Powering two circuits from one battery

Discussion in 'Power Electronics' started by dooi, Aug 18, 2012.

1. dooi

4
0
Aug 18, 2012
Hi,
I'm a begginner here and hope someone can help.
I have two circuits, an RF receiver and an inline amplifer.
The RF receiver draws approximately 60mA.
The amplifier draws approximately 40mA.
I wish to house the two circuits in one unit and power by one 9V battery.
I am guessing that I can simply use resistors to balance the voltage / current, but not sure how to determine correct configuration.

Your assistance will be greatly appreciated.

Cheers!
D.

2. CocaCola

3,635
5
Apr 7, 2012
Skip the 9 Volt, it's energy inefficient for a 1.5 need...

You would be better using 2 AAA batteries in parallel, no waste and a longer rung time in nearly the same space as a 9V battery...

No need to balance the circuits or anything if you wire the batteries in parallel, the output will be 1.5 Volts nominal and you simply hook up both circuits in parallel to the battery...

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Last edited: Aug 18, 2012
3. dooi

4
0
Aug 18, 2012
Thanks CocaCola.
I thought a 9V would give longer run time, but if 2 AAA batteries will last longer, that's what I'll use.
I might even be able to squeeze in 2 AAs in the casing I have; I want to minimise battery replacements.

4. dooi

4
0
Aug 18, 2012
Scratch that re 2 AAs; Battery clip wont fit.
2 AAA in parallel it will be.
Thanks again CocaCola.

5. CocaCola

3,635
5
Apr 7, 2012
9V batteries have HORRIBLE run time... Compounded exponentially even further when you are wasting or converting 7.5 Volts...

2 AAA batteries as I have shown, will give you about 4-5 times the run time vs a 9V...
2 AA batteries wired as shown, will give you about 9-10 times the run time vs a 9V...

If you use an over the counter battery case, make sure to rewire it as almost all are series wired...

1,114
159
Aug 13, 2011
...which is difficult to do as often it requires cutting a hard spring wire in a difficult location, soldering near soft plastic and other difficulties. It will usually be easier to mount two single cell holders side by side than to find and purchase a parallel-wired holder or modify a series-wired holder.

7. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,481
2,830
Jan 21, 2010
Note that 1 x AA (if you can fit it) will be better than 2 x AAA.

The main reason is economic. AAA's cost more than AA, and if you're using them up twice as fast...

edit: using them up twice as fast, not because you'd be using 2 of them, but because individually they have half (or less) the capacity of an AA cell.