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Battery dos and don'ts

Friday, February 1, 2019 - 08:00
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The demand on the vehicle's battery is increasing as technology continues to move us toward an all-electric future. Start/stop systems place additional loads that adds additional stress to the battery and modern charging systems are designed to supply just enough to keep the battery alive. Add to that the fact that modern electronics is less tolerant of weakness in the battery than ever before and you can see that it is important for us, as professional technicians, to be able to properly service and test them.

But what are the common mistakes we are making when servicing and testing batteries? What are the proper methods we should be employing? To find out, I talked to several industry experts and asked their opinions. Here's what I learned.

Be careful when taking your OCV measurements. If the reading is questionable, access the battery terminals/posts directly, especially on side post or remotely mounted batteries.

AGM or flooded?

According to Jim O'Hara of Clore Automotive, " The biggest issue we see when testing lead acid batteries...is being completely unable to identify the battery’s construction or misidentifying the battery’s construction. Digital testers rely on judgement maps for each of their testable batteries.  Identifying an AGM battery as flooded or vice versa could yield inaccurate results." O'Hara adds, "If a battery is truly bad, it likely won’t matter, but if a battery is marginal, it very much will. Also, many technicians have trouble with the terms AGM and Gel, thinking that AGM batteries are Gel batteries.  They are not.  Finally, many technicians do not properly identify spiral batteries as AGM construction.  Our testers have an AGM Spiral setting vs AGM Flat Plate setting to try to distinguish between the different types and make it clear to users that Spiral batteries are typically AGM construction."

My contacts at EnerSys, the makers of ODYSSEY batteries, echoed O'Hara's comments. "Identifying the type of battery the technician is dealing with is probably the biggest hurdle. Sometimes it is not clear what type of battery is in the vehicle, or what type of battery is supposed to be in the vehicle. Some vehicles come from the factory with an AGM battery, and must be replaced with an AGM battery. Gone are the days of buying the cheapest battery available that happens to fit. Always pay careful attention to the recommendation of the manufacturer.  This not only applies to battery type, but also CCA rating. Never put in a battery rated for less than what was original equipment."

Properly identifying the battery design is also critical when it comes to maintaining the battery, whether it's the responsibility of the vehicle's charging system or your shop's battery charger. Patrick McLaughlin, Exide Technologies Product Manager-Transportation, offers, " AGM batteries do not have maintenance requirements, however, the charging profile is different than a conventional flooded battery. AGM batteries are more sensitive to overcharge due (to) the internal gas recombination cycle. Some battery chargers will have Flooded and AGM settings which essentially toggle the maximum charge voltage up or down to match each technology." It's easy, then, to understand that misidentifying an AGM battery as a conventional flooded design and trying to correct a low State of Charge (SOC) with your old, high powered, shop charger will actually cause more harm than good.

Speaking of SOC

We all understand that one of the very first measurements we need to take when assessing the condition of the battery is the Open Circuit Voltage (OCV). But is your OCV measurement accurate and what minimums are acceptable before proceeding with further tests?

Davis Knauer, Vice President Automotive Battery and Diversified Products Engineering for East Penn Manufacturing has this to say, "Accurate testing requires a minimum State-of-Charge level. A rested open-circuit voltage (that means it's been over 24 hours since the battery has been exposed to charging) of 12.4 minimum is required for load testing."

Make sure that the battery mounting is secure to minimize the impact of vibration on the battery. If any form of deflector or heat shield was originally fitted, be sure to reinstall them as well.

Where you test can also have an impact on your test results. If you just brought the car in and connected your meter or handheld battery tester to the battery's cable ends, your test results may be suspect. This is especially true if you're trying to test a remotely mounted battery using the jump points under the hood. According to the pros at Bosch, "(When a tester is hooked up to the battery cables, especially side terminals), corrosion on the underside of a terminal, unseen by techs, can prevent tester clamps from making good contact. Techs should always clean terminals and cables prior to testing or replacing a battery."

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