While many vehicles used only one wire (the L terminal), there were quite a few that populated the regulator’s connector with two or three circuits, and this led to a major source of confusion that still exists today! Nearly every time I look at an alternator it conjures up fond memories of growing up in a family-owned auto electric shop. In the 1980s, Chrysler pioneered voltage regulation with an engine control computer on its first EFI systems. The RVC systems use a Hall effect type current sensor that sends a PWM signal at 128Hz to the BCM. You can also scope the F and L terminals to watch the regulator ground the voltage pulled up by the PCM on the L terminal and observe the 400Hz signal on the F terminal displaying the duty cycle that the rotor winding is receiving (see Fig. A voltmeter, […] I said the alternator is “likely good” if you touched the test light probe to the L terminal and it began to charge. It’s designed to monitor vehicle voltage and only charge the battery when necessary. Naturally, DTCs will be set that will have to be cleared. Take advantage of our easy plug & play retrofit kit using 100% factory Before we venture too far out into the deep water on the latest charging systems, let’s do a bit of review. More than 2,700 new EV charging plugs will triple the size of the nation’s largest public fast charging network. It does provide a signal to the L terminal for exciting the regulator and does receive a ground on that circuit when the engine is stopped or the alternator has failed, just as before when the circuit was connected to the charge lamp in the cluster. During this one-hour webinar, Jim Lewis, instructor/course developer for … And speaking of PIDs, since the BCM is the module in charge of logic for this system, you’ll find up to 20 PIDs under a heading titled Charging Info when searching for charging system PIDs within the BCM. Keeping batteries charged with just the right voltage and maintaining greater than 80% state of charge (SOC) helps them last longer. If you’re working on a GM product, whether it’s a 1989 or 2004 model, you can determine with a simple test whether a charge problem is due to a defective alternator or a problem with one of those four wires going to the regulator. The L stands for “Lamp” and goes exactly to where you might think it would—to the charge lamp indicator. Load shedding has been a function of the body control module (BCM) in both the older CS series alternators (four-terminal regulator) and the newer Regulated Voltage Control (two-terminal regulator) systems. In addition to nurturing the battery into longer life by maintaining proper state of charge, RVC allows the charging voltage to drop below the 13.8 to 14.8 volts to which we’re all accustomed. The alternator’s pulley turns slower when the engine is idling, causing less output. As the alternator duty cycle changes, so does the alternator’s output. The system also monitors the battery to determine its condition and charge it in a way that prolongs its life. Every tech has heard an engine bog down when the alternator’s output ramped up in response to increased electrical load. In fact, when there’s a greater alternator load on the engine during deceleration, that load contributes to engine braking—something that’s good for brake pad life as well. If the first idle boost doesn’t do the trick, subsequent idle boosts are commanded before a more aggressive action is enabled—reducing power to certain power-consuming accessories, such as the rear window defogger grid. The reduced voltage provided by the test light will provide the necessary excitation signal for the regulator to come to life. MEDIA | This sensor stays powered up long after the ignition switch is turned off. If the CS series of GM alternators weren’t smart enough for you, we have the latest systems called Regulated Voltage Control (RVC) showing up on the scene in the mid 2000s. ET entitled “GM Smart Charging System Diagnostics.”. This means the battery puts out less voltage in cold temperatures and needs more voltage to charge. Smart charging refers to a charging system where electric vehicles, charging stations and charging operators share data connections. One change with voltage regulation did take place in the mid-’80s. Headlamp Mode. Okay, it’s time for a little more voltage now that the lights are on. If the alternator “sings” and your voltmeter jumps up to show charging voltage, the alternator is likely good and you must move your focus to the wiring leading to the regulator connection. If you are an installer looking to receive qualified customer leads for your EV inst The greater the current supplied to the slip rings, the more voltage (and current) the alternator puts out. Historically speaking, the description just given is pretty much the way it’s been since voltage regulators moved off the firewall and into the back of the alternator in the 1970s. In the previous article, we discussed the issues and operations related to the charging systems in common use today. GM's new wireless EV battery management system will help trim electric vehicle costs down to the bone, with an assist from Honda and Nikola. A case history demonstrating GM smart charging system diagnostic procedures. Next, connect the alligator clip of a conventional test light (not the newer LED style) to a nearby source of battery positive. Before you try to tackle these newer GM systems you should refresh your memory with a review of the older charging systems. ET entitled “GM Smart Charging System Diagnostics.” During this one-hour webinar, Jim Lewis, instructor/course developer for … You’ll see two things right off the bat on RVC vehicles tipping you to the presence of this latest technology: First, you’ll see a two-wire voltage regulator connection instead of the familiar four-wire connection. the problem is i think (not sure) that the optima battery is just so much better than the stock battery that when you turn the headlights on or the blower or the wipers (all these should trigger 13.9v charge mode). To keep this smart charging system visit manageable, we’ll focus on GM passenger cars and light-duty trucks. Before we venture too far out into the deep water on the latest charging systems… GM