I have a 1997 4runner that doesn't start up on cold mornings (colder than 0°C/32°F). When I turn the ignition, there's no noise, the battery is dead and I have to charge it up to get the the car started so I can use it in the morning.
However, I've discovered that if I disconnect the positive and negative cables from the battery (i.e. disconnect the battery from the car) the night before, and then reconnect them in the morning, she starts up perfectly. (The same thing happened when I installed a new battery).
It seems like when I leave the battery connected overnight that something is draining the power from it? Would a block heater fix the problem?

Any ideas would be greatly appreciated, thanks.

 

Seems like you got some sort of parasitic draw on your battery. Does this happen on warmer days too if you leave it for the same amount of time?

 

It just happens on those cold winter mornings. When Spring comes around it works fine again. It's just annoying having to disconnect and reconnect the battery all the time in winter and I'd like to fix the problem if possible.

 

Batteries work harder in the cold. I would get a good multimeter and check for a parasitic draw like Chickenman said. Could be a visor light staying on or something like that. Most common culprits I've seen for excessive draw are aftermarket alarm systems. Especially the ones with a built in gps