# Please help me charge this phone battery... **URL:** \ **Category:** Factual Questions\ **Created:** [June 25, 2010, 8:57pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530 "2010-06-25T20:57:04Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [June 25, 2010, 8:57pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/1 "2010-06-25T20:57:04Z")
Please look at the back of [this battery](http://www.flickr.com/photos/49289187@N02/4734061362/). Now look at this [cheap charger from Hong Kong](http://www.flickr.com/photos/49289187@N02/4734074138), that came with the battery. How should I connected it? It doesn’t have any instructions, and if there are four contacts on the battery, which connect with the two contacts on the charger? The charger contacts slide back and forth, so they have to be positioned to the correct terminals. I guess it’s a “universal” thing. Can anyone help? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 25, 2010, 9:02pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/2 "2010-06-25T21:02:18Z")
Brought to you in “Blur-O-Vision” If I’m reading it correctly, the outer two contacts are marked + and -. I would use those. ---
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [June 25, 2010, 10:21pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/3 "2010-06-25T22:21:32Z")
> [@beowulff](#): > > Brought to you in “Blur-O-Vision” Sorry. > [@beowulff](#): > > If I’m reading it correctly, the outer two contacts are marked + and -. I would use those. Well, not really. The “+” and the “-” are just there, not underneath. In any case, what are the inner contacts all about, then? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 25, 2010, 10:24pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/4 "2010-06-25T22:24:43Z")
> [@guizot](#): > > Sorry.Well, not really. The “+” and the “-” are just there, not underneath. > > In any case, what are the inner contacts all about, then? They are usually there to provide a temperature reading from the battery pack. On some batteries, they connect to a “smart” battery controller. I don’t know which this pack has. ---
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [June 25, 2010, 10:41pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/5 "2010-06-25T22:41:00Z")
> [@beowulff](#): > > They are usually there to provide a temperature reading from the battery pack. On some batteries, they connect to a “smart” battery controller. I don’t know which this pack has. Okay, thanks. Now, short of using a multi-meter, which I don’t have handy, how can I know which of the terminals on the charger is which? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 25, 2010, 11:01pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/6 "2010-06-25T23:01:40Z")
> [@guizot](#): > > Okay, thanks. Now, short of using a multi-meter, which I don’t have handy, how can I know which of the terminals on the charger is which? Wow. I hope you saved some bucks on this charger. You could rig up a “science experiment” with a battery and an LED, in series with the charger, and see which direction makes the LED brighter. It might just be way easier to take it to a Radio Shack and use one of their meters. ---
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [June 26, 2010, 1:51am UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/7 "2010-06-26T01:51:52Z")
> [@beowulff](#): > > Wow. I hope you saved some bucks on this charger. Well, you know the deal. Let’s just say I rarely spend more on lunch. > [@beowulff](#): > > You could rig up a “science experiment” with a battery and an LED, in series with the charger, and see which direction makes the LED brighter. > > It might just be way easier to take it to a Radio Shack and use one of their meters. What if I try it one way, and then see if it works. If it doesn’t, then the other way is correct? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [June 26, 2010, 2:50pm UTC](https://boards.straightdope.com/t/please-help-me-charge-this-phone-battery/544530/8 "2010-06-26T14:50:48Z")
> [@guizot](#): > > Well, you know the deal. Let’s just say I rarely spend more on lunch.What if I try it one way, and then see if it works. If it doesn’t, then the other way is correct? If the positive terminal of the charger is wired to the negative terminal of the battery, the light will be brighter than if the negative terminal of the charger is wired to the negative terminal of the battery. You must use an LED with a current-limiting resistor, or you will burn it out. Also, LEDs only illuminate with the correct polarity, so make sure you have it wired right.