What is a power cube?

Solution 1:

Someone posted this "Power cube" summary on the Ingress community. She tested it out so others would not make the same mistakes as she did to waste these "precious/mysterious" cubes.

What does it do?
It's essentially like a mana/health potion from any other game. It recharges your XM bar up to the value of the cube itself. So a level 4 cube will inject you with 4k XM.

Does it increase your XM bar above cap?
No. It only refills the bar you already have (up to its own value).

What happens if it's worth more than the XM you need?
In short, the overspill fizzles. The cube is consumed utterly on use, and will only give you up to the full amount, as much as you have room for. For example, I had 1348 XM short of 100%, used a 4000XM cube, so I gained 1348 to bring me to 100% and the other 2652XM just dissipated into the ether.

What does it look/sound like?
It's pretty nifty! Swirley gold XM droplets spiral around you while a "chargin' mah laz0rs!" sound effect revs up. There is no residue once the cube's power has been used. EDIT: Courtesy of +Fevenis Silverwind : Power Cube animation (RAW)

Can you use cubes of a higher level than yourself?
Nope! The 'Use' button is greyed out, and trying to click it gets an "insufficient access" error.

Can you use a cube while already at 100% XM?
Yes, and it'll be totally wasted. So don't. (Thanks +Alexandre Luna Barros for the sacrifice).

I'm not getting any cubes from hacking, whassup with that?!?
They are dropping for people, but it still seems to be rather hit and miss. My theory is that the portals need their 'loot tables' to be refreshed post-update, either by flipping them, or waiting on the daily decay. Hopefully over the course of the next day any stubborn portals will get updated, and in the meantime try not to get too frustrated. Also, bad luck is bad, but not permanent, so try not to despair if you're burning out and still not seeing any just yet!

Link to G+: https://plus.google.com/113226483052150160303/posts/2dSSuN43Xt2

Solution 2:

From here:

They contain their Level * 1000 XM.

Warning: They will not function until the next Ingress app update!

Solution 3:

just got one, options are to drop or use and it has 5000 XM....assume it recharges XM