Charge Batteries by Idling Tow Vehicle?

is a hairpin alternator the same as a horseshoe alternator? In other words, the outside magnetic field is not generated by excited current at the start through an outside wire wrapping, creating the magnetic field for the rotor inside to react with, it is a hard neodynium magnet in the shape of a horse shoe or hair pin U?

MEXICOWANDERER wrote:
John & Angela :)

A newer Ford is one of those vehicles that can have a Hairpin Alternator. That ought to "Make Your Day".

This is not a good idea for serious long-term Boondocking, but works great for those weekend and three day holiday getaways

Agreed. It's kind of a back up for us...although we have done without hesitation when required.

Hey, what's a hairpin alternator.

I see. Charge the TT with the truck only in emergency. And use jumper cables not the 7-pin connector. Then get a solar set-up. I guess the wire and diode is to charge the toad if we had one. Thanks, all!

John & Angela :)

A newer Ford is one of those vehicles that can have a Hairpin Alternator. That ought to "Make Your Day".

This is not a good idea for serious long-term Boondocking, but works great for those weekend and three day holiday getaways

I wouldn't recommend it for a trailer battery charging through the 7 wire harness but for the class C motorhome bunch you can kind a make it work. But you need to put in some decent size wiring. We made a direct run of 2 or 4 gauge (can't remember) from the alternator on the V10 to the 2 AGM batteries in the coach. We also put a meter in line. When they are run down we will see charge rates north of 40 amps at idle, sometimes quite a bit north. A v10 is quieter than any generator I have ever heard, ANYWHERE. Fuel usage is around 1/2 gal an hour. Wear and tear, couldn't give a care. I bought it to use it. It already has over 150,000 K on it and a couple hundred hours idling probably won't hurt it. Beats hauling around a generator and fuel, neither which I have room for.

Having said that we have around 400 watts of solar on the roof, which works great until you have endless days of rain.

Too each his own.

Tow charging can be formulated so it makes a lot of sense all the way to needing a straight jacket and rubber room.

What matters 99% of the issue is how many amperes does the tow vehicle make available at the towed vehicle's batteries. If you are attempting to charge a pair of 27's or 3-cell batteries and your vehicle and jumpers can not deliver a big number of amperes at idle, then charging that way is a waste of time and money.

Here's an ideal setup:

A tow vehicle with a HAIRPIN alternator that has an idling potential of total charge acceptance of the batteries. This means a 200 amp or greater hairpin alternator that idles dead slow at 500 engine RPM and can deliver 115 amperes. Not many tow vehicles have factory hairpin alternators - they are relatively new on the scene.

A pair of jumper cables with COPPER wire at least 4 gauge in diameter. At 100 amps 2 gauge is better yet.

Every generator-less motorhome not pulling a toad is every bit as vulnerable as a tow vehicle as far as "getting stranded". At least with a tow vehicle the hood can be raised, which will help to cool any alternator.

A marginal tow vehicle charging system coupled with garbage grade jumper-cables quickly jerks the idea of tow vehicle charging, into the "dumb idea" side of the issue.

For most, a more rational way out would be to get a 1,500 watt generator, and configure a 36-amp Megawatt to do the battery charging. It would make a lot more sense.

I never consider my tow vehicle as part of my energy management program.

I NEVER jump start anyone with my TV
Don't pull anyone who is stuck (accidental air bag deployment)
Don't want my RV electrical system to touch my TV system.
Don't want to add wear to my alternator or risk being stranded. (Alt is least of things)

I figure the RV can stand on it's own or it cant.

Idling is about the worst condition to expose your engine to. Vehicles that see prolonged idling are usually listed under severe duty maintenance programs.

You can find other links where some will say it wont hurt, so do what you think is best.....

Idle


Bearing damage

We don't RV with a towable (a small Class C motorhome), but we do sometimes idle the engine for an hour or so for the initial boost charge of our RV batteries before we start up a very small Honda generator for 3-4 hours to bring up the batteries to around 90% of full charge. Here's how we do it and what the conditions are:

- We use AGM batteries, which charge faster than regular batteries.

- The wiring between the engine alternator is short and a large size, 6 AWG.

- Our idling engine is a gas Ford V10, which is whisper quiet when idling (a lot of ambulances have it and sit idling) ... and once it's catalytic converter is hot, there are no fumes we can notice coming from it's exhaust pipe.

- The V10 came with a large stock alternator ... 130 amp.

A few days ago we drycamped for several days. After about the 3rd day the batteries needed topping up. We started up the V10 and ran it at an idle. It's alternator output immediately spiked to 80 amps, and then slowly tapered down to around 30 amps during the next hour of idling. At that point we probably had restored around 40-45 amp hours back into the batteries. I could then take the batteries around a 90% charge with the tiny Honda, or the built-in coach generator.

The type of batteries, the size and length of the cable, the large stock alternator, and the quiet engine idle made this type of quick and convenient boost coach battery charging possible. I can monitor this happening because of a digital ammeter and digital voltmeter mounted on the dash in the cab.

When on the open road between camping sites for 4-5 hours, the engine alternator will bring the coach batteries to 100% ... which I can determine because at that point current is no longer flowing into the batteries according to the ammeter.

Before solar and quiet small generators, idling the main engine was the only way to top up coach batteries. I had a 1969 Chinook motorhome way back when for awhile that was designed to use this method ... except it's alternator wasn't anywhere near the capacity of modern ones.

Terryallan wrote:

romore wrote:
Al you will do is waste fuel and annoy the neighbors, you would need to run at a high idle for an extended period of time to recharge depleted house batteries. Plug into shore power or use a QUIETgenerator.

So called Quiet generators annoy the neighbors as much as a truck running. where we dry camp. You can hear a "quiet" generator running 100 yard away.

To the op. you can charge the batt with the TV. But it will take awhile

While you obviously don't like generators, would you prefer a contractor type or quiet generators. I have a quiet generator and have had many people come by to comment on how they can't believe just how quiet it is. So quiet generators certainly do have their place. I use mine to charge my house batteries when needed. Works great. I also use it to run the AC when no shore power is available.

Flatfive wrote:
What is WyoTraveler talking about: " a diode and 10 ft of wire"?

I have no idea.