Searched the forum but didn't see this topic specifically. I just went out and measured, but I don't see how I'm going to fit a second battery under the hood anywhere. At least not one the same size as my current.

Leaning toward behind the passenger seat. Any big concerns I'm not thinking about?

Batteries in the passenger compartment need to be sealed (not VRLA or maintenance free SEALED to preventing them from venting fumes into the passenger compartment, the cables also have to be properly run and protected from chafing and fused at BOTH ends - personally I think it's a bad idea.

Look under the car, under the rear seats - I believe there's enough space to fit a battery (or two) under there, but you'll need to custom fabricate a frame to mount & secure them, and as above the wiring will need to be protected.

Under the hood - 2003 & later production were fitted with a different windscreen washer reservoir, one that sits inside the wheel arch with just the filler neck visible under the hood - this reservoir can be fitted to the earlier cars freeing that space up - there should be pictures of this type of installation over at auszookers.com

http://www.auszookers.com/forum/viewtopic.php?f=37&t=55182
http://www.auszookers.com/forum/viewtopic.php?f=5&t=36845

These are great ideas! Thanks!

Batteries in the passenger compartment need to be sealed (not VRLA or maintenance free SEALED to preventing them from venting fumes into the passenger compartment, the cables also have to be properly run and protected from chafing and fused at BOTH ends - personally I think it's a bad idea.

Look under the car, under the rear seats - I believe there's enough space to fit a battery (or two) under there, but you'll need to custom fabricate a frame to mount & secure them, and as above the wiring will need to be protected.

Under the hood - 2003 & later production were fitted with a different windscreen washer reservoir, one that sits inside the wheel arch with just the filler neck visible under the hood - this reservoir can be fitted to the earlier cars freeing that space up - there should be pictures of this type of installation over at auszookers.com

http://www.auszookers.com/forum/viewtopic.php?f=37&t=55182
http://www.auszookers.com/forum/viewtopic.php?f=5&t=36845