mastreb wrote:...1) Why buy an 80 lb. thrust motor @ 24V and then run it at half-throttle, when you can just get a 55lb. thrust motor @12V and avoid all of the complexity of a hybrid 24v/12v system? Especially given that you've got a gas motor for problems? Electrical motors like to be run at 90% of capacity. Before I'd go to a 24V system I'd go to dual 12V motors......
Good questions
. I went with the 80 for a couple reasons after doing some research....
Use Variable Speed Motors: Using a variable speed motor (vs. a fixed speed motor) generally results in significantly longer run times. Variable motors are more expensive – generally about $100 more than a comparable fixed-speed model – but are more energy efficient, especially at slower speeds. They are also much more convenient as they allow you to dial in the speed to the exact setting you want vs. having to select from pre-set speeds. For more details, see these notes on fixed vs. variable speed motors.
Buy a Larger Motor: Larger 24v and 36v multi-battery trolling motors are able to provide the same thrust as smaller motors with less amperage draw, which results in longer run times. If you need seriously long run time for your smaller boat, it may make sense to buy a 24v or 36v motor.
http://www.trollingmotors.net/trolling-motor-run-time
I could get the 80 in a salt-water version that had the variable speed motor and from what a couple sources said, like the one above, it would be more efficient at slower speeds. I think from reading what people have said that have used a 55 on their boat (some X's and S's) they have to run it pretty hard and it won't really handle any kind of wind/current situation very well. The 80 I'm hoping will have some reserve for that if needed.
One thing I want to use this for is anchoring by myself. When I approach an anchorage I should be able to switch to the trolling motor and set the autopilot in the direction I want to head (remember I anchor in remote anchorages with no other boats). One feature you can do according to the Minn Kota tech with the variable speed 80 is cut the power to it off and on and it will stay at the same speed setting. I'm going to put a bypass solenoid around the main cut-off switch to the motor. Then I'll be able to plug in at the bow with a remote switch where I can operate the solenoid and pulse the motor and stop it when I get to the point where I want to drop the anchor.
I couldn't do any of this with the gas motor and might have to do it in higher winds with the trolling motor and would like to know that it might handle them. Here is a chart that shows motors being sized by boat size...
The weight of the S on the water is probably approaching 4000 lbs. As you mentioned I do always have the 9.8 HP but I'd still like a little cushion with this motor.
mastreb wrote:... By my math, your motor will draw something like 30 amps (half rated power) at 24v for (say) 5 hours per day, for a total draw of 3.6ah per day. Under normal insolation conditions, considering sun angle, latitude, etc. maybe half that each day. The good news is you need only double your solar production to avoid worrying about generators at all.
30 amps for 5 hours would be 150 amp/hr. The tech figured that running the motor at about 10 amps should give me a boat speed of about 2-3 kt. (we will see if that is right). I'm hoping that the 360 watts, out of 560 total, that are devoted to the trolling motor will give 4-5 hours of run time a day with good sun.
The MorningStar MPPT controller I bought can be run as either a 12 volt or 24 volt charge controller. I'll run it in the 24 volt mode so no problems there. I also have come up with a way to charge the 2 trolling motor batteries with 3 switches and 3 relays for under $75 from the 12 volt gen-set if I ever want to do that also. Can't really see much of a need but will have it.
mastreb wrote:......THEN I'd build a switching system that allowed me to direct drive the trolling motor with the solar panels, all batteries, chargers, and controllers lined out, for maximum efficiency. Seriously just panels in parallel connected to the trolling motor. Whatever sun there is, that's how fast you go. Switch over to battery charge when you're in port.
Also with the motor connected to the batteries at the same time the 24 volt charge controller is connected the motor will be basically running on the panels and not the batteries.
mastreb wrote:....My opinion, I'd go with a transom mount 55lb. motor...
No room on the transom, the outboard is there
. I'm about finished with the mount that is between the outboard and the ladder. Should be done with that today and get on to the mounts for the additional 360 watts of solar,
Sumner
