I need to power a tape recorder, and I have some really old rechargable batteries lying around that wouldd do the job. However, some of them are rated at 1.2 amps per hour, and some are rated at 1.6. Is it all right to mix them? I know you cannot use batteries of different chemistries together, such as nickle-cadmium and nickle metal hydride, but these are all nickle cadmium. What can I do?