It is supposed to hold 2kWh of energy and could charge the Amp on a granny lead at 6 amps, about 1.4kW, ought to last for an hour and 25 mins. I suspect it won't hold that charge rate for that long say 1 hour 10 mins before its over heating and done.
At 4 miles per kWh that's a notional 6 miles, allowing for losses, seems a lot of money for little gain.

The Ampera needs about 12kWh to charge from flat to full.

 

I don't know about the Ampera but some cars are picky about earthing which a portable battery does not have. I'd expect a Renault Zoe to refuse to charge from a battery pack.

 

If one were to use a portable charging station like one of these: would it charge a car (like my Ampera) if it says 2300W or is it too low? I know that my Ampera charges at 3kW

Bjorn Nyland has used a similar power bank to act as an emergency recovery service in a few YouTube videos. If you search his channel you will find quite a few tests using different cars. One of those is shown below, starting at the place where he uses the power bank. He carries that large unit around so that he can deliberately run an EV totally flat to see what happens and then grabs a few miles, after an hour's wait, to get to a charger.

A very cumbersome and expensive method of adding a few miles. Meaning that it would have to be constantly charged itself and also add a substantial weight penalty and fill most of the boot. It's a solution for an extremely edge-case problem. But not a particularly good one.

It would probably work in an Ampera, but seriously, do you really want to spend that amount of cash just in case you really cock things up and need a couple of miles?

 

All pretty pointless and expensive in my eyes. If you need to carry one around with you then you need either a bigger range vehicle, or you need to have a word with yourself about constantly running out of charge.

 

Or get yourself one of those

...and don't forget to bring the wife and kids!
'Alright guys, daddy's going for icecream. Let me know when you're at 10% and I'll be right back. Chocolate or strawberry?'

 

With around 2kWh, if you really need a portable charger, I'd guess you'd be better off with a small petrol generator and a can of petrol since it would probably be better weight to energy. Consider the size (energy storage) of the Ampera's battery with the portable energy store. It might get you ~5miles.

 

My Ampera runs fine on petrol when the battery is exhausted