Earth for Leisure Battery

[Jev88]

Hello Funsters.
I am planning a Battery to Battery maintainer. I know that both batteries need a common Earth. I also know that I only really need to run a single Positive to Positive wire between the battery terminals.
That is easy at the Engine battery as clearly it goes straight from Negative terminal to chassis (in two places now). The Leisure battery is connected to my Plug-In Systems controller by two wires. So how do I know the leisure battery is also earthed to chassis? Apologies if that is a silly question?
Can I add a simple extra Earth strap from Leisure to chassis below or will that upset the system, or is it simply not required and I can assume the Leisure battery must go to chassis somehow?

 

[Richard n Ann]

Our leisure battery is earthed to chassis. To check measure from the positive terminal to the chassis and you should get the full battery voltage.
An extra earth strap won't hurt anything.

 

[Jev88]

Our leisure battery is earthed to chassis. To check measure from the positive terminal to the chassis and you should get the full battery voltage.
An extra earth strap won't hurt anything.

Thanks. I was assuming that would be the case (extra earth can't hurt) but wanted to double check

 

[autorouter]

If your leisure battery is charged by the alternator when the engine is running, it must have a negative connection running all the way back to the alternator, through the chassis and earth straps.

 

[Jev88]

If your leisure battery is charged by the alternator when the engine is running, it must have a negative connection running all the way back to the alternator, through the chassis and earth straps.

No, my older Motorhome battery is not charged by engine. Only on hookup via Controller panel or drip fed by solar.

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[nicholsong]

No, my older Motorhome battery is not charged by engine. Only on hookup via Controller panel or drip fed by solar.

What?!

So you could not go off-site?

 

[autorouter]

No, my older Motorhome battery is not charged by engine. Only on hookup via Controller panel or drip fed by solar.

In that case, just fit a strap to some chassis metalwork from the negative terminal. Although that might be easier said than done. Hab wiring in a coach-built MH is usually both positive and negative, because there's usually no easy metallic path through the bodywork for the negative return.

About the only thing it's likely to cause a problem is if the controller measures the battery current along the negative line, to use when calculating the battery state of charge. But most likely it only measures the voltage, which won't be affected.

 

[TheBig1]

if it's the autocruise in your avatar there should be a split charge relay on the firewall near your battery beside the fridge 12v relay

 

[Jev88]

if it's the autocruise in your avatar there should be a split charge relay on the firewall near your battery beside the fridge 12v relay

Errrrr.... interesting. I don't think I have tried measuring leisure battery with engine running. I have the rocker switch on controller (Plugin Systems) that allows me to use engine battery to power habitation in emergency and also effects which battery is charged when on hook up. Never checked if it charged Leisure if left in HAB Battery position? Is that what you mean?
GREEN wire is to fridge I think (had to clean it up when we first got the MH). Perhaps RED wire is what you mention?

Long story short, if I fitted a Battery Master type widget next to engine battery and used that red line might that work?

 

[Jev88]

What?!

So you could not go off-site?

Of course we do. Make sure charged at home and solar panel to keep topped up.

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[TheBig1]

the standard colour for the split charge as a hangover from caravans and towbars is Red. But it could be any random colour