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So I know an average PP3 9-volt battery has about 500mAh of capacity. If I wanted to, for example, draw 3.5 amps, the battery would last about 8 or 9 minutes, though that would be assuming the battery is even capable of outputting 3.5 amps, which is what I'm worried about. I've looked up several datasheets including ones from Duracell and Energizer and none of them mention maximum current.

For the project I'm making, I have several options for parts that would have different loads on the circuit (rough calculations):

  • 26.45V @ 2.27A
  • 16.64V @ 3.54A
  • 10.56V @ 3.76A
  • 6.56V @ 8.90A

I want to use common batteries (like 9-volt) and stack them in series to get the needed voltage, I also would rather go a little over the needed voltage than under. So the 26.45V option is good because I can use 3 9-volts to get 27V, but the 10.56V isn't because one battery is too little and two is way too much.

All the batteries I've found are either common size, or car batteries that can output 1000 amps, I'm struggling to find something in between, or even know if the common ones can handle it.

With all that being said, how can I find out for a given battery what current it can handle, and what type of battery/how many would be best for my project given the several options for parts and loads.

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    \$\begingroup\$ You won't get that sort of current from a reasonable number of PP3s... Do cells like 18650 count as "common"? Don't forget that the discharge curve is not at all flat - your plan for 3x PP3 will hit 28.5v when fresh and unloaded (i.e: 9.5v per PP3), but will very quickly fall to below 24v (i.e: 8v per PP3), which may be unacceptable for your application. The key you're after is ESR which plays directly into current delivery and temperature rise. \$\endgroup\$
    – Attie
    Commented Mar 27 at 23:07
  • \$\begingroup\$ @Attie Thanks for the response, I have a few followups: 1. The device would only be running for 30 seconds at a time, and battery replacements wouldn't be too much of a problem, I'd just like for the batteries to be ones you could find in a Walmart or something (that's what I mean by common). 2. Looking back at the Duracell datasheet, it has nothing on internal resistance, but there is an impedance which is measured in "m-ohms" (I'm guessing milliohms). How would I use that to calculate the maximum current output? \$\endgroup\$
    – Ombrezz
    Commented Mar 27 at 23:51
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    \$\begingroup\$ @Ombrezz this site is not a forum... all info and all of the question must be edited into the question \$\endgroup\$
    – jsotola
    Commented Mar 28 at 0:05
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    \$\begingroup\$ How accurate does the voltage need to be? Batteries will drop voltage over time so the best bet may be to use a buck/boost converter to regulate the supply. That will also give you a much wider range of batteries to choose from. \$\endgroup\$
    – Finbarr
    Commented Mar 28 at 0:42

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Ability to supply current from a battery is limited by internal impedance of the battery. The impedance value is dependent on manufacturing technology and physical battery size.

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The first-order approximation of internal impedance is easily measurable with an ordinary DMM and a load resistor. Please start by visiting some introductory places like Sparkfun for explanations and examples.

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