Battery type detection - rechargeable or not?

If a cell is totally "flat" then it may be impossible to reliably determine the polarity via electrical means: it may be shorted or open. If a cell is very low (say under 200mV), again it may be impossible to reliably determine *correct* polarity, as misuse could have reverse-charged the cell. Naturally, if the cell is effectively open, it will not be possible to electrically determine if it was inserted into the charger (use a mechanical detector or mechanical means allowing insertion in only the preferred direction). Since you stated "rechargeable", there is no reliable way to electrically determine if a fresh or new cell is a rechargeable or not. The Eveready Renewal cells were alkaline rechargeable and had the same electrical characteristics as non-rechargeable alkalines; both similar to the carbon-zinc cells.

Have fun.

It's rare that a battery is completely flat so I reckon both could be done by checking to see if there's a voltage at the terminals.

Graham

Most all flat batteries are shorted. Perhaps charging a battery for a short time and measuring the voltage. Near 1.2 volts, likely to be a rechargable type.

greg

Add: severely limit the charging current, while monitoring voltage and temperature.