Quote:
Originally Posted by Goran
Are you sure your resistor in series method is accurate? What's your multimeter's resolution/accuracy when measuring voltage and resistance.
Seems to me you are multiplying error bars of several different measurements (battery voltage, voltage accross resistor, resistance, etc) and your R2 (the resistance of the whole car) is an unknown? Have a go at calculating your error bars for fun 
The meter I bough claims 0.01A resolution and +/-2% and 5 units precision, for my measurement of 0.18A I work out the error to be +/-0.054A a bit high, true, but to get a much more accurate current reading you will need to spend several hundred pounds on a accurate meter.
http://www.maplin.co.uk/p/uni-trend-...FezHtAodmRIAhg |
supposed to be accurate to 1mV , checked it against my nephews professional meter and it seemed to be about that . I suppose it doesn't matter if it is slightly out as long as it is consistant , certainly more precise than the cheap clamp meter I tried
latest development ...went to check the voltage on the battery after another 24 hours and it had dropped by .03 volts ;at this point I noticed that , with the boot open as before , the indicator lights beside the door lock buttons were illuminated even though the doors hadn't been locked and the doors hadn't been opened ...that doesn't seem to be correct , or does it ? unfotunately I tried the lock/unlock buttons on the remote without checking the doors had self locked last time I was in the car , just opened the boot which wasn't locked so I guess not
anyway , pulled the central locking pump fuse and the drain dropped by 10mA to 90 , probably because the boot lights are on the same circuit and , at a guess , they were pulling that ...can't remember what festoon bulbs are rated at ; at least I know that the pump can't be the problem
looks like I will have to pull each fuse to see if anything is giving a serious drain , seems crazy that you couldn't leave the car at the airport for a couple of weeks and be sure it will start even with a good battery