Any USB passthrough can be plugged into either a computer or a wall outlet (with an adapter). [A
2 amp AC to USB Adapter, such as the one sold by
MadVapes, is recommended ... and is required for certain passthroughs.]
In general, there are two types of PT those
with batteries and those with
out. The
battery PTs (such as the eGO PT shown above and most 510 PTs shown below) provide constant power at the same ~3.3V as the 510 or eGO battery.
Those with
out battery deliver up to 5V (full 5V when connected to a wall outlet; somewhat less when plugged into a computer).
You're probably thinking of the eGO PTs, which function either as a regular eGO battery or PT. When used as a PT, they have no greater "power" than any other eGO, but the mAh (i.e., how long you can vape between charges) is, in a sense, infinite (or, at least, until the battery goes kaput). When used as a regular (untethered) battery, most versions are 650 mAh, although
Cignot also sells a 1000 mAh version for an additional $4. It is, of course, longer (not the cord, but the battery).
Which mAh version you should get depends on how you feel about that extra length (and four bucks). If the extra length doesn't bother you, the 1000 mAh version will keep you vaping 54% longer when you are out and about ... and certainly is worth the $4.
If you want more
power (i.e., a more intense vape without having to use LR atomizers or cartomizers),
direct PTs (without battery) are the way to go. For example, the inexpensive skinny style sold by
MadVapes and
ElectronicStix ... or more expensive, sturdier versions. Sturdier versions include the $39
Acrylic 5 volt 510 Passthroughs sold by MadVapes and the $60
VP-PT sold with its own USB Power Pack by VaprLife.