Why can not the rechargeable battery be mixed with a regular battery?
Rechargeable battery is used in the storage of lithium, lithium can be multiple charge discharge. While the ordinary battery is mercury. Both with the discharge speed is not the same. So can not be mixed use.
Mixed with the internal resistance, but this time the internal resistance of the battery is high, the ordinary battery is low (regardless of the resistance with the use of time and change), irregular discharge current to make the battery fever serious. May cause the battery to leak or explode (theoretically).
Theoretically not, because the rechargeable battery and ordinary battery internal resistance is different, ordinary battery bigger.
If it is lithium battery, then it is no problem, but according to your description is not a lithium battery, but nickel and hydrogen and the like, this rechargeable battery voltage is only 1.2V, is not available.
Because the dry battery with the rechargeable battery is completely different types of batteries, and the voltage is not the same, the general dry battery voltage is 3.6V can be directly driven.