Another consideration to look is reverse polarity.

A series diode will protect you against it. So will a cleverly-designed
battery holder.

However, any choices you make really depend on the final product, the
quantity you expect to make, how reliable you need it to be, and how much
money you can throw at it.

This issue has been beat to death recently, perhaps you should also check
the archives at google groups.

Cheers,

Bob

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