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I am designing a glove-controlled robotic hand using Arduino UNO and XBEE. For the hand itself I am using the adafruit 16 channel PWM Servo Shield and using 5 SG90 servos for each finger.

My problem is that the USB ports of a computer will simply not provide enough power so I'm wanting to use alkaline batteries.

Would 4x AA provide enough power for the entire system, or should I use a 9V or even 12V battery?

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    \$\begingroup\$ The correct voltage is whatever voltage all those things require. The more important question is how much current is required to operate everything - that will determine the required battery capacity. \$\endgroup\$
    – Peter Bennett
    Commented Feb 26, 2021 at 3:43
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    \$\begingroup\$ It also depends how they are connected together. Surely the manuals of the products will tell how to use them and with which voltages? \$\endgroup\$
    – Justme
    Commented Feb 26, 2021 at 5:13
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    \$\begingroup\$ You should look at the specs for each device to make this determination. Many servos are rated to 6V but can handle a stack of 4 alkaline batteries without smoking. The Arduino and XBee, not so much. The ATMEL328 has an absolute maximum of 6V and will not tolerate 4 fresh alkalines (~6.5V) and the on-board regulator is not LDO and needs 7V to operate well. There are numerous XBee modules and some of them run at 3.3V and won't tolerate 5V. Datasheets are your friend. \$\endgroup\$
    – ScienceGeyser
    Commented Feb 26, 2021 at 5:17
  • \$\begingroup\$ Welcome to EE.SE. You may have noticed from the comments, that your problem in fact is a collection of different problems. Power management for a collection of circuits is a discipline on its own. From the way you asked your question I assume you could not anticipate that complexity. I seriously recommend to dig into textbooks or online tutorials. E.g. start here for an overview: baldengineer.com/regulator-basics.html \$\endgroup\$
    – Ariser
    Commented Feb 26, 2021 at 9:15

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Your best bet is some battery source and a regulator to put it down to 5V (it seems that all your gear is more or less 5V powered). It was already commented that some onboard regulator could need 7V, for example.

I would, however, worry more about your current budged, powering something like 20 servos will need probably more than 1A (check your datasheet)

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Sounds like a USB power bank might fit your needs, though if you attempt to drive all the motors at once under load it might be too much current.

At least the voltage will be regulated to 5V and the battery charge and protection will be taken care of.

The average and peak currents will determine how long a charge will last and whether the maximum output current is adequate respectively. One of those servos can draw several hundred mA under load, and you might be able to get 2.4A total out of the power bank, so it is not necessarily adequate.

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