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That is excellent info. I am really wanting to understand this before I go welding on the pods so I have the proper amount to tru-hulls. How do you charge a 36 volt system? So I am getting really mixed answers on the whole 36v verse 12v. I want to go 12v because of the simplicity and cost, but I am worried by the amount of thrust. What does everyone think about 12v powering a K-350? I won't want to have a motor ment to drive me to the dive site, but I am a little concerned about slight currents. I am also a little concerened about burning up motors and such. I don't think I would ever run full blast (except in an emergency), but I don't want to build this thing and end up ripping out all electronics because I made a mistake. At my place of business one of the things we sell is batteries. Interstate makes a marine battery that has 1,200 cold crank amp, so amps I'm not to worried about. I really appriciate the wealth of knowledge here. It has saved me from making lots of mistakes. Thanks, Scott Waters From: ShellyDalg@aol.com Date: Thu, 25 Feb 2010 13:06:54 -0500 Subject: Re: [PSUBS-MAILIST] electrical question To: personal_submersibles@psubs.org Hi Scott. It's not a problem to use 12 volt motors. MinnKota has some smaller powered ones available.
If you are using an interior motor with the shaft going through the hull, there are 12 volt motors available too. It's just more efficient to use 36 volt motors. A sub with only one 12 volt battery won't go very far or very fast.
A small 12 volt MinnKota trolling motor like one used to push a small fishing boat will run about two or three hours on a fully charged 12 volt marine deep cycle battery. ( at half speed ) It won't push very hard though.
A submarine has a LOT more drag than a little 12 foot boat on the surface. If there is any water current at all the small 12 volt motor won't be able to counteract the forces applied to the submerged vessel.
If the sub was small enough and there was no current it could be useful to "putz" around near shore in a lake but you wouldn't be able to move very far or go down very deep before you ran out of power. It's just more efficient to use higher voltage motors. Higher voltage with lower amp draw for the same horsepower. Lower voltage with higher amp draw means pushing the motor at max and abusing the batteries. You would save a little money by buying a cheaper ( smaller ) motor but the motor will wear out faster and the batteries will take a beating too.
Batteries cost more than the motors.
An underpowered sub could be quite dangerous as well. Any water current at all or maybe a little wave action could easily push an underpowered sub into the rocks, drive it down, or into all sorts of trouble.
There have been subs built with NO motors. Karl Stanley's first sub "C-Bug" had no motors. It used variable ballast to move through the water. It worked quite well but it had limitations in maneuverability. His new sub has 4 X 36 volt motors.
I have 4 X 36 volt motors on my little sub, but in reality, I will be running them at 1/4 speed most of the time.
No strain on the motors or batteries, so life span of the system should be good. The power is there if I need it for short bursts of speed or to fight against a current but a full power burst puts a big strain on the battery system.
A 12 volt motor is so small that running it a full bore all the time would cause over heating of the whole system.
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