Questions regarding Air Compressor and Dual Battery Mod

[warmonger]

Rhombus,

The Extreme Air and the Blow Jax I used are one and the same. I paid $335 for mine including the continuous duty solenoid and a circuit breaker that kicks butt.

But there is one thing I can tell you for sure, you WON"T squeeze that baby under your hood without some major surgery. Lest you have any doubts, ask either Synchro or Carlton about the size of mine. My system is a rocketship compared to the lower cost compressors. I just wasn't interested in listening to it run for 10 - 15 minutes while it built 125 psi. I also wanted air tool capability, something that came VERY close to being used on Friday at the Nissan plant when I got one heckuva big nail in my r/f tire. By some miracle I didn't lose air and was able to make it over to Wally World to get it fixed before Tellico.

As for mounting a battery where I mounted my air tanks, it will take some vivid imagination. It may be able to be done, but it will take some work to figure it out.

[OffroadX]

A pair of the half-size 6-volt Optimas, 1 per side wired in series might do the trick...

Brent

[rhombus]

Warmonger - Thanks for the info. I ordered an ARB comp today and will use that until I find a place (if i do) for a dual battery setup. The cost was cheaper than I thought and I can mount it under the hood. This will be the system that I will use for this summer and then maybe in the fall I will look at a better system.

I think that I might try and get a box made for the spare tire is.
This seems to be a good place to put some stuff and still have the cargo area. This will take time to figure out and I would like to have a compressor now so the ARB fits the bill.

OffroadX - I have been asking around about that and all people that I have talked with have not recommend using 2 6v batteries.

[warmonger]

Rhombus,

I don't know that I would recommend using the spare tire well for a battery. I have put my truck on top of the spare tire so many times it would make your head spin. I can see using it for an air tank if you relocated your spare, but I don't think a battery would survive if you put all 4,000 lbs of Xterra on top of it. Just a thought.

The Warmonger

[rhombus]

I also thought about that and would want the box that is built to be very tough (like a skid plate).
This would take some time to design and find a good mounting place (to take the possible weight of the truck).
I forget who mentioned it (maybe FSR) about a box with access from the inside of the hatch and sealed from below (for water).

My other suggestion for a battery was to build a really big hood scoop and tuck it in there

I'm sure you know how hard it is to find a place for a battery.
I just wish that there was a stock place under the hood

[warmonger]

Rhombus,

If you're willing to forgo some non-essential luxury items, like the cruise control, the alarm horn, fuel lines and the rest of the worthless junk piled up on the right side you can put it next to your other battery! :licker:

For that matter, save some fuel by ripping out the motor and putting an electric golf cart motor and 6 batteries. That way you qualify for a tax break and you now have sufficient power to run ALL the electrical accessories you want! (Just kidding!)

I believe sooner or later with all the accessories being added to our X's, dual batteries will become an issue. I just fixed before it became an issue. Anyone who undertakes a project of this scope, should be a well above average mechanic with a solid background in electrical design and implementation. Not only do you have to make the alternator work, you also have to make the dual batteries run the factory electrical EXACTLY as designed. This requires a great deal of planning and work. It also helps to have access to all kinds of neat electrical connectors. Otherwise it will be a huge mess of wires and if a problem does occur, you will have a tough time finding it if you don't have it set up right.

I can tell you the advantages and disadvantages to my system. First, it does take up some space in the back of the truck. Since I don't use the interior bike rack (Mine stay on the roof), this hasn't been much of an issue. You will lose the interior bike rack in the installation though. You will also have to rework the rear carpet to have access to the rear tie downs. It will also be a little harder to change your tire since the left side battery sits on top of the jack cover. There was no way around that because of the design of the cover.

The great thing about it is the fact that I now have a jump start any time I need it. My system uses a bridgable isolator that with the turn of a knob will jump start the main battery from the auxillary. It also allows me to run my high current draw accessories (lights, compressor, etc) with the confidence of not worrying about if I am wiping out the battery. If I do, I just turn them of until I recharge the battery. I can also get away with running more accessories on my main side for longer since I know in a worst case scenario, I can always jump start it from the aux battery.

Something was brought up to me this weekend by Richard that would hold true if you are winching on a single battery. Somebody told him that if you have the engine off, you will have more current available for winching. That is true, but, there is a caveat. If you have the engine off during winching, you can't provide assistance to the winch through the vehicles driveline. You are doing a dead pull. Yes, the engine will draw current while it is running, but when you consider the increased current necessary for an unassisted pull, the difference is overridden.

With dual batterie isolated, you have the full power of the auxillary battery going to the winch without the engine being a limiting factor. You still have a draw on the alternator, but even at 2,000 rpms, the alternator output on an Xterra is miniscule compared to the current your winch needs to continue operation.

