High capacity relay or switch?

I'm working on a project where a switch needs to go between two very high loads, that are about 80 amps @ 12 volts. I considered using a relay, but the problem there is that (I think) the relay consumes power while engaged, and may overheat over time. That's a problem, since the switch will be engaged for weeks at a time.

I'm wondering if anyone has any advice for a way to switch between two very high loads?

Thanks for any advice.

Solenoid type relay rated for continuous operation. Do not use a starter solenoid as these draw lots of current and are only rated for a few seconds.

Something like one of these, but from somewhere local so you don't end up paying extortionate postage charges.

http://compare.ebay.co.uk/like/360407366657?var=lv<yp=AllFixedPriceItemTypes&var=sbar&_lwgsi=y&cbt=y&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=63&ff19=0