Increasing DC (battery) voltage.. on the go!

Discussion in 'General Electronics Chat' started by ssj.long, Apr 29, 2011.

  1. ssj.long

    Thread Starter New Member

    Apr 27, 2011
    Heh, by on the go, I mean mobile application. (I admit, I have no idea how to do this, stationary or mobile.) I'm trying to wire LEDs to the underside of an umbrella. Kind of counterbalance the dreariness of days that warrant umbrella use.

    I was ready to use three AA batteries as the power supply but that's a little bulky for an umbrella - especially when you go to close it. Google became overwhelming.

    I read about operational amplifiers, transistors, NPN, transformers. Those all sounded very similar for my particular case. An inverter, a Cockcroft-Walton ladder.. no idea. A charge pump did sound more promising for this project. A switching regulator, DC bus, oscillator, etc. were all suggested to someone in a similar situation.

    Common collector circuits were where my eyes crosses and I decided to make this post. Think you could point me in the right direction or possibly make a suggestion for a particular component, knowing the situation?

    -oh, and in my travels I read that the voltage of a battery falls as it is discharged. Is that true too? How would I compensate for that?

    Thanks in advance - I just found this site a few days ago.. never have a lurked for such a short amount of time before I got interested enough to make an account! Well done, AAC.
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009

    Build battery storage into the handle (think flashlight)..
    Before you get crazy you need to decide how many and what size/type of LED's you want.. A single/small group of LEDs can run for a long time on a small battery without resorting to anything fancy..
    And yes battery voltage goes down as its discharged.. Typically that just means your LED's will get a little dimmer as the batteries start to die.
  3. ssj.long

    Thread Starter New Member

    Apr 27, 2011
    Unfortunately it seems like the handle will be too small. I was hoping for that too, to have a push button right on the handle. I may look for a different umbrella. Otherwise I'm going to be securing the battery holder further up so that it isn't visible and doesn't impact the opening/closing of the umbrella.

    But I apologize, I should have explained my plan more clearly. The SMD LEDs will be wired in vertical strips ( radial striations, not concentric circles.) I think I'll wait to receive and test the SMDs before deciding on a number. Most likely between 50-100; I'll test them on a battery prior to installation to see how they look at different periods in the battery cycle.

    I like the last comment too - I don't really want anything fancy. So there's no capacitor, minitransformer or something that could push 1.2v to 3.5? I'm willing to sacrifice some space seeing as it'll be taken up by more batteries otherwise.

    Thanks for the help!
  4. Audioguru

    New Member

    Dec 20, 2007
    100 LEDs at only 10mA each is a total current of 1A. Three AA alkaline battery cells can power them for about 10 minutes or 15 minutes with the LEDs dimming all the time.
    Four AA Ni-MH rechargeable battery cells can power 100 LEDs for about 1.8 hours per charge and the LEDs will not dim until near the end.

    Using a circuit to increase the battery voltage will simply use even more current and light the LEDs for less time. One AA Ni-MH cell with a circuit to stepup its 1.2V to 4V will have a current of about 4A and will light 100 LEDs for about 15 minutes per charge. You will see the LEDs dim all the time.
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    While current or voltage can be increased, POWER is a constant. The amount of power needed will not change no matter how you manipulate the voltage or current. Adding circuit parts, or components will only increase the amount of power 'wasted' as heat in those components and do nothing to change the original power requirements of your LED's.

    Use innovation and think of another way to add more batteries. Nothing else will increase the power reserve available to the LED's
  6. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    Good response, Kermit2... I will have to remember your answer, because this question arises often...