Well, using these AA-batteries in a holder for 4 batteries i find unsafe as the batteries can fall out and loose contact. It is also much more practical to recharge a batterypack instead of 4 individual batteries, which due to their voltage on 1,2 volt only gives 4,8 volt to the receiver, but a battery pack contaning 5 batteries -or cells- give 6 volt. I don't think that 2-300 kr for a battery pack is that expensive either. This summer i bought a battery pack at the cost of 1100 kr if that shocks you But that is another story.

For charging the battery pack i use a computer charger, these costs from 4-500 kr, but you can get cheaper ones that you simply plug in the wall and in the battery.