How much Volts and mAh can I out into a 5 mW green laser

[Lolegend]

Even the best violet diode we have right now (around 1 watt) is hard to see the beam in a dark room. Even more so if you happen to be one of the people who's eyes don't pick up on the 405nm wavelength very well.
Most any green diode you get you'll be able to see a beam in a dark room.
Check out DTR's sale page on here to get a good idea of some commonly accessible diodes available.

Thanks for the help on the diodes I think I'll stick with green then.

 

[GSS]

That unstable dot and beam unfortunatly is typical of that type of cheaper pointers. Its hit or miss that you might get a good one. Putting more power to it like has been said is a temporary fix and it will kill it soon. You don't have to pay a fortune for a good green one with the beam and dot that you will be happy with. It might be cheaper than you think.
I don't know the UK laws but maby some will chime in.
Check out Sta "Guide to begineers and which companys are good and bad.
http://laserpointerforums.com/f41/guide-company-should-buy-97936.html
This should give you a start.

 

[Cyparagon]

Clearly 2.4v isn't plenty

And in that case, buying a pointer with a regulator will still be far cheaper than buying NiZn cells with a charger.

Spending $11 to partially repair a $2 device is just goofy. Just get a half-decent $8 pointer instead.