Dead battery; what chews up power with ignition "on"?

[Steampunk]

I guess this section is the most appropriate to post this;

I accidentally left the key in the ignition over a 24hour period on the "ON" position and found the battery completely dead the next night. I've done this twice

Long story short, no interior lights or accessories are switched on, neither is it alarmed/immobilised, with the only two things that you can see being powered are the clock on my OEM radio/cassette unit, and my MegaSquirt (a few LED's lit-up).

Could these two things really soak up the entire battery over a day?

If not, what else can be eating up the power?

BTW, the battery is in good condition, ie. cranks normal.

[jerrah]

Car batteries aren't really designed for sustained usage. AFAIK they're really only good for cranking and then you're using the alternator for running accessories.

[bruce]

Your making it easy for someone to steal your car.

[Mr Morlock]

even an interior light left on will kill the battery. If cars are not being used regularly it might be an idea to use a trickle charger. One simply has to remember not to leave parkers, interior lights and ignition on. I guess most of us get caught out occassionally- many moderns have auto lights out.

[Alex]

fuel pump??

[NMX516]

The fuel pump will only run for 10 seconds or so. The ECU will remain on for the whole time, and will draw just as much power as when the car is running. Power will be running to all of the sensors, so air flow meter, air temp sensor, water temp sensor etc etc will all be primed and waiting for the car to start... Dash lights would also help to flatten the battery. Also remember that the battery only has to lose a couple of volts of charge to be unable to start the car or power any of the 12V accessories...

[AJ]

yup, everything that can use battery power WILL use it, & as Gerard said the ECU is just like a baby laptop, leave it running & it'll happily kill your battery....................good thing MX5's don't have points & an old skool coil, or you'd be replacing them & several other parts in the ignition side of things pulling a stunt like that Andrew..........LOL

[Steampunk]

Leaving the igntion on in a distributor equipped car kills the dizzy?! Shite! well you learn something new everyday.

Thanks for the replies guys, it alleviates my concern of thinking that there is some electrical "leak" somewhere.

Two brain-farts in 11 years ain't bad hey?