## It was a relatively well known practice in WW2 (and possibly before) that if your torch/flashlight battery was getting a little flat, a few quick touches to a vehicle battery would restore a fair bit of charge. This information became more public knowledge in the UK, post WW2 when times were tough, and a number of articles were published on it. I cannot now find any, but the earliest article I have read was a 1953 one in "Wireless World" by R W Hallows with some designs and an analysis of these simple methods. Also, in 1953, "Radio and Hobbies" (Australian) published a design for a portable valve radio featuring dry battery reactivation. Then in 1955, a device was sold in Holland called the "Electrophoor" which recharged zinc-carbon cells using periodic current reversal. The "Electrophoor" was a very simple device and so many copies followed. To counter their popularity, and a probable dent in sales, the manufacturers started a campaign to convince the public that recharging was dangerous. In the mid 70s there was a successful court case in Japan by the pro-charging lobby to defeat this BS! I first came across this in the early 1960's while living in a small town in North Otago. The chap who ran the local picture theatre had very deep pockets, so used to retrieve the D Cells from the "Usherettes" torches after the Saturday night screening, and put them into a homemade charger. He claimed they lasted for years. From circa 1975-6 an UK engineer, Rod Cooper, wrote a number of articles on how to do this safely and effectively. Apart from the cost saving, he was appalled by the waste of raw materials and production capacity by throwing away good cells. He wrote "The idea that it is dangerous to recharge dry cells seems to have taken root in the UK, assisted, I am sorry to say, by the dissemination of manufacturers propaganda by the technical press"! Yes, there are limits, a cell cannot be fully discharged, in fact for the recharging to work the depth of discharge should not exceed 30-40% and it cannot be repeated forever, but 20 such successful charges are typical. He published technical articles, again in Wireless World, and I seem to have lost some of my early copies. However, I do still have copies of the following detailed articles:
  • "Better Use of Dry Batteries" by Rod Cooper, Practical Electronics, June and July 1986, 7 pages and updated in the May 1987 issue.
  • "Charge Alkaline Cells" by Rod Cooper, Electronics World, Mar 1997, 6 pages.
  • "A Dry Cell Charger" by Peter Philips, Electronics Australia, Jan 1995. This is a fully detailed 7 page construction article.
  • In TNX Electronic Projects No3, August 1993, Rayovac Corporation announced the sale of rechargeable alkaline dry cells and a companion charger that were good for 25 charge/discharge cycles.
I, and a few other colleagues did recharge dry cells mainly to prove it was effective, but then by around 1985 NiCads became reasonable priced Today, I'd imagine that few would be bothered, given the very low cost of throwaway AA cells in 2-buck-shops (Where almost nothing is 2 bucks!) Very high quality NiMH cells (The Panasonic Eneloop) for $4-5, and Li cells built into most appliances. But it can be done, and was for probably 40-50 years, safely and effectively.

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