Battery life myths

All of us have heard the conventional wisdom that you should never keep your batteries plugged in to charg to max for extended periods of time. Suypposedly, doing so will weaken the battery so that when you do go roaming away from the plug, you won't get as much charge. That suggests that batteries are like muscles - you need to work them out to build them up.

Is that true? My sister bought her 700m and asked me this question so I turn to the Collective here for discussion.

My first reaction was, that must be a wive's tale. But then again, batteries are essentially chemical in nature, and there could be saturation effects. I'm not a chemist, as is probably obvious

I do have a 3-year old Dell D800 which spends 99% of its time plugged in, so this question is not purely academic for me either.

 

Well, leaving the battery in while on AC does nothing, the connection between AC/Battery automatically cuts off once the battery is full.

Hmmm, I'm not sure about the chemistry of it, but from what I've tried, the battery lasts just as long on the 1st charge to the 25x charge.

Then again, it's still too early to say.

 

Oh, you'll have to search the site, but I recall some pretty lengthy and detailed threads covering batteries. As I recall, the significant effects were time and heat. Li-ion batteries start to gradually lose performance from the minute they come off the factory line. The rate probably accelerates between 1 and 2 years after you buy it, which would account for why manufacturers only warrant the battery for 1 year. Ivan at P1 told me to expect a solid year, maybe as long as 18 months before battery performance gets bad.

The thread I refer to also mentioned that letting the battery get really warm can also degrade performance.

And, lastly, when my N5010's battery life started to degrade, I did a little bit of searching and found that batteries are also rated for current draw. Ask a battery to supply more current than it's rated for and you will quickly degrade it's performance. I suspect that may be one reason my battery hasn't lasted very long. I may be exceeding the current rating for my battery. I'll have to look into that and see...