Battery Wiring

[Doggitz]

I could use some help.

I need help with the original battery wiring in an SII. I'm looking for practicality, not necessarily historic correctness. Some owner before me ran 6 ga jumper cable between the battery box and the engine. He cut off the large alligator clamps and attached standard battery terminals. The car has been converted to negative ground with an alternator. He (I assume it was a he) then ran the cables out the holes in the battery box without grommets (+ and -) under the car up into the engine compartment where he attached them for subsequent distribution. UGH, what a horrible way to butcher a beautiful car! I cannot find any info in the Workshop Manual on how the battery cables got to the engine compartment from the battery box. Did they go under the car (beneath the floorboard), beneath the carpet, through the side wells, etc? I plan to get some real 4 ga wire and ground the negative lead to the frame near the battery box. Or, I could run the negative lead up front as well, and ground it to the frame there, as well as to the engine.
I plan to put a large fuse in the line before the wire leaves the battery box (with grommets, of course) . This will protect against a short in the line on the way up to the engine. Not sure what value to use, but somewhere around 150 A "feels" right. I need to check on the current draw of my starter. I wonder if anyone else has done this for protection against short circuits. I plan to use a Littlefuse Mega fuse holder and the corresponding fuses.

I would appreciate any input/guidance.

Thanks

Fred

 

[Barry]

These threads would be a good starting place:

https://forum.sunbeamalpine.org/index.php?threads/burned-wire.30202/

https://forum.sunbeamalpine.org/index.php?threads/dummy-voltage-regulator-question.29660/#post-214289


I strongly agree with loose_electron (Jerry) about a 350A fuse in the non-grounded cable between the battery and the starter solenoid and a 30-50A fuse between the solenoid and the ignition switch.

I appreciate the originality issue, but 2 fuses and old brittle wiring is a problem looking for a time and place.

 

[Asm109]

I don't know how Rootes did it , but the Battery ground cable should be attached to the engine block. Then the car body should have a good ground wire to the block.
Reason? Starter current is the big dog. You want the lowest resistance path for that current and that means directly back to the battery.

 

[sunalp]

Fred,
I sent you a whole bunch of info on how to install the harness. You should contact me and I'll explain
how you should proceed. We can overcome anything a PO ( or DPO) has done to your car.
Cheers!
Steve

 

[hartmandm]

In the later series V, the negative ground cable from the battery connects to a bolt on the battery box. The positive cable enters the cabin just above the floor behind the seats, goes towards the left side of the car and then runs towards the engine bay along the outside edge of the floor and inner sill, underneath the carpet.

The engine gets its ground from a ground strap across the gearbox mounts.

I would expect the car chassis can move as many electrons as a battery cable with less resistance.



Along left hand floor + inner sill:


Engine ground strap:


Mike

 

[Asm109]

every connection point has resistance and is a potential failure point.
Rootes method.
1. Battery ground post to cable1
2. Cable 1 to battery box.
3. Chassis to cable 2
4. Cable 2 to engine block.


My Method.
1. Battery ground post to cable 1.
2. Cable 1 to engine block.


Remember the whole electrical system was designed by geniuses who thought 2 fuses were enough. And the fuses "protected" wires that are too small to carry the fuses rated current.

 

[Doggitz]

Thanks to everyone for your responses. I am formulating a plan.

Steve - I have harness. I will give you a call

Thanks

Fred