How do I test the amount of electrical draw there is from my vehicles battery when the car is off and at rest.?
You use an amp meter (which is often one of the functions of a multi-meter) and the easiest thing to do is to remove one of the battery terminals and connect the amp meter to the battery and then to the cable so all current must pass through the meter – just don’t try to start the engine with it like this, you will fry the meter! It is normal for a car to draw a small amount of current from the battery when it is off so it can power the clock and other things, so if it is parked for 3 or 4 months, the battery does not stand a chance. Try driving it for at least 45 minutes once a week or disconnect the battery when it is parked and trickle charge the battery about once a month, or leave the battery connected and charge the battery about every two weeks.
You have good answers there. The test will need to be done with a GOOD battery. Disconnecting the negative cable is safer, in case you should touch the spanner to metalwork while trying to remove the positive. If your multimeter is a digital one, it is not important which lead from it goes to the battery post, and which to the removed cable. They will indicate a current flow, and measure it correctly, either way round. If it’s an amalogue meter, it will need to be connected correctly. It could be wise to set the meter up initially on the highest current range, usually 10 or 20 amps. There is usually a separate socket for the red/ positive meter lead for this. If the indicated current is down to a fraction of an amp, you can then safely change the meter lead/ switch to read a lower range. It looks like your best bet for leaving the vehicle for long periods, would be to connect a trickle charger to it. Make sure the floating current is not excessive, or the electrolyte will lose water to
You disconnect the positive battery terminal and you connect an ammeter with the + lead to the battery and the – lead to the now disconnected battery terminal. The current drain should be less than 0.1 amps. Bear in mind that your battery was not meant to be not charged for that long and they will self discharge in 2-3 months. If you are not going to be driving a vehicle for a long time, econnect a trickle charger on it, rated at say 2 amps.
