Parralell Batteries to run a 12v pump???

If you have a 24v truck , then your two batteries are in series. So you can just clip across ONE battery to run your 12 pump.

As footloose stated, the batteries (if 12 volt) would be connected in series to provide 24 volts. This means that the positive pole on one battery will be connected to the negative pole on the second battery.

Therefore, you would need to connect your 12 volt pump to the FIRST battery.
Just check which one has the negative connected to chassis earth and connect your positive aligator clip to the positive pole on this battery. The negative aligator clip can be connected to the negitive pole on the same battery, or to the chassis somewhere.

Wisey,

I'd suggest you do a search on 24v in the forum to check out problems associated with taking power from one battery.

Yes it can be done, not a problem. But the critical issue is not the draw but the recharging of the batteries.

There are two ways those of us with 24v systems address the same problem you have.

There are two batteries, the high battery is where the 24v comes from , the low battery is where the battery negative is connected to earth. Yes you can connect your leads across only one battery, but most of us with permanent installations use what is called a centre tap - which is getting 12v from either the negative pole of the high battery or the positive pole of the low battery , and using a common earth.

But you CANNOT take current from one battery without leading to the batteries becoming unbalanced in their charge. When this happens, they will not charge evenly as they do now and one will become stuffed due to low charge and the other boil dry and become stuffed from overcharging.

You have three options:

1 Buy a 24v pump from a boating shop. This would be my recommendation.
2 Run your 12v pump from a 24v to 12v reducer so equal current is drawn from both batteries. The reducer needs to be connected via a relay so as to not slowly drain the batteries when vehicle is off.
3 Take your 12v from one battery and buy a REdarc Voltage equaliser which ensures the batteries remain equally charged.

If you are considering running other 12v equipment, then choose options one or two. If you are only going to use this pump, or other 24v gear, stick with 24v and don't worry about running two voltage systems. It will do your head in if you're not careful!!

Keeping as much straight 24v makes good electrical sense as you need smaller cabling as current draw is half that of 12v units for the same power output - more or less. It can be a little difficult to source and maybe more expensive, but boating shops are good places to look, as are truck stores.

All the best
Tim

OR
Draw power from one battery for a set time , then draw power from 2nd battery for similar (doesn't need to be exact) time.
Techie

Tim, V8

Slow night at work is it ? :)))

Tim, the equaliser you use, how does it work and how do you connect 12v to it? Is it the same thing as what would be connected to the truck radio to bring it from 24v down to 12v?

Thanks for your knowledge
Andy