# Internal resistance of batteries

Discussion in 'Electronic Components' started by Norm Dresner, Sep 17, 2004.

1. ### Norm DresnerGuest

In "The Art of Electronics" [Horowitz & Hill, 2nd Ed, p9], they state
"For example, a standard 9 volt alkaline battery behaves like a perfect
9 volt voltage source in series with a 3 ohm resistor ..."

Where can I find information on the internal resistance of other battery
types and voltages?

TIA
Norm

2. ### Watson A.Name - \Watt Sun, the Dark Remover\Guest

It depends on the state of discharge of the cell. Any info you get
would be for the average of many cells, and your particular cell could
vary widely from that average. ALkalines are much lower than
zinc-carbon. You can calculate the value for a cell by doing this:
http://www.buchmann.ca/Chap9-page2.asp

3. ### Tim ShoppaGuest

For a while . There are battery specifications that go into far more
details, if you really need them. The usual assumption is that
the internal resistance remains constant as the battery is discharged
but it goes up as the "perfect battery" inside goes down in voltage.
Unless you have an esoteric (but becoming more common) pulse application
the published discharge curves are quite usable.
The big-name manufacturers are pretty good about offering tech information
on their websites, e.g.

http://data.energizer.com/batteryinfo/application_manuals/cylindrical_alkaline.htm

http://data.energizer.com/batteryinfo/other_available/datasheet.htm

and other links on that site. Often you don't see all the numbers
for the 9V models but they are "just" 6 AAAA in series most of the time,
and sometimes they offer the numbers/graphs for the AAAA's.

Tim.

4. ### Tim ShoppaGuest

For some purposes, this is all the data you need. For most purposes,
a discharge curve is more useful. For more esoteric stuff like
pulse applications you can either synthesize the supplied information
into a good guess, or measure your own discharge curve for your unique
application.
For example

http://data.energizer.com/batteryinfo/application_manuals/cylindrical_alkaline.htm

http://data.energizer.com/batteryinfo/other_available/datasheet.htm

Different manufacturers offer different levels of detail (from zilch
to excellent).

Tim.

5. ### Ross HerbertGuest

|In "The Art of Electronics" [Horowitz & Hill, 2nd Ed, p9], they state
| "For example, a standard 9 volt alkaline battery behaves like a perfect
|9 volt voltage source in series with a 3 ohm resistor ..."
|
|Where can I find information on the internal resistance of other battery
|types and voltages?
|
| TIA
| Norm

Some good info here http://www.buchmann.ca/

Haven't read it myself so can't comment on whether it has everything
you want to know.

their new hand-held battery analyser (CA-12) which reputedly gives an
asessment of Cold Cranking Amps CCA and Reserve Capacity (RC) for
automotive and other industrial batteries.

7. ### Norm DresnerGuest

Looks like some good stuff there. I'll browse later when I have the time to
explore.

Thanks
Norm