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I'm helping my brother (8) build a small toy car powered by a tiny 3V motor that we have at home. Most tutorials we've found on the internet suggest using a 9V battery, but never specify the voltage of motor they're using.

As I only have basic and theoretical knowledge in electronics, I'm assuming I should power the motor with equal voltage (3V). Could I use a couple of AAA batteries in series (which, frankly, I have no idea how to do except maybe use electrical tape to hold them together) to do power the motor? Would it be enough? Should we use the 9V battery instead?

I'm just... trying to make sure we don't hurt ourselves or burn the house down.

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    \$\begingroup\$ I would go with the AAA. The 9V would overspeed the motor. \$\endgroup\$ – DKNguyen Nov 15 '19 at 17:01
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Yes, supply approximately 3 V. (If you were to use higher voltage, you might need additional current limitation to avoid burning out the motor.)

You can connect AAA in series to add up the voltages, for example using a battery holder like https://www.sparkfun.com/products/14219 with a built-in switch:

AAA battery holder picture

You can also move up to AA for longer running time. There are many variants of battery holders available.

You will need basic soldering skills and it doesn't hurt to buy a cheap multimeter. I'd say you're running minimal risks with so low voltages. A 9 V battery will sting if you put your tongue to the terminals but that's pretty much it. Oh, and most people burn themselves on a solder iron once before learning to show proper care. You might be able to wrap the stripped wire ends on the motor terminals to avoid the soldering.

Have fun! :-)

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  • \$\begingroup\$ Thank you! I had thought those battery holders ran in parallel (because, well, they look parallel) but thank you for letting me know they run in series! We'll definitely try the wire wrapping method first, because I'm not sure I can control my brother with a solder iron. Hah. \$\endgroup\$ – AndiPandi Nov 15 '19 at 17:10
  • \$\begingroup\$ I'm not an expert but I think all of these holders are in series. \$\endgroup\$ – Anders Petersson Nov 15 '19 at 17:16
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    \$\begingroup\$ There's always oddball combinations, but for all practical purposes, yes, those holders are all in series. \$\endgroup\$ – TimWescott Nov 15 '19 at 17:40
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    \$\begingroup\$ Just a friendly safety reminder that when experimenting, please use standard 1.5V alkaline batteries instead of rechargeable batteries. Accidental short-circuiting of standard AA batteries is unlikely to cause much damage, but rechargeable AA batteries can provide much more current that it might heat up small wires red hot and melt the insulation around them. \$\endgroup\$ – Justme Nov 15 '19 at 23:19

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