Twin battery

[loot]

Hi guys. I've got the wiring diagrams but they aren't very clear.

Does anyone know what I need to add on a 2017 mk1 transit custom for twin batteries? On my custom i had 2 batteries and they both had the bms on them.

My brother just wants the second battery. Is it just a relay then activation in config that's required or secondary wiring under the floor to the main fusebox too? Thanks

[Chug]

If you download the BEMM for the van it should have a list of parts/numbers that are needed for adding a second battery, it does in our mk7 one anyway.

https://www.fordpro.co.uk/en-gb/special ... lications/

[loot]

If you download the BEMM for the van it should have a list of parts/numbers that are needed for adding a second battery, it does in our mk7 one anyway.

https://www.fordpro.co.uk/en-gb/special ... lications/

Cheers chug I don't seem to have access to that.

I may have bemm downloaded already.

But the mk7 shows adding a leisure battery I think and not the factory battery saver relay and wiring and config. I don't think they want us to have access to that. I assume the custom will be the same?

[Altransit]

Is this what you need:-

viewtopic.php?f=18&t=196252

Only difference is that the Custom swaps battery positions I think.

[Chug]

I just had a look.... from 2016 custom bemm
Battery Cables and Components
A vehicle ordered with a single battery can be
converted to twin standard batteries or to High
Performance Deep Cycle AGM batteries. When
converting to the standard it is necessary
to order an additional single battery to the same
specification as the original fit. Alternatively when
converting to the High Performance Deep Cycle
AGM batteries it is necessary to replace the
original battery with two AGM batteries of the
same type. The battery part numbers for each
option is shown later in this section.

Screenshot 2025-03-13 at 22-10-09 TransitCustomTourneoCustom2016_75_ENGLISH.pdf.png

[loot]

Hmm this looks like it just adds a second battery in parallel to add capacity but it doesn't look like it is isolated at ignition off ? Bms jumpers maybe just a bridge similar to the brake pad dummy plug?

[Chug]

If you look in the BEMM it has diagrams for twin battery with parts listed and a man of your talent should be able to figure it out

[loot]

If you look in the BEMM it has diagrams for twin battery with parts listed and a man of your talent should be able to figure it out

Cheers I'll try and get hold of it

[loot]

Is this what you need:-

viewtopic.php?f=18&t=196252

Only difference is that the Custom swaps battery positions I think.

Cheers Al but it's for a custom

[loot]

Got bemm it's actually interesting and shows more configurations that I thought. 2 batteries with split charge,or 2 batteries in parallel without split charge. And 3 batteries.

[Chug]

Got bemm it's actually interesting and shows more configurations that I thought. 2 batteries with split charge,or 2 batteries in parallel without split charge. And 3 batteries.

There ya go then, we got there eventually

[loot]

Got bemm it's actually interesting and shows more configurations that I thought. 2 batteries with split charge,or 2 batteries in parallel without split charge. And 3 batteries.

There ya go then, we got there eventually

Hopefully.

Right so my brother has a 2017 custom but mk1pre facelift but euro 6 panther engine. It's the deep metallic blue and limited I think. Anyway, single battery and like like no battery monitor sensors on the live cable for the battery. It's it normal for 1 to not have it at all? Cheers. He has a battery drain and from Saturday to Monday it is dead and needs a jump. He has a new battery but this has been an on going problem. He removed the interior bulbs. I'm only asking as I though if fitting the dual battery relay etc but it occurred to me that maybe he should have the battery sensor? If so,would it not be there cause it not to charge the battery?

[Chug]

Maybe try putting the VIn in Catcar and see if anything shows up in the battery section.

[loot]

I thought cat car no longer worked? But I'll try that thanks

[metalworker0]

I think regardless of whether you have twin battery set up or an isolater ..I think you have a fault called a parasitic battery drain.

Think you should be doing a parasitic drain test, this is to find an electrical leak.

Here is something i posted a couple of months back ..not going to be typing it out all the time, so i create full explanation posts, that i can refer back to, so that i only have to do it once .


First just go over the van, look for rodent damage to wires and pay attention to wiring that goes from alternator to starter motor look at connections there.

Then test your battery / batteries ..sometimes a buggered battery will create as high drain

At this stage you ask yourself - are you confident about performing the parasitic test set up, that i'm about to explain, or not and are you maybe better to pay an auto electrician to perform this test,

THE PARASITIC TEST -

This test may create more fault codes - so you need forscan to put it right afterwards


On to the the test

Done by taking live terminal off battery ..and putting multimeter set at amps between live terminal on battery and the cable you've just taken off, if amps are high, a cheap multimeter just will not do it.

Well that's how you would do it old school, what with you having a modern vehicle that you can actually bugger modules etc up for good, says you have to be very careful and know what you are doing.
Plus it has this smart charging, i think, that's an extra complication, and stop start another extra complication.

ONCE multimeter connected - Start pulling fuses until it stops the high amp drain (that's what i suspect) ....if that does not happen you then start pulling relays, no results you then go onto the same test with engine running.n as the condition may only exist with it running.

The fuse numbers relays and their functions can be found in the owners hand book.

acording to google AI anything above 50-85 milliamps (mA) is a drain .....that's after the systems in the van have gone into sleep mode, 140 mA is enough to drain a 50AH battery in about a fortnight. with a weekend you are looking for far in excess of this with two plus 90 amp hour batteries.

others things that can cause this drain is alternator diode pack ..for that, to check you would be disconnecting alternator

all the best.mark