General Question

intro24's avatar

Why do chargers over charge?

Asked by intro24 (1434points) August 10th, 2008 from iPhone

Are there common chargers out there that stop charging your electronics (phone, laptop, etc.) automatically after it’s got a full charge. If not then why?


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2 Answers

RandomMrdan's avatar

well…I wouldn’t necessarily say it over charges…more like, it takes it to a full 100% charge, and the moment it drops to 99%, it charges it again….I’ve never seen my phone go past 100% on a charge….so in a sense, it’s a continual state of charging, but never over charges. Simply unplug it when it is fully charged to reduce the chance of developing any sort of memory in the battery. ...on a laptop, simply take the battery out once you’re on a full charge, and just use the AC wall adapter. And once you’re ready to get on the go again, put the battery back in your laptop.

I’ve not seen any chargers that will turn themselves off once you reach a full charge, and then not recharge it once it drops below 100%. At least in the world of retail I haven’t seen anything like it. And as far as not having something like that…not sure, probably has something to do with the cost to benefit to include a feature like that. I have however seen chargers that will give a green light to indicate a full charge, and and orange/red light if it is charging still.

Hope it helped.

IchtheosaurusRex's avatar

Chargers for NiMH and especially Lithium Ion batteries regulate the charging current and will stop charging the batteries once they reach full charge. In a computer, the battery itself has a controller to disconnect the charging current once the battery has reached full charge. I’ve noticed that the charger for my Makita power drill will allow the battery that’s sitting in it to self discharge if I leave it in there for a long time; NiMHs self discharge over a period of weeks. I have to pull the battery out and re-insert it to get the charger to reset itself. Some power tools continue to use NiCds for that reason.

Lead-acid and NiCd batteries can be charged with just about anything that has an open circuit voltage greater than the open circuit voltage of the battery when it’s fully charged. Just a transformer and a diode will do, However, both types of batteries can be overcharged in this fashion, so you want to monitor how long you’ve charged them.

NiCds develop a memory effect. Other types of rechargeable batteries don’t; however, most should not be deep discharged unless they’re rated for it. Fully discharging a Lithium Ion battery can flat-out kill it. Lead-acid cells recover from deep discharge, but it shortens their lives. NiCds, on the other hand, need to be fully discharged periodically to remain healthy.

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