In article , Dave Plowman (News)
wrote:
In article , Huge
wrote:
P.S. re-reading your posting, the reason people suggest disconnecting
the battery is that most modern cars have a substantial current drain
even when switched off (I've measured it at several hundred
milliamperes). This will rapidly flatten and then ruin a car battery.
Which is why I use a float/trickle charger (sometimes called a "battery
conditioner").

If you take a fairly normal (large) 75 amp hour battery, a drain of 1 amp
would flatten it in 3 days. Pro rata for a lower current. And it would
fail to start before the battery was totally flat.

Most cars can last about 3 weeks without being run. Which would suggest a
quiescent current draw of rather under 100mA. But it may be higher until
the electrics finally go to sleep.

The main source of current drain is probably the radio. When you switch it
off, you're only turning off the amplifier, the tuning bits, etc, are still
powered. Alarms also take a bit of power.

--
from KT24 in Surrey, England