

Re: 12 vs. 24V

From the context of your post, you seem to already know the right choice. <br /><br />If you are just looking to get in around docks or areas without spooking fish the 55lb 12V may do everything you expect it to do. However, if you plan to fish a shoreline all around the lake via your trolling motor the 24V may be a better choice. The 12V will often cut your day short where the 24V will afford you the power to stay out when the fish are biting.<br /><br />Now the bad news... You will need two batteries and ideally a 2 bank onboard charger. It's a little bigger investment out of the gate but with today's gas prices will have you break even sooner than getting from point A to point B with an old fuel guzzling outboard.<br /><br />I have a 24V 74 lb Power Drive and have been pleased with it. The autopilot feature petered out last season but MK replaced it under warranty with no great hassle.

 

[birdy3897]

Re: 12 vs. 24V

So your saying the 24 volt will definatly last longer than the 12 volt as far as run time and keeping consistant power?

 

[18rabbit]

Re: 12 vs. 24V

In theory, no. In reality, yes. Higher voltage is more efficient, tho prob not enough that you will notice unless you compare the two side by side or have a lot of tm experience. Given the choice, I'd take the higher voltage. But keep in mind, higher v often means stepping away from the norm and anytime you do that you incure add'l expenses, as was pointed out above; 2 batts, diff charger, etc.

 

[rickdb1boat]

Re: 12 vs. 24V

Originally posted by BIRDY3897:<br /> So your saying the 24 volt will definatly last longer than the 12 volt as far as run time and keeping consistant power?

No doubt about it....

 

[LubeDude]

Re: 12 vs. 24V

Even though I run 12 volts, I also run two batteries. I dont think that a 24 volt will last as long as my 12 volt with two batteries. I could be wrong, but I dont think so. Ive had 24 volt systems, and I think my present set-up is better.

 

[tommays]

Re: 12 vs. 24V

its all about the AMP HOURS that the battery set up has to give in a day without being run so low it gets dammaged<br /><br />if its 50 and your drawing 10 your going to max out at 5 hours.<br /><br />i have some 24 volt things set up with (4) giant 6 volt batterys that will run a crazy amount of time.<br /><br />Of corse its it a 500 dollar set of batterys but it will out last the bunny<br /><br /><br />tommays

 

[imported_bjs]

Re: 12 vs. 24V

new bass boats have 36 volts there must be a reason for 36 or 24.go for the 24 volt

 

[Silvertip]

Re: 12 vs. 24V

12, 24, and 36V systems obviously have limits as to the maximum thrust the motors provide. There is no free lunch when it comes to electric power. The big motors don't necessarily provide more run time. They do however allow pushing a bigger boat around a little quicker because they have more thrust. If there were a such a thing as a 40# 36V motor, obviously it would run longer than a 100# 36V motor on a full charge. If a 12V 55# motor gets the job done, simply install two 12V batteries with a switch and double your on-water time. Much cheaper and a single bank charger can charge both batteries. Unfortunately your boat is probably at the limit for a 55 so you may be better off with a 24V especially if you fish big water and must deal with wind. Otherwise, a 12V 55 would probably work.

 

[LubeDude]

Re: 12 vs. 24V

Something else you may want to concider is that you have a lot more surface for wind to hit than if you had a real Bass Boat that is lower to the waterline. I had a 15' trihull once, (My first boat), I bought a used 24 volt motor and when it was windy, I was glad to have it. But way back then I think that it was just a 40 #'er.

