a good 12v dc supply

[kane]

Ouch, sounds painful.

Can someone also tell me about the danger of charging nimh batteries in series?

Charging in series is ok although if the packs are not very well matched you could end up with one pack undercharged or overcharged.

In parallel is a no no. One pack will end up taking the current and could result in fire or explosion. You should never leave NiMH or NiCd connected in parallel as one pack will discharge into the other with the same result.

[mattsdragons]

so 2 9.6v packs with the same mAh rating in series would be fine to charge?

[Laser]

yeah if the cells are the same, in sereis its basically having a 19.2v pack