In 1994, GM, clearly conflicted over being forced to build the EV1,
purchased control of the NiMH batteries and proceeded to suppress them
because of limitations. They would not recharge above 90 degrees F.

However, in Jan., 1995, an abrupt change occurred as GM poured
millions into solving that problem. The EV1, originally designed for
Lead-acid batteries, had a battery tunnel which was not suited for
NiMH batteries, which are sensitive to excessive heat. The GM upper
management, forseeing the return of expensive oil and the need for
cutting-edge technology, decided to release the EV1 with superior
lead-acid batteries from Panasonic, bypassing their Delco arm, which
had formerly insisted on supplying batteries for the EV1.