Second Battery.

[Daveyboy]

Had a call-out last night, I've got 2 outward facing worklights fitted inside back of van, left them switched on all night, like a t**t. Went out to unlock it this morning and central locking was not working, the drivers door unlocked on the key but nothing else. Turned the key in the ignition and it fired up first thing, only problem was that I had to re-enter the radio code. What a good idea the second battery is to forgetful old farts like me

[winterheating]

thats handy.

are you going to take the flat battery off and charge it proparly, cos it will never be fully charged if you just let the alt do it.

[Vee4]

What a good idea the second battery is to forgetful old farts like me

Good to hear that it worked as intended - I ordered twin batteries on the new Mk7 mostly because I was concerned about the amount of stuff that's on all the time whether you like it or not, draining the battery while it's parked. It might save me from myself too, as in your case.

are you going to take the flat battery off and charge it proparly, cos it will never be fully charged if you just let the alt do it.

Can you explain in more detail why that would be?

[winterheating]

cos once a battery is flat the alt will top it up to power, but it will never be at full capacity till its trickle charged correctly.

if you test a battery and its 12.6 it will be 20% capacity, but if it where at 12.9 it would show full capacity.
(dont know if them figures are correct but you get the idea)

[tyman]

Can i ask how you have a 2nd battery fitted as would like to fit extra lights in rear on my 05. Is it just a case of linking neg. & pos together? cheers

[Vee4]

it will never be at full capacity till its trickle charged correctly.

Would a good, long run (or several long runs, eventually) not do the trick? Those batteries are rather inaccessible under the seat! Could you trickle charge the second battery 'in reverse' by connecting a charger to the 'cigar lighter' socket while the van is parked? I have a solar panel that is supposed to work that way.

[sc_BK]

Can i ask how you have a 2nd battery fitted as would like to fit extra lights in rear on my 05. Is it just a case of linking neg. & pos together? cheers

If you wire it up like that they will both run down at the same time.
You could use some kind of split charge system or just an isolater switch on the pos cable

[winterheating]

it will never be at full capacity till its trickle charged correctly.

Would a good, long run (or several long runs, eventually) not do the trick? Those batteries are rather inaccessible under the seat! Could you trickle charge the second battery 'in reverse' by connecting a charger to the 'cigar lighter' socket while the van is parked? I have a solar panel that is supposed to work that way.

i was thinking of fitting a few of them solar panels to the roof of my van, taking the load off the alt and helping extra lights.

[Vee4]

Can i ask how you have a 2nd battery fitted as would like to fit extra lights in rear on my 05. Is it just a case of linking neg. & pos together? cheers

See Jezclayton's post for the kosher way to do it on a Mk7:

viewtopic.php?f=5&t=29055&start=0

This kind of installation is very common on campers. The following site has a good description of the two common methods of keeping the batteries from talking to each other (i.e. relays or diodes):

http://www.marcleleisure.co.uk/store/circuits.php

If you search the Forum for 'second battery' you will find hundreds of references:

search.php?st=0&sk=t&sd=d&keywords=second+battery

[Daveyboy]

I thought the second battery was fitted as standard to all mk7's, don't think mine was specifically ordered with it if not

[Vee4]

I thought the second battery was fitted as standard to all mk7's, don't think mine was specifically ordered with it if not

It's an option on 260, 280 and 300 FWD models. If you order the rear auxiliary power point (sounds grand but is in reality a cigar lighter socket in the right rear door pillar), the second battery is added automatically.

[Daveyboy]

Ah that explains it mines a 350 and has a rear 12v socket.