You cannot do it like that. The voltage curve on a battery drops very little
for ages, then if any of the cells are lower capacity than others there is a
quite sudden drop by 2v or so, and at that time, the low cell is being
reverse charged by the current passing through the load. Not a good thing to
occur.

Brian

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"Cliff Topp" wrote in message ...
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?