OT: Laptop batteries

[The Natural Philosopher]

Ok, that probably rules out virtualisation as the simple solution, then.

[John Walliker]

The Samsung N350 netbook has a BIOS option which allows the charger to stop when the Li-ion battery is 70% charged. Hopefully this will solve the degradation problem when the computer is continuously mains powered.

John

[Peter Crosland]

When laptop batteries were of the nickel-cadmium variety then continual charging was detrimental. The more modern lithium ion batteries are much more tolerant of being continually charged. The bottom line is follow the manufacturer's guidance.

Peter Crosland

[Grimly Curmudgeon]

I can vouch for the veracity of that 'common knowledge', at least as far as older laptops goes. I had an old Dell Inspiron that killed its batteries over a couple of months through me leaving it on charge 24/7 as I (wrongly) assumed the internal circuitry would look after the state of charge and protect the batteries from over-charging or discharging. With a new set of batteries, they lasted for years, only charging once a month if the laptop wasn't in regular use.

[therustyone]

you may find options in control panel; power setting for charging the battery, certainly on Sony and HP.

"Max performance" will charge the battery to max volts but reduce its life on continuous charge. "Max battery" or similar will stop charging a bit below max (80% charge on Sony's) and this should preserve it under continuous charge.

John

[Weatherlawyer]

No idea about the on offing bit but what operating system are you using. A lot of cheap 2nd hand laptops have come on the market in the last year or two with Vista on them. I imagine that farts methane like a big old dog.

An early version of Ubuntu should be a little lighter. And there are any number of cut down Linux distros for the brave.

[Andrew Gabriel]

LiIon batteries need a microcontroller to control their charging and it will prevent overcharging (because over charging will cause the battery to burst into flames).

You can charge them with a dumb analogue circuit, but then you have to charge them more slowly and you can only charge them to 2/3rds of their capacity, and given the importance of battery life in laptops, none are going to be designed that way.

You might decide not to leave laptops on charge for a long time just because there's always a small risk the power supply or charging circuit might fail when you're not there and do something nasty.

Also, if you are using a laptop battery of unknown condition, always make sure it doesn't self-heat when charging. For a working battery, charging is very efficient with almost all the energy going into the chemical energy storage and very little wasted as heat. If a LiIon battery is getting hot, it's not working properly, and the potential for a LiIon battery to turn into an uncontrolled firework if it goes wrong is too great to risk in my view.

[The Natural Philosopher]

raging oversimplification to the point of being essentially wrong.

The cell is never fully charged: there is a reasonably safe final voltage of about 4.2v. Simple constant voltage/current limiting resistor in series of 4.2v will fully charge EVENTUALLY. constant current with a

4.2v clamp will do the same, quicker.

It he cells are poorly matched, doing that to each cell; is optimal.

MOST of the smarts is there to prevent overcharging of a good cell when a pack is made up of series elements.

Plus thermistors to detect abnormally hiogh temps.

In My RC world that's a good sign its working very well indeed.

Packs after dumping their little all in under 4 exciting minutes may well be pretty warm.

and the potential

Mostly happens when charging, or simply as a result of getting really hot: the chemistry is crucial. Flammable organic solvent elctrolytes make good batteries and even better bombs. .

[Grumps]

Thanks to all that commented. Some interesting stuff.