Smart Charge Systems with Dave Hobbs. The new GM charging system is actually called the electrical power management system. On some models the third terminal is marked I for “Ignition” and acts as a backup for regulator turn-on voltage should the bulb in the cluster fail to provide voltage to the L terminal. Unlike SI (series integral) alternators with the older two-wire regulators, the newer design CS series alternators eliminated unmanaged load dump (fast field ramp-up) that caused the rough idle and stalling issues when the electrical loads were suddenly turned on. Think of this as a mild form of what hybrid vehicles do with regenerative braking. Historically speaking, the description just given is pretty much the way it’s been since voltage regulators moved off the firewall and into the back of the alternator in the 1970s. You may encounter output PIDs in the section of the PCM titled Electrical/Theft. As with earlier non-RVC, four-terminal CS series alternators, the L terminal can be commanded on and off by going into the PCM and selecting output control. The letters P, L, F and S were stamped on these regulators to identify the terminals. These CS series machines gradually ramped up their fields with a 400Hz pulse-width modulated (PWM) output from the regulator to the rotor’s brushes. Pretty basic stuff, right? Some aftermarket alternator rebuilders try a little too hard to reduce their part numbers to a leaner inventory, creating alternators that charge but may not charge properly. Charging rates as high as 15 volts are observable on some vehicles, depending on current demand and battery SOC, along with values as low as 12.9 volts. Charging system problems may cause various vehicle issues, such as transmission shift and pressure control problems, DTCs, and driveability-related complaints. At-Home Charging for Electric Vehicles (EVs) | General Motors This is also a scan tool PID—nice to know when diagnosing a battery rundown problem on a RVC-equipped GM vehicle. Your test light will do the job of the cluster’s charge light. Although the BCM is the “brains” for the non-stand-alone RVC system, it’s the PCM that actually carries out the commands to control the L terminal with a PWM output to control the alternator’s charge rate. This allows a hybrid vehicle’s DC-to-DC converter to tailor a perfect charge rate into the vehicle’s 12-volt battery. The job of the voltage regulator has always been to control the amount of electrical energy (field current) in the rotor via electrical power supplied to the brushes on the rotor’s slip rings. If this circuit goes open, the default charge rate from the alternator is 13.8 volts. Be-fore we venture too far out into the deep water on the latest charging systems, let’s do a bit of review. https://www.freep.com/story/money/cars/general-motors/2020/07/31/ To accomplish these tasks, a rotating electromagnetic field called a rotor induces an electrical charge into three windings that are 120° out-of-phase. This may occur with the key on and the engine off. Helping the battery achieve the SOC goal has been the job of another smart charge feature called load shedding that has actually been around for well over a decade. If the battery can maintain an 80% SOC with 13 volts at a particular temperature, why would we want to charge it at 14.8 volts? The DC-to-DC converter receives serial bus messages from a BCM or PCM on the vehicle responsible for the equivalent of RVC functions. The difference now is this PCM connection to the regulator’s L terminal can inhibit sending the excitation signal to that circuit, which would prevent the alternator from charging. The lower the battery’s temperature, the lower its chemical and electrical reactivity. GM’s regulated voltage control systems changed in 1994 when they began using the BCM and the PCM. After the engine starts, the PCM uses the circuit leading to the regulator’s L terminal as an input. Faraday’s law of induction tells us why this occurs, but that doesn’t help the PCM with engine management. Batteries are sensitive to temperature. When you’re cruising in Fuel Economy Mode (lower charge voltage), you can charge harder during a brief period of deceleration without sacrificing fuel economy or overcharging the battery. Higher voltage comes at a price of increased drive belt load. Speaking of hybrid vehicles, DC-to-DC converters (high voltage in, conventional 14 volts out) come online whenever hybrid systems are powered up. This change caused confusion that has lasted until the pres­ent day, due to the variations of systems using one or more of those four-terminal regulators. The changes will be subtle, as the rate of change varies from 10 to 20mV per minute. The P stands for “Phase” and is the output of one leg of the three stator windings, giving a tach signal to a diesel engine controller. As electrical loads such as the headlights, blower motor or rear defogger are added, the regulator senses a reduced voltage and applies more power to the rotor, allowing the alternator to keep up with the electrical demand. If it doesn’t start charging, the alternator is definitely bad and it’s time to sell a new or reman unit to the customer. These fundamentals have changed very little until the last five years for ... Posawatz said that GM’s OnStar system can allow for communications, ... That could allow for much of the smart charging that could help stabilize the grid. That’s enough theory; now on to something practical! DETROIT and LOS ANGELES – General Motors and EVgo plan to triple the size of the nation’s largest public fast charging network by adding more than 2,700 new fast chargers over the next five years, a move set to help accelerate widespread electric vehicle adoption. Not a bad idea considering that many techs reading this have never seen the inside of an alternator, as the art of rebuilding has becomes a thing of the past for most shops. Although the image of a full field test with a pocket screwdriver making sparks in the D hole of a Delcotron is outdated, simple tests for outsmarting today’s so-called smart charging systems are out there for the tech who’s willing to learn what makes these latest systems tick. It does so to delay the introduction of