|
When the car is switched off, disconnect the + from the battery and sit a multimeter inline with the + and the power cable, set the multimeter to current and see how much is being drawn. It is important to note that you should only do this when the car is switched off - a multimeter usually is fused at 10A, trying to fling the car over on the starter with the multimeter inline will upset the multimeter.
Once you can see how much current is being drawn whilst the car is off, you can easily calculate how long the car battery will last. For example, if the battery is 70Ahr, which means I can draw 70 amps for one hour before it goes flat, but it also means I can draw 1 amp for 70 hours before it flattens.
Unless the alarm is physically setting the siren off (false alarms etc..) then I would not of thought it would draw much current as it is likely to only be a MCU, which draw milliamps at the most.
Are you sure the battery is being charged correctly? Run the car up and test the voltage across the battery, it should be near +13.8v. When the battery goes flat, are you charging it with a mains charger? Are you sure the mains charger is fully topping up the battery?
Dependant on the age of your current battery it might be a good idea anyway to invest in a brand new one, and even if its not that, at least you'll have a spare!
Matt.
|