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I have an old tv with an IR remote control. It has become quite bothering for me to change the remote control's batteries every other week. I thought to myself why not connect a Chinese phone battery (which costs not more than 2 bucks) to the remote and I'd only have to recharge the battery probably every other week but that is would be wonderful because I don't have to get out of home to buy a pair of batteries.

I got a phone battery which is 3.7 and my remote control takes two AAA batteries (1.5+1.5=3). I thought why not? that 0.7 volts could not short circuit the remote. As soon as I wired the battery to the remote and I pressed a button, the remote's light turned on and that was its last breath. I put new batteries (AAA ones) in and I couldn't get it work again. I also noticed when I put the AAA batteries back in, the remote's IC was really hot. I can only come to conclusion (my Electronics not being that good since 7th grade) that 0.7 difference in voltage did indeed short circuit the remote.

But I am not going to give up. I have turned up here to find out how I can do this no matter how many remotes or batteries I am going to ruin.

Your help is much appreciated.

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closed as off-topic by tcrosley, Leon Heller, Ricardo, Daniel Grillo, Matt Young Feb 5 '15 at 13:28

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – tcrosley, Leon Heller, Ricardo, Daniel Grillo
If this question can be reworded to fit the rules in the help center, please edit the question.

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If you bought a rechargable battery that was listed as 3.7v it may have been a single cell lithium battery. The differnt versions of these can be listed as being from 3.3v to 3.8v output. However this output value is only the nominal voltage, (somewhat of an average). The actual fully charged state of these batteries may be as high as 4.2v.

So it seems you'll be buying a new universal remote very soon. To achieve better battery live you could try buying the special lithium batteries that are listed as 1.5v. These are available in sizes matching common tubular alkiline batteries and will last much longer. If you still want to go the rechargeable route look for the newer rechargeable alkiline or NiMH batteries, these are sometimes sold in packages with a charger included. Many fully stocked department stores carry these.

Last but not least, if you still want to do some extra testing first get yourself a small voltmeter. Test the output voltage of the batteries you intend to use. In some cases you might get away with placing a single doide in line with the battery. (for example if you had placed a silicone diode (eg. 1N4001) in series with your first battery the voltage would have been no more than 3.5v.) Each silicone diode placed in series will drop the voltage by about 0.7v. This methode is a bit wasteful as the extra power is just lost to heating up the diode slightly.

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Use a regulator to bring down the voltage from 3.7V (4.2V at maximum charge) battery down to ~2.5V. As for your remote, if you have to replace the batteries every 2 weeks, buy better batteries and a new remote... I use my tv remote daily and I only have to switch out the batteries... well, I got the remote 2 years ago with the cheapo batteries included. Still haven't changed them.

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