Ford special vehicles say that you mustnt use a split charge sytem relay as the main brain monitors battery condition battery current supply and charge received and alternator output. 095170 page 3 of 4 rev 4 1 24 20 routing the power cables continued 15.

36a3b Ford Transit Tail Light Wiring Diagram Wiring Library
Ford transit dual battery wiring diagram. Both gas version come standard with 1 battery. The 2nd battery for a gas engine is on the frame rail beneath the side door. Jim archer wrotewiring came out of a later mk6 i believe it all looks pretty much the same as my original cables bar the twin battery terminals and split charge relaythe main positive cable from the relay is the same bar the swìtched live feed wire sheathed to it. Walk through of the steps we took to install a secondary deep cycle battery in a 2002 gmc astro van for powering additional appliances and electronics including mini fridge fan and inverter for. Ordering the 230 amp alternator option gets you 2 batteries. Ford transit battery wiring instructions dpn.
The 2005 wiring diagram doesnt show the 2nd battery being standard with rear ac. Ford offers the twin battery option to meet the needs of trade persons to handle various small electronics. Connect the positive lead to the m6 stud on the positive battery clamp. Ordering the upfitter switch set requires getting the 230 amp alternator and of course the second battery. I did take some pics but they were on my old phone. I mistook the battery bracket that the relay is mounted to as the aux battery bracket when it is the primary battery bracket it is mounted to.
Reuse the m6 lock nut when possible figure 4. This is important according to the info as the alternator oputput is actually restricted when a large demand for current is present. I found my mistake.