Battery restoration? WTF is that?
Nickel-Cadmium batteries can develop a 'memory' that causes loss of capacity in service, but you are referring to conditions of poor maintenance, mini. Providing batteries are maintained in accordance with the instructions there are no problems. Aircraft MPD's provide for regular battery maintenance and once in the shop the CMM's for Nickel Cadmium batteries approved for use in aircraft include such essential elements as electrolyte level adjustment, capacity testing and deep cycling, that restore the battery's condition. If the conditions that lead to thermal runaway or apparent loss of capacity exist, then the aircraft and its systems are not being maintained in accordance with the legal requirements.
In the current situation in UK, the certification of electrical systems (including batteries) is being passed from the E & I avionics specialists to the Airframe and Engine trades without proper training and experience requirements. It may be that one consequence of this policy will be a new spate of exploding batteries.
I mean, what could be complicated about looking after batteries eh?