The chances of any adverse safety event are very small. The only concern is voltage compatibility. If they designed the device with a relatively high cut off voltage, then the NiMH cells may give short battery life. I have some little portable radios that are that way.

But I have also designed half a dozen AA powered toys and we ALWAYS designed the low-voltage cutoff so that the toy would work well with NiMH batteries. So you may have to try it to see if there is any problem.

I can't tell you that there is no risk of damage or injury etc. But I can tell you that I would not hesitate to try it with NiMH cells. Also, I think it is bad form for any company to insist that you only use disposable cells nowadays. So complaining to customer service may be in order.

The chances of any adverse safety event are very small. The only concern is voltage compatibility. If they designed the device with a relatively high cut off voltage, then the NiMH cells may give short battery life. I have some little portable radios that are that way.

But I have also designed half a dozen AA powered toys and we ALWAYS designed the low-voltage cutoff so that the toy would work well with NiMH batteries. So you may have to try it to see if there is any problem. Since they sell a rechargeable pack, I guess it likely WILL work with NiMH.

I can't tell you that there is no risk of damage or injury etc. But I can tell you that I would not hesitate to try it with NiMH cells. Also, I think it is bad form for any company to insist that you only use disposable cells nowadays. So complaining to customer service may be in order.