section_path: Other inventions and projects/Rechargeable battery
section_name: Rechargeable battery
paragraph_text: Rechargeable battery
  
  In the late 1890s, Edison worked on developing a lighter, more efficient rechargeable battery (at that time called an "accumulator"). He looked on them as something customers could use to power their phonographs but saw other uses for an improved battery, including electric automobiles. The then available lead acid rechargeable batteries were not very efficient and that market was already tied up by other companies so Edison pursued using alkaline instead of acid. He had his lab work on many types of materials (going through some 10,000 combinations), eventually settling on a nickel-iron combination. Besides his experimenting Edison also probably had access to the 1899 patents for a nickel–iron battery by the Swedish inventor Waldemar Jungner.
  
  Edison obtained a US and European patent for his nickel–iron battery in 1901 and founded the Edison Storage Battery Company, and by 1904 it had 450 people working there. The first rechargeable batteries they produced were for electric cars, but there were many defects, with customers complaining about the product. When the capital of the company was exhausted, Edison paid for the company with his private money. Edison did not demonstrate a mature product until 1910: a very efficient and durable nickel-iron-battery with lye as the electrolyte. The nickel–iron battery was never very successful; by the time it was ready, electric cars were disappearing, and lead acid batteries had become the standard for turning over gas-powered car starter motors.