alternator charging capacity test procedure ver 4

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Caterpillar Confidential: Green

Alternator Charging Capacity

Test Procedure

Version 4

CAT Electronics

Starting and Charging Systems

Last Updated: 10 May 2012

Author: Sam Revach

1




Overview - Alternator Charging Capacity

Purpose: Test alternator charging capacity.

This test will verify proper sizing of alternator and battery charging capacity.

The procedure has three elements with testing at,

1. Low Idle

2. High idle

3. Hibernation mode

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Procedure - Alternator Charging CapacityInstructions

1. Install a current probe on the battery output cable and alternator output cable.

Install volt meter across battery packs and alternator terminals. (see diagram)

2. Measure machine total load by incrementally turning on and measuring all machine loads, starting

with ‘Key Switch’ on, (see attached sample).

3. Partially discharge batteries to ~(80%) state of charge {~(24.9V)} by turning on all possible electrical

loads for (20 to 30) minutes without engine running. Monitor voltage and current draw from

batteries.

a. This ensures that during testing the batteries will accept a charge and alternator will be at full

output.

b. Orient battery current probe so that the polarity of the reading is ‘positive’. In this case,

batteries are discharging when reading is positive, and charging when reading is negative.

Machine total load




Procedure – Alternator Charging Capacity

4. Start engine and operate at low idle. Ensure all possible electrical loads are on.

Record instantaneous & simultaneous current and voltage measurements.

Notes:

a. Since values change rapidly as batteries recharge, measurements should be taken quickly andsimultaneously from alternator & battery. (Two people are needed to record the data. One of them

will give the signal to record).

b. Machine loads = (Alternator current) + (Battery current)

Keep in mind that the batteries may be discharging, ‘adding to’ (+), OR charging, ‘taking from’

the alternator (-).

5. Run engine up to high idle and repeat measurements (as above).

6. While at low idle, take (3) additional simultaneous measurements of alternator & battery current at (2)

minutes intervals in ‘steady state’ conditions (i.e. after the engine idled for a few minutes).

7. If engine has a hibernate mode at very low engine speed, then allow engine to drop down into

hibernate mode and take measurements from alternator and batteries as earlier.




Acceptance Cr iteria

1. Alternator can meet machine electrical load* + customer loads** at all engine speeds.

2. Alternator can charge batteries at 10A. per parallel set of batteries.

* Allowance should be provided for fully loaded transmission ECM.** Customer loads, such as, fire suppression system, added radios - required for operation in quarries etc. Such loads may

vary from 5A to 20A, as needed.

Note: If battery current measure is positive polarity, then the alternator is not meeting demand of machine electricalloads and batteries are being discharged.

Test complete.


Battery

Frame

Power

Distribution

Frame

Alternator

Machine Loads

Battery current

Probe

Al ternator

Current probe

Al ternator voltage

Battery voltage

(-)

(+)(+)





Suggested Measurement Chart:





Version Log

May 10, 12Sam Revach Added comments for acceptance criteria regarding transmission ECM and

customer loads.

4

Sam Revach

Sam Revach

Sam Revach

Author

Jan 24, 11Clarified instruction #3 with (bat. V), notes and recording chart.3

Nov 6, 09 Added incremental machine loads and steady state measurements2

Jan 30, 091st Release.1

DateChange DescriptionVersion

alternator charging capacity test procedure ver 4

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