For testing of Smart Alternators, refer to the pre-sets for Smart Charging and the Smart Charging Help Topic.
The purpose of this test is to assess the charging rate of the alternator in relation to the electrical load on the battery. Any charge taken from the battery must be replaced by the alternator. The output of the alternator is regulated and must neither under- or over-charge the battery.
Note: If the current (Channel B) is reading a negative value, check that the arrow located on the inside of the jaw on the current clamp is facing the direction of alternator current flow.
In the waveform below, Channel A indicates a stable battery voltage with no spikes or ripples. Channel B indicates the current flowing into the system with even peaks.
Note: The periodic spikes evident can be attributed to induced spikes from the injection circuit and are of no concern.
Refer to vehicle technical data for specific test conditions and results.
In a typical example, there should be a minimum of 10 amps output from the alternator when the engine is running and the headlamps and heater blower are switched on max:
|2 x headlamps at 60 watts||120 watts|
|Heater blower max speed||120 watts|
|240 watts divided by 24 volts = 10 amps.|
The recommended regulated voltage varies slightly between motor manufacturers but 24-volt vehicles are typically between 26 and 28 volts. It is equally important that the system is neither under- or over-charging.
The current available from the alternator may vary depending on the style of the charging system, alternator installed, engine speed, battery load/state of charge and drive pulley arrangement.
PicoScope can reveal some alternator faults, such as a faulty diode, that cannot be detected by simply checking the output current or the regulated voltage. Please refer to our Guided Test Alternator AC ripple/diode test for this additional test procedure.
You can read more about alternators in our Online training section under Technical information – The alternator.
This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.
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