hey guys, im about to relocate my battery in the boot of my mk1 escort. I am complete amature when it comes to electrics so thought I should ask if there is anything I need to consider? wheres the best place to earth? Do I need to add a fuse or something? or just run the positive cable all the way from the engine bay to the boot? thanks in advance! Dave.
Just run it to the boot but as a precaution I would double the thickness of the std cable as it's a longer run. As for earth, it just needs to go to a good earth point preferably a point where you can find a captive nut welded to the body. Again I would upgrade the earth cable too and make sure all cable connections are good,clean and tight.
Don't need a fuse
as above, but make the earth connection somewhere in the boot thus keeping cable length and volt drop to a minimum
Wouldn't it be a good idea to have a fuse as close to the battery as possible?
Depends how likely it will be to get damaged sufficiently to short out to the body as its about the only way to pop a 150 / 200A fuse, short of a seized starter!Originally Posted by 5tox
I'd use 25mm sq Red cable from boot to front and a similar short black direct to body in the boot - the whole body and chassis is a lot of metal acting as earth. Mine had cable inside the car, tight down the nearside tunnel as I had a battery cut-off for isolation but i've since reverted to battery back in the front.
You would be a fool to have so much permanently live 12v cable without a fuse. These cars crumple like tin cans in accidents meaning wherever you run the battery feed it will always be at risk of cutting through the insulation and shorting. I am sure you don't want to be in a car accident with the car on fire. Also, over time the insulation can/could easily rub through just through vibration causing a short, a fire and the loss of your car. Maybe you like risk though?
For the sake of 4 pounds, put a fuse in there!!!!!!!!
1970 Mk1 Escort Tarmac Rally Car
Use at least 25sq cable, 32sq ideally to minimise voltage drop. Earth as close to the battery in the boot as mentioned. Ive mounted the battery in the boot before without a fuse, loads of people do it, BUT… im older now and more cautious so I always fit a fuse as close to the battery as possible, its not worth the risk.
A cheap way to get a large sq cable with a fuse built in is to go to a breakers yard and pull the cable from a BMW, most bimmers have their battery in the boot and the cable is huge, which will help minimise voltage drop. (Get the cable from a diesel bimmer if you can, it might be larger.... that’s just a guess, I can’t confirm…)
zero gauge wire
A circuit breaker (reusable as opposed to fuse, and more appropriate at handling current draw when starting) as close as possible to battery
An Optima or similar sealed type battery, that can be mounted at any angle.
Regards,
Kevin
What amperage circuit breaker should I use? Thanks
you want 250A maybe more if you have a really high compression motor
But bear in mind the current carrying capacity of the cable - 25mm sq good for 170A, 35mm sq ok for 240A - bit pointless having a breaker that doesn't trip before the cable melts LOL!
i dont get technical on this, i just know what i see fitted to cars that come through our workshops day in day out
car manufacturers typically use 250-500A fuses on the starter circuit so are you saying they are getting it wrong? a typical petrol starter will draw 120A on cranking sometimes more, the initial surge is higher.
we quite often come across blown 250A fuses where people have tried to start something in gear, never seen a melted cable because of it though
Those high-amp fuses are there to protect the battery from blowing up in case of a short.
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