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Wednesday, June 27, 2007

Tech Tip: How AGM Battery Technology is Meeting Today’s Vehicle Demands


As featured in the June 2007 issue of Motor Age, WORLDPAC Training Institute’s (WTI) Rob Morrell discusses AGM Battery Technology.

Modern Battery Testing and Replacement

Batteries have been around for an amazingly long time, the oldest known discoveries are from 250 BC in what is now Baghdad, Iraq. The “Baghdad battery” was used for electroplating among other things. Batteries were rediscovered by Alessandro Volta in 1800, after which the volt was named as a unit of electrical potential.

Today, the pace of electronics development in cars and trucks has easily outpaced the battery technology needed to power all this advanced technology for any length of time. One historically recent improvement for the automotive world has been the use of AGM (Absorbed Glass Mat) batteries in the most sophisticated and power hungry vehicles. These batteries are more deep cycle in nature and considered to be more durable within certain parameters. AGM recombinant batteries have a very low internal resistance reducing heat during high charge/discharge levels and very low static charge loss of about 1% to 3% per month.

AGM batteries are used in vehicles with high potential load, therefore an AGM battery should only be replaced with another AGM Battery of equal capacity. This is a common mistake to replace an AGM with a regular wet lead acid battery and may destroy the regular wet battery within a couple weeks because of the high demands on it.

Charging of the AGM battery also needs special attention; the charging voltage cannot exceed 14.8 volts even for short periods of time without damaging an AGM battery. AGM Batteries can withstand very high charging currents but not voltage, a slow charge is always the best, most efficient practice. High heat from an engine compartment can also dramatically reduce the AGM battery life; these batteries were never designed for higher temperatures.

Testing a high capacity AGM battery can be somewhat tricky. You must begin with a fully charged battery (see ‘Battery Condition’ chart below), you can usually remove the surface charge by turning the key on for about three minutes. Conductance battery testers can usually work well if they have the right information, but appear to be more accurate with wet type batteries than AGM models; AGM batteries sometimes give false positive results. A load test is the best testing method to avoid unnecessary comebacks. WORLD SOURCE ONE batteries are exact fit quality batteries manufactured in the U.S.A.

AGM batteries should be load tested for 15 seconds at:
- 1/2 the CCA rating (Cold Cranking Amps)
- 3 times the Ah rating (Amp hour rating)
Note: The voltage must not drop below 9.7 volts for the duration of the test.

Battery Condition
12.65 V = 100% charge
12.45 V = 75% charge
12.24 V = 50% charge
12.06 V = 25% charge
11.89 V = 0% charge

For more information about WORLD SOURCE ONE batteries, click here.

For additional reading on batteries, click here to view ‘Why Batteries Are Dying Young’, a Motor Age article that was first published in the June 20, 2007 Scoop electronic newsletter.

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