 

[Barnacle_Bill]

Re: 12 vs. 24V

For a given situation a 24V system will use 1/2 the power and a 36V system 1/3 the power that a 12V system will use. Ohm's law, electronics 101

 

[imported_bjs]

Re: 12 vs. 24V

ive had a 12 volt trolling motor and have a 24 volt hands down the 24 volt is a lot better in ks the wind blows everyday.and the 24 volt kick butt over the 12 volt im sure the wind blows were you live to.i would go with 24 thats just my opinion.i just bought a new 24 mg i love it

 

[Silvertip]

Re: 12 vs. 24V

IB - I think you missed my point and are not making a valid comparison. Your numbers are correct assuming the 12, 24, and 36V motors all have the same maximum thrust (power) rating. Using a 1 HP motor for example (740W at 100% efficieny) a 12V motor would draw 62Amps. Now don't get excited here. I'm using 1 HP as an example. A 12V motor is probably in the 3/4 HP or less range. A 24V would draw 30A. A 36 would draw only 20A. Your ok to this point. My point however is that 24 and 36V motors have much higher thrust (hence power) ratings. So lets use the same 1 HP for a 12V motor (740W), 2 HP for a 24 (1480W), and 3 HP for a 36 (2220W). Dividing each of those Wattages by their respective voltages produces exactly the same current draw. The difference is that the 24 and 36 will move a heavier boat better than a 12 because it has more power. Fact is however, at their maximum power settings, all motors will draw the same power. Power is not free. Basic Ohms law. <br />The only advantage that the 24 or 36V motors have in power consumption is at a lesser power setting than a 12 or 24 would need to maintain boat control. At wide open settings -- no advantage except speed and that's a big "IF" depending on weight and hull design. In this gentleman's situation, if a single 12V battery and 55# motor doesn't last all day, but otherwise gets the job done, why spend a considerable amount of extra money on a 24V or 36V motor, two or three batteries, and a dual or triple charger, add all the weight, just to extend the time. Adding a simple battery switch and an extra battery gets the job done with a 12V motor and a single output on-board charger. That's "economics 101". Granted, if the 12V motor doesn't get the job done regarless of time on the water, a step up in power is needed.

 

[--GQ--]

Re: 12 vs. 24V

It is best to operate at higher voltage. Since your equipment resistance is constant, higher voltage will reduce the current thus reducing the I square R loss. Heat loss is exponentially proportional to the current flowing thru the conductors and the equipment it is feeding. Depending on the size of your motor under normal operating conditions, your batteries will last slightly longer.<br /><br />Note: At 24v, the current is half of that at 12v.

 

[Silvertip]

Re: 12 vs. 24V

GQ -- you miss the point too. No disagreement that with a given 1 HP motor operating at 12V and a 1 HP motor operating on 24 or 36V have correspondingly less current draw. However the trolling motors being discussed are not the same power output so at maximum power they draw the same provided like voltage, their power output is proportional disregarding the loses you mention. I agree that a 55# 12V motor will not run as long as say a 65# 24V or a 75# 36V. These are not fair comparisons. A 24V motor with twice the output of a 12V or a 36V motor with three times the output of a 12V all will draw the same power.

 

[Barnacle_Bill]

Re: 12 vs. 24V

Upinsmoke, I agree with what you are saying. Thats why I said for a given situation. Your explaination with the 1HP motor is what I was trying to get across. Thanks for making it clearer for me.

 

[--GQ--]

Re: 12 vs. 24V

I'm not sure which "point" i missed, but my point is this. Disreguard the motor thrust rating you mentioned wether its 12, 24, or 32, it makes no different regarding what I stated. When given a choice, it is best to go with the higher voltage for many reasons: I square R, Eddy current and histerises.<br /><br />My point is this. I square R (heat loss) is due exponentially proportional to the amount of current drawn by the equipment (motor). Current flowing thru a conductor is not constant. Heat loss at 100 amps is more than twice the heat loss at 50 amps. Hint the I square. Example: suppose a 12v motor draws 4amps. Now the same motor rated at 24v would drawe 2 amps. The I square value for the 12v motor is 16. While the I square value for the 24v motor is only 4. As you can see, doubling the voltage reduces the heat loss by a factor of 4.<br /><br />Again reguardless of the equipment you're feeding: higher voltage is more efficient. In essence your battery is putting out more power and get less from your motor. Ofcourse it is imposible to achieve a power input/output of 1 to 1 ratio, but you're better off with the higher voltage and you can quote me your batteries will last longer.<br /><br />Note: Eddy current ans histerises are due to motor characteristics