Earth for Sterling

[PetenAli]

Just sorting out wiring for new 50amp Sterling B2B charger. Am I right in thinking that all the earthing has to go through the cranking battery earth?

The reason I'm asking is because I have a petrol so cranking battery is under O/S front seat. Leisure batteries are going to be at bottom of wardrobe and Sterling charger is going to be under the Waeco fridge, meaning that there has to be a long run of 35mm² cable on the positive side from cranking battery to charger to leisure batteries. If there has to be a common earth then that will require the same run of earth cable, but if I can make a good earth near the wardrobe it will cut down the amount of cable considerably.

The instructions with the charger certainly suggest a common earth with cranking battery and so do other wiring diagrams that I've seen but just checking...

Thanks,

Pete

[CJH]

I've heard this advice too. Others will probably know better, but I believe the recommendation for an earth cable back to the battery is because of concerns about getting a good connection the vehicle body - it has to be a big terminal, with a good connection over a large contact area. Such a vehicle earth will also then rely on a good chassis earth at the other end, near the battery. A dedicated earth cable back to the battery avoids both of those problems, but of course it still requires you to use a good sized terminal and to make a good connection with the battery terminal.

If you can ensure that the earth connections are up to the job, circuit-wise I can't see what difference it would make.

[California Dreamin]

I know its recommended but its hard to believe that a 50amp B to B charger needs 200+amps hard wiring.... and that the maximum charge of 50amps would only be for a limited time yet still requires such a massive gauge wire specification. Is that thicker than the starter cable? which is much longer and can be carrying up to 150/160amps on a petrol.
I guess its all to do with critical voltage drop and how that effects charging.

Martin

[ninja.turtle007]

I know its recommended but its hard to believe that a 50amp B to B charger needs 200+amps hard wiring.... and that the maximum charge of 50amps would only be for a limited time yet still requires such a massive gauge wire specification. Is that thicker than the starter cable? which is much longer and can be carrying up to 150/160amps on a petrol.
I guess its all to do with critical voltage drop and how that effects charging.

Martin

I have this setup with control panel so I can monitor charge rates etc. It only draws 50a if the batteries are pretty flat and as you have said it's not for long.

I have earthed my sterling charger and batteries to the body.

[AdrianC]

Am I right in thinking that all the earthing has to go through the cranking battery earth?

The instructions with the charger certainly suggest a common earth with cranking battery and so do other wiring diagrams that I've seen but just checking...

ALL the metal in the van is a "common earth" with the starter and leisure batteries - and it's got much higher current carrying capacity than any bit of wire.

There's no way the Sterling's going to be needing a heavier earth than the starter motor or alternator, yet they manage just fine using the bodyshell as an earth.

[PetenAli]

Thanks everyone and sorry for the delay in replying.

That's really helpful and I am not going to run the earth all the way back to the cranking battery. I wonder if Sterling recommend this because so much of their gear is designed for use on boats?

Anyhow, now I will sort out a sensible place to earth the batteries and the charger. Where did you find worked well Tom?

Also got to find an auto electrician with the gear to solder up all the HD cable.

Need to get this done before Patrick's Mendip event.

[v-lux]

Pete, you're bang on with the boat assumption. All electrical installs on boats require seperate earths.

Re the cable and terminals, technically they should be crimped and not soldered. I've got a set of crimps you can borrow if needed, but won't be before the mendips event. However I could bring them along and give you a hand terminating the cables if you like. You could run the cables beforehand to save time.

Al

[PetenAli]

Pete, you're bang on with the boat assumption. All electrical installs on boats require seperate earths.

Re the cable and terminals, technically they should be crimped and not soldered. I've got a set of crimps you can borrow if needed, but won't be before the mendips event. However I could bring them along and give you a hand terminating the cables if you like. You could run the cables beforehand to save time.

Al

That's a great offer Al - thanks very much. I will sort out the earths and do all the cable runs so they just need crimping. Something else I've learnt as I thought stuff like this needed to be soldered.