3v coins cells to light a mini bulb, Need Help pls!

[Lorraine847]

This is probably rather simple, but I am having trouble and am asking for help.

I have a "mini lamp" (miniature light bulb) that I bought at Radio Shack, 1.5 volts - 25mA. I need to light it with a tiny battery so I've been looking at hearing aid batteries and small coin cell batteries. I need a battery that can fit into a spot that is 5/8", so I tried a hearing aid battery #317 23-816 1.5v. That didn't work, the light was extremely dim. I added another of the same battery by stacking (in a series), still too dim but better. I then tested it with a 3v CR 2025 lithium coin cell battery just because and that worked perfectly... but that battery is too large (it's about the size of a nickel). So I then tried a 3v CR 1025 23-791, too dim and it just dims out to nothing in about 1-2 seconds, added another, same, too dim and it turns off in 1-2 seconds.

What am I doing wrong?

And why does the smaller 3v battery (3v CR 1025 23-791) not keep the bulb lit? Even when I add another?

Thanks so much for any help you can give!
-Lorraine

 

[3lectrokid]

are you sure its only 25ma because that seems as much as a a small LED but a bulb turns about 95% of energy into heat. I'm guessing that the batteries are not powerful enough to power the bulb and are very quickly running out of power. hearing aids use minuscule amounts of power and so can last a long time without needing new batteries.

Dave

 

[Lorraine847]

Yup, 25mA. Does this mean that even adding more batteries won't help?

-Lorraine

 

[Reloadron]

This is probably rather simple, but I am having trouble and am asking for help.

I have a "mini lamp" (miniature light bulb) that I bought at Radio Shack, 1.5 volts - 25mA. I need to light it with a tiny battery so I've been looking at hearing aid batteries and small coin cell batteries. I need a battery that can fit into a spot that is 5/8", so I tried a hearing aid battery #317 23-816 1.5v. That didn't work, the light was extremely dim. I added another of the same battery by stacking (in a series), still too dim but better. I then tested it with a 3v CR 2025 lithium coin cell battery just because and that worked perfectly... but that battery is too large (it's about the size of a nickel). So I then tried a 3v CR 1025 23-791, too dim and it just dims out to nothing in about 1-2 seconds, added another, same, too dim and it turns off in 1-2 seconds.

What am I doing wrong?

And why does the smaller 3v battery (3v CR 1025 23-791) not keep the bulb lit? Even when I add another?

Thanks so much for any help you can give!
-Lorraine

Before all else you have a small incandescent lamp rated for 1.5 Volts at 25 mA (.025 Amp). You need a battery capable of 1.5 volts and the required current. Using batteries of a higher voltage will not get things done and if you find a 3 volt battery capable of the current the bulb will have a very short life before it burns out.

A CR2025 is a 3 volt battery and depending on manufacturer rated at about 160 mAH (milli Amp Hours). A CR1025 is a 3 volt battery but only rated at about 30 mAH. That is about 1/5th what a CR2025 is. This assumes brand new fresh batteries.

Unfortunately you have a situation where you have a tiny bulb that requires at least 25 mA at 1.5 volts. You need a 1.5 volt battery capable of likely 250 mA for decent operation. You have space limitations that really seem to preclude finding a battery that will work.

Again, you want a 1.5 volt and not a 3.0 volt battery. Your lamp is excessively loading some of your coin cell batteries. Thus the rapid dimming of the bulb.

Check the data sheets for various batteries.

Ron

 

[Lorraine847]

That makes sense Ron, thanks so much! I knew I was thinking about it the wrong way. That's why I initially bought the 1.5v hearing aid battery. I will look for a 1.5v battery with 250mA. This seems kind of hard to find, mA for batteries isn't readily listed, but I'll keep looking.

Another question along these lines, what if I use a 12v 60mA miniature bulb with a 12v alkaline battery (the one that looks like a AAA battery)? Do you think that will work?

-Lorraine

 

[Lorraine847]

Does a parallel connection increase mA while keeping the original voltage? If so, could I then connect a few small coin cells that will equal the 250mA and still be at 1.5v?

-Lorraine

 

[Reloadron]

Does a parallel connection increase mA while keeping the original voltage? If so, could I then connect a few small coin cells that will equal the 250mA and still be at 1.5v?

-Lorraine

Yes, when we parallel batteries of the same voltage we get that voltage but we increase the ability to deliver current. Now what you can do is if you have a battery part number for example CR2032 then you try Google with terms like CR2032 Data Sheet or CR2032 Specifications and that gets you data sheets just like this. The mAH ratings will vary slightly from manufacturer to manufacturer. There is a caveat to all this mAH stuff however. If a battery spec sheet says for example 250 mAH you get the warm fuzzy feeling the battery will deliver 250 mA to a load for an hour before it is dead and that is far from true. A Google of terms like Battery Discharge Rates should prove enlightening and informative. We won't get into it because there are hundreds of batteries with different compositions and discharge rates. For common batteries like a basic AA a Google of AA Battery Current gets you data sheets that look like this. So I hope all that helps a little.

Ron

 

[crutschow]

Another question along these lines, what if I use a 12v 60mA miniature bulb with a 12v alkaline battery (the one that looks like a AAA battery)? Do you think that will work?

If you can use an AAA size battery then why not use a standard 1.5V AAA alkaline battery with your 1.5V bulb? There is also an N size 1.5V alkaline that is shorter.

 

[4pyros]

Your inrush current may be killing your batterys. Paralleling batterys may help but can you use a LED? Andy