6 replies to this topic

[DLuders]

Want to make a REALLY SMALL remote-control vehicle or robot, but can't figure out how to squeeze in a big Power Functions battery box?  Well, some fellow figured out a way of using a SMALL 9V disposable battery (like the ones used for smoke detectors) in a Lego Power Functions application:  http://mocpages.com/moc.php/168223 .  He used it in a small model of a Shays Locomotive by utilizing research by Philo (Phillippe Hurbain) and adapting it.  

Although a 9V battery may not last very long (compared to 6 ea. AA batteries or TLG's Power Functions rechargable battery), it may be useful in smaller MOCs.  Really, do you power-up your MOCs for more than a few minutes at a time anyway?  

[Zblj]

You dont need all that fancy wirring... Just use the old 9V battery box, one extension/adapter cable and 2 small pieces of alu foil. You put two msall pieces of foil to cover the front 2 and rear 2 conrtacts and place the PF receiver on top to *squeeze* it into contact. Than you just ahve to watch out for polarity and it works. I used this technique in my mini offroader.

[DLuders]

Zblj, to make sure that I understand you correctly, did you place 2 ea. small aluminum foil strips on top of the pairs of electrical contacts of the #60656 "Electric, Power Functions Extension Wire with one Light Bluish Gray End (length 20cm)" ( http://www.bricklink...tem.asp?P=60656 )  AFTER it was already snapped onto the old-style #5115 9V Battery Box?  Maybe you meant some other "old" battery box pictured on http://www.bricklink...p?q=battery box .  

Any "old" 9V Lego Battery Box is bound to be HUGE compared to the tiny 9V alkaline battery mentioned in the original post.  I'm not sure what advantage your setup would offer.  Could you elaborate?

[CP5670]

I think he's referring to the this 9V box that appeared in many System sets. It accepts a single 9V battery, although it was mainly designed for lights and the built-in switch doesn't let you change the polarity.

[DLuders]

Oh, I never had one of those #4760c01 "Electric 9V Battery Box Small Assembly with Gray Switch" units.  So Zblj, does the correct combination could look like this?

    

[Zblj]

Yeah box, extension cable

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and PF's. If the IR receiver doesnt start up, than quickly change polarity

[Jetro]

Alternatively, if you don't mind modding the part and don't want that much cable you can do it like this: