# Voltage sources in parallel [duplicate]

This question already has an answer here:

If we attach two voltage source of same value than what happens? I mean what's the difference between using a single voltage source and two same valued voltage sources in parallel? As they both supply same voltage in the circuit.

## marked as duplicate by Dmitry Grigoryev, JRE, Voltage Spike, Dave Tweed♦Dec 20 '16 at 1:46

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

• – Amit Hasan Sep 8 '14 at 6:17
• Is this a theoretical question or does it apply to batteries (a significantly different answer). – Andy aka Sep 8 '14 at 7:24

## 2 Answers

Then you'll have the same voltage, but with more available charge, i.e. hooking up 20 AA batteries in parallel will still have a 1.5 volts across the load(for ideal batteries), but it will take a lot longer for that pack to drain than it would a single battery. Those batteries will also be able to supply more current than a single battery.

Theoretically:
It makes only sense to put voltage sources in parallel if they have the same voltage, otherwise there would be infinite current (ideal voltage soucre can provide infinite current).
Two voltage sorces in parallel is exactly the same as one.

Practically:
Real voltage sources always have internal resitance or can simulate an ideal voltage source only up to some maximum current. So it makes sense to connect two voltage sources in parallel to increases the maximum current that can be provided.
(If both sources don't provide exactly the same voltage precausions have to be taken that the maximum current isn't exceeded just by compensation the voltage difference. E.g. by adding a small resistor in series to both voltage sources).