# Two parallel voltage sources? What happens?

Discussion in 'General Electronics Chat' started by John5788, Jul 8, 2009.

1. ### John5788 Thread Starter Active Member

Apr 2, 2009
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0
I am curious what happens in a circuit like this:

PSpice wont let me simulate it, gives me an error.

What would happen if I built a small circuit like this? Does the 12V just end up charging the 5V battery?

2. ### bertus Administrator

Apr 5, 2008
15,796
2,382
Hello,

There will be a large current from the 12 Volts battery to the 5 Volts battery,
that is only limited by the internal resistance of the batteries.

Greetings,
Bertus

3. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,990
1,115
Added a small resistance in series with both voltage sources.
Then PSpice will simulate this circuit

4. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
515
Have you done any network theorems?

You can solve this using superposition, Kirchoff or Thevenin.

5. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,785
771
I doono about charging the battery but it will definitely blow it up in practice

Rifaa

6. ### viip Member

Apr 16, 2009
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practically due to internal resistances current will flow in to 5v battery....but still i think am gonna try it....lets see how will it smell during blowing job []

7. ### millwood Guest

I would put a resistor in serial with one of the batteries, like 10ohm 10w, or something like that.

batteries have very low internal resistance (from a few mohm to 30-50mohm, depending on the type). a 5v voltage drop over this kind of resistance will cause massive amount of current.

I see sparks, .

8. ### hobbyist Distinguished Member

Aug 10, 2008
772
61
1.) Who knows, since it's 2 electrodes seperated by a electrolyte, maybe initially it would act like a capacitor??? Before overheating......

2) .But then again when you do dc analysis (superposition) on it you replace it with a short.
So it would be a low value resistor in parrallel with the 1 K.

I say, # 2. is my final answer...

Last edited: Jul 8, 2009
9. ### Von Active Member

Oct 29, 2008
65
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Batteries are not equivalent to electrical "shorts".

Why do you expect it to ACT like (or simulate) one?

Do it outside!

10. ### millwood Guest

they are, at least during a short burst.

if you were to parallel two batteries, the current going from the high voltaged one to the low voltaged one will just be the voltage differential / total internal resistance of the two amps.

in this case, the total internal resistance is likely in the .1ohm range, and the voltage differential is 5v. so you are talking about a 50amp current flow.

spark!