Using an AAA battery to work a 220v clipper in N. America

If you are looking to swap out the AC-DC adaptor for AAA cells... you should take a look here : http://data.energizer.com/PDFs/E92.pdf

Please note this is an AAA datasheet, you mentioned AA as well... which will have a higher capacity and higher current output, but the same characteristics still apply.
Remember that drawing high currents will decrease the effective capacity of the cell, you can always run more than one battery in parallel to help combat this.

 

You're right, but you need to be certain that the batteries you choose can actually run the device long enough to make it worth it.
Personally, I think you should visit a local Best-Buy or 'The Source', and simply buy an AC-DC adaptor that matches the numbers.

Output voltage should be matched exactly, and output current (500mA) must be the same or greater.

 

I'd say 1.5V batteries should be fine, although the clippers would run a little faster. More than 1 cell in parallel would be best as previously mentioned, but if you want to get a closer voltage match and make it more economical you could use (rechargeable) NiCd or NiMH cells. Their output voltage is about 1.2V during their useful life. NiMH are better in terms of capacity. Again, I'd parallel up at least two, or even four.
(Or you could send the clipper to me here in Australia - our mains power is 240VAC. )

 

You can't connect them in series or the voltage will be increased, they need to be connected in parallel as shown below. (I'd go with AA, too, rather than AAA, for the higher capacity.)
Edit: I forgot to add - NiCd and NiMH aren't 'exactly' 1.2V. They start out a fraction higher straight after charging then drop to 1.2V after a short while and stay there until nearing the end. They should be discharged to about 1V per cell, then recharged. Perfect for your application.

 

Always fully charge the cells. You can pretty well ignore the slightly higher initial voltage after charging. It will almost immediately drop to 1.2V under load, when the clippers are turned on. If you were to only charge to 1.2V, the battery capacity would be very low and the clippers would run out of oomph, (a technical term), very fast.

Never do this. A very high current uncontrolled current would flow, flattening the batteries almost instantly and potentially damaging them.

Regarding discharging to 1V per cell, just run the clippers until they're no longer useful, but don't completely discharge the batteries to 0V and you'll be fine.

If using NiCd cells, it's a good idea to always discharge as above, until no longer useful, to prevent 'memory effect'. Memory effect is caused by only partly discharging the cells before recharging, and results in reduced capacity. Google NiCd memory effect if you're interested in more info on this. It's not truly 'memory', but acts like it.
NiMH also have memory effect, but nowhere near as bad as NiCd cells.

Edit: Another point to keep in mind is that at the high discharge rate of the clippers, 1.2A, I think you said, the batteries won't actually deliver their full rated capacity. As an example, a 9V NiCd that I'm currently building a charger for is rated at 160mAh, and in it's current application it is being discharged at 40mA and only lasts for 2 hours, giving an effective capacity of only 80mAh.

 

I don't think you're going to be very pleased with the run time per charge running that thing on batteries.

You mentioned that 1.2V is a rare value for wall wart type power supplies. This is true and causes me to wonder if that's the correct voltage or if maybe due to some mislabeling or bad molding, the output is actually 12V. If you could get a friendly electrician to hook it up to 240VAC and measure the output, we'd know for certain. Even if the output is 1.2V, it would not be that hard to find or modify a supply to match and it eliminates the expense and charging hassle of batteries.

 

I've got a small beard trimmer that operates on 3 AA cells in parallel, and the run-time isn't too bad. I can easily get enough time out of a set to cut all the hair off my head 2 or 3 times with enough charge to do my beard every now and then.

According to http://data.energizer.com/PDFs/E91.pdf
A pair of AA cells should last about 90 minutes. (1500mA Capacity at 500mA discharge) (Which seems high, but I'd be happy with 60 minutes)

 

I was wondering myself if it was really 12V and not 1.2V, but figured it's possibly a moving coil type mechanism and not an electric motor.
I'd personally buy a couple of normal carbon-zinc cells first to test it, before going to the trouble and expense of buying NiCd or NiMH cells to run it. (And a charger if you don't already have one.)

 

very unusual power supply, 240ac to 1.2v

buy a D cell battery and power it from that!