Re-chargeable batteries

[FrankSG]

I have a question for anyone who knows anything about re-chargeable batteries. I have a flashlight that I plug into an electrical receptacle to charge the battery. When the battery is fully charged, I unplug it. It then sits around for quite awhile before I use it. Sometimes, by then the batteries have lost their charge. My question is: If I just let it plugged in and never unplug it, will that harm the batteries after a period of time since it is constantly plugged in? Thanks
~Frank~

[jlreich]

Hi Frank.

I haven't had such a device for awhile, but when I did I just left them plugged in at all times so the batteries were charged when I need them.

If you still have it, take a look in the manual. It should say if it is OK to leave it plugged in all the time or not.

Hope that helps.

[mjc]

That is a big maybe...

It depends on battery type, charging circuit in the flashlight...phase of the moon and whether or not it feels like it.

Seriously, some types of rechargeable batteries can handle it, some can't. Some rechargers are built to run that way...plugged in all the time, fully regulated charging circuit that can tell how much charge they have and vary its out put to keep them full without overcharging...

[malcore]

Overcharging batteries can reduce the capacity of the battery. Like mjc said, chargers vary. Some use trickle charging, some have a microprocessor that reads a battery's charge and regulates the recharge and some just assume the battery is spent and charge at full rate. If you are not sure what type of recharger yours is, the best thing to do to help keep a fully charged battery from losing capacity is to store it in the freezer after charging.

Some FAQs here: http://www.greenbatteries.com/bachfa.html

[FrankSG]

Thanks for the feedback. After reading it, I decided what I'm going to do. It's pretty old and I probable don't have the manual anymore--and I'm probably due for a new one anyway. So, I'm just going to let it plugged in. If it ruins it, I'll have and an excuse to buy a new one. I'll then read the manual.

[pangea33]

Seriously, some types of rechargeable batteries can handle it, some can't.
Older Nickel Cadmium (http://en.wikipedia.org/wiki/Nickel-cadmium_battery) batteries are the ones with charge memories. If they aren't fully discharged periodically, they'll begin to lose their charge very fast. They're really harmful to the environment too, and many people don't bother to dispose of them at a recycling facility. The newer Lithium ion (http://en.wikipedia.org/wiki/Lithium_ion) batteries are now the most commonly used, they're safer for the environment, and they don't have the problem with charge memory.

I'll wager your old flashlight uses NiCads, and also that it's about shot from remaining plugged in all the time. A replacement shouldn't be too expensive though.

[PrntRhd]

My preferred flashlight is the new type with LEDs for the light and a shaking (induction coil) mechanism that charges a capacitor and hold the potential for 5-10 minutes at a time. Never goes dead, no NiCad problem.
http://www.lnt.com/product/index.jsp?productId=2151044

[mjc]

I like the crank ones better than shake ones...