Since there are only 2 cells you might be able to do this mechanically.
By having a raised ridge around the positive terminal, that only fits the
positive terminal and would be open circuit it the battery near the
positive terminal was inserted backwards.

On Mon, 31 May 1999, Peter Homann wrote:

> Hi,
>
> I need to protect my PIC16LF84 against reverse polarity. Currently I'm
> running the circuit of 2 x 1.5 N cells (2/3 AAA). I want to protect the
> circuitry from the batteries being inserted the wrong way.
>
> I'm not keen to put a diode in series with the batteries as I'll loose 0.6V.
>
> Thanks,
>
> Peter.
> ---
> Peter Homann    Email:  peterh@adacel.com.au
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