9V Battery With 5V Voltage Regulator?

[jedidove]

I just got my kit for Christmas and built it. Works great! I was a little surprised at the size of the board itself. The pictures made it seem a little bigger. I realized that it's really all to blame on the batteries in terms of size/weight. This got me thinking about powering it by a 9V with a 5V regulator. The 9V is a lot closer to the size of the board, plus the 5V would make it more powerful than the 2AA and even the 3AA (and much smaller). The only question I guess is would I need to put in a current limiting resistor? Or worse, is 9V current lower than 2-3AA? Would I gain significant power? Would I lose any longevity of components or battery life?

[franklin97355]

A 9v Energizer has from 400 to 600 mah while a AA has 1000 to 3000 mah according to their data sheets.

[richms]

9v are basically the most useless of batteries for anything but a really really small load. they have really high internal resistance since they are basically a stack of big coin cells or some really tiny things smaller than a AAA.

Since you are generally starved for current with things like this, a higher internal resistance will not help. It may work a little better, it may work a lot worse - the choice of cell will affect it a great deal.

But in anycase, I doubt any 9v will out perform 3 AAA nimh in series or a mid sized LiPo for this. Would be interesting to see what current you are taking in each case, but when I have tried measuring that sort of low voltage medium current on my elcheapo meter, the meter has had a large effect on the current consumed.

[Agent24]

Yeah a 9v Battery + 5v regulator would work, but it would probably go flat rather quick.

If you want a small battery, LiIon or LiPo would be the way to go, if you can find a pack small enough. Mobile phone batteries might be just the thing. But then of course you have to make sure you have the correct charger, so you don't blow the battery up.

I personally use 3x AA NiMH Cells (2800mAh) in my custom built TV-B-Gone, which work great.

[jedidove]

I knew 9V's were a bunch of AAAA's in series then packaged so I figured they might have pretty crappy current and capacity. The cell phone battery idea doesn't sound too shabby. It sounds like I'm probably best off with the AA's though for now. Maybe I'll do a cell phone battery when/if I decide to make a new one from scratch with an IR jammer built in.

3AA's is definitely too bulky. How big of a range difference do you see?

[richms]

Dollarstores around here have a USB plugged clamp to recharge any old cellphone LiPo - they are slow as (50mA I think) but they work fine, that and a found moble battery would be a great powersource for it. I am probably going to use some of my old BL-5c's from my old junk nokia to play with in the new year.

[Agent24]

3AA's is definitely too bulky. How big of a range difference do you see?

To be honest I have not really tested range. I chose 3x AA because I wanted to use NiMH and so with 1.2v per cell it made more sense to me to use 3 for maximum power.

The other thing is mine doesn't use the same LEDs as in the official kit, as I couldn't buy them in NZ, so that may change the range too.