please help in understanding internal resistance of a battery

[sidharth]

internal resistance of a battery ?
i understands internal resistance of specific materials wire, but battery

please help

tks
sid

 

[Nigel Goodwin]

Think of it simply as a resistor in series with one of the wires - but as it's inside the battery, you can't see it.

 

[sidharth]

so, it means , we have I max = V source / (R battery + R wire) according to ohms law,in acircuit with battery, wire, and compound resistance in series ?

tks
sid

 

[Nigel Goodwin]

Yes, all in series.

Usually the internal resistance is so low that it can be ignored - but as the battery dies it's internal resistance increases.

 

[sidharth]

thanks a lot.

sid

 

[RCinFLA]

There are several components to battery internal resistance. The effective resistance is the internal electrical connection resistance plus a complex relationship of chemical reactions resistance. High current draw can deplete the local chemicals and ions migration necessary to maintain current production so effective resistance goes up. After some rest time or lower current draw the kinetic movement will re-equalize and effect resistance will go down again.

All these kinetic chemical processes can be modeled as a series of different R-C time constants.

 

[sidharth]

thanks, understud

 

[Grossel]

Back on school, we tested and measured the internal resistance for different types of batteries. Don't assume the R'internal is constant. Mostly it vary as the load vary.

 

[colin55]

We say a battery has an internal resistance because, as the resistance decreases, a battery can deliver a higher current.
It follows that if a battery has zero internal resistance, it will deliver an infinite current. Since a battery cannot deliver an infinite current, it must have an internal resistance.