E34: Battery transfer (front to rear seat)

[shogun]

I do not know where they are in your car and if they should be there, justed wanted to show that heat shield.

[moots]

QUOTE: ferret, the ones in malaysian market somehow doesn't come with the head shield (for the exhaust side) :UNQUOTE

then you must be missing this on your ride as i still have the heatshield fitted as OEM,secured by 2 screws.this shields the battery from the exhaust manifold.and if you still intend to go ahead with this mod,you will have to route the same gauge cable that is used at the current setup.

[bones]

whats up grand master, iv'e got a 1989 525I and just completed the swap.its a breeze.you allready have the 4 guage starter wire and the 10 guage accessory wire under the rear seat.i simply cut the battery connector off the starter cable under the hood,crimp or solder a 4 guage copper lug with 1/4 inch mounting hole onto the big wire and do the same on the 10 guage wire.now using the existing shunt connector box mount the starter wire to the big wire side and the 10 guage wire to the other side of the bus.do the same thing under the rear seat,but you will only have one positive battery wire connection in this shunt connector box.make sure you are attaching the battery wire to the bus side.there is a spare screw mounting position in both of these shunt boxes but without the bus bar you wont have any contact.the existing 3/8 lug ground under the seat will work fine,mount youre negative battery terminal there and youre done.i even used the original battery holdown bracket from under the hood to secure the battery,youll have to flatten it out and drill a mounting hole further back to extend it to the battery.THE MOST IMPORTANT THING TO REMEMBER IS THAT YOU ARE CARRYING THE CURRENT FARTHER TO THE LOAD,DONT DO ANY MARATHON STARTER CYCLES,IF THE CAR WONT START WITHIN A 15 SECOND DUTY CYCLE STOP CRANKING AND ALLOW THE CIRCUIT AND STARTER TO COOL FOR AT LEAST 3 MINUTES BEFORE YOU TRY AGAIN.ALSO DONT HOLD THE KEY ON WITH A LOW BATTERY SLOW STARTER,THIS WILL ALSO BUILD ALOT OF HEAT REALLY FAST. Bones.

[bones]

whats up grand master, iv'e got a 1989 525I and just completed the swap.its a breeze.you allready have the 4 guage starter wire and the 10 guage accessory wire under the rear seat.i simply cut the battery connector off the starter cable under the hood,crimp or solder a 4 guage copper lug with 1/4 inch mounting hole onto the big wire and do the same on the 10 guage wire.now using the existing shunt connector box mount the starter wire to the big wire side and the 10 guage wire to the other side of the bus.do the same thing under the rear seat,but you will only have one positive battery wire connection in this shunt connector box.make sure you are attaching the battery wire to the bus side.there is a spare screw mounting position in both of these shunt boxes but without the bus bar you wont have any contact.the existing 3/8 lug ground under the seat will work fine,mount youre negative battery terminal there and youre done.i even used the original battery holdown bracket from under the hood to secure the battery,youll have to flatten it out and drill a mounting hole further back to extend it to the battery.THE MOST IMPORTANT THING TO REMEMBER IS THAT YOU ARE CARRYING THE CURRENT FARTHER TO THE LOAD,DONT DO ANY MARATHON STARTER CYCLES,IF THE CAR WONT START WITHIN A 15 SECOND DUTY CYCLE STOP CRANKING AND ALLOW THE CIRCUIT AND STARTER TO COOL FOR AT LEAST 3 MINUTES BEFORE YOU TRY AGAIN.ALSO DONT HOLD THE KEY ON WITH A LOW BATTERY SLOW STARTER,THIS WILL ALSO BUILD ALOT OF HEAT REALLY FAST. Bones.

[ktteoh]

bones, do you have some pictures of what you have done or modify for your case?

[ktteoh]

bones, some questions i have:

1. i have a black fuse box (call it fuse_B = your shunt connector) under the rear seat - refer picture 1. however it's just a single link - unlike the one in the engine bay which is dual link. there is black wire coming into fuse_B and a red wire coming out of it. using a multimeter i verified that the black wire is connected to the front shunt box (fuse_A).
- is the red wire 10 gauge and the black wire 4 gauge?

2. about your caveat "DONT DO ANY MARATHON STARTER..." - does this apply to cars where the battery is installed under the rear seat by factory default - are they having a thicker wire?

3. the 3rd. picture shows what i believe is the relationship between the 2 shunt boxes (rear seat and front engine) - is it about right? the dotted lines show where the 'moved' battery should be inserted.

[bones]

kitteoh,sorry for the delay on the response.under rear seat issue,the main thing to accomplish under the rear seat is to put the fuseable link in between the battery connection and the two outbound circuits,ie red and black wires.the black wire will carry your starter circuit current and the red wire will carry chassis power or accessory circuits.simply make sure that when you connect your battery under the rear seat that there are no other wires attached on the same side of the fusible link that your battery connection is on.your under hood connections look correctly terminated from a fused standpoint.in reguards to the starter duty cycle times,im simply limiting the potential for murphys law to occur.you know "anything that can happen might happen" ive changed the phrase a little to suit my needs since im faced with mechanical challenges in aviation on a daily basis.

[bones]

folks/shogun/ferret, i did some multimeter tracing and have some ideas. wanted to run it past these forum for feedback and advice.

the 1st. diagram shows what the wiring is right now and the dotted lines are where i'm going to tap into after the transfer.
2nd. diagram show where the 2nd. fuse holder (item in center of the picture).

questions:
1. will the main fuse (FUSE a) in the engine bay take the current load when starting the engine bay (now that the current is coming from the back)?

2. will the wiring harness (3) (the one connecting front to back) take the load?

3. where is the best grounding point in the rear seat - can i use of the rear seat belt bolts?

i keep looking at the photos of your wiring under the back seat and im not seeing the 4 guage black wire thats in my 89 525I.your black wire is a larger guage than the red correct?

[ktteoh]

yes the black wire is thicker than the red one - it's hidden under the mass of brown (earth) wires.

you can see the black wire coming out on the 2nd. picture (shunt connector in the engine bay) - it's the one having the fusible link across.

i keep looking at the photos of your wiring under the back seat and im not seeing the 4 guage black wire thats in my 89 525I.your black wire is a larger guage than the red correct?

[bones]

kitteoh,this might be misswired in the engine compartment.the fuseible link should protect chassis electrical from the starter circuit.the fuseible link cant be inline with the starter.it provides a fused conducter for all other circuits to draw from.i would connect the rear battery wire and the engine compartment starter wire using one screw on the bus bar.mount one side of the fuse next to it,then mount your smaller gauge wire on the other side of the fuse and that should be perfect.