AnalogTalk

The battery discharging behavior changes with various parameters, such as battery chemical type, load current, temperature, and aging. The figure below shows the general behavior of battery discharging curves of several battery chemical types.  The battery discharging curve of most batteries is almost flat until it reaches about 80% of its full range, and then falls off sharply after that. Intelligent battery chargers, or delta V chargers look for this drop off.
Since the battery’s internal chemical reaction is largely governed by voltage and temperature, the battery discharging behavior is greatly affected by the temperature.  The low temperature limit is determined by the freezing temperature of the electrolyte.  Most batteries do not work well below -40°C.  The battery performs better at higher temperatures because the chemical reaction processing is accelerated.  However, the rate of undesirable chemical reactions increases and results in a decrease of battery life.  At extremely high temperatures, the active chemicals become unstable and can destroy the battery and your laptop.

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Battery Management

Sony has announced a new type of lithium ion rechargeable battery that greatly improves power and life performance (better stability for fewer exploding laptops of course).

The Olivine-type lithium iron phosphate used is a perfect cathode material due to its robust crystal structure and stable performance, even at high temperatures. These batteries have a high power density of 1800W/kg, and extended life span of approximately 2,000 charge-discharge cycles.

It is claimed that these new batteries will provide 80% capacity retention after those 2,000 charge-discharge cycles is also able to charge in a half hour. Power tools is an ideal use,where then it will gradually infiltrate its way to consumer electronic electronic devices.

More here

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MCP73213 LiFePO4 Battery Charger

We have all heard the horror stories of laptop batteries blowing up or favorite tunes players burning a hole through someone’s jeans. The reasons for the magic smoke escapes vary from poor battery cell construction to overheating and poor charging mechanisms, yet all agree: magic smoke should stay inside our electronics.  While it is up to battery manufacturers to cage the magic smoke inside the batteries, plenty can be done outside the battery to prevent smoke escapes from other parts of the electronic device.

Case in point: Overvoltage Protection (OVP) on a battery charger circuit. OVP allows the battery charger to shut down in case the input voltage goes too high and prevents the circuit from overheating. And, as we know, overheating is smokes’ most notorious escape accomplice.  The value added by battery chargers with this feature is fast making it a standard so in your next design make sure OVP is on the feature list.

If you’re like us, you work on a laptop and bring it to meetings to check the latest analog news (a.k.a. surf) while the managers drone. HP recently recalled 70,000 laptop batteries and now they’re recalling more!  To be on the safe side don’t use your laptop as a, well, laptop.

Hewlett-Packard Co, the world’s largest PC maker, is recalling 15,000 laptop batteries distributed in China because of a danger they could overheat, China said on Tuesday on its quality inspections web site. More here.

Also reminds us to look for features like overvoltage and thermal protection while designing the battery charging system for portable products.  Don’t want to get in HP’s hot situation.

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MCP73113 Li-Ion/Li-Polymer Battery Charge Management Controller with OVP