Four Myths About AGM Battery Service

Four Myths About AGM Battery Service

Packing a lot of power for their size and weight, AGM batteries offer many benefits. Because they are relatively new to the market, we dispel a few AGM battery service myths.

battery-testing

Have you noticed how batteries are moving into the trunks and under the seats of more and more late-model vehicles? Chances are, if the battery is not under the hood, it’s an absorbent glass mat (AGM) or gel cell battery.

Packing a lot of power for their size and weight, these batteries offer many benefits. They are sealed, so in the event of an accident, acid won’t spill out. They can be installed at odd angles. And their lighter weight allows manufacturers to shave off a few pounds from the vehicle.

Because they are relatively new to the market, I’d like to dispel a few AGM battery service myths:

 

MYTH: You can use your regular battery charger on AGM or gel cell batteries.

False. These batteries like to be charged slow and low. Many AGM/gel cell battery chargers have microprocessors that collect information from the battery and adjust the current and voltage accordingly. Some have different settings for charging flooded, gel and AGM batteries. Overcharging can kill these batteries.

Also, alternators are not chargers. Don’t rely on an alternator to do the work of a charger. If a battery is discharged to the point that it cannot start the vehicle, use a charger as soon as possible to make sure the battery gets fully charged.

 

MYTH: AGMs and gel cells can be tested the same way as conventional batteries.

False. These types of batteries have lower internal resistance than flooded batteries. Older capacitance battery testers/analyzers may not be able to accurately read these batteries. Most new battery analyzers have a special mode for AGM/gel cell batteries. Old-school load testers might not provide conclusive results.

 

MYTH: AGM or gel cell battery replacement is the same as flooded battery replacement.

True and false. While the installation of the battery may be the same for the two battery styles, some vehicles require an extra step to tell the vehicle that the battery has been replaced. Newer GM vehicles have a battery sensor module on the negative battery cable, while Ford has its Battery Monitoring System. Other manufacturers have similar systems. These systems require recalibration with a scan tool if the battery is replaced. If the system is not recalibrated, the alternator might overcharge the new battery, causing the battery to fail soon after replacement.

 

MYTH: Voltages are the same when the vehicle is running on late-model vehicles.

False. Automakers are trying every trick in the book to increase fuel efficiency. The latest strategy is regulating the operation of the alternator. This strategy includes determining when and under what conditions the battery is charged.

A late-model vehicle could be running at idle with less than 13 volts at the battery, and the alternator light will not be illuminated. If the tech revs the engine, the voltage may not rise. But, when the right throttle, cruise speed or electrical load criteria are met, it will control the alternator and produce enough energy to accommodate the load and the battery’s state of charge.

These late-model vehicles can calculate what’s happening in the battery. Some systems are so sensitive that they can detect if the owner has attached wires to the battery posts to power aftermarket accessories. This is why a scan tool or modern, dedicated battery tester might be required to test and replace batteries in the future.

 

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Scan Tool Tech

While systems can and will differ, here’s a look at common ADAS features, their general configurations and calibration requirements.

scan tool tech

Advanced Driver Assistance Systems (ADAS) require the use of a scan tool for diagnostics, and the majority of the time, it’s required for post-repair calibration. ADAS, like any other system, requires a diagnostic routine, which begins with a base knowledge of the system. Knowing ADAS will help understand fault symptoms and scan tool data for the most efficient diagnosis.While systems can and will differ, here’s a look at common ADAS features, their general configurations and calibration requirements.Parking assist sensors, of which there can be more than one, are generally located in the front and rear bumpers. They are the inputs that affect active parking assist and parking collision warnings. Any time they are disturbed in any manner, a static calibration must be performed with a scan tool.Side object sensors, sometimes called collision avoidance sensors, are commonly located in the rear bumper. These sensors provide input for blind spot warnings, lane change alerts and rear cross traffic warnings. Static calibration with a scan tool is required when these are removed or replaced.Rear vision cameras will be located in the rear decklid, liftgate or tailgate, and act as either a backup camera alone, or part of a surround view system if the vehicle is so equipped. These cameras generally require a dynamic calibration, and no scan tool is required.A forward-looking camera is sometimes located behind the grille, and usually part of a surround view system. These too do not require a scan tool, but a dynamic calibration must be performed when they are removed or replaced.Different ADAS features may have dedicated control modules which can be located in various areas, often behind interior panels. As with most control modules, these require scan tool programming when replaced and, depending on the system, both static and dynamic calibrations may be required.The Haptic Seat Motor creates the vibration to provide a safety alert for blind spot, forward collision, lane departure, lane keep assist, parking collision and rear cross traffic warnings. These motors, sometimes called seat warning actuators, generally require no type of calibration.Cameras located in a sideview mirror are part of surround view systems. These require calibration when removed or replaced, but most of them dynamic, and no scan tool is required.The steering angle sensor located in the steering column is an input for lane keep assistance, and a static calibration is required with a scan tool any time it is removed or replaced, or any time a wheel alignment is performed.Last, but not least, is the front view, or forward-looking camera located in the windshield area. This camera is a vital part of adaptive cruise control, automatic emergency braking, automatic high beam headlights, forward collision and lane departure warnings, and lane keeping assistance. A scan tool and static and dynamic calibration are required after removal and replacement, but also after windshield removal or replacement, or any service that affects the ride height of the vehicle. TS

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