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Are you able to use the battery supplied with the Nikon D70 in a D70s body........and have any members tried this at all.......

If it fits, it works.
The only difference between the EN-EL3 and the EN-EL3a is the newer battery as supplied with the D70s has higher capacity (i.e. longer life). Same voltage/etc.

Someone asked this few days ago,
Yes, it can be used in between the two models, the EN-EL3a with extra of 150mAH but you won't notice lot of difference when using them on the both 70/70s.

Yeah, Nikon reckon you'll get an extra 500 shots using the ENEL3A in the D70s so I'd say it would be the same with the D70.
Bob.