field current into the rotor during engine start-up. Are You Smarter Than a ‘Smart’ Charging System. Don’t forget to look in the Body Controls section of your scan tool when clearing codes, in addition to the PCM. © 2021 Hearst Business Publishing, Inc. | Not a bad idea It was found that as engines became smaller and developed less torque, the sudden reaction to an increased load on the accessory drive belt sometimes caused a rough idle/vibration, or even engine stalling. Without going too deep into that, I’ll just say that GM had good reasons to use one, two, three or all four of those regulator terminals, so the one-size-fits-all reman part may give you grief. Privacy policy | Remember Faraday’s law? The PWM signal from the PCM to the L terminal on these two-wire regulators varies from 10% to 90%, with the latter being the higher voltage command (15.5 volts). To keep this smart charging system visit manageable, we’ll focus on GM passenger cars and light-duty trucks. Black Book. Every bit counts with today’s fuel economy goals. If this continues for very long, the battery can drop below the desired 80% SOC. To keep this smart charging system visit manageable, we’ll focus on GM passenger cars and light-duty trucks. Load shedding basically is a function of the BCM or another module on the serial bus (Power Mode Master) watching battery voltage and doing something about it if it gets too low. And thats what the Dealer told me they also printed me the Smart charging system specs/rule sheet that explains the different modes and what triggers the system to charge etc. Finally, touch the test light probe to the L terminal of the voltage regulator, as shown in the photo at left. Qmerit assists electric vehicle owners in finding certified home EV charging station installers in their area, that have been vetted, credentialed, and insured, to complete their residential EV charger installation. Depending on the model and year, the newer GM RVC charging systems may include up to nine different charging rates strategies, among them: Battery Sulfation Mode. No sense hammering a battery that has given up the ghost! Power steering pressure switches and a/c compressor request/control circuits all helped with idle quality, but there was nothing to tip off the engine management computer that an increased load was occurring from the alternator’s varying field current. The SARVC module is also known as a generator battery control module (GBCM) and is located within a list of body modules on the scan tool. On GM applications with Regulated Voltage Control, the Body Control Module actually oversees the charging system and determines the best charging rate for different operating modes. On RVC vehicles, you’ll see the charge voltage fluctuate while driving or even while running the engine in the bay. Not to be outdone, GM and others joined the ranks of OEMs using some form of strategy to tie engine management and voltage regulation together. We're sure you've got the smarts to handle that. On some systems you’ll see 15.5 volts with the engine running and a light electrical load applied. By knowing how these new systems work, you can keep outsmarting the latest smart charging systems that show up in your bays! The current sensor in the SARVC system is built into a full-fledged electronic module complete with a Class 2 serial bus circuit to receive and transmit information. If it sees a ground on that circuit, such as when the alternator senses a problem internally, the PCM then sends a serial bus message to the cluster requesting the charging indicator to come on. ¸SئU‡e[‚V`ÿ îhïô)‰~ê²_š²£ç´i*§ö¹ª Rdk“Äeùd¼ éÙÈeÞa;[©9Ú¼Mo‹¶cݨLs)2O#!ãšôÓÈá p´°(ª When the alternator is not charging, that L terminal will be grounded (the test light will glow), and when it is charging, the light will go off. GM working on ultra fast charging system for electric cars like the Chevy Bolt EV (Updated) Eric C. Evarts September 4, 2018 Comment Now! To understand where we are now, it’s important to know where we’ve been. called smart charging systems are out there for the tech who’s willing to learn what makes these latest systems tick. The National Institute for Automotive Service Excellence (ASE) is hosting a free webinar for service technicians on Friday, Dec. 4, at 4 p.m. While Chrysler did indeed use an external temperature sensor to sense battery temperature for its PCM-controlled voltage regulation, GM always used a thermistor built into the voltage regulator to sense underhood temperatures for charge rate compensation. Why would it do that? The primary missions for any alternator are to maintain a charge on the battery and keep up with the vehicle’s electrical accessory demand. Comparing with uncontrolled charging, smart charging will flatten the electricity usage peak by shifting the peak due to vehicle charging away from the peak due to other consumption. Second, you’ll notice a funny-looking sensor or module wrapped around either the negative or positive battery cable. Equipment from independent suppliers is not covered by the GM New Vehicle Limited Warranty. To be clear, GM’s RVC systems use alternators with field currents that truly are controlled by logic external to the alternator. Regulated Voltage Control uses information from the battery current sensor, calculated battery temperature and system voltage to determine what the perfect voltage to supply the battery with is. To understand where we are now, it’s important to know where we’ve been. It does not. When idling with a heavy electrical accessory load applied, the alternator may not be able to keep up, and the voltage to the battery drops below 12 volts. The answer is, in almost all cases, the L terminal. With a voltmeter connected to the battery, simply disconnect the voltage regulator, then start the engine. The PCM signals the voltage regulator to control the charging output of the alternator. These fundamentals have changed very little until the last five years for GM. Fuel Economy Mode. Alternators that put out less voltage help engines use less fuel. Eric C. Evarts September 4, 2018 Comment Now! This should tell you if you’re dealing with a good, old-fashioned alternator problem or a vehicle wiring or module problem.