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I have a project I am doing where I have to control three simple peristaltic pumps with an Arduino. Originally I started with cheap $13 6 V pumps powered with 9 V batteries which only worked for a day, then wouldn't even work when connected directly to the battery. The circuit works in Tinkercad, so I assume the system failed because the pumps were cheap.

I bought nicer 12 V pumps, but now I'm wondering what battery/power supply I should use to make these things run. Ideally they'd be as small as possible. The website says that it requires "0.7 A" at 12 V, but I'm not really sure where to find a battery to match those specs.

Here's a photo of the pump:

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    \$\begingroup\$ If by "9 V batteries" you mean PP3 batteries, then they only have a small amount of energy stored, so they would not last very long. Even more so after stepping down the voltage to the correct 6 V for the pumps. \$\endgroup\$ Mar 28, 2023 at 18:47
  • \$\begingroup\$ @AndrewMorton yes they are pp3, when i measure the voltage across the battery it says that there's still around 9V. it's only when i connect the pump that the voltage drops to almost nothing. how should I correct for this? im assuming by using something better than PP3s (whether for 6v or 12v pumps). Sorry if this is a dumb question, but I'm more of a software engineer who's doing some circuit stuff for my senior design project. \$\endgroup\$
    – JG98
    Mar 28, 2023 at 18:50
  • \$\begingroup\$ You would ideally need a mains-powered supply. Is that an option? \$\endgroup\$ Mar 28, 2023 at 18:59
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    \$\begingroup\$ Does this project have to be independently powered, or can you use an outlet? If you can, a simple 12VDC wall plug with a barrel jack would work. \$\endgroup\$
    – InBedded16
    Mar 28, 2023 at 19:03
  • \$\begingroup\$ @InBedded16 ideally it was going to be a portable battery, but if there's no reasonable way to do it with batteries I can use a power supply. The reason I used a battery is because I thought it wouldn't be an issue. \$\endgroup\$
    – JG98
    Mar 28, 2023 at 19:14

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Your setup didn't fail because the pumps were cheap, it failed because 9V batteries are not suited for motors of any significant size. Here are the discharge curves for a few different brands of PP3 9V batteries under 1A loads:

9V battery discharge curves

Image source: PowerStream - Testing 9 Volt Batteries for mAH capacity and voltage sag during discharge

You can see that the voltage starts well below 9V and very quickly (within seconds) falls below 7V and hangs out around 5-6V before falling off a cliff after a few minutes - 4.2 minutes for the Duracell - when the battery is considered "dead". 9V batteries are very well for smoke detectors or remote controls where the current draw is measured in microamps or milliamps, but for pumps you will need something designed for high current instead of longevity.

As you can also see from the curves, the voltage is not constant over the discharge range so you will also need to figure out how you want to deliver a relatively constant 12V to your motors. This is fairly easily accomplished with a DC-DC converter that can also boost the battery voltage. Fully-integrated modules are available that require no extra parts, just be sure to size it appropriately for both the continuous current draw of your motor and the initial starting surge of up to 3x the continuous current.

The very popular 18650 lithium-ion batteries have capacities ~2000mAh, an order of magnitude higher than a 9V and can handle 1A discharge rates easily. Some of them have integrated charge circuitry or I would find a charging system compatible with your batteries. Purchasing bare cells is not worth your time or effort. Wall warts are another option if the device doesn't need to be portable.

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  • \$\begingroup\$ thank you so much! Haven't tried the solutions yet, but it all makes sense. I greatly appreciate the detailed answer. \$\endgroup\$
    – JG98
    Mar 29, 2023 at 1:07
  • \$\begingroup\$ A power bank with a 12 V outlet would fundamentally have the same 18650s plus safety and charging circuitry, and the cost would probably be less than building it yourself. Also consider 12 V lead-acid (car) batteries. \$\endgroup\$
    – user71659
    Mar 29, 2023 at 4:40
  • \$\begingroup\$ For some projects, C- or D-cell NiMH would be a good option as well \$\endgroup\$
    – Chris H
    Mar 29, 2023 at 8:45

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