Alternator Charging Question - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Garrett Custom · 08-17-2015, 07:48 AM

I just completed a 1200 mile road trip yesterday. Had a blast but my question is what is everyon's normal alternator output? Mine varied from 12.5 to 14.6 the majority of the trip it was around 12.5 to 13.8. The battery light never came on though, I'm thinking probably have a weak diode in the alternator or battery maybe getting old.

1MtnGoat · 08-17-2015, 08:30 AM

It's totally normal. The simple version is - the voltage varies depending on the electrical needs and state of battery charge. Alternator actually turns off at times and all is run on the battery. There are a number of threads on this if you do a search.

winterboy8 · 08-17-2015, 09:12 AM

Yeah, if you keep an eye on it, you'll see that it varies depending on the need of the system. If you search the forum, there's some good write ups on the system, how it works and how much variation you should see.

Freaked me out the first time I saw it too.

ABADZL1 · 08-22-2015, 01:50 PM

Charging System Operation

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:

Battery Sulfation Mode
Charge Mode
Fuel Economy Mode
Headlamp Mode
Start Up Mode
Voltage Reduction Mode

The engine control module (ECM) controls the generator through the generator turn ON signal circuit. The ECM monitors the generator performance though the generator field duty cycle signal circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–95 percent. Between 0–5 percent and 95–100 percent are for diagnostic purposes. The following table shows the commanded duty cycle and output voltage of the generator:

Commanded Duty Cycle

Generator Output Voltage

10%

11 V

20%

11.56 V

30%

12.12 V

40%

12.68 V

50%

13.25 V

60%

13.81 V

70%

14.37 V

80%

14.94 V

90%

15.5 V

The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is PWM signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–99 percent. Between 0–5 percent and 100 percent are for diagnostic purposes.

08-17-2015, 07:48 AM	#1
Garrett Custom Drives: 2012 Camaro ZL1, 2000 Silverado LT Join Date: Dec 2013 Location: Pensacola, FL Posts: 160	Alternator Charging Question I just completed a 1200 mile road trip yesterday. Had a blast but my question is what is everyon's normal alternator output? Mine varied from 12.5 to 14.6 the majority of the trip it was around 12.5 to 13.8. The battery light never came on though, I'm thinking probably have a weak diode in the alternator or battery maybe getting old. __________________ v/r Roger 2012 ZL-1 #1076 2016 Explorer XLT (wife's) 2002 Ducati ST4S 2000 Silverado LT 1995 Triumph Daytona 1200 Last edited by Garrett Custom; 08-17-2015 at 07:49 AM. Reason: Damn autocorrect

08-17-2015, 08:30 AM	#2
1MtnGoat Drives: '12 SIM ZL1, 1 of 49 Join Date: Sep 2011 Location: Eastern TN Posts: 459	It's totally normal. The simple version is - the voltage varies depending on the electrical needs and state of battery charge. Alternator actually turns off at times and all is run on the battery. There are a number of threads on this if you do a search. __________________ Under Hood - Painted strut bar ends w/custom Polished Stainless mounting hardware, E2 CC, RotoFab CAI, ZL1 underhood decal, Amsoil oil, Black billet strut covers, Metco pulleys, intercooler reservoir, JRE 75 RWHP package. Chassis - Hawk ceramic brake pads, ZL1 wheel decals, Amsoil fluids Interior - A pillar gauge pod w/Aeroforce Interceptor gauges, Polished ZL1 speaker rings, ZL1 mats and console lid, Custom GPS mount Exterior - 3M clear bra, LED driving lights, PIAA Plasma Ion yellow fog lights, Window tint, CF bowties, Technostalgia sequential tail lights

08-17-2015, 09:12 AM	#3
winterboy8 Drives: 2015 ZL1 Blue Velvet Metallic Join Date: Mar 2015 Location: Melbourne, FL Posts: 720 View My Garage	Yeah, if you keep an eye on it, you'll see that it varies depending on the need of the system. If you search the forum, there's some good write ups on the system, how it works and how much variation you should see. Freaked me out the first time I saw it too. __________________ Roto-Fab CAI, ARH LT, SW 3" catback, JRE tune, Elite-2 CC, VMAX TB, Big Gulp, WW II relo, Lingenfelter S/C reservoir

08-22-2015, 01:50 PM	#4
ABADZL1 ZL1 Pilot Drives: 2013 ZL1 Join Date: Apr 2014 Location: TN Posts: 1,670 View My Garage	Charging System Operation The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include: Battery Sulfation Mode Charge Mode Fuel Economy Mode Headlamp Mode Start Up Mode Voltage Reduction Mode The engine control module (ECM) controls the generator through the generator turn ON signal circuit. The ECM monitors the generator performance though the generator field duty cycle signal circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–95 percent. Between 0–5 percent and 95–100 percent are for diagnostic purposes. The following table shows the commanded duty cycle and output voltage of the generator: Commanded Duty Cycle Generator Output Voltage 10% 11 V 20% 11.56 V 30% 12.12 V 40% 12.68 V 50% 13.25 V 60% 13.81 V 70% 14.37 V 80% 14.94 V 90% 15.5 V The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is PWM signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–99 percent. Between 0–5 percent and 100 percent are for diagnostic purposes. __________________ GP Tuning 2.5 Cam, RPS Carbon Twin Clutch, Ported Blower, Kook's Headers, Cold Air Inductions CAI, ID850's, 9.17 Lower, 2.5 Upper, JMS BAP, Pedders Front Radius Arm Inserts, Whiteline Subframe Inserts, Tuned by me with HP Tuners Idle Clip Link...........https://www.youtube.com/watch?v=gTL8S9eHwbs