The phrase "an external power source" is correct and usable in written English.
It can be used when referring to a power supply that is not built into a device, often in technical or electronic contexts.
Example: "The device requires an external power source to function properly."
Alternatives: "an outside power supply" or "a separate power source".
Additionally, reducing the potential difference required to perform electroporation enables the development of electroporation devices that utilize small power sources (such as batteries), and could potentially facilitate the creation of electroporation devices that do not require an external power source (self-powered electroporation devices).
A typical, unrestored vintage camper may have a hand-pump sink with a small water storage tank, a kerosene or propane heater, a gas stove and a 110-volt refrigerator that must be plugged in to an external power source, and possibly even a propane-powered lighting system.
Zankel Hall should be a place where artists feel empowered without an external power source.
Electricity comes from three rechargeable batteries that plug into an external power source.
A PAPAW typically consists of an ultralight manual wheelchair with an external power source (batteries and motors).
When the battery is recharged, either by a car generator or by an external power source, the two chemical reactions are reversed.
Now, scientists have developed a simple, bootlike exoskeleton that can boost a walker's efficiency without any external power source.
It's expected to retail for £45 (and is available via Kickstarter pre-order for £35), and maybe best of all, it doesn't require a constant external power source, unlike a lot of similar options.
Considering the large number and small scale of sensors, the implantation of traditional power supply will be a big challenge, and developing self-powered sensors that can employ the ambient environmental energy and not dependent on a battery or external power source is highly desired [5, 6, 7].
Though some may prefer not having to buy batteries and keep changing them, the advantage for others is that if you're on the road where charging is impossible, or overseas without an adapter -- and even your external power source has run out -- a battery-powered charger will save you.
For those suspicious of the parachute solution, there's ResQline, a system, designed by a New Jersey company, that requires no external power source.
