Parasitic battery drain troubleshooting using clamp meter

Battery drain is the discharge of current from a battery.

A battery is used to store electricity. It is used as supplementary and/or backup source of electrical power.

Parasitic drain is the discharge of current from a battery when the battery is not in use. When this drain is beyond normal threshold, we say that there is parasitic drain problem.

A clamp meter is used to measure current by clamping on the current carrying conductor and not by direct probing of the cable.

There are quite a number of issues that can cause parasitic battery drain.


Causes of parasitic battery drain

1. Weak battery

2. Poor/dirty/corroded termimal

3. Faulty grounds

4. Drain from car accessories

5. Security system of the car

6. Interior lights

7. Faulty wiring

8. Faulty alternator/diode

Some of these causes will be explained towards the end of this article.



Parasitic drain also known as phantom drain is undesirable excessive current draw from the battery when the car is turned off and resting. This battery drain can be very frustrating because it can send several car batteries packing if it's root cause cannot be determined on time.

Usually, when the car is resting, any battery current draw above 500 milliamps is regarded as Parasitic but this can vary between cars, especially with modern cars. This shall be a topic of another day. I prefer to tell you how to use a clamp meter to troubleshoot Parasitic battery drain today.


Different ways of measuring current:

1. Connecting an ammeter in series circuit to measure current.
2. Using a clamp meter by clamping a current carrying conductor (commonly wire).Clamp meters have wide jaws that clamps around an electrical conductor to provide non-contact current measurement.
We can measure current without disconnecting the circuit to create a series connection with an ammeter. The meter does not have to physically touch the circuit that we want to measure its current.

Most clamp meters can also measure voltage, capacitance, frequency, resistance, temperature, continuity and more...

It is safer and more convenient to use a clamp meter because there won't be fear of passing high current through the ammeter or fear of making errors in connection.

There are different types of clamp meter but the type that we need is hall effect type which can measure both direct and alternating currents and are more sensitive.

In electromagnetic principle, when current flows through a conducting material, it causes the generation of magnetic flux around that conductor. It is through this magnetic flux that the clamp meter measures current because the amount of flux generated is directly proportional to the amount of current passing through the conductor.

I recommend that a clamp meter with detachable/remote screen should be used if it is available. With this type of clamp meter, it is easier to measure currents of individual circuits because you will not have to disconnect each circuit. For instance, you can clamp the wire that powers the radio amplifier. You can also camp a circuit in the boot, close the boot and use the remote screen to monitor it.


Things to ensure before carrying out battery drain test

1. The car's battery is a known good one and is fully charged.
2.The battery terminal can be washed with water and soda to ensure a clean terminal with good electrical contact.
3. Put off all electrical accessories like radio, wiper, heaters, lights and so on...
4. Close all doors and boot
5. Leave car to seat for about 30 minutes because some modern car's electronics do not go into sleep mode immediately the car is turned off.