How hot should NiMH's get in the charger



New subscriber here.

I have a set of Sony AA size NiMH's that are the original batteries
which came with the charger. Upon charging for a couple hours, they
are almost too hot to hold in my hand.

Normal? Safe? Advice?

Second question: Is there any reason to fear using other brands of
NiMH's in the same charger?

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