I wanna place my battery outside of the engine bay (for El Camino 1970). My idea was to place the battery behind the bench on pass side.
I know the positive side on doing this, cleaning up the engine bay. But what are the negative sides? Will there be loss of power from the battery? And where do I connect the min pole? Can I connect this to the floor sheet metal?

Hope somebody can help and share some experiences. Tnx!

Just make sure to get larger cables. Since they are longer, there will be more voltage drop through them. It would also would be a good idea to put the battery in a box or have some type of cover to go over the terminals.

you can do this easily, if this is a driver car and racing regulation compliance is not needed
you will want a vented battery box that can be secured to the floor.
you will want to run the negative ground cable to the engine block.
positive to the starter solenoid terminal.
use grommets on the cables passing thru the floor.

if you are needing to meet racing regulations requiring a shut-off switch = this could be more complicated.

I would not want to share the passenger compartment with a battery for the following reasons:

1) They are heavy and in an accident, could break loose.
2) They are full of acid and can explode or rupture under certain conditions (short or accident).
3) They vent hydrogen.

It could be a high price to pay for a clean engine compartment.

Tom

I would not want to share the passenger compartment with a battery for the following reasons:

1) They are heavy and in an accident, could break loose.
Absolutely true. 50+ lbs of battery will bust your pelvis or spine pretty good if it hits you from behind.
2) They are full of acid and can explode or rupture under certain conditions (short or accident).
3) They vent hydrogen.
Which is why I'm so disappointed that so many cars have the battery under the rear seat. My Trailblazer, about a bazillion VW (old) Beetles, and plenty of others hide the battery under the rear seat cushion. The VW had a little plastic guard over the + terminal, so the metal seat springs wouldn't spark against the battery.

Overall, I'd suggest being careful about where you re-locate the battery.

I tossed my battery and entire cabling system in my Elco and mounted the batt in the smuggler's compt on pass side.
Details:

1. Optima Red Top
2. Billet mount firmly installed between the fwd wall (interior divider) and the lateral brace
Mount locations for the Jeg's billet Optima mount are tabbed, welded, with flange
nuts also welded to the backside of tabs where necessary.
3. Heavy gauge multi-strand welding-style cable passes from battery to heavy duty
Moroso switch mounted so that the switch can be thrown on/off from inside the car.
4. Cable continues from switch to an all-steel insert where the flapper valve was on pass
side, which now contains a through-panel connector
5. Cable begins again inside at flapper valve, and proceeds fwd up along trans tunnel and
up the firewall to where the heater used to be and terminates in another through-
panel connector.
6. Now inside engine compartment, a very short run to the remote solenoid providing
power to the solenoid and to the rest of the car.
7. The ground side has a 1" wide braided s/s strap from terminal directly to the body
about 6" from the battery.
8. There is also a 1-0 (one ought) multi-strand welding cable from the (-) terminal which
runs from the battery thru the drain hole in the floor and is lagged directly to the
frame.
9. Another 1-0 welding cable runs from the Idler arm mount on the frame directly to the
engine block.
10. There are multiple small 12 guage ground wires connecting the core support, fenders,
frame to firewall, etc.
11. All cable connections are soldered and sealed with shrink tubing using a heat gun
not a match or torch (important).
12. Adel clamps are used generously, everywhere.

I run EFI, computers, Digital 6, HPC II, and communications equipment, and have zero
electrical issues.

Prior to doing this, the EFI suffered from lack of e- supply, and there were other issues.
It is very important to remember this:
*** Benjamin Franklin got it wrong... electricity flows from (-) to (+), and not the way
we always thought--- this means that the "ground" is actually the supply, and
without a well-grounded layout, the system will always be struggling for a
supply of electrons, and hence one thing will "steal" electrons from another, and
you end up with the usual weird stuff that happens when "grounds" are poor.***

The flow of electrons is what electricity really is- and the reason the neg terminal is called that is simple... that is where the electrons (-) are found. "Positive" only means it is empty of (-)... think about it.

Knowing this is important, because with this on your mind you usually end up doing a better job designing your electrical system, or upgrade to an existing.

In this pic you can see the final run of the (+) cable from the thru-panel connector to the solenoid. The appearance and use of top-grade terminals is typical of the entire system.
http://i20.photobucket.com/albums/b203/aero80/digi6install.jpg

In this pic you can see in the reflection in the pass valve cover the high quality alternator connector. This is very important in the design of a modern muscle car electrical system, since it is basically the only way the alternator has to supply the e- system.
http://i20.photobucket.com/albums/b203/aero80/ratcoexc.jpg

Hope this helps !

Eric