parasitic drain by Alternator Options

[yellowchinaman]

At first I thought my battery wasnt holding its charge. But with my new setup I found out with a multi meter that power is dropping as soon as the engine is off.
I did a parasitic drain test and discovered that by dis connecting my alternator, it stopped dropping!!!
WTF????
Can somone pls explain as to how its possible my alternator is draining power when off?

This post has been edited by yellowchinaman: May 22, 2014 - 12:07 PM

[Special_Edy]

The battery voltage is dropping? The battery usually has to stabilize after charging, but if it continues to drop it may be bad.
If you are performing a parasitic drain test your multimeter should be set to milliamps in DC, not voltage. Amperage is the measure of current flowing, voltage is simply the measure of the potential of energy between two sources. There should be 5 to 20 milliamps (mA) present in most vehicles. Make sure you remove either the negative or positive battery clamp and use the multimeter probes to bridge the gap between the battery post and clamp. This way, electricity flows through your multimeter to complete the circuit, and the multimeter can measure the amount of energy flowing through the electrical system. Just dont turn on a bunch of lights or power on the car with the multimeter bridgeding the circuit, I wouldnt even recommend opening the doors. Most amateur multimeters can only handle 3-10amps tops while measuring amperage before they blow their fuse or short out. If you determine you have a higher than normal drain on your battery, you should pull the fuses one at a time and to find which specific circuit is pulling the excess current. Voltage is irrelevant to this test, it can only be used to test the relative charge of the battery and whether the alternator is functioning.

If electricity was water, amps would be the speed at which water flowed through a pipe. Voltage would be the pressure difference between the inlet and the outlet of the system, or the height difference between the water tower and your faucet. Resistance could be considered the diameter of the pipe and power or wattage would be the liter per hour flow through the pipe.

The alternator could create odd voltages when powered down, it is a magnetic core which spins. These magnets could cause fluctating, miniscule amounts of voltage even at a dead stop. There are diodes present in the alternator which should prevent it from consuming electricity, they also have a shutoff circuit below ~500rpm so that the starter isnt trying to turn the alternator when you start the car. If alternators werent designed this way as well as being AC instead of DC, they would spool up like an electric motor when connected to the battery.


Sorry if I'm talking down to you in any of this, I know you probably already know most or all of what I said but its hard to gauge from the short posts on this topic. My minor is going to be Electrical Engineering.

This post has been edited by Special_Edy: May 22, 2014 - 5:06 PM