Small/Cheap Gasoline Generator –> Battery Charger

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TRFrederick

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Aug 1, 2009
10
Hunter 23.5 Various
We like to stay out on the Colorado lakes for a few nights at a time in our H23.5. The single battery runs down and I'm thinking of getting a very small gasoline-powered generator to run a battery charger. Unfortunately the Suzuki 4-hp outboard only has a 40W coil so that wouldn't do it.

20 Amps into the battery for 2-3 hours a day should do it. 20A @ 12V = 240W; add say 20% for charger efficiency gets my need up to 290 Watts.

The least expensive generator I've found is the Generac ix800 for $350. Does anyone know of something about half this size (and hopefully, price)?

As a side note, it seems there was a 250W (350W peak) generator back in the 60s called the "Tiny Tiger." Wish they still made them. I see they come up on eBay once in a while but I need something that is trouble-free, not 40 years old.

Thanks,
 
kloudie1

kloudie1

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Nov 6, 2006
10,007
Hunter 34 Mandeville Louisiana
Ya might want to look at this one or one similar..
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=66619
They are $99 at my local store.. If you pick up a "Car and Driver" magazine, there is a coupon in it for 20% off which would get it down to around $80 at a store.
Or if ya want 4 stroke: http://cgi.ebay.com/NEW-4-Cycle-Por...emQQptZLH_DefaultDomain_0?hash=item3ca6258fdb
Or if ya want 4 stroke and the latest inverter technology..
http://cgi.ebay.com/ETQ-800-WATT-PO...iewItemQQptZBI_Generators?hash=item58845a9ade
 
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Sumner

Sumner

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Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
intensity said:
..........I'm thinking of getting a very small gasoline-powered generator to run a battery charger............,
Click to expand
We had a similar problem as I use a CPAP machine at night and it uses about 36-48 amp hours a night.

You mentioned running a battery charger off the generator. Some of the generators have 12 volt charging in them. Problem is they are usually under 10 amp chargers and most I saw were only 4-6 amp chargers. Now if you get a bigger battery charger and run it with the generator most of those are only 12-15 amps so still a relative low charge level. Non of these options make for a very efficient means of charging a battery in my opinion.



I made a 12 volt charger myself with a 63 amp GM alternator powered by a Honda engine.




Now you have a charger that was designed and built to charge 12 volt batteries and does a fine job of it. I was going to use a cheaper engine from Harbor Freight, but decided to bite the bullet on the Honda and have no regrets.

The rest of the build is here with links to how other people made these.

http://purplesagetradingpost.com/sumner/macgregor/outside-14.html

They don't have to be made with all of the aluminum like I did.

Are you sure you need that much electricity per day? Seems high if you aren't in a situation like I'm in. Since building the charger I've added a ............

http://purplesagetradingpost.com/sumner/macgregor/09-01-09-19-Solar Panel.jpg

http://purplesagetradingpost.com/sumner/macgregor/outside-22.html

......... solar panel and it now supplies most of the power we need. It has cut my generator run time probably to 1/3. We are going to add a second one since we are going to add a frig to the boat. One of these is less money than the generator. 40 watt panels are now $135.00. See the link on my site to them. If you are only out for a couple days have you considered adding a second battery and charging both before you leave?

Well hope this helps and good luck,

Sum

Our Trips to Lake Powell, UT - Kootenay Lake, Canada - Priest Lake, ID

Our Mac Pages

Mac Links
 
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B

Benny

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Sep 27, 2008
1,149
Hunter 320 Tampa, FL
The least expensive way would be to add a second battery thus doubling your present capacity. Before diving into any solution first define your needs. Perform a power survey to determine by your appliances and fixtures and their run time just how many amps you consume in a 24 hour period. If your consumption is around 20 amps a day you just need a solution that would provide those 20 amps. By adding a 2nd battery you would probably increase the storage capacity to around 180 to 200 amps. To maintain battery life it is recommended that batteries do not be frequently discharged more than 50% of their capacity so you could "safely" use 90 to 100 amps. At 20 amps a day you have approximately 5 days of power before the need to recharge. If your usage is larger than 20 amps or should you need to lengthen the number of days between recharges then you would need to move up to an on board recharging system. I concur that the least expensive method would be to run a small portable gas powered generator. I would stay away from the 2 stroke units as they are noisy and the exaust fumes can be a bit much, but a relatively cheap 4 stroke unit would do the job. Vector makes a multi stage 30 amp charger that retails for around $29 and that should fairly provide for your recharging needs. A battery can only be charged as fast as its acceptance rate will allow.
 
