# Time batteries may remain safely in charger **URL:** \ **Category:** Factual Questions\ **Created:** [November 21, 2004, 2:00am UTC](https://boards.straightdope.com/t/time-batteries-may-remain-safely-in-charger/275897 "2004-11-21T02:00:44Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![OliverTwistofLime](https://avatars.discourse-cdn.com/v4/letter/o/b487fb/32.png) [@OliverTwistofLime](https://boards.straightdope.com/u/OliverTwistofLime)\ **Post date:** [November 21, 2004, 2:00am UTC](https://boards.straightdope.com/t/time-batteries-may-remain-safely-in-charger/275897/1 "2004-11-21T02:00:44Z")
If this has been discussed previously, please direct me to the site. After my cell phone is placed in its charger turns from red light to green indicating that is fully charged, how long can I safely leave it fully charged in the charger? I remember that if one leaves rechargeable batteries in the charger after they are fully charged, that this is a no-no because this hastens the demise of the batteries. Pkease straighten me out on the above. ---
**Author:** ![rfgdxm](https://avatars.discourse-cdn.com/v4/letter/r/c0e974/32.png) [@rfgdxm](https://boards.straightdope.com/u/rfgdxm)\ **Post date:** [November 21, 2004, 4:19am UTC](https://boards.straightdope.com/t/time-batteries-may-remain-safely-in-charger/275897/2 "2004-11-21T04:19:31Z")
Simple answer: as long as you want. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [November 21, 2004, 5:57am UTC](https://boards.straightdope.com/t/time-batteries-may-remain-safely-in-charger/275897/3 "2004-11-21T05:57:47Z")
Yes, as long as you want. The green light indicates the charger has recognized that the battery is fully charged and has **stopped charging** it. (Don’t do this on old chargers, which don’t have any such indicator. They may be continuous chargers, which will damage the battery.) ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 21, 2004, 6:06am UTC](https://boards.straightdope.com/t/time-batteries-may-remain-safely-in-charger/275897/4 "2004-11-21T06:06:56Z")
Actually, the correct answer is “it depends”. On some chargers, the light turns green (or whatever color) to indicate not that charging has stopped, but that the charging rate has been _reduced_. Typically, these chargers will rapid charge the battery until it reaches ~90% capacity, at which point the charger will drop the charging current to a trickle to top it off and maintain the charge. Many, if not most, of these will not ever stop the charging current completely. Other chargers will shut off the charging current entirely when the battery has been charged to capacity. You should look in the user’s manual that came with your phone. Leaving your battery on a trickle charge for a day or so won’t degrade the performance significantly, as long as you don’t make a habit of it, particularly with the newer NiMH and Li-ion chemistries. ---
**Author:** ![vinniepaz](https://avatars.discourse-cdn.com/v4/letter/v/b4bc9f/32.png) [@vinniepaz](https://boards.straightdope.com/u/vinniepaz)\ **Post date:** [November 21, 2004, 6:13am UTC](https://boards.straightdope.com/t/time-batteries-may-remain-safely-in-charger/275897/5 "2004-11-21T06:13:35Z")
I put my cell phone on the charger when i go to bed, and it’s often charged before i fall asleep, but i dont remove it. Would this be bad for it? I’ve been doing it for a year now… I know that you said only some phone continue the trickle affect, but assuming mine does. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 21, 2004, 6:16am UTC](https://boards.straightdope.com/t/time-batteries-may-remain-safely-in-charger/275897/6 "2004-11-21T06:16:16Z")
If you’ve been doing it for a year, and haven’t noticed any adverse battery performance, I’d say either your charger isn’t overcharging the batteries, or the battery design is robust enough to handle your particular charging habits. I wouldn’t worry about it.