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The (Charged) Word October 14, 2010

Posted by bobv451 in ideas, inventions, iPad, web & computers.
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Gordon seemed to think I was denigrating his technical knowledge. Not so. I was commenting more on the state of the field when this kind of info isn’t immediately available. I’ve known Gordon for, ummm, more than three decades and he is the go-to tech guru guy as well as a valued friend. Knows Apple products, works for Oracle–you know, those teeny little tech companies nobody’s heard of. Here’s what Gordon says about lithium ion batteries and it would seem to be Gospel. Live, it, love it, discharge it.

Here’s what he says:

Proper Care Extends Li-Ion Battery Life

“Perhaps one of the worst locations for a Li-ion battery is in a laptop computer when used daily on a desktop with the charger connected. Laptops typically run warm or even hot, raising the battery temperature, and the charger is maintaining the battery near 100% charge. Both of these conditions shorten battery life, which could be as short as six months to a year. If possible, the user should be instructed to remove the battery and use the ac adapter for powering the laptop when used as a desktop computer. A properly cared for laptop battery can have a service life of two to four years or more.”

“Always maintaining a Li-ion battery in a fully charged condition will shorten its lifetime.”

For increased cycle life

* Use partial-discharge cycles

Using only 20% or 30% of the battery capacity before recharging will extend cycle life considerably. As a general rule, 5 to 10 shallow discharge cycles are equal to one full discharge cycle. Although partial-discharge cycles can number in the thousands, keeping the battery in a fully charged state also shortens battery life. Full discharge cycles (down to 2.5 V or 3 V, depending on chemistry) should be avoided if possible.
* Avoid charging to 100% capacity

Selecting a lower float voltage can do this. Reducing the float voltage will increase cycle life and service life at the expense of reduced battery capacity. A 100-mV to 300-mV drop in float voltage can increase cycle life from two to five times or more. Li-ion cobalt chemistries are more sensitive to a higher float voltage than other chemistries. Li-ion phosphate cells typically have a lower float voltage than the more common Li-ion batteries.
* Select the correct charge termination method

* Limit the battery temperature

* Avoid high charge and discharge currents

* Avoid very deep discharges (below 2 V or 2.5 V)

Very deep discharges will quickly, permanently damage a Li-ion battery. Internal metal plating can occur causing a short circuit, making the battery unusable and unsafe. Most Li-ion batteries have protection circuitry within their battery packs that open the battery connection if the battery voltage is less than 2.5 V or exceeds 4.3 V, or if the battery current exceeds a predefined threshold level when charging or discharging.

Tomorrow, a thought on revitalizing those ghost towns.

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