AGM batteries; what's all the fuss?

The following is a re-post of an article that appeared in partsandpeople.com on 9/1/15;
Are you charging and testing your customers’ batteries using the same equipment you were just a few years ago? If so, you may cause irreversible damage by using the wrong charger, and you may needlessly condemn a perfectly good battery by using an incorrect testing regimen.
As automotive manufacturers incorporate new fuel-saving features to try to meet NHTSA’s 2025 CAFE standard of 54.5 MPG, in many cases the construction of even seemingly simple components such as batteries has changed, and they now require more care and advanced equipment for maintenance and testing.
“Batteries are quickly evolving, and it’s going to be a task for everyone to keep up with. I think the systems are going to continue to evolve as manufacturers chase fuel efficiency,” said Jim O’Hara, vice president of marketing for Clore Automotive, which manufactures and sells the SOLAR brand of battery chargers and testers, among several of its product lines.
In an absorbed glass mat (AGM) battery, the electrolyte is no longer free to slosh about within the battery’s case but is instead absorbed by fine fiberglass mats surrounding each lead plate. Compared to its flooded lead-acid predecessor — the use of which is decreasing — the AGM battery offers a number of advantages, including a better ability to meet the higher electrical demands of accessory-laden newer vehicles.
AGM batteries have existed as a specialty battery for some time and were installed as OE in a small number of production vehicles beginning in 2001. But what is driving this industrywide evolution is the adoption of start-stop technology, which instead of idling the engine at a traffic light, shuts it down and restarts it as soon as the driver taps the accelerator pedal.
The different construction of AGM batteries requires different equipment to accurately diagnose them and to not shorten their life when charging, O’Hara said. The way chargers have been designed for 50 years, in which the charger’s amperage output decreases as the battery’s voltage increases, is now obsolete for those batteries, he said.
“All of the newer battery types cannot accept that,” O’Hara said. “Shops have to have an AGM-compatible charger, whether it’s a wheel charger, a portable charger, our charger or somebody else’s, you have to have it.”
Older-style electromechanical chargers have largely gone by the wayside at Clore in the past few years, O’Hara said. Today, most units incorporate microprocessor control for greater accuracy, in terms of both charging voltage and the charging process, using a precise charging algorithm.
As O’Hara explained, when an older-type battery charger is first put on a discharged battery, current input (amps) is high and voltage is low. As it nears a full charge, battery voltage can get quite high, which can damage an AGM battery.
“A flooded battery — and this is talking in really general terms — will take a charge well into the 15s, and even to 16 volts, even though a fully charged battery is 12.8 volts. It’s very forgiving,” O’Hara said. “That’s not the case with an AGM battery. If you talk to any of the battery manufacturers, they’ll tell you somewhere in the range of 14-14.7 volts is the top of the range at 70 degrees Fahrenheit.”
With “smart” microprocessor-controlled multistep charging, the technician selects the type of battery and the desired charging rate. The charger first enters a sensing phase, in which it inputs small pulses of energy into the battery to determine its condition, O’Hara said, adding that the chargers can charge all types of batteries: standard, AGM, gel cell, spiral wound, marine, and deep cycle.
“Then, for a known good battery, it jumps into the bulk charging phase,” he said. “That’s a constant current charging phase — that’s how we’re putting most of the energy into the battery. When the battery reaches approximately 90 percent state of charge, we switch from constant current – constant amperage — to a constant voltage absorption mode. We’re going to hold the voltage at a specific target based on the battery type selected and then let the amperage recede.”
The last charging phase is the completion phase, which used to be called “equalization”, O’Hara said, to get all cells to the same charged state.
For the average DIYer, Clore offers Charge-It-brand chargers with those features, he said. For serious DIYers and car care shops, it offers SOLAR brand chargers such as the 20/10/2-amp Pro-Logix 2320C, which are available for about $100 or less, and which meet California’s and Oregon’s requirements for efficiency.
Testing requires additional care
Further complicating matters, there is no universal start/stop system, O’Hara said. For example, GM models such as the 2014-and-up Chevrolet Malibu Eco and the 2015 Chevrolet Impala with the Ecotec 4-cylinder have both a start-stop AGM battery under the hood, and a traditional AGM battery in the trunk as an auxiliary battery for high-electrical-load conditions when the engine is not running. As another example, the 2015 Ford F-150 with the 2.7 EcoBoost engine relies on only one start-stop AGM battery.
Technicians need to be aware of how a two-battery electrical system works to properly diagnose a problem (often requiring testing of each battery) and to select the proper mode on newer equipment such as Clore’s SOLAR BA327, which tests 6- and 12-volt batteries up to 2,000 CCA, with an integrated printer to show the customer the test results. O’Hara recommended that technicians refer to their information provider for guidance on the testing regimen for each vehicle.
Clore believes in the benefits of digital testing, which include being able to reliably test discharged batteries in time-sensitive situations such as a retail customer at a parts store, O’Hara said. But for technicians who swear by the time-tested method of using a carbon-pile tester, Clore has also introduced updated models of those.
“We hear some say you can’t test an AGM battery that way. But we also hear the defense that ‘the job of the battery is to start the car. If it holds the load, what are you telling me I can’t test?’” he said.
‘Hood up: charger goes on’
With more and more vehicle systems relying on a fully charged battery for reliable operation, including braking systems, O’Hara said he sees an emerging trend: having a small charger in each technician’s bay so that a charger can be used to maintain battery voltage while the vehicle is being worked on.
“We’re seeing the role of the charger change,” O’Hara said. “Charging was always a reactive process, but really, it’s becoming a proactive need.”