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I know that is probably an extremely stupid question but Can I get 12V out of a 3.6V battery? I have a faulty LED hula hoop (which currently has rows of LED's, some broken!) and I want to insert a strip of LED's (Like theses ones (which say that they run at 12V)) but the battery I have in there at the moment is a 3.6Volt battery.

Is there anyway to boost the charge to make it work? What voltage do LED's usually run from?

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    \$\begingroup\$ The search term you're looking for is boost convertor. \$\endgroup\$ – Matt Young Jun 9 '15 at 19:12
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    \$\begingroup\$ The math for that strip is suspicious. Says .4 A per meter, so 24 W per roll, yet says 48 W, and if it works like it shows in the picture, should really be like 6 Amps or 72 W. \$\endgroup\$ – Passerby Jun 9 '15 at 19:49
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The listing says it takes 0.4A/meter @ 12v, which is 2A since the strip is 5m long; but elsewhere it says it takes 48W/5m which would be 4A. I'll err on the high side and use the 4A figure. That's 137 mA per LED since there are 300 LEDs, which seems reasonable for superbight LEDs.

You're not going to find a boost converter that can handle 4A. Plus, that would mean you would be drawing around 16A from your battery:

$$\frac{\frac{12v}{3.6v}*\times 4A}{0.85} = 15.6A$$

where the 0.85 represents 85% efficiency.

With one 1300 mAh 3.6v battery, based on that, it appears you'd be able to light the strip for a 5 minutes or so. But you'll never get 16A out of a single battery. So it ain't going to happen.

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  • \$\begingroup\$ Are you saying you cannot get 85% efficiency from a boost converter? \$\endgroup\$ – KyranF Jun 9 '15 at 22:08
  • \$\begingroup\$ @KyranF I was being conservative. I realize a lot of times it is the 90% range. In this case the number doesn't mater that much. \$\endgroup\$ – tcrosley Jun 9 '15 at 22:20
  • \$\begingroup\$ You could just add more batteries in parallel, since there are more than one battery the load will be less on each battery, i'd suggest atleast 6, 4 will do but battery's life will be shorter \$\endgroup\$ – bakriawad Jun 9 '15 at 22:54
  • \$\begingroup\$ @bakriawad A cell phone type 3.7v battery is typically around 1300 mAh. You can get 3 cells bundled together for RC use, rated at 4.5 Ah. So with two of these packs in parallel, you would be able to light the strip for 1/2 hour or so. That assumes you can draw 2.6A per battery, or 2C, which should be okay. OP didn't say how long he needed the strip to be lit, or how many batteries he's willing to use (the question says just one 3.6v battery). \$\endgroup\$ – tcrosley Jun 9 '15 at 23:39

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