In article ,
Cliff Topp wrote:
All modern cars will have an amount of quiescent current draw to power
things like the alarm, the clock, the radio presets and so on when the
car is parked up and switched off. I've seen it written somewhere that
around 50mA can be considered 'normal'.

My question is - if the quiescent current draw is 50mA (0.05A), how do
I calculate voltage drop per hour?

For instance, if I park the car up at 10pm and the battery is showing
12.5V, with a 50mA draw overnight what will the voltage be at, say,
9am?

Just what a battery reads voltage wise (to decimal points) has a lot to do
with the individual battery. You can work out how long the battery will
last by its capacity in amp.hrs. And knowing the quiescent load. Using
that, discharging by half seems to be the maximum that will allow the car
to start OK. As a very rough guide.

But the capacity of a battery deteriorates with age.

--
*Letting a cat out of the bag is easier than putting it back in *

Dave Plowman London SW
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