Pleo battery pack
by pintokitkat, published
Pleo is an autonomous robotic dinosaur whose battery packs are quite expensive.
The design is to allow you to use ordinary AA Ni-MH batteries and the original (ie Ugobe) green battery charger. Don't use it in the white 'egg' charger - that's for Lipoly batteries and I am confident they aren't compatible.
Update - May 2013 - The green photos
v7 is a redesign following the failure of a laptop mouse that had a spring loaded reel to wind the cable on. Taking the reel apart I found a wonderful spring that can be cut and bent to make the battery connections.
Update - May 2013
V7 using pieces of flat coil spring rescued from a broken mouse reel, cut pieces about an inch long and bend them into a M then feed them up through the slots in the top and bottom to make the battery connections. It is also a good idea to bend the very ends back up a little to allow the batteries to squash them without biting into the plastic.
Instead of soldering the resistor or thermistor in place, insert it into the slot underneath the bottom plate and bend the ends round so they make contact with the bottom of the battery cells. Glue it in place (see the photo of the green pack).
The little block gets glued into the space marked underneath using a bit of dip (acetone with plastic bits melted in - think Roger Rabbit) or superglue. Dip works best.
I printed the parts using .2 layer height and 100% fill as the tall tower structures need to be solid.
Use a raft and support as the tower part has a block underneath which won't print properly otherwise.
There's also a depression in the underside shaped like a tennis racket leading to a small hole. The hole is to pass one leg of the thermistor (or 12k ohm resistor - see disclaimer below). The other leg of the thermistor (or resistor) is coiled at the end and is trapped below the negative end of a cell and the spring in the battery cavity of the Pleo.
Use sticky copper tape to make a tennis racket shaped piece that fits in the depression and solder the end of the thermistor (or resistor) that pokes through the hole, to it.
Then cut five more pieces of copper tape and stick them across the pips on the top and bottom plates to create the connections across the cells.
Bundle six cells together, alternating their orientation and hold them together by taping a piece of paper around them. Don't stick the cells together as if they can move relative to each other, it makes them more likely to touch their respective pips. Slot the battery pack over the towers making sure there is a positive end next to the tennis racket and a negative end where the thermistor (resistor) loop is.
Use two 3mm screws to fasten the top to the towers and then two more to fasten the very top on, trapping the swivel part in between, but allowing it still to swivel (see photos).
A bit of sanding and whittling might be required, but the one I made seems to work fine.
Disclaimer: Using a resistor instead of a thermistor stops the battery pack cutting out if it overheats. Pleo won't operate if there isn't about 12k ohm resistance across those two contacts. The resistor works though, and I've never had any problem with using a resistor instead, but it's up to you. I'm not responsible if you damage your dino-chum.
I've marked it as a work in progress, although I don't intend to make changes unless someone tries it and finds a problem.
I seem to have bits floating all over the place so I have uploaded the four pieces separately. If anyone can tell me how to put things on the base plane in Sketchup, I'd be really grateful!