mk 7 transit Why does my van have two batteries

[gordiea]

My van has two batteries connected via a DELPHI VERSION 3.5 battery junction box 3BF01.

I can see that one battery is connected to -

passenger junction box power start relevant and to starter motor and alternator.

The other is connected to -

passenger junction box power supply non-start relevant,heated screen front left,heated screen left right, standard relay box power supply non-start relevant, engine junction box non-start relevant. Also 3 x customer connections.

I had thought that the second battery was simply only for the 3 x customer connections, so why, assuming the alternator is capable of running everything required whilst the engine is running, are all the other things connected to the second battery ?

Also how is the charging carried out from the alternator ? is it simultaneous, starter battery priority, or what ?

Any advice appreciated

Thanks very much

[sootymax]

sounds like your van was ready for some aux equipment to be fitted might have been ordered by someone else to that spec no it will have a split charge relay charges main batt first

[gordiea]

Thanks Sootymax

Yes, it was supplied for conversion to a motorhome but I still can't understand why the second battery is used so much for the base vehicle too, it seems a bit like saying, OK you want extra battery facility, you can have one, but we want to keep some of it for the original van as it can't manage on it's main battery anyway.

Any ideas I'm confused ?

[lostpaul67]

Lifted straight from Ford Brochure-April 2008

Energy Management

Rear-wheel drive, all-wheel drive and 330/350Fwd models are equipped with twin batteries as standard (option on 260/280/300 Fwd models).
This arrangement allows the second battery to power whatever accessory is needed when the engine is switched off, leaving the primary battery in a high state of charge for dependable start and run operation.

[john leeman]

Some of the vans supplied to the rail track infastructure work, ie Jarvis etc have heavy duty set up for all their electrics, microwaves, lights, small hoists ect. It may have been destined to be one of those, Cancelled order ? J.L.

[ake]

Like lostpaul said, now standard on lots of transits due to the ever increasing electrical demands

[Spooky_b329]

Got it on my chassis cab, three times now I've got to the van, found the central locking didn't work/interior lights didn't come on when door opened etc.

Each time its been because I left the interior light on...van makes a few clicking noises when you turn the ignition and then fires up instantly on the key. Second battery was so flat that even the radio had lost its code.

[gordiea]

Thanks everyone for your replies.

Initially we had a faulty second battery (it was replaced under warranty) but the strange thing I found was, that, having disconnected the second battery the vehicle locking did not work at all so I assumed the locking was operated by the main/starter battery. When I reconnected the second battery (it was very flat) the locking worked OK.

Checking which battery was drawing the current for the locking function proved to be coming from the main/starter battery. So why the locking does'nt work if the second battery is disconnected is still a mystery to me. Maybe just some resistance across the second battery cables is required.

[FixOrRepairDaily]

Q1. On the 2 battery models which is reserve and which main
Q2 if the main is flat will the reserve automatically chip in
Q3 if answer to Q2 is no will it do any harm to connect some jump leads in parallel to main battery as a boost

Many thanks for your help, this forum has been a life saver

[Altransit]

On a Mk7, the rearmost battery is the starter battery, and the front battery is the aux battery which powers all of the electrics when the engine isn't running.
If the front battery goes flat, the central locking won't work, and the radio will most likely lose its code, depending on how "flat" the battery is. The van 'should' still start from the rear battery, unless that is failing also.
You can jump start the van by using the jump point under the bonnet, but it still may struggle if both batteries are flat

[knobby1]

Q1. On the 2 battery models which is reserve and which main
Q2 if the main is flat will the reserve automatically chip in
Q3 if answer to Q2 is no will it do any harm to connect some jump leads in parallel to main battery as a boost

Many thanks for your help, this forum has been a life saver

Thread is well over 12 years old now..(Holy thread revival Batman ).

They are as Andz said, also "all" Mk7 RWD's come with twin bateries as standard and was a factory option for the FWD's.

Lord Knobrot

[mariuzzu74]

Sorry if I connect to this thread, but my Transit also has 2 batteries.
I don't have the use and maintenance booklet!
Can you tell me how to disassemble the seat to get the batteries out?
Thank you

[Altransit]

Can you tell me how to disassemble the seat to get the batteries out?
Thank you

I use a 3/8" drive 13mm socket with a long extension bar to remove the four 13mm nuts, one at each corner, and lift the seat off the base and onto the passenger seat. If you want to take it out, you'll need to unbolt the seat belt lower mount.

[mariuzzu74]

Hi Altransit and thank you so much!!!

[blfmtriv]

thanks for the info, i,m nearly ready to change my batteries as well