Can I run different voltage LEDs off a 9V battery?

I have a small project that uses a 3 light LED list that runs off of 3 AAA (4.5V) batteries, but I also want to power a 12V LED string (for cars about 24" long) and I am uncertain the mA draw for either. This is for a follow-up to fine tune my son's 2014 Halloween costume.

I run the 12V string off of 10 LR-44 batteries and get about 3 hours use out of these, so I know the mAh draw is relatively small. I'd like to extend the use of the 24" string. The 3 LED light goes for days on the AAA's. 

Because both lights are used for the same application, I wanted to see if I could join them together in a single power source and power off of 1-9V or 2-9V (in serial for a total of 18V) batteries. I think my preference would be the 18V with an in-line resistor, but I do not know which resistor to use.

Is this the correct approach?

What are other alternatives?

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Wired_Mist2 years ago

It really depends on how much current your light strips are using. Without a doubt I sugest you use a 5v regulator for the lower power LED's. For 12v, I'm not sure about how much heat a resistor would create; I can see it getting toasty ! Try to find a 12v regulator with sufficient amperage at your local electronics store. My favourite is the 5Amp LM1084 only downside, it needs some extra circuitry to function. As per the battery, Personaly, I would use a small 12v sealed battery(Rechargeable, Bonus!). If it needs to be portable and you value lightweight over battery life your 2x 9V idea could work.

You will get a better answer if you could provide the current consumption, or the rating in watts would also help

Does anyone have any suggestions about how you would find things like current consumption of an LED array? I too am trying to find out how to power a series of LEDs (in my case it is a series of 24 blinking Pet Collar LEDs (e.g.

http://www.amazon.com/HomeFusion-Collar-Flashing-Flasher-Visibility/dp/B00L59NG3S) but there is no details anywhere about how much current it draws or what resisters are in them or anything. The original poster says specifically; "I am uncertain the mA draw for either". Many products, just don't have that information. So if it is important, how do you find out what it is?

A 9V battery is about the worst power source you can use. They don't hold much power. You would be better off with a battery pack of 6 AAA batteries. You'll need at least a 12V power source to run the LEDs. A voltage regulator may be needed to drop the voltage to a more reasonable level for the 3 LED light.

There are worst batteries in the amount of Power, but not in convenience and size ! ..... Plus you can get a 9 volt Lithium at half the weight, 5 X the Power and unfortunately nine times the cost.

I get over Four hours from 9V driving that six dollar 12volt 15 blue LED strip in my ible and it is really really bright at night and that is with a series diode in that is bypassed to flash the eyes. https://www.instructables.com/id/STYRO-ROBOT-HEAD-L...

Then there are small people like my grand son may Not want drag 6 individual AAA batteries around.

Finally I'm tired of everyone mocking the 9 volt.....

It is just a matter of preference which battery best suits the purpose intended.

Consider the energy is related to weight 68g not counting a 10g holder for six AAA and only 36g for you know what......

BTW that weight information was just gleaned from an electronic scale, powered by ..... you guessed it, A 9 volt battery for over three years !


............. Thanks for letting me vent :-)

iceng2 years ago

I suspect the 12 volt string has its own resistors and can run off 9 volts like this

But we need the current flow that feeds the 3 LED on 4.5 volts in order to size a resistor for the 9 volt battery..

iceng iceng2 years ago

BTW Major Tom ie Space Oddity is one of my favorite songs by Bowie


Step 7... for the above unworking link

iceng iceng2 years ago

Here is the image