These are all something to think about as you take on a project o this magnitude. It has its good points and bad points. You have to determine if for you, the ends justify the means.

[Philosopher]

Originally posted by warmonger
Something was brought up to me this weekend by Richard that would hold true if you are winching on a single battery. Somebody told him that if you have the engine off, you will have more current available for winching. That is true, but, there is a caveat. If you have the engine off during winching, you can't provide assistance to the winch through the vehicles driveline. You are doing a dead pull. Yes, the engine will draw current while it is running, but when you consider the increased current necessary for an unassisted pull, the difference is overridden.

Jusy FYI for everyone - it is a common recommendation that if you run an electric winch for longer than a couple minutes, you should 1. keep the vehicle's motor revved up to about 3K RPM and 2. check the winch motor (by touching it with your hand) every 5- 10 minutes to see if it is becoming hot (warm is normal, hot means cut it off for a while).

[ScottG]

I don't think a running engine draws current from the battery. The alternator charges the batter when the engine is running. You can disconnect the battery while the engine is running and the engine will continue to run off the alternator. I don't know, am I missing something?

[xterrabull]

Originally posted by warmonger

Something was brought up to me this weekend by Richard that would hold true if you are winching on a single battery. Somebody told him that if you have the engine off, you will have more current available for winching. That is true, but, there is a caveat. If you have the engine off during winching, you can't provide assistance to the winch through the vehicles driveline. You are doing a dead pull. Yes, the engine will draw current while it is running, but when you consider the increased current necessary for an unassisted pull, the difference is overridden.

Warmonger,
I probably need to be educated here: I was under the impression that with the car running, you could still use all the current the battery can supply, but you just can't charge it as fast as you use it if you exceed the alternators output (i.e., the alternator output is what determines the speed with which you can charge your battery); so, if you exceed the output of your alternator, you will drain your battery but at a *slower* rate than you would if the car wasn't running at all.
This was my impression, can you shed some light?
Thanks

[Philosopher]

Originally posted by ScottG
You can disconnect the battery while the engine is running and the engine will continue to run off the alternator.

True, for a little bit. Then the engine will die.

What I was saying is that if you don't run (rev) your engine somewhat while winching for a length of time, your battery will start to drain (happened to us in Kentucky when we had to winch an X for about an hour off and on without the engine revving - the battery light came on later that night).

[ScottG]

Originally posted by Philosopher


True, for a little bit. Then the engine will die.

What I was saying is that if you don't run (rev) your engine somewhat while winching for a length of time, your battery will start to drain (happened to us in Kentucky when we had to winch an X for about an hour off and on without the engine revving - the battery light came on later that night).

I agree with you. I was responding to Warmonger, but you type faster than me With my old GMC truck, I could take the battery out of the truck and it would run fine. You just need to make sure the battery cables don't bounce around and touch each other. I haven't tried with the X, but if the engine dies, that's probably a sign of a weak alternator.

BTW can anyone tell my why when I try to quote one sentence I get the whole paragraph?

[rhombus]

warmonger
Thanks for the tips. The issues that you mentioned are the same ones why I really want to have a dual setup in my truck.

The trouble is I'm a computer guy not a mechanic
You aren't also selling a How-2 for dual batteries with electrical plans are you?


I have a guy at a 4x4 shop that can do the work for me I just need to come up with the plan.

I liked the idea of adding a box because then I would have more room for the install.

[warmonger]

Your engine will run off the alternator until you hit a red light unless you keep the rpms up. On a factory alternator, (this is why they s@#$) the idle output is real low, to the tune of about 10 -15 amps output. This is not enough to run an electronic vehicle for long. You can shut off the A/C, radio, etc to conserve, but sooner or later, the alternator will put out insufficient juice to run the vehicle.

Older vehicles were not an issue since they had carbs and the only thing electronic on most was the ignition. This of course doesn't include the 1979 - up models which is when computer controlled autos came into their own.

As for the diagramming and photos, I started out shooting the project, but it became so huge that it would have sucked up every ounce of space on my website. Not to mention it became so technical that posting it in such a way that anyone could do it was impossible (I always try to write my how-tos so anyone can do it if they follow instructions).

I actually had to go in and repower my relay centers under the hood in order to power the PCM off of the new setup. I had to rewire the alternator, the starter and all other main power feeds based on where I wanted them to be fed from, the main or auxillary battery. The battery cables are 1/0 and 2/0 cable and all battery terminal connectors are hand soldered on and the cable custom made by me to fit. I preplanned what accessories I would be running off the batteries and made darn sure that wires were in place to make it work, including my voltmeter that reads voltage from both batteries at the flip of a switch.

It took me two months of planning and work to make it fly. I wish I could say it was a cake walk but it wasn't. It was expensive and time consuming, but damn well worth the trouble now that I look back on it.