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My 2xAA battery mod to my Tacho ...

 

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Well there I was , reaching for my tacho to get a RPM reading on a Electric motor prop combo and .......... nothing !  Once again a dead battery .

I can tell you I was a little miffed , and on opening the tacho and finding the button cell ( I didn't remember what size / voltage it was ) to be 3v , I decided no more . It was time to mod the tacho to AA batteries ( 2xAA = 3v )  ... 

I started by cutting up the button cell carrier inside the tacho , then drilling a hole for the AA battery case wires . The case is hot glued to the tacho cover and the leads soldered to the board on the inside , you know !  Positive to positive and negative to negative .  Then screwing the covers back and inserting some AA batteries ..

And viola , it works just fine ...   No more expensive rubbish button cells , now I can use cheap rubbish AA batteries ...