Burned by lithium ion

You would think that as a person who has written about battery technology I would know how to get the most out of a cell phone battery.

But last week, just 10 months after purchasing an LG VX6100 cellular phone from Verizon Wireless, my lithium ion battery went dead. And it's all my fault. Sort of.

At the Verizon store last May I had followed the sales person as we circled around the store, gathering up all of the essential accoutrements for my new phone. There was the soft lambskin carrying case with the belt clip that I somehow lost in the laundry within the first month; there was the "hands free" head set that lets me legally chatter away while driving and ignoring the road; and the essential car battery charger.

That last accessory, the only one I ever really used, turns out to have been the cuplrit.

I knew from my discussions with Isidor Buchmann at Cadex Electronics that lithium ion batteries need to be treated properly. The batteries are good for about 300 to 500 full charges, says Buchman in his Battery University book. I knew they didn't like to be fully discharged. I knew that they could have "fuel guage" problems where the battery life indicator was out of sync with the actual charge level and that this could be remedied by periodically fully discharging the unit (Buchmann recommends a full discharge every 30 cycles). I knew that the battery, if treated properly, should last 2-3 years. So why did mine last 10 months?

I paid atttention when Buchman said "The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery." So when I travelled in the car I kept the phone plugged in, topping it off constantly.

Oops.

I knew that high charge voltages or charge rates can kill a battery. Was that the problem? I wondered whether I should have been plugging the unit into the cigarette lighter adapter instead of the higher voltage "accessory outlet" in the Subaru Forester.

I tried battery CPR and fully discharged the battery and tried recharging it. No luck. The battery was dead on arrival.

Then I called my local Verizon store and spoke to a technician. The problem, he said, is that only the VX6100's wall charger is smart enough to know when the battery is fully charged. "It knows when to stop," he said,  but the car charger doesn't. It just keeps charging away. That "forced charge," when applied every day, will wear out the battery prematurely, he warned. "Use the car charger for emergency purposes only," he advised.

In my case this story has a happy ending. Since the phone is in warranty, I can return the unit and as long as there are no signs of battery abuse (fortunately I didn't throw it against a wall in frustration) they will replace it free of charge. But I still have unanswered questions.

Why didn't they tell me about this potential problem before? Like, when they handed me the car charger? I found nothing about this in my manual and a search of the Verizon Web site also turned up nothing on the subject.

Then there is the obvious follow-up question: why doesn't Verizon or LG offer a smart car battery charger that avoids this problem?

The tech couldn't answer that, of course, but he did offer a few other tips, such as to turn off the phone when charging it overnight. That doesn't affect battery life but does allow the phone to "reboot" once a day to avoid freeze-ups. As to which outlet to use in the car, he said either is safe when used properly, but he recommended using the higher voltage accessory outlet, when available.

Just remember to unplug it before the battery is fully charged or like me you'll end up buying a new battery in 10 months.