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What is the max current I could draw from a 9V battery?  I'm looking to draw 150 mA aka 0.15A  from a power source.  Does a 12V battery have a higher current rating?

[Reply #1 on:]

What is the max current I could draw from a 9V battery?

I don't think the answer depends on which 9v battery you are talking about right? I can draw about 5ma out of my wimpy 9v battery and I think your super-duper 9v battery can do no better.

[Reply #2 on:]

If you are talking about a PP3 style battery, the alkaline version has a capacity of around 600mAH.  So for any sensible lifespan you are looking at a useful maximum of around 30mA.

Battery capacity is usually a measure of AH capacity and is based on physical size rather than rated voltage.  In essence a large battery has greater capacity than a smaller one of the same voltage and hence may be considered as capable of greater current capability.

As to maximum current, it all depends on chemistry, how long you want to draw current, how much money you have to spend, etc.  As a simple rule, I would suggest you use AH/20 as a useful yardstick.   The current versus AH capacity is not linear.  For example, taking the above example, you might only get 10 hours at 30mA (300mAH) but you might get 1500 hours if you only drew 1mA (1500mAH).

If you have a particular battery in mind, simply enter its model into a google search and somewhere in there you'll get an AH capacity rating (that's what I did to establish the first line, above)

[Reply #3 on:]

What is the max current I could draw from a 9V battery?  I'm looking to draw 150 mA aka 0.15A  from a power source.  Does a 12V battery have a higher current rating?

Depends on the specific battery you are talking about. A 12vdc lead acid car battery can supply a lot more continuous current then a much smaller 12 volt battery. Small 9 volt batteries are designed to power smoke alarms for a couple of years but won't supply 150ma for even a day.

Lefty

[Reply #4 on:]

Here is the datasheet for a Duracell 9V battery.  They don't list a "maximum" current.  From the graphs, at 50 mA it looks like you are down to 7V in 5-10 hours.   

[Reply #5 on:]

What is the max current I could draw from a 9V battery? 

As much as the battery technology of the 9V battery will allow. If you mean those small square 9V batteries then not a lot for not long. However, if you mean a Lithium Polymer battery then in excess of 10 to 20A .

[Reply #6 on:]

Here http://data.energizer.com/PDFs/522.pdf is the datasheet for the Energizer alkaline 9V battery. Here http://data.energizer.com/PDFs/la522.pdf is the one for the lithium version. You can get the answer to your question from these sheets.

For 150mA @ 9V, consider using 6xAA cells instead.

[Reply #7 on:]

why does the slope on the constant current performance decrease instead of increasing over time?  The lines start at around 80hrs.  

Will a 12V block battery with coiled terminals provide 150mA?  You know the 6 inch tall by 3.5 inch width battery sold at Lowes Hardware Store.  I'll use alligator clips from it to the breadboard (+/-) rows.

[Reply #8 on:]

12V block battery with coiled terminals

Are you perhaps talking about a lantern battery?
http://www.newark.com/energizer/529/alkaline-battery-6v-lantern/dp/02H5588
They typically can supply power in the 10-25 AH range, depending on their chemistry. But they are usually only available in 6V sizes. When you move up to the the 12V sizes, they switch to bolt terminals.

[Reply #9 on:]

That sounds like it can just barely draw 150mA aka .15A from this 6V lantern battery.  Doing the math i get .25Ah/.15A=1.7h which is fine for the project I'm doing.  I could just disconnect battery when not in use.

[Reply #10 on:]

Which lantern battery are you looking at?
The one I referenced is capable of 26 AH, not .25AH.
It should last around a week at 150mA.

[Reply #11 on:]

oh yeah, you're right!