charging a second battery for 12v on board air?

[black dawg]

first, what I am trying to do is put a winch motor powered compressor on my burb. I built a compressor out of a york and an old winch motor. It works very good, but draws 200 amps. My plan is to mount it underneath, with its own battery very close. I would like to limit the amperage from the alt to this battery (may be better for the alt?) to like 10 or 20 amps.

is it possible to limit the amperage or is this not needed?

 

[4X4HIGH]

Why not run the York from the engine and not have to worry about another battery or how many amps it takes to run a winch motor? At 200 amps to run the motor you would also need to upgrade the alternator to a high output and also upgrade the wires from the alternator as well.

 

[black dawg]

at this point I am not totally happy with my engine trans combo, and dont want to spend time fabbing the york to this engine only to have to do it again. I do realize that ddriven off of the engine is ideal, i have had a couple set up that way.

 

[4X4HIGH]

at this point I am not totally happy with my engine trans combo, and dont want to spend time fabbing the york to this engine only to have to do it again. I do realize that ddriven off of the engine is ideal, i have had a couple set up that way.

Fabbing a bracket sounds alot easier and cheaper than buying a bunch of other parts to make it work like you want and even then i'll bet the winch motor wont last long serving duty as a drive for a York compressor.

 

[black dawg]

I am also concerned about the motor life, but filling up all four tires (from 0 to 40 psi) takes about 4.5 minutes,(including walking from tire to tire) and I tried doing this a couple times, the motor gets to 130 deg (in my 60 deg shop). takes about 45 seconds to go from 5 psi to 40 psi.

There are units out there that mine is built very similar to, that I havent heard anything bad about. (maybe I havent looked hard enough??)

I thought about having a switch at the end of my air hose, so that the motor was only running when I need it to pump. No tank, and just an open ended hose.

 

[Blue85]

I have heard of guys choosing monster electric compressors over mechanically driven ones. You could look up those projects for other ideas - I think there was one here.

A couple of ideas-

1) Just run a battery isolator. When the compressor is on, the aux battery will probably get the whole available alternator output. The engine can certainly run for 45 seconds or whatever with no charging, but chances are the aux battery will continue to get the majority of the charge for a while after the compressor cycles off - the aux battery will be a lot lower.

2) Somebody probably makes an isolator that favors one battery over the other and wouldn't let the main battery run down - look at marine suppliers?

3) You could charge through a resistor. If the main system is 13.5V and the aux runs down to 11.5V, an 0.10 Ohm would limit charging current to 20A. That's only 40W, but I would use a really big resistor, like 200W. This could potentially ruin the aux battery if the alternator doesn't run for really long times to "float" the 20mOhm battery up to voltage.

4) Somebody must make a DC-DC battery charger that lets you charge a 12V battery from a 12V system at a controlled rate.

 

[black dawg]

well, got it all hooked up and functional. I will use it for a while, and then try some fine tuning. Right now I am running an open ended air hose, with a switch on the end, so the compressor run time is kept to a minimum.

I hope the motor holds up.

 

[Macumazahn]

Sounds like a neat idea. I would think the engine will hold up to moderate use, but then again you never can tell for sure.

Can you post pics if you have time? I'd like to see the setup.

 

[black dawg]

not setup for pictures, sorry. There is a commercially available compressor that mine looks very similar to.

 

[Blue85]

Is 200A the measured current with your compressor or is that the rating for the winch? I'm just thinking that the compressor may be lower load than winching.

 

[black dawg]

Is 200A the measured current with your compressor or is that the rating for the winch? I'm just thinking that the compressor may be lower load than winching.

200 amps was while pumping up a tire. This motor has been sitting for quite some time though, I will check after I get some use on it.