Why do Rechargable Batteries Lose Their Capacity to Held Energy?

[Rhondazvous]

I have a talking book player with a rechargeable battery. It tells me how much battery power is left when I turn it on. I've noticed that whenever I inadvertently allow the battery to run dead, it's capacity to hold energy diminishes by several hours. Time alone doesn't seem to diminish it however. For instance, when I first got it, the battery lasted 28 hours fully charged. When I fell asleep and it ran dead, it would only hold 23 hours fully charged. Why?

[Faith No More]

Any battery issue is by definition a chemistry problem. In a healthy battery, ions flow freely between a cathode and an anode. Charging a battery forces ions from the cathode to the anode; using the battery reverses the flow.

Over time, this process wears out the cathode, which results in reduced capacity. A high-end lithium-polymer battery can lose about 20 percent of its capacity after 1000 charge cycles. Another way to think of this is to imagine that every time you recharge your laptop, you shave a few seconds off its maximum battery life. Erratic charging and heat speed up this degradatio

http://www.popularmechanics.com/technolo...e-6705747/

Google is your friend, you know.

[Jackalope]

Goddidit.

[vorlon13]

Batteries are not mentioned in Scripture so they are instruments of SATAN.

Thou art damned.

[AFTT47]

The one I'm most familiar with is lead-acid, like a car battery. Like most battery types, they suffer from self-discharge. In their discharged state, the lead can sulfate and harden which destroys its ability to store energy. It is different for other battery types but in all cases, permanent chemical changes occur because of age and heat. In most cases, being left in a discharged state is a problem too as well as being drained to the point where it's nearly dead even for a short time.

[ignoramus]

Rhonda, with modern lithium power tools, they don't like being drained completely.
In fact, the electronics in the battery packs cuts their power off at a certain level (when we think they are fully drained) so we won't drain them further.

Not sure if your gadget has this failsafe protection. Try not to let it drain completely if possible.

[Angrboda]

I think they just get tired.