OK to leave in cradle for days?

[terrypin]

For days or sometimes weeks my iPAQ 2210 never leaves its cradle. Is that OK for the lithium battery? Presumably there's some intelligent charging, dropping to a trickle current?

What prompted me to ask is that over the last couple of years I've had two batteries go 'bad' on me. The last one ran out of charge after less than an hour recently, and I noticed it was slightly bulging in the middle. (BTW, that caused the battery cover to occasionally spring open, which I'd wrongly assumed was a mechanical fault.)

FWIW, both of these failed batteries have been the 1000 mAH replacements, 'new', bought on ebay.

Any feedback/advice would be appreciated please.

--
Terry, East Grinstead, UK

[nork]

If anyone has an answer to his question i would like to know about it too.
thanks

[Reid Kistler]

FWIW, read an article recently on one of the PC-oriented "magazine" sites that claimed a NOTEBOOK's battery could be harmed by leaving the unit constantly hooked up to its AC adapter / charger.

By extension, it seems logical that this should apply to PDA batteries as well....

(Personal experience suggests that running a notebook on battery power, on a fairly regular basis, DOES help extend battery life - but have not attempted a Real Study.)

[Sven Johannsen]

Let me take a stab. Note: IMHO, YMMV, and other assorted caveats. LIon were touted for their lack of 'memory'. That was normally associated with NiCads. That was the feature that caused them to assume you only wanted them to work for half an hour if you consistantly used them for half an hour and then recharged them. LIon also tend to maintain their charge, when not in a device, better than a NiCad, in the same situation. They also don't like to be fully discharged.

In my experience, you can leave LIon devices on charge for a significant amount of time...as long as...you pull them off and let them do their job periodically. That means let them run a device to near full discharge once in a while. Not full discharge mind you, but near full discharge, then charge it back up.

If you aren't going to be using the device for a period of time, it seems to be best to charge the battery, and remove it from the device. I've done that and put it back months later with just a little loss in charge. Unfortunately with an iPAQ 2210 (Pre-WM5), you get a significant loss in data, i.e. hard reset. I would recommend a good backup program. With newer devices, of course the persistant memory keeps it all good for you, and some devices (notably cell phones/smartphones) can actually be turned off, not just suspended. I've had smartphones turned off in a drawer for a month or two, and pulled them out, booted and had almost full charge available.

So, no, in my opinion/experience, LIons don't really like being left on a charger indefinately. It does appear to shorten their overall life, and their efficacy in use. But, it is not like you need to constantly cycle charge/discharge. If you let the thing do it's job every week or two, that seems to work.

As far as poor performance/bulging...not all batteries are created equal. Even good batteries can go bad, but there is a higher tendancy for those that grew up on the wrong side of the tracks.

[kdarling]

Li's persistent memory is of the digital sort. The onboard cpu calculates remaining power, but can get thrown off over time. Eventually it lies to the device, telling it that it's low on power when it really isn't. Thus a full discharge cycle is needed every month or two, to reset the calculations.

As for leaving it in the cradle, I do that for years with test devices. They seem to do okay, unlike my laptop batteries which fail after a year or so being powered all the time.

The key is heat. The more heat, the less time a Li battery lasts.

[nork]

So that means if you, say, a pda, you should let it drain the battery down to nothing once in a while? Is that what you are saying?
If you do that have to start from scratch to re-install any 3rd party programs after you have re-synched.
I have a pda, a Casio E-125. It has been happily working for me for, oh, about 7 yrs. I hadnt used it for a couple months and i went to turn it on and nothing happened. And i think i had disconnected the cradle in error so i think the battery ran right down.
I just ordered a battery for it, i hope thats the problem. I tried testing the battery with my limited knowledge of how to do that. Since there are 3 metal "fingers", i forget what they are called, i moved the test leads around and still got no reading so i figure the battery is dead.