T

TRFrederick

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Aug 1, 2009
10
Hunter 23.5 Various
All,

Thanks very much for your thoughts! Very helpful. At this point, it does seem like adding a second battery is the best way to go for us, thanks Benny. I'll just have to design an appropriate bracket/tie-down so it doesn't flail around in there during trailering. We can always add the generator later if needed; thanks to Koichi & Kloudie1 for more options than I could find.

In the meantime I've ordered this DOC Wattson model R102 battery monitor:
http://www.rc-electronics-usa.com/ammeters/rv-battery-monitor.html
So that I can more accurately assess our usage this season.

Sum: Beautiful work on your mods. Thanks very much for all the info you share on the web; I have seen and used your pages in the past. I also use CPAP but have not been using it on the boat; sleeping on my side is ok for a couple nights. It sure would be better, though, to add the generator and be able to use the CPAP for the longer outings that we'll hopefully be able to take.

Thanks very much, all!

PS: Seems like such a shame that the outboard engine can't double as a generator. I wonder about the feasibility of having a quick-mount generator that could somehow attach to the flywheel with the engine cover off...
 
Sumner

Sumner

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Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
intensity said:
..............Seems like such a shame that the outboard engine can't double as a generator. I wonder about the feasibility of having a quick-mount generator that could somehow attach to the flywheel with the engine cover off...
Click to expand
Glad some of my stuff has helped.

On the above comment I've been told that some people have seen an alternator attached to the top of the motor and I could imagine doing it, but I've never seen pictures and decided to not go that route myself. Right now one pull on the Honda and we have electricity. I have an exhaust that goes down to ...........................



.............. near the water, but not in it. I'm a little concerned about going into the water and maybe getting back pressure the engine isn't designed for, but might try it. The exhaust gets most of the exhaust noise and all of the fumes away from the cockpit. The remaining noise is caused by vibration while it runs. I'm going to put some rubber mounts on over the winter and see if that helps.

If you need more than the 2 batteries I would first spend $150 on a 40 watt solar panel (see my other link for where to buy it) and the controller. Even if it didn't keep up with the CPAP I'll bet if you started with 2 charged batteries and had the solar panel helping you could go a week before the batteries where too discharged. Then sleep on your side for a couple nights and let the panel catch up :). I'm ok too usually if I'm on my side, but there is no guarantee I'll stay that way all night :cry: and I don't like what happens then.

I got an LED volt meter that reads in tenths from the same place I got the panel for about $40 and it is very accurate......



....... an I monitor the batteries and the charging with it. I also got an amp meter that is the same brand that I still have to mount. As was posted the battery will only charge at a certain rate and that will diminish as it goes to full charge. With the amp meter I'll be able to see when I've reached the point of diminishing returns. Also with it I'll be able to tell exactly how much amperage anything on the boat requires/uses.

Good luck,

Sum

Our Trips to Lake Powell, UT - Kootenay Lake, Canada - Priest Lake, ID

Our Mac Pages

Mac Links
 
Rick Webb

Rick Webb

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Jun 2, 2004
3,458
Hunter 23.5 Fort Walton Yacht Club, Florida
I Added a Battery and Moved Them

I added a piece of Starboard in the locker under the V berth. I 5200'd it to the top of the ballast tank then put the battery boxes on top of it. The battery charger and battery selector switch is mounted on the bulkhead in the same locker. There were pictures of it in the old Photo Forum I'll look to see if I can find them.
 
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