- Thread starter Myles1970
- Start date
Myles1970
Member
- Messages
- 929
- Location
- Monaghan, Ireland
Thanks everyone, I've just ordered 4m 35mm2. I'll use the 16mm2 that I have to run the earth back to the passenger footwell junction box, and I'll daisy chain on to the engine block. I'll also fit earth straps from the block to the chassis legs, so there'll be continuity right through the chassis. The oem has a ground point on the rear lamp panel, so I'll add an earth strap to that from the battery - ve terminal....can't do any harm. I'll run the 35mm cable, fused at the battery, directly to the starter, and daisy chain from there to the alternator harness, I have a hydraulic crimp tool and I'm not afraid to use it so losses should be minimal. I might as well use the oem fuel pump feed to trigger a relay in the boot and power the fuel pump directly from the battery...
All makes sense now, after several Guinness (it is father's day after ALL)
All makes sense now, after several Guinness (it is father's day after ALL)
hotponyshoes
Member
- Messages
- 7,536
- Location
- Somerset. Uk
I've got a drum of double-insulated 35mm copper if you need any.
Also 25mm single insulated that's a bit dusty/dirty, that's probably cheaper than new 16mm...
Also 25mm single insulated that's a bit dusty/dirty, that's probably cheaper than new 16mm...
- Messages
- 23,398
- Location
- Birmingham
Just make sure the earth return path to battery matches the cross section of the 35mm starter supply because the same amount of current passes through it.
Myles1970
Member
- Messages
- 929
- Location
- Monaghan, Ireland
Surely the body shell also acts as a conductor?
Myles1970
Member
- Messages
- 929
- Location
- Monaghan, Ireland
Thanks, I ordered some last night
But I'll bear it in mind in case I need any more
- Messages
- 23,398
- Location
- Birmingham
It does, but the cables from the battery ground to bodyshell and bodyshell to engine block/starter have to be able to carry the current drawn on the starter supply.
Myles1970
Member
- Messages
- 929
- Location
- Monaghan, Ireland
I see what you're getting at now, cheers
hotponyshoes
Member
- Messages
- 7,536
- Location
- Somerset. Uk
Some of them have a sealed "fuse" in the cable. It's connected to the airbag system and blows automatically in an accident.
It probably cheaper to buy the cable and a maxifuse holder than the loom anyway as I expect most breakers will want to sell the loom complete.
I've relocated a few batteries. The main thing is that it can handle the starter current. I think I used 24mm on the last one I did, 1.6 civic, no issues at all.
Once the engine is running there is only likely to be a few tens of amps most of the time (remember the alternator is powering all the accessories on a running engine so even with heated seats etc on you only have the charging current going back through to the battery itself. Bit of a simplification but the point being that even with a hundred amp's worth of accessories on - and you'd struggle to draw that much on any car - the actual current going to/from the battery will be less than that).
This is kinda obvious but do make sure the cable is well protected. I sheathed the full length in convoluted tubing and obviously went through a grommet at the firewall.
Might be worth adding a fusible link too. Maybe even a battery isolater.
Once the engine is running there is only likely to be a few tens of amps most of the time (remember the alternator is powering all the accessories on a running engine so even with heated seats etc on you only have the charging current going back through to the battery itself. Bit of a simplification but the point being that even with a hundred amp's worth of accessories on - and you'd struggle to draw that much on any car - the actual current going to/from the battery will be less than that).
This is kinda obvious but do make sure the cable is well protected. I sheathed the full length in convoluted tubing and obviously went through a grommet at the firewall.
Might be worth adding a fusible link too. Maybe even a battery isolater.
