Negative ground wire is a vague term on a boat. There's "chassis ground", 'earth ground', "battery ground", and bonding wires, all sometimes confused.
In a DC charging system you are not concerned with any "ground" unless you've got AC inverters or chargers added into the mix. You've only got battery pos and neg, and any device that indicates it needs a 'ground' should specify what it wants if battery neg is not going to be good enough.
With an inboard engine, usually there will be a central point on the engine block/mount that is used to tie the battery neg to the engine block and made into a common electrical ground point at the same time. Running all grounds to one central point (preferably the neg battery terminal or the first connection from it) prevents 'ground loops' from happening.
Ground loops are a gremlin that can happen when different "grounds" are not all at the exact same electrical potential (voltage) because of voltage losses between the different locations. In a system as simple as yours--that shouldn't be an issue.
Please keep in mind that a wind gen does not care about what size your battery's are and a controller is very advised. A good gust can send one of those things to charge 70volts!!! in your 12 volt system that would be very bad.
Also keep in mind that you must keep every thing very far away from the tip of the blades in a 10 mph wind the end of the blade is travelng at over 200mph on a 22" blade.. It will make short work of what ever gets in the way.
The going chain of thought is 6-7 to 1 at the tip. On a factory designed systems, private and home built are usually more like 7-9. I have seen some scary ones.
There are a few variables with wind gen's.
Size of the generator.
pitch of the blade
length of the blade
type of generator
If your system is the unloading type and gets a gust of wind that is " to much" for the battery's to take, it unloads the generator.
The only thing that controls the rpm of a generator is load and wind. If the next gust catches an unloaded gen the the rpm may peak much higher than you may expect. Most store bought systems will not over speed but i have seen a few. The home built systems or modified systems " more blades, longer blades, higher pitch blades can over speed wildly.
I have built a few in my time and have mounted them is some strange places. I do not have one on my boat, yet.. The space confines and the close proximity to people keep me from doing that.
I did not wish to hijack this thread only supply information that i would want to know in the same situation.
I've also built an 'Internet wind turbine' and am in the process of setting up the battery connection system with the charge controller dieselboy linked. If my separate blocking diode ever arrives in the mail to keep the battery from spinning the blades, I'll let everyone know how it goes.
At least the assembly and mounting went all right - before I'd balanced the blades, I was getting 10 volts output in a light wind. Once the setup is finished I'll have a better idea how effective it'll actually be for recharging batteries.
So far I'm probably ~$150-200 into this project though, which would cover several months of my tiny power bill - even as a liveaboard! C'est la vie.
By the way pablo, what are you using for your dump load? I was thinking about a few 12V lights in series or a 12V automotive heater myself. . .
""By the way pablo, what are you using for your dump load? I was thinking about a few 12V lights in series or a 12V automotive heater myself. . .""
I keep two sets of battery's on my boat and was planning to cycle between shore/house battery's and engine battery's to try to keep the load even.
I ran a small demo unit when i thought about doing a 12volt charging system and had a photo tach on the blades. When the dump happened the blade speed jumped up 700 rpm.. and that was in a less then 10 mph wind.
I would love to talk more on the subject, maybe a new thread?
I made the blades out of PVC, and since I have no machining skill I just used a circular piece of plywood as the blade hub and JBWelded it to the motor post. This proved not strong enough to withstand me dropping it last week, so I'm going to use thickened epoxy next.
The mount is a 10' length of 3/4" electrical conduit set into the lazarette about 1.5 feet with two 1/8" guy wires connected via hose clamps. This is convenient for me since my battery bank is inside that locker, so my wiring can just go down the pole and into the battery.
The generator mount is just a 2x4 with a metal flange screwed on the bottom and a 10" length of 1/2" pipe nested inside the conduit to allow it to turn into the wind. So far the pole holds up to 30 degree tilts without bucking the generator or bending too much, but that's without the blades reinstalled.
Three cheers for low-tech solutions!
dieselboy: Your RPMs are amazing! Your blades must be well-designed. I'm curious what your system will do once both your starter and house banks are completely full. From what I've read about the wind charge control, it's best not to let the turbine ever spin freely (which is what your 700 rpm story sounds like) since it can either A) break the blades or B) spin at such high voltage that when it diverts back to the battery it causes damage.
Instead I've seen it recommended to keep the turbine connected straight to the battery all the time and have the charge controller turn on a dump load from the battery when it's full. This way there's no abrupt switching from one generator output to another, and the battery will bleed off its own excess rather than shunt the generator output to a load that could potentially put too much resistance on the motor and burn it out. The linked charge controller uses this method.