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"Following incidents involving batteries used in AT&T U-verse network cabinets, the company is replacing 17,000 similar batteries, all manufactured by Avestor," writes an AT&T spokesman, in an email to Light Reading.

"Normally, we would work with a vendor to diagnose problems and develop solutions. We can't do that in this case because Avestor filed for bankruptcy in October 2006 and closed shortly thereafter. As a result, we have decided to move forward with the removal of all Avestor batteries as quickly as possible," the spokesman adds.

AT&T says it has no immediate guess as to how quickly it can replace all those batteries. The carrier also declined to speculate on the costs of such an endeavor.

A company spokesman does note, however, that AT&T stopped deploying Avestor batteries during the first quarter of 2007. The company announced a new battery supplier in July 2007. (See AT&T Eyes Batteries in Explosion Probe.)

Whatever the timing and cost, it won't be trivial, according to industry analyst Kermit Ross, principal of Millenium Marketing.

"It's no small task to change out the batteries in thousands of remote cabinets, especially when many of them are already powered up and handling working U-verse subscribers," Ross says. "It looks like a multi-million dollar job, considering the cost of replacement batteries plus the labor to install them. They'll probably need to change the wiring to the batteries, too."

Bad Battery Background

AT&T's troubles with Avestor surfaced in October 2006, when an equipment cabinet exploded in a suburban Houston neighborhood, startling homeowners and ripping out a sizable chunk of fencing from one elderly couple's yard. (See AT&T Investigates DSLAM Explosion.)

In January 2007, another incident occurred just 20 miles away from the first one. This time the cabinet caught on fire, though that was quickly extinguished. However, the concerns about the safety of the batteries powering the cabinets kept growing. (See AT&T Confirms Second VRAD Fire.)

Following the first two Houston incidents, AT&T hired a leading scientific consulting firm to investigate the cause of the October 2006 equipment cabinet explosion and the January 2007 equipment fire.

The consulting firm, Exponent, concluded that the problems were caused by manufacturing defects, that the battery's safety features and overall design were "sound", and "concluded that the risk of hazardous failures with this battery is as low, if not lower, than the risk with alternative batteries." (See AT&T: Defect Caused VRAD Explosion.)

Light Reading requested a copy of the Exponent report from AT&T, but has not yet received one.

But Wait... There's More

AT&T now admits it had two more incidents before the end of 2007 -- one small fire in an equipment cabinet and one cabinet explosion. The small fire occured in one of AT&T's cabinets near Cleveland, the carrier says, though it won't elaborate on the location.

But on Christmas Day, a cabinet at the corner of 64th Street and North Avenue in Wauwatosa, Wis., exploded and burned violently, according to city officials and a blog post on SaveAccess.

Local officials there used Light Reading's reporting on the earlier cabinet fires to learn how Avestor's lithium metal polymer batteries had been a factor in previous AT&T equipment cabinet incidents. (See Exclusive Photos: Fire to the Node.)

In the Wauwatosa fire, the main cabinet door was "displaced and landed about 5 to 6 feet southwest of the cabinet," according to Assistant Chief Jeffrey S. Hevey, Wauwatosa's fire marshal, who spoke with Light Reading on Monday.

Hevey reckons the cabinet door, which probably weighs 50 to 60 pounds, was blown off during the cabinet's explosion because the "bolts and rivets were sheared off cleanly", which suggests "a sudden, powerful displacement."

The cabinet that exploded in Wauwatosa sat next to a two-story office building with an exterior brick wall, so the building only suffered water damage (as the fire was extinguished) and some melted vinyl shutters as a result of the fire. Though companies transporting Avestor lithium metal polymer batteries are required to adhere to special hazardous material (hazmat) procedures, Hevey says the scene of the fire wasn't treated as a hazmat fire because, "basically, we didn't know much about it."

Wauwatosa residents report that AT&T moved quickly on the scene, clearing the debris and installing a new cabinet within 7 hours of the explosion.

Now, all the controversy surrounding AT&T's cabinets has come full circle. The batteries, once deemed to be safe and sound by independent experts, have failed at least four times now, and the carrier has committed to continuing its removal and replacement of the 17,000 Avestor batteries spread out across its network.

On the one hand, AT&T pushed past the experts and is addressing a potentially huge public safety risk. "As we gained experience with these batteries, we felt that they no longer met our stringent safety and performance criteria," an AT&T spokesman told Light Reading on Monday.

On the other hand, Millennium Marketing's Ross says the carrier could have acted more quickly: "It would have been much less disruptive and costly to have addressed this problem a year ago, when it first cropped up."

— Phil Harvey, Editor, Light Reading