I have a new hp34c that came with 1.5 volt off-the-shelf alkalines installed. I was concerned about any physical stress that the slightly too-long batteries may have been causing on the PCB, so I bought a pair of rechargable tip-less NiCds. The battery clips in the calculator have been flattened out because of the alkalines, and I did not want to bend them back out, so I padded the extra space with some tin foil and the new NiCds are a perfect fit.
But I am now concerned that they are 1.2 volts instead of 1.5 volts. Will this slightly lower voltage be a problem for the calculator? hpmuseum's battery spec page recommends a pair of radio shack NiCds which are also 1.2 volts.