Battery Maintenance

[rleguillow]

So I have a question for all you electronics wizards out there.

I have a PRS-700 that is still running well, though the battery seems to be wearing out now (never did get two weeks or 80000 pages or whatever, but I manage okay with it).

Now I've purchased a PRS-650 that should arrive soon (eBay catch - sorry, not in a store somewhere). Not planning to give up the 700 at this point. I want it for the times when I do read in the dark, like waiting for a movie to start, or out on my porch far into the evening.

But I know batteries don't just hold charges forever - the charge seeps away. Which means I have to plan ahead for sitting on the porch, or leave it plugged in.

With these devices, does it hurt the battery to leave it plugged in when not reading it? So far the usual I've done is overnight, so I haven't a clue. I recall being told if batteries weren't fully discharged that they sort of forgot their real capacity... but I don't know what kind of batteries those were (if it was true at all).
I learn so much from these forums - I'm sure I'll get an answer for this one.

[delphin]

Originally Posted by rleguillow

With these devices, does it hurt the battery to leave it plugged in when not reading it? So far the usual I've done is overnight, so I haven't a clue. I recall being told if batteries weren't fully discharged that they sort of forgot their real capacity... but I don't know what kind of batteries those were (if it was true at all).
I learn so much from these forums - I'm sure I'll get an answer for this one.

Leaving the device plugged in will keep the battery topped off at 80% to 100% charge.

According to Wikipedia a lithium battery that is fully charged to 100% can loose a little capacity every year, but in practical terms it depends on where the Sony engineers set the upper charge termination point.

Sometimes for longer cell life in devices without replaceable batteries they set the upper charge limit a little lower than the actual 100% point to avoid the peak charge effect reducing the capacity over time, and if this is the case you can basically leave the device on the charger forever with no ill effects.

I had a cell phone that I left on constant charge every single day when not in use for several years on the same lithium battery, and at the end of that time the battery had lost only about half it's original talk time.

One thing you do want to avoid is letting the cells drop all the way down to fully discharged, which is many times more damaging and can destroy them quickly. The Sony will shut down before this point is reached, but if it is then not charged for several weeks, the small residual drain in the circuits can flatline your battery and kill it.

So by keeping it on charge, you could loose a little capacity over time, but very little, and it's better than the alternative of letting it go dead, because if that happens, particularly to an older battery, it may just die and never hold a charge again.

[Wordeater]

the battery on your 700 an Li-on battery or a Ni-cad battery. The two are not the same animal. Li-on batteries don't develop the 'memory' issue of previous generation rechargeables. I do believe you don't want an Li-on battery to go completely flat however.


WE

[Wetdogeared]

Originally Posted by Wordeater

the battery on your 700 an Li-on battery or a Ni-cad battery. The two are not the same animal. Li-on batteries don't develop the 'memory' issue of previous generation rechargeables. I do believe you don't want an Li-on battery to go completely flat however.


WE

The PRS-700 uses a Li-ion battery. I try not to discharge mine past one bar. I think it has been also suggested that if you plan on storing (not using) your reader for any length of time, the battery should be left at about 2 bars and the reader turned off, not just put to sleep.

[rleguillow]

Originally Posted by Wordeater

IS the battery on your 700 an Li-on battery or a Ni-cad battery. The two are not the same animal. Li-on batteries don't develop the 'memory' issue of previous generation rechargeables. I do believe you don't want an Li-on battery to go completely flat however.


WE

Yes - as Wetdogeared said, it is Li-on, at least according to the box. Sorry, been away for a day or two.

[rleguillow]

Originally Posted by Wetdogeared

I think it has been also suggested that if you plan on storing (not using) your reader for any length of time, the battery should be left at about 2 bars and the reader turned off, not just put to sleep.

WE, my memory is that to truly turn it off, you slide the on/off bar to the right and hold it for a few seconds, rather than just slide and let go? Sorry - can't check, don't want to disturb anyone going to get it.