wiring up a compressor

[tuckertrucker]

hi all, so I'm mounting a 12v compressor in the engine bay of my Safari for ease of access and to get it out of the way in the back. My one concern is that my safari is 24v and therefore has two 12v batteries in series. So I will be wiring my compressor to only one battery which will mean the batteries will drain unevenly when the compressor is in use.
Will this impact the life of the battery and the effeciency of the charging system.
Or will the battery with the greatest charge just bring the other up to its level and hence the compressor will draw power from one battery?

[Rock Trol]

Will the compressor run on 24volt? Might be worth checking with the manufacturer.

[Cuppa]

Not a good idea to tap off 12v from the 24v bank. You need a 24v to 12v converter so it takes power evenly from both batteries in the bank. A charge equaliser could be used to achieve the same result, but the converter is easier to understand. You will need to size it to suit the amps that your compressor (plus anything else you use which is 12v) draws.

[tuckertrucker]

Ill check the 24v thing, as for the voltage reducer, I know there is one somewhere in the truck (i havent found it yet) because the stereo is 12v. Any ideas where it'd be hiding?

I've considered setting up an auxiliary battery for running things like chargers, other lights, perhaps this compressor, but I'm not to sure how it would be charged in this 24v system, would the auxilliary need to be a 24v bank as well?

[tuckertrucker]

would it be possible to draw a +ve directly from each of the batteries, and a -ve from both batteries. This would effectively put the batteries into parallel so the compressor would only receive 12v. Both batteries would be drained, and both batteries would still only be 12v while in series providing the rest of the truck with 24v

[BigRAWesty]

Would it be that big of an issue though if the motor is running when using?

[threedogs]

Be wary mounting a compressor under the bonnet if it has a "thermal cutout"
Under bonnet temps may trip it

[Cuppa]

Would it be that big of an issue though if the motor is running when using?


Yes. One battery will be overcharged & will die a premature death.

[Cuppa]

Ill check the 24v thing, as for the voltage reducer, I know there is one somewhere in the truck (i havent found it yet) because the stereo is 12v. Any ideas where it'd be hiding?

I've considered setting up an auxiliary battery for running things like chargers, other lights, perhaps this compressor, but I'm not to sure how it would be charged in this 24v system, would the auxilliary need to be a 24v bank as well?

The ‘voltage reducer’ used for the radio will be very unlikely to have the capacity to run a compressor.

http://caravanandmotorhomebooks.com/12-volts-dc-from-24-volts-dc/

[Cuppa]

would it be possible to draw a +ve directly from each of the batteries, and a -ve from both batteries. This would effectively put the batteries into parallel so the compressor would only receive 12v. Both batteries would be drained, and both batteries would still only be 12v while in series providing the rest of the truck with 24v


No, you cant have batteries in series & in parallel at the same time. One or the other.

[tuckertrucker]

bumma, i was really thinking that might work

And I've lost faith in the idea of it being under the bonnet now, theres not really any room to mount it now ive had a good look. I might build a compartment in the rear for it and the aux battery, dunno yet.

[Cuppa]

There is a simple solution if you want to use an auxiliary battery (12v) to run the compressor. A redarc BCDC 1240 will accept 24v to charge a 12v battery. (It will also enable you to connect solar panel(s) to charge the aux battery without needing to buy a another solar regulator if you want to do that down the track).



http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=62388&stc=1

[tuckertrucker]

Thanks for that cuppa, I always thought that you couldn't earth a 12v battery to a 24v earth. Obviously its doable haha, I might need to brush up on my electrical skills