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AGM Batteries and Electrical System Diagnosis


AgmReady_main_imageThis is the next in a series of articles that survey the latest thoughts and trending topics within the realm of vehicle electrical and electronic service. As we attend shows and communicate with technicians and shops via the phone and email, one of the key areas we are asked about is that of the AGM battery. Our first two articles address the AGM battery and its implications for aftermarket service requirements. From there, we move into the area of electrical system diagnosis with two great articles addressing different diagnostic issues.

AGM Batteries – A Comprehensive Guide
We’ll start with this comprehensive overview of AGM batteries by Ann Neal in the latest issue of Modern Tire Dealer. The article covers everything from what makes AGM batteries different from flooded batteries, why AGM batteries are becoming increasingly popular, the major advantages of AGM batteries and the service issues involved with them. Full disclosure: we were among several suppliers who contributed to this article.

Click the above image to view the entire Article.


AGM Batteries – The Straight Skinny on Service
This article, by Dan Marinucci on, specifically focuses on the issues related to servicing AGM batteries. Despite the fact that the article is over 2 years old, it is accurate, informative and current with today’s AGM batteries. It is quick and easy and well worth the read. It brings together many key aspects of AGM battery service, including this gem:

PL2510_A1“Fifth, be sure you’ve got an up-to-date battery charger that’s AGM-capable. You won’t regret the investment. Charging an AGM battery is similar to charging a traditional battery, but it’s difficult to charge an AGM unit completely—let alone do it quickly—without the appropriate battery charger.” We couldn’t agree more.
Read the rest of the article


13 Starting System Testing Tips
Another quick, easy and focused article, this piece by Andrew Markel from provides 13 Alternator and Battery Testing and Diagnostic Tips. Just like it says, it provides 13 tips designed to make diagnosing and servicing starting system issues quicker and easier. Number 9 is one we have focused on in the past and is well worth highlighting:

0-full-field“#9 Put The Car To Bed Before Testing For Parasitic Draw: As a rule, the key-off current drain on most late-model vehicles should be less than 50 milliamps (mA). But on some vehicles it might be normal to have even greater draws for up to 10 minutes after the keys have been removed from the ignition. During this period, the serial data buses could be communicating and performing some digital housekeeping. Also, systems like air ride, the evaporative emissions system and auxiliary water pumps could still be active long after the vehicle has been parked. This is why on some modern vehicles service information, an OBDII breakout box and a scan tool are necessary to solve some intermittent parasitic power drains.”  Read the rest of the article.


Electrical System Diagnosis Requires a Plan
Our last highlighted article is by Albin Moore, a frequent contributor to our blog, on In this detailed article, Mr. Moore makes the case for starting every electrical system diagnosis with a clear plan (often accompanied by a wiring diagram). He then identifies the most common electrical circuit problems: open circuits, short to ground, internal shorts between two wires in a harness or high resistance in the circuit. He wraps the article up with an example of an intermittent short circuit issue on a 1997 Subaru Outback, detailing the investigative process he used to identify the offending component. He concludes the article with a question:


1997 Subaru“The problem was found and fixed in short order. How long would this repair have taken without a logical diagnostic process?”
Read the rest of the article.





We hope these articles and resources are helpful to you as you diagnosis, repair and service vehicle electrical systems. Between the four above articles, there are many tips and tricks that could help you work quicker, smarter or more effectively. Please let us know in the comments if you find anything particularly useful. We’d appreciate it.







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