explaining voltage drop - purkeys

ExplainingVoltage Drop

JUNE 18, 2015

800-219-1269 | [email protected]

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About the Presenter

Larry has over 20 years’ experience working with heavy duty fleets. He is an outstanding trainer and uses his extensive experience to help his customers make the best choices for their electrical needs.

He has been awarded the prestigious Recognized Associate Award from the Technology & Maintenance Council. Larry’s knowledge of electrical systems enables him to help his customers identify and remedy a fleets’ electrical issues.

[email protected]

Larry Rambeaux | Southern Region Sales & Service Engineer


Voltage is electrical pressure.

Voltage drop is anyresistance that impedescurrent flow, causinga drop in voltage.

Red Lead = 12.5 VoltsBlack Lead = 0 ________ 12.5 Volts

What is Voltage?

CAP

VDC-AC

Hz% RANGE HOLD REL

MODE

HZ% °C°F

10ADC-A

C

mADC-AC

uADC-AC

10A

uAmA COM

V HZ%CAP°F °C

OFF


Example on the positive side.

Red Lead = 12.5Black Lead = 12.5 ______ 0 Volts

How to Read Voltage Drop with No Current Flowing

CAP

VDC-AC

Hz% RANGE HOLD REL

MODE

HZ% °C°F

10ADC-A

C

mADC-AC

uADC-AC

10A

uAmA COM

V HZ%CAP°F °C

OFF

v

CAP

VDC-AC

Hz% RANGE HOLD REL

MODE

HZ% °C°F

10ADC-A

C

mADC-AC

uADC-AC

10A

uAmA COM

V HZ%CAP°F °C

OFF

v


How to Read Voltage Drop with No Current Flowing

Example on the negative side.

Red Lead = 0.00Black Lead = 0.00 ______ 0 Volts


How to Read Voltage Drop with Current Flowing

CAP

VDC-AC

Hz% RANGE HOLD REL

MODE

HZ% °C°F

10ADC-A

C

mADC-AC

uADC-AC

10A

uAmA COM

V HZ%CAP°F °C

OFF

CAP

VDC-AC

Hz% RANGE HOLD REL

MODE

HZ% °C°F

10ADC-A

C

mADC-AC

uADC-AC

10A

uAmA COM

V HZ%CAP°F °C

OFF

VV8.50VV

Example of performing a voltage drop check while the circuit is loaded.

Red Lead = 8.50Black Lead = 0.00 ______ 8.5 Volts

Red Lead = 7.00Black Lead = 0.30 ______ 6.7 Volts


An example of testing with a variable load tester.

- Operator Sensitive- Repeatability Difficult- Does Provide a Load

Variable Load Testers


Automated Tester With Fixed Load

Example of testing with a known fixed load.

- Easily Repeatable - Easy to Operate- Accurate


Effects of Voltage Drop

The effects of voltage drop on engine crank ability on a WARM day.

Starter DrawAmps

Starter Circuit Resistance

Voltage Drop in Cranking Circuit

Cranking Speed Lost per 1 Volt

Total Cranking Speed Lost

1) 700 x .00075 = .525 x 30 = 15.75

2) 700 x .001 = .700 x 30 = 21.00

3) 700 x .0015 = 1.12 x 30 = 33.60

4) 700 x .002 = 1.40 x 30 = 42.00

IMPACT ON STARTER SPEED CAUSED BY VOLTAGE DROPGiven: For every 1 volt drop in cranking system you will lose 30 Rpm’s of cranking speed.

Examples:700 Starter Draw Amps @ 70˚ F1600 Starter Draw Amps @ 20˚ F1900 Starter Draw Amps @ 0˚ FCranking Circuit

1) New Specs - .0000752) Used Specs - .0013) Out of Spec - .00154) Out of Spec - .002

700 Amps @ 70˚ F


Effects of Voltage Drop

The effects of voltage drop on engine crank ability on a COLD day.

Starter DrawAmps

Starter Circuit Resistance

Voltage Drop in Cranking Circuit

Cranking Speed Lost per 1 Volt

Total Cranking Speed Lost

1) 1600 x .00075 = 1.2 x 30 = 36

2) 1600 x .001 = 1.6 x 30 = 48

3) 1600 x .0015 = 2.56 x 30 = 76.8

4) 1600 x .002 = 3.2 x 30 = 96.0

IMPACT ON STARTER SPEED CAUSED BY VOLTAGE DROPGiven: For every 1 volt drop in cranking system you will lose 30 Rpm’s of cranking speed.

Examples:700 Starter Draw Amps @ 70˚ F1600 Starter Draw Amps @ 20˚ F1900 Starter Draw Amps @ 0˚ FCranking Circuit

1) New Specs - .0000752) Used Specs - .0013) Out of Spec - .00154) Out of Spec - .002

1600 Amps @ 20˚ F


These testing procedures can be applied to any electrical circuit.

Voltage DropBatteryPositive

BatteryNegative

LightPositive

LightNegative

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Questions & Answers

14

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explaining voltage drop - purkeys

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