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Old 02-09-2013, 03:19   #91
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Re: 12vdc generators - any good ones out there?

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Originally Posted by goboatingnow View Post
Fantastic -- if you're on a severe budget, that's absolutely the way to go

Add a 170 pounds battery charger (probably find used for 100 quid), and you're in business.

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Old 02-09-2013, 09:26   #92
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Re: 12vdc generators - any good ones out there?

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I just had a look at their website. First version available for testing early in 2013. Lets see the results.

I can imagine a range of problems very similar to the rotary engine. Rotor seal problems, heat transfer problems, not very efficient.
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Old 02-09-2013, 10:03   #93
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Re: 12vdc generators - any good ones out there?

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I just had a look at their website. First version available for testing early in 2013. Lets see the results.

I can imagine a range of problems very similar to the rotary engine. Rotor seal problems, heat transfer problems, not very efficient.
What struck me was their claim of 50% fuel to work efficiency, which is quite a lot better than a regular diesel. Love to see it work though.
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Old 02-09-2013, 13:08   #94
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Re: 12vdc generators - any good ones out there?

an earlier post suggested solar and after reading your design criteria (assuming i understood it correctly) i would agree. here's why: being a bare bones boat with a small battery bank, and as you say occasional use.
why not just bungie tie a $100 dollar panel and call it a day?
no fuel, no exhaust, minimal weight.
i did this 2 years ago just to enter the solar tech world and see how it all worked.
To date i have not had a low battery. And oh do i use electric, laptop cell phones, anchor light....etc etc. During the winter months i leave it on deck and the batteries are essentially maintenance free.
Probably the best $100 I've spent. Now I'm looking to a real "hardwired" and mounted system.
If it's about jump starting a friends boat, can you just yank a battery to get him/her running?
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Old 02-09-2013, 15:04   #95
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the oil companies are still buying up patents left right center for all sorts of technology so learn how to feel locked in a tightly controlled environment.
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Old 02-09-2013, 17:30   #96
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Re: 12vdc generators - any good ones out there?

Another thought is to just bring some chargedup 12v batteries with you to the boat,
and bring them back to charge up for the next time you go out.

An small engine is going to make quite a racket unless you take a lot of care
to put in something, but also let's it stay aircooled.
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Old 02-09-2013, 17:45   #97
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Re: 12vdc generators - any good ones out there?

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Fantastic -- if you're on a severe budget, that's absolutely the way to go

Add a 170 pounds battery charger (probably find used for 100 quid), and you're in business.

Those little 2 stroke gens are all over. Harbor freight sells them. I bought one a couple years ago for $79. Never started it...It's still out there in the box. ....got it just in case when I had a trawler as backup. (boats without sails as backup make me nervous!) No idea if they are any good or not.
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Old 02-09-2013, 18:31   #98
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I bought one of them. It lasted 3 hours
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Old 02-09-2013, 18:52   #99
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Re: 12vdc generators - any good ones out there?

They are a bit loud also...
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Old 02-09-2013, 18:57   #100
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Re: 12vdc generators - any good ones out there?

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It is important to keep in mind that car-type alternators will not do the job without external regulation. They are made to run a car's electrical loads while the engine is running, and to replace -- very inefficiently, but efficiency is not required -- the very small amount of battery power used up in starting. They do not produce enough voltage to recharge a battery which has been deep cycled -- that is, a battery which has been used as a power source without an engine running. As a result, if you attempt to recharge a deep-cycled battery with an unregulated car alternator, it will stop putting much power into the battery long before the battery is well charged, leaving it chronically undercharged while requiring unnecessarily long generator runs.
I'm going to keep that possibility in mind. It is one of the issues that kicks around the back of my head as a possible inadequacy of this little gizmo. That having been said, I think that I am still going to build the first prototype with a stock car alternator, & see what it will actually do for myself. I am trying to keep this thing small, low weight & Spartan in general. I think that I would probably add a booster switch that attached a small resistor network to the sense wire before I went to an external regulator, but if an external regulator is what I need, then I will also consider that option when my other options fail.

