Zinc-Carbon Battery charger

They are cheap. The electrolyte used to leak but today they are usually much better protected. If they should leak then they will corrode all the copper in your equipment. the corrosion will travel down wires and eat its way through Printed Circuit Boards (PCBs). At high temperatures (25 degrees or more) Zinc-Carbon batteries will give up to 25% more capacity but the shelf-life will deteriorate very rapidly. Around freezing point their shelf-life can be extended by as much as 300% so one tip is to store them in the refrigerator.

Unfortunately they must be thrown away when they are exhausted. You can extend their life by up to 60% by using "Dirty-DC" to recharge them but this will also reduce the shelf-life.

Ry should be about 1.5 x greater than Rx. The resistors are determined by the charging current you want. With the circuit shown and size AA cells in a pack of ten cells, the battery voltage will be 15 volts. Discharge the battery to no less than 25%. To replace 350mA/H back into the battery over 10 hours we need to charge at 35mA.

Rx = (24 - 15 - 0.7) / (3 x 0.035) = 79 ohms

Ry = (24 - 15) / (2 x 0.035) = 128

You can also cook exhausted battery cells in the oven. About 80 degrees centigrade for five to ten minutes, no more or they may explode. This technique was demonstrated on UK TV in the series "Steptoe & Son" (h�r i Sverige i "Albert och Herbert"). I do not reccomend that you should try to sell the cells again as new batteries!

Source : http://web.telia.com/~u85920178/begin/batt-00.htm