Power supply question

[Delthefunky]

Just got a new laptop, and I have a question I've always wondered. Is it best to keep it plugged in as often as possible, or let the battery drain before giving it a full charge? Thanks.

[Canada 02]

lithium ion batteries do not have a memory effect, so full discharge is not necessary. in fact, full discharge of lithium batteries can be bad

[GoinAllTheWay]

Ya, Lithium batteries don't have memory but best not to let them run below 30% charge.

[sclitheroe]

Also best not to leave them at 100% charge all the time either - at full charge the cells are under a great deal of electrochemical stress since they have so much potential energy stored up. Wikipedia says a lithium ion left at full charge at room temperature loses about 20% of its capacity per year.

Probably not a bad idea to run unplugged once a week or so, draining down to around the 30% mark before plugging back in.

[GoinAllTheWay]

/\/\

Good to know.

[Hack&Lube]

If you are one of those people who leave the laptop plugged in all the time, remove your battery. The slow trickle charge will kill it.

Don't let the battery drain below 30%, it will impair battery life in the long term. Don't leave it plugged in either though, @ 100% capacity.

I usually charge the battery to 100% full and then physically remove it as long as my laptop is plugged in. I only plug the battery back in when I need to move or when I need it to be portable. I never discharge the battery below 30% either if I can help it.

[sclitheroe]

Originally Posted by Hack&Lube

If you are one of those people who leave the laptop plugged in all the time, remove your battery. The slow trickle charge will kill it.

I usually charge the battery to 100% full and then physically remove it as long as my laptop is plugged in. I only plug the battery back in when I need to move or when I need it to be portable. I never discharge the battery below 30% either if I can help it.

This is incorrect advice. Storing a lithium ion battery at 100% charge will still lead to irreversible capacity loss. The batteries should be stored in a cool location, with somewhere in the neighborhood of 40-50% charge.

Note also that many lithium battery packs have voltage monitoring and charge control circuitry in them that is active even when the battery is removed - in this case, a battery left out of a portable device for long term storage will easily be drained to a very low capacity, leading yet again to permanent capacity loss

Second, there is NO trickle charge built into any lithium ion battery system, to do so would cause permanent damage to the cells. When a lithium ion pack is 100% charged, it's done - no more current is supplied by the charger. The damage that you perceive to be from trickle charging is in fact from simply being allowed to sit at 100% charge for indefinite periods of time, in a warm environment (the bowels of your laptop).

Finally, a little advertised fact is that lithium ion batteries have a finite shelf life regardless of how you use them. They are basically degrading from the time they are manufactured, and will last 3-4 years before you start to see significant capacity loss, regardless of how many charge cycles you put on them. That's why you should buy a replacement battery pack when you need it, not before and then store it - you want something as new from the factory as possible..