Why Don't My Batteries Last Long Anymore?
Rechargeable batteries are tricky little beasts composed of electrodes and electrolytes formed from assorted compounds such as lithium ion and nickel metal hydride.
As a side effect of the chemical reaction taking place inside, batteries heat up during operation, which causes the electrolytes to bend and warp. Recharging a battery reverses the chemical reaction, but it doesn't straighten out the plates. When a battery is used over and over, the continued warping starts to affect the chemical reaction, reducing the maximum charge the battery can hold.
Lithium ion batteries can typically survive up to 500 full discharges before losing enough of their maximum capacity to require replacement, but this depends on dozens of variables, including the battery's normal storage temperature. For example, leaving batteries in a hot car for an extended period could render them useless within about three months.
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