Taking a power feed from leisure batteries

haydnw2 · Dec 21, 2020

Thanks to advice on another thread, I now have external lights permanently and discreetly wired into place, with wireless control. I eventually spliced these into the rear light fitting to get power, but there are some other things I'd like to do, and so I need a proper power feed. Advice in the other thread seems to suggest that I can attach cables directly to the terminals on the rear battery (T5 SE), or alternatively that I should connect the negative to the shunt instead for optimal performance. However, @Loz 's diagram in the resources section shows that the negative terminal is connected to the shunt anyway, so I can't see what difference it would make? Plus access to the shunt is far too much hassle (assuming it's still under the fridge on a late T5.1 SE). Another suggestion is to connect to the body instead.

Is there a definitive method by which I should be grabbing power?

Calimili · Dec 21, 2020

I attached an Anderson plug with two wires directly to the + and + of the battery under the left front seat. That's were I plug the MPPT charger for the portable solar, but I can attached anything to it, to draw power .

Alan Andrews · Dec 21, 2020

I think that VW provide an option to give you an additional power supply feed for accessories. They do this from the leisure battery beneath the passenger seat.

The shunt on the negative terminal is used by the internal battery smart charging system.

The question is about how much current you want to draw from the leisure battery?

Rodney · Dec 21, 2020

I fitted an Anderson plug inside the 240 mains inlet flap, this is connected to the rear leisure battery,
I use it to power a winch for my boat trailer, You can still connect the 240 power connecter as well when needed. best bit is no holes drilled into van.

Loz · Dec 21, 2020

Just attach your negative to the chassis, that way you wont be bypassing the shunt and your control panel will always be able to measure the current flow.

WelshGas · Dec 22, 2020

haydnw2 said:
Thanks to advice on another thread, I now have external lights permanently and discreetly wired into place, with wireless control. I eventually spliced these into the rear light fitting to get power, but there are some other things I'd like to do, and so I need a proper power feed. Advice in the other thread seems to suggest that I can attach cables directly to the terminals on the rear battery (T5 SE), or alternatively that I should connect the negative to the shunt instead for optimal performance. However, @Loz 's diagram in the resources section shows that the negative terminal is connected to the shunt anyway, so I can't see what difference it would make? Plus access to the shunt is far too much hassle (assuming it's still under the fridge on a late T5.1 SE). Another suggestion is to connect to the body instead.

Is there a definitive method by which I should be grabbing power?

1. Do you want to wire these accessories in permanently?
2. Do you just want a socket to plug them in?
3. Do you want 1 or 2 in the boot or in the passenger compartment?

If 1 consider a small fusebox. +tve wired to +tve of one of the Leisure Batteries, which one depending on position as in 3.
-tve can be wired to local chassis earth point or one near fusebox or plug or to an Earth Buss which is wired to a local earthing point.
Using a fusebox avoids multiple in line fuses.

haydnw2 · Dec 23, 2020

Thanks again everyone. Sounds like I need to go to an earth point then. Is there a list of locations anywhere? I'm not yet entirely sure where I want the feed to be, as I think I'll want to do stuff at the front and the back of the van. I'm favouring the back, though, because I'd quite like to attach the solar panel negative to the earth too, so that the Cali control panel reading is accurate all the time. A ready-made earth point at the back of the vehicle would therefore be handy (to avoid feeding a fairly thick cable all the way to the front carpet stud and/or passenger seat bolt as per @Loz 's DC-DC charger installation post).

To answer @WelshGas 's questions, I'm looking to wire in some LED strip lights, and then maybe have somewhere to plug in a pressure washer for my bike occasionally (could easily be a socket on the end of cable though, rather than mounted into the wardrobe, for example). I'm also doing some reading on USB-C Power Delivery (PD), to see what, if any, the requirements are to support that - it would be nice to have the option to fast-charge tablets and a laptop, and while the BusBoxx project seems to have worked for our phones, it feels like something more permanent would be a bit neater (i.e. skipping the extra cabling faff between the 12V socket and the shoe box socket). Despite appearances, I am actually taking in new info doing all of this, and slowly getting better at it all (I swapped the roof light the other day, with no dramas!), so as my ability improves I become more keen on getting everything neat and elegant as well as just functional!