How do you measure battery charger current?

To measure the current flowing from a battery charger to a battery, you need to use a multimeter in the correct configuration. Here's how:

Using a Multimeter to Measure Battery Charger Current

A multimeter is the most common tool for measuring current. The critical point is to connect it correctly to avoid damaging the meter.

Key Steps:

1. Set up the multimeter:

   • Turn on your multimeter.
   • Select the appropriate current measurement setting (usually labeled as "A" for Amperes). Choose either AC or DC current depending on your charger type. For most battery chargers, you'll want DC current.
   • If your multimeter has different current ranges (e.g., mA, A), start with the highest range and decrease it until you get a readable value. This prevents overloading the meter.

2. Connect the Multimeter in Series:

   • Crucially, you must connect the multimeter in series with the circuit. This means breaking the circuit and inserting the multimeter so that all the current flows through the meter.
   • Disconnect either the positive or negative wire between the battery charger and the battery.
   • Connect one probe of the multimeter to the disconnected wire from the battery charger.
   • Connect the other probe of the multimeter to the battery terminal where you disconnected the wire.
   • The reference states: "put your meter in series with the circuit (I.e between the battery charger and the battery itself, and set the measurement switch to current if you want to use your multimeter".

3. Read the Current Value:

   • Once everything is connected, the multimeter will display the current flowing from the charger to the battery.
   • Take note of the units (mA or A).

WARNING:

• Never connect the multimeter in parallel (across) the battery charger and the battery. This creates a short circuit and will likely blow the multimeter's fuse, or potentially damage the meter or the battery/charger. The reference cautions against this, stating: "do not put it in parallel as this will blow your multimeter most likely!".

Example:

Imagine you have a simple charger connected to a car battery. To measure the charging current:

1. Disconnect the positive (+) terminal from the battery.
2. Connect the red (+) probe of your multimeter to the disconnected positive wire from the charger.
3. Connect the black (-) probe of your multimeter to the positive (+) terminal on the battery.
4. Read the current displayed on the multimeter.

By following these steps, you can safely and accurately measure the current flowing from a battery charger to a battery.