fitting a second battery

[TheCake]

i have a single battery mk7 i want to add a second battery just to increase capacity, what would be the correct way of wiring it up?

[knobby1]

i have a single battery mk7 i want to add a second battery just to increase capacity, what would be the correct way of wiring it up?

Just get the set of "twin" battery cables out of a RWD from a breakers. You may also need the connection relay which lives at the rear of the battery box.

The Mk7 batteries aren't connected in parallel "all the time" like a twin battery Mk6, they're only connected together when ignition is turned on, via the relay.

Lord Knobrot

[Altransit]

If you want them to function as per the factory twin battery system, you'll need :-
1/ second battery,
2/ twin battery hold down bar,
3/ twin battery plastic cover,
4/ twin vent tube,

as well as the twin set of leads, and the large connector relay.
When it's fitted, you'll need someone with Ford IDS or Forscan to "tell" the BCM that you have two batteries.


If you just want to connect them in parallel to double the cranking power, as per Mk6, you'll still need items 1-4, as above, plus a couple of extra main leads to piggy back onto the existing ones, although the proper twin leads would be tidier.

[TheCake]

think ill go the mk6 route for cost reasons, ive got a second battery that may need replacing anyway, tried the bar thats in there and it holds both batteries securely i dont have a plastic cover (not sure where single one went either as i had to take the thing off so many times to jump it in the past) no clue what the twin vent tube looks like, ive had a perusal on ebay but im stumped, i know this sounds silly but how should i connect them so i dont bugger the van?

[knobby1]

think ill go the mk6 route for cost reasons, ive got a second battery that may need replacing anyway, tried the bar thats in there and it holds both batteries securely i dont have a plastic cover (not sure where single one went either as i had to take the thing off so many times to jump it in the past) no clue what the twin vent tube looks like, ive had a perusal on ebay but im stumped, i know this sounds silly but how should i connect them so i dont bugger the van?

You can connect them in simple parallel like a Mk6...the van won't know the difference, it will just act like a higher capacity battery.

Lord Knobrot

[TheCake]

so by parallel im assuming batt 1 is connected to existing cables then we go pos from batt 1 to pos batt 2 and neg from batt 1 to neg on batt 2, as from iirc running them in sequence increases voltage? which we dont want we just want a higher ah (capacity)

[knobby1]

so by parallel im assuming batt 1 is connected to existing cables then we go pos from batt 1 to pos batt 2 and neg from batt 1 to neg on batt 2, as from iirc running them in sequence increases voltage? which we dont want we just want a higher ah (capacity)

Correct...you'll just be essentially making a bigger battery, not higher voltage. 24v trucks often have two 12v batteries connected in "series". Parallel increases capacity, series increases voltage.

Lord knobrot

[TheCake]

excellent, is there anything else id need to do software wise? ie using forscan to tell the van there are 2 batteries or does it not matter if i do them parallel?

[Altransit]

You don't need to change any settings with Forscan, as far as the van is concerned you haven't changed anything.