Using your vehicle's alternator for additional power

[AK1NS]

I'm  interested in hearing your opinions and advice on using my vehicle's 180 amp alternator for adding some significant extra power for a new 16' EMCOMM trailer.
I did this trick already during Sandy for 5 days successfully via a small Kia Rhondo and its 60 A alternator.  It worked quite well, but I'm now looking to do it on a larger scale for the new trailer.

I used the Kia's little alternator output into a marine battery rated at 105AH, and then ran an inverter from that for a total of 2,000 watts output at 120VAC for moderate periods for a microwave, lighting and a space heater at different times. The Kia's 12 gal gas tank lasted 5 days at idle between fill ups so it was quite efficient, and I used it wisely in the driveway with the jumpers running into a well-sealed window in my den.

The new trailer will contain 2 banks of 6vdc 220AH batteries wired in series-parallel, providing 12vdc out at 440AH.  Rather than drop big bucks on an Onan generator, I'm thinking of using the car's 180A alternator to keep these charged and to run at least two 2500 watt inverters.  There will also be a 200w regulated solar charging system, plus 1 Honda EU2000 and  I have 1 Briggs 5.5KW generator for the trailer but it's a gas pig and way noisy,and I don't want to use it.  This combination would provide sufficient power for the 120vac devices on the trailer; computers, some lighting, certain power supplies.  Heat and AC in the trailer will be powered by another power source.

So if the new car (2016 Durango hemi) idles for 4-6 hours and burns a few gals of gas, it's a lot better than dealing with fuel, noise, weather etc.  I would just "plug in" the Durango to the trailer via heavy duty battery cables, keep all the car's accessories and lights off, and let it idle at sufficient rpms to run the alternator at a reasonable speed and produce the power I need at 12vdc.

Following my neighbor's Sandy trick, the Durango's fuel pump will also have a fuel pump bypass valve to fill up portable gas tanks, so I don't have to lug those to gas stations. That gizmo was well designed and custom made, with a safety circuit to prevent it from operation accept under certain pre-conditions and protocols,  so one didn't burn up one's car. Very slick to see him do that during Sandy.

What say you?

Thanks kindly,
Dave Akins   WQWN605,  AK1NS
DEC, Nassau Cty ARES
Pres, ARCECS

[T.j.]

That's a lot to take in there Dave but I'll do my best to help. If you haven't already,  take a look at Kussmaul Electronics at www.kussmaul.com This equipment has become standard in the emergency service industry. They offer everything from shore line charging kits, inverters, auto air pumps, high idle kits, ect. Just a cool place to find some functional 12v/110v equipment for this type of build. Oh yeah, they are on Long Island too :-)

Let's start with this if we say
Power = Volts - Amps
120 Watts = 120 volts - 1 amp
120 watts = 12 volts - 10 amp

Then in theory 2500 watts will equate to a 250amp draw on the 12v side. Ouch*

Now these numbers are just estimates so electricians please don't yell at me. With that being said, reserve capacity is huge when it comes to big loads. Batteries like to be discharged slowly so the more the merrier.

As far as the charging system on the durango is concerned,  180 amp alternator will not be 180 amps at idle. Vehicles these days are becoming somewhat amperage hogs with the additional modules the manufacturers keep adding. Some vehicles can have near 16 devices powered up that you don't even see. Static amperage draw on a vehicle like this could exceed 50 amps alone. I've ran a similar setup like this before for short term use like you did and was successful with its operation but I don't think it's the best for long term usage. Biggest issue is the beating the 12v side gets stepping it up to 110v.

Not that this trailer would ever be disconnected from its assigned vehicle but to be dependent on another vehicle could present a problem. I kinda like the hole non-dependant idea where as if the trailer needed to be dropped somewhere it could still operate without a issue. What about 2 honda's mounted with a shared fuel cell? Run each Honda to a separate set of 110v breakers and use one as a primary and other as secondary or both at once? I must say I'm intrigued by the fuel pump bypass that was installed on your neighbors car. I amagine with the proper safety precautions that alone is a pleasure to be able to utilize in a deployment.

That's enough for now, will let some others chime in. Whatever you decide to do I'm sure it will be over engineered and we'll put together :-)

[Mike_708]

Hello,

      That sounds like a great idea, but here are a few flaws in that problem. First is if you idle an engine for to meany hours consecutively you will prematurely age the motor. Witch it will not last you as long as you had planned. You'll find that more problems start to occur in the early ages of mileage. Unless you have a Diesel of course, there meant to idol for long periods of time.


     First thing is this, the battery needs charge from the alternator witch really only happens with movement, even though the alternator will charge the battery at an idol but it will take 3 or 4 X's longer than normal. and if the alternator idols for long periods of time with out change in RPM's (stop go stop go) the diodes will eventually take a shit. Then you'd have to change the battery and alternator.

    Second thins is this, if an engine idols for long periods of time also you may develop buildup on your spark plugs ( if its a hemi 5.7 there's 16 of them suckers in there 2 per cylinder)  witch in turn will cause poor gas Mileage. and engine needs air too cool may get too hot just sitting there.

    MY best bet  if you are going to do that is go get your self a nice Diesel truck there meant to idol for longer periods of time, and plus they use next to no gas!
 
     What you have mentioned is possible and it is a GREAT idea, i just would hate to see you have to spend all this money on fixing premature failure on whatever may happen.

[Joey 810]

Why don't you go pickup a 7 HP engine @ harbor freight and build it around two alternators from a junk yard? Find a belt size that would work for you. I would build it with two idler wheels on each side along with an alternator on each side as well. Seems like a cool project to try. Set the idle around 2000 RPM and call it a day. 

[Phreak480]

And put a good muffler on it with an add on exhaust stack that puts the final output a few feet higher than ones head.  That height will keep the noise a bit above you and make it seem quieter.

[Kevin WQRE722]

Why don't you go pickup a 7 HP engine @ harbor freight and build it around two alternators from a junk yard? Find a belt size that would work for you. I would build it with two idler wheels on each side along with an alternator on each side as well. Seems like a cool project to try. Set the idle around 2000 RPM and call it a day. 

the only problem with this is when a large load is put on an alternator it requires a lot more torque to keep the alternator going. a small engine like this would not be able to handle the work load. and before you reply asking me "then how come generators can do it"  that's because generators are not spinning alternators that are producing 12vdc they are spinning generac's that are producing 120vac the windings and bearings are completely different and are specifically designed to be spun at a specific rpm and torque rating(usually perfectly matched to a specific engine

[Kevin WQRE722]

dave ther are a lot of other factors that need to be thought about but at the current moment I cant spend an hour or so typing it up. the next time I see you we will talk. but I will also try to come up with a smaller version of it and make a post out of it.