Common ground chassis or cable?

[[email protected] Junior Member Find all posts View Profile Close [email protected]]

Hi, i am installing my dual battery system using Projecta Dc dc charger and optima 34.
My question is: do i run both negative cable of battery and charger to the vehicle frame to use the body as return,( i can see the factory earth cable connected to a point that is in pretty much the same place of other side of engine bay, probably 10cm below bonnet?)
Or join both negative cables and then run a 6 b&s negative cable to negarive terminal of cranking battery?
WOr I need both?
Or i am totally wrong?

Thanks in advance.

[brogers Advanced Member Find all posts View Profile Close brogers]

Hi, i am installing my dual battery system using Projecta Dc dc charger and optima 34.
My question is: do i run both negative cable of battery and charger to the vehicle frame to use the body as return,( i can see the factory earth cable connected to a point that is in pretty much the same place of other side of engine bay, probably 10cm below bonnet?)
Or join both negative cables and then run a 6 b&s negative cable to negarive terminal of cranking battery?
WOr I need both?
Or i am totally wrong?

Thanks in advance.

Hello,

I'm not an expert, but in conjunction with folk who know what they are doing, I have now wired up two prados (and couple of other cars) with dual battery systems etc.

This is what I know.

Your question will get diametrically opposed responses from those who firmly believe in using a chassis as earth return, to those who firmly oppose using the chassis as part of the earth return...the correct answer is that it depends, and also what is cost effective, what is easy, what is durable, and what is fixable if it fails and what works in your circumstance.

The negative strap from the car to the start battery negative terminal on some vehicles is sometimes not so big, so on some cars, depending on what you do, the factory earth needs to be checked or even upgraded.

Soooo, this is what I have done....(very basically, I have done quite a bit but I wont go into the full detail unless you need more info then I'm happy to share)


I have run a positive cable (with a fuse at the battery end), to my DC DC charger in the rear drawer setup, and a positive from the DCDC charger (with a fuse at the aux battery) to the aux battery in the rear of my Prado, AND I have also run a dedicated negative cable from the start battery to the DC DC charger etc, etc.

Its was just easy that way for me to do, its easy to understand, I didn't have to look about for a good earthing point that was away from getting damaged (or which can corrode or become loose over time), and it just means I keep the charging circuit somewhat separate from the chassis itself....others will have good arguments for both ways, and good arguments for and against DC DC chargers etc etc. It really depends where you are putting your battery in the car, what you are running with your battery, how long you plan to stay in one place, and if you are also running power to a trailer or camper/caravan, and if you are using a dc dc charger etc.

So far I am very happy with my set up, it works very well, whilst you can save money by using the chassis as an earth return and not have to buy another length of black cable, but please, listen to what others say, there are good arguments for and against running a dedicated earth from the negative terminal, or just earthing to the vehicles chassis.

I decided to interfere as little as humanly possible with the factory vehicle electrics, and wanted to just run a good positive and a good negative cable from the start battery, as thick as I could of good quality dedicated Australian made 12v automotive cable (i cant remember the guage but its as thick as I could really have used I recon...probably) , and just keep things clearly separated from the vehicle itself as much as possible.

Remember cars can and have caught fire, and if you do the wrong thing you could easily create a fault or worse without the right cabling, cable protection, fusing, and solid connections etc.

I hope that helps somewhat...currently I'm a believer in running both positive and negative cables from the start battery,,,but that's just my set up.
Let us know what you are thinking of doing.

[[email protected] Junior Member Find all posts View Profile Close [email protected]]

Hello,

I'm not an expert, but in conjunction with folk who know what they are doing, I have now wired up two prados (and couple of other cars) with dual battery systems etc.

This is what I know.

Your question will get diametrically opposed responses from those who firmly believe in using a chassis as earth return, to those who firmly oppose using the chassis as part of the earth return...the correct answer is that it depends, and also what is cost effective, what is easy, what is durable, and what is fixable if it fails and what works in your circumstance.

The negative strap from the car to the start battery negative terminal on some vehicles is sometimes not so big, so on some cars, depending on what you do, the factory earth needs to be checked or even upgraded.

Soooo, this is what I have done....(very basically, I have done quite a bit but I wont go into the full detail unless you need more info then I'm happy to share)


I have run a positive cable (with a fuse at the battery end), to my DC DC charger in the rear drawer setup, and a positive from the DCDC charger (with a fuse at the aux battery) to the aux battery in the rear of my Prado, AND I have also run a dedicated negative cable from the start battery to the DC DC charger etc, etc.

Its was just easy that way for me to do, its easy to understand, I didn't have to look about for a good earthing point that was away from getting damaged (or which can corrode or become loose over time), and it just means I keep the charging circuit somewhat separate from the chassis itself....others will have good arguments for both ways, and good arguments for and against DC DC chargers etc etc. It really depends where you are putting your battery in the car, what you are running with your battery, how long you plan to stay in one place, and if you are also running power to a trailer or camper/caravan, and if you are using a dc dc charger etc.

So far I am very happy with my set up, it works very well, whilst you can save money by using the chassis as an earth return and not have to buy another length of black cable, but please, listen to what others say, there are good arguments for and against running a dedicated earth from the negative terminal, or just earthing to the vehicles chassis.

I decided to interfere as little as humanly possible with the factory vehicle electrics, and wanted to just run a good positive and a good negative cable from the start battery, as thick as I could of good quality dedicated Australian made 12v automotive cable (i cant remember the guage but its as thick as I could really have used I recon...probably) , and just keep things clearly separated from the vehicle itself as much as possible.

Remember cars can and have caught fire, and if you do the wrong thing you could easily create a fault or worse without the right cabling, cable protection, fusing, and solid connections etc.

I hope that helps somewhat...currently I'm a believer in running both positive and negative cables from the start battery,,,but that's just my set up.
Let us know what you are thinking of doing.

Thank you for your reply.
So for my setup which is under bonnet, i can run two negative cables, one directly from negative terminal of auxiliary battery to starting battery negative terminal, another directly from the dc dc charger's negative cable (in my case the black cable) to starting negative one?

Btw, is it actually the negative cable carry load (electron ), while positive cable provides voltage difference to drive the electron by linking two positive terminal? Have left high school a few years, so can't remember clearly ��

[Corigator Avid PP Poster! Find all posts View Profile Close Corigator]

Btw, is it actually the negative cable carry load (electron ), while positive cable provides voltage difference to drive the electron by linking two positive terminal? Have left high school a few years, so can't remember clearly ��

LEOHCAO -

Both cables carry the current.

You won't go wrong running a negative cable between the batteries.

[Rdae1981 Junior Member Find all posts View Profile Close Rdae1981]

I earthed mine back to the engine block and have had no issues, if you look at the block there are several M10 and M12 threads there just give it a clean and find the right length bolt and away you go.