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You don't need to pee on the electric fence yourself, so to speak -- others have gone before you and the data is available.
I'm trying to minimize my time on that fence, & that is why I am here discussing this project now. I appreciate the data that you & others have posted, but I have not yet found all the data that I wanted on dc gen-sets of the size that I am looking for, so I expect that I will eventually need to belly up to that fence for at least a short while. Thank you for helping to reduce the time that I will need to spend there.
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Old 02-09-2013, 19:06   #101
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Re: 12vdc generators - any good ones out there?

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Originally Posted by goboatingnow View Post
Thanks for coming up with that link. I had hoped that you might have been speaking about something that I hadn't seen before. Unfortunately, that looks to be almost exactly the same as a generator that I got from O'riely's several years ago. That unit could be made to work with a little more equipment thrown in, but I think that I'm still going to stay with plan A for now.

Thanks again,
Jim
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Old 02-09-2013, 19:07   #102
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Re: 12vdc generators - any good ones out there?

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Originally Posted by nimblemotors View Post
Another thought is to just bring some chargedup 12v batteries with you to the boat,
and bring them back to charge up for the next time you go out.
If this little gizmo ends up being too big, too heavy or too poor of a performer, that may be what I end up doing.
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Old 02-09-2013, 20:28   #103
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Re: 12vdc generators - any good ones out there?

I like the portable solar option, that sounds like all you need unless you are really looking to fiddle and reinvent the horse.
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Old 02-09-2013, 23:52   #104
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Re: 12vdc generators - any good ones out there?

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Originally Posted by pbiJim View Post
I appreciate the data that you & others have posted, but I have not yet found all the data that I wanted on dc gen-sets of the size that I am looking for, so I expect that I will eventually need to belly up to that fence for at least a short while. Thank you for helping to reduce the time that I will need to spend there.
Check this out:

Microcogen.info/***/SOMRAD Forums - Index

You've gotten a lot of sound advice on here based on theory (don't overload the engine; derate engine sufficiently), and some sound advice based on experience (don't hope you'll get useful charging without external regulation, so figure in the cost of that when you decide whether this is worthwhile or not).

But only one guy on here I know -- Lloyd; goes by Flying Cloud -- has actually built a homebrew generator. Lloyd spent months or years building his, and he's a professional marine electrician. It would help you if he would chime in, I'm sure.

Here's another place to talk to people who have actually done it: Microcogen.info/***/SOMRAD Forums - Index. Very interesting site; I wasted some time on it last night. One thing you can gather from the conversations of dozens of people who have actually built generators, is that it is not a trivial matter to get the engine sized right and get the pulley ratios right.

From that site, I also learned more than I ever thought there was to know about how alternators work. Very cool.
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Old 03-09-2013, 01:47   #105
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Re: 12vdc generators - any good ones out there?

I have actually built two of these gadgets. For the first one I removed the 240v alternator from a genset I had and mounted the Honda engine and 12v alternator on a 1/4" alloy plate.

I used an alloy pulley on the engine and a v belt drive. I used the internal regulator which came with the alternator and this arrangement worked well.

After using it as a 12v charger for about a year I bought a small lathe which required 240v AC so I put the 240v alternator back on the Honda engine to power the lathe as I only have a 300watt inverter.

I found this to be a fairly easy project which I knocked off in about two days of fairly casual work.

During my next winter peregrination to warmer tropical climes I found I had a battery problem due to the extra time the fridge had to run in the tropics. The Honda -auto alternator gadget had worked so well that I bought a 4 stroke lawnmower engine and hung the alternator underneath it in a direct drive arrangement. This was also implemented in two to three days.

Both these gadgets worked well and their fabrication was carried out using mainly hand tools, the only outside work being the machining of the pulley on the first to fit the Honda output shaft.

However the second one was much noisier than the first probably reflecting it's lawn mowing heritage.
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