On 22 Jan 2006 at 22:50, Pedro Drummond wrote:
> My friend's Renault Clio has a 45Ah battery. After not being used for "some"
> days, the car won't start. Something around 8 to 12 days, she guesses. Now I
> have one question, phrased two ways:
> 
> 1) Turning off everything I can in the car, how much current should I expect
> to measure being drained from the battery? On a healthy system I figure it
> should be about 20mA, some mA for the internal clock, some for the radio
> memory, some for an idle on-board computer.

Factory equipment should draw less than 10mA, more like 5mA. Add-ons can draw much more, 
depending on what they are. Car stereos and alarms can be quite sloppy. Also if the car stereo is wired 
with the switched power lead getting power all the time, you need look no further. The output stages are 
not switched by the power switch in today's stereos.
 
> 2) How low is too low for a 45Ah car battery? When will autonomous ignition
> become impossible? Is it half of its capacity enough?

Above freezing, the car should start with the battery half-charged. As the battery ages, the total capacity 
decreases, so at 4 years, the 45 Ah battery is now only 22.5Ah, more or less. So in freezing weather, 4 
years is the typical life of a car battery.

However, I have 8 years on my car battery and it still starts fine, and a friend has a 1990 Toyota truck with 
the original battery (California climate). I almost believe him, too :)

Obviously, your mileage may vary.

Cheerful regards,

Bob
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