running air compressor from aux battery

[junglejuice]

When measuring the voltage drop is that under load or no load?

[XJeepers]

under load it was like .07 or something (2 years ago now). I am sure I could get is down more, but I would consider .07 acceptable. I haven't had any problems with the dual batt system, I was more concerned about the air compressor not getting enough juice from the aux batt alone and the compressor running too slow as a result.

[anthonygubbin]

I sometimes run the comp without the engine running but only for 2-3 minutes as it draws too much. It works pretty well but does pick up a little bit once I crank up the engine.

Regards A

[junglejuice]

Ag your load is around around 20a max for that figure, that isn't allowing for drop across the fuses (must be fused both ends for a rear mounted battery) and also not taking into account the drop across the controller so I can only assume the reading was taken with signicantly less load then you might realise as a battery can pull 30A or more quite easily when charging not including any load like a fridge etc.

Xjeepers, to get that kind of voltage drop again this is not taking into account fusing and controller drop your "load" is less then 10A which is far less then the charging current of a battery.

I really hope you guys are running fuses at both ends very close to the batteries?

I connected the feed to my aux battery directly to the alternator to take the extra load of the aux battery and fridges plus compressor etc off the factory wiring, in my OBD1 Xj the starting battery terminal voltage when the car is running is 14.16V, the no terminal voltage at the alternator is 14.7V.
With my aux battery drawing around 30A the drop across my cable works out at approx 0.08V not including the two fuses and controller, add in two Weaco's and that number will increase....

Don't forget the fuses at BOTH ends....

[anthonygubbin]

Originally Posted by junglejuice

Don't forget the fuses at BOTH ends....

All fused JJ I have like seven or more fused lines. I get tired of soldering blade fuse lines in.

Regards A

[anthonygubbin]

I like the idea of running the aux from the alternator JJ. But how does the solenoid work since it cuts the circuit at 12.4 I think? Do you have two lots of wire one from the alt and another to the battery or have you just left the main battery out of the equasion?

Regards A

[anthonygubbin]

My set up is a little different I have the rear aux connected to the front on a separate cable. But all my accessories have their own cables going through the fire wall running off the main aux. I only installed a third battery as I was not getting enough running time out of one aux with a fridge, laptop and other stuff running off it. I was having to run the engine everyday for like 40-50mins. Or the batteries would get too low.

Regards A