Battery manufacturers insist that only specially designed nickel-cadmium cells should be recharged, and that ordinary alkaline or zinc chloride batteries will explode.
Ever Ready, the battery company, says recharging can generate unpredictable levels of gas that can cause the internal carbon rod in zinc batteries to fly out under pressure and the highly corrosive paste inside alkaline batteries to leak.
But Andy White, 32, who works for the Innovations mail order company, claims his Battery Manager, launched yesterday at the Science Museum, is safe because it includes a microprocessor that constantly monitors the battery as it recharges.
He says the unit - which comes in two sizes at pounds 29.99 and pounds 39.99 - sends 500,000 pulses into the cell every second while its chip checks the battery voltage and how fast this changes. If the battery charges up too quickly the unit slows down, so lowering the chance of gas building up.
'We have tested thousands of batteries and have not had a bang,' Mr White said. 'It's not something that is impossible to do, but up until now the technology has been too expensive and under-researched.'
Shares in Kleeneze, the holding company behind Innovations, shot up 44p yesterday to close at 226p.
Mr White said that an accredited laboratory tested his unit on all leading battery brands and found they could be recharged about 20 times, extending their original life tenfold.
Each charge cycle takes between eight and 12 hours. The unit works on zinc chloride, alkaline, alkaline and nickel-cadmium rechargeables and mercury-free batteries.
Mr White said yesterday he had yet to receive a threatening letter from a battery manufacturer. 'I think they are resigned to it,' he said.