The charger/wallwart/powersupply is just a very simple switcher, with primary side feedback and regulation. Quite likely to be rather poor with load, and can give a varying output with load.
As to the clippers, the charger is a simple current limit, and charges the cells at a current that will fully charge then in around 3 hours, then cook them afterwards. With the new 2200mAh cells you want to charge at a lower current, so replace the 33R resistor with a 68R to 120R 1W unit, and then the cells will take between 8-12 hours to fully charge. NimH cells do not like overcharge, so charging to less than full will do no harm, unlike overcharge which will shorten life considerably. then you can use the original charger, or use another that gives between 6-8VDC at 300ma or so in place of it. Old Nokia charger will do, it gives normally 6V.
