Replace Glo Pals Light Up Cube Batteries

Glo Pals light-up cubes have sealed batteries to meet USA safety standards and minimize choking hazards; once the battery dies, the entire cube must be recycled.

I replaced them by cutting a hole in the back which has to be sealed afterwards. I don't know how this affects the safety requirement.

The little light up cube batteries are 3 LR41 cells (7.9mm diameter, 3.6mm thick, 1.5V). They are held in a clear sleeve, likely heat shrunk, in the cube.

To replace them you have to cut a rectangular hole (13.5mm x 8mm) in the back above the batteries with, for example, a rotary tool fitted with a cutting disc then pry the batteries out with a sharp tool.

While the device is open, use the opportunity to clean the battery contacts of corrosion.

Replace the batteries (no need for the sleeve) and insert a small plastic sheet (folded over tape or cutout from some packaging - about 8mm x 8mm should be ok)) between the white circuit board and the 3 batteries just in case there is some conductive track exposed at the side of the board where the batteries may touch. Note that the negative side of the battery stack (the smaller electrode) faces the left if you have the cube back facing you and the hole you cut at the top. There is a small black component on the other side of the board which is on the same side as the negative electrode.

Check that the device works by placing a cotton swap dipped in water across the two electrodes accessible through the slots in the clear cover. The LED should light up.

Place some sealant (I used silicone but nail varnish should be OK too) around the edge of the hole, all the way around the hole, so that the cover seals the hole completely from water ingress. The back of the cube is not flat so be sure to apply enough to fill the spaces. You may also need to fill any grooves left from the cutting.

Avoid the vinegar smelling silicone, rather use the "neutral"  or "sensor safe" sealant. The acetic acid vapours produced by the common silicone sealant can corrode the electronics in the light up cube. I used "Flex Seal liquid rubber" from the big orange hardware store. You can also use 2 part epoxy for a relatively permanent seal that will be difficult to redo for a subsequent battery replacement.

Insert the cover and check that the edges are all sealed. Feel free to cover the back of the cover in case you think it’s not watertight. Nail varnish may be a good alternative to silicone. 

If you have placed enough sealant to properly seal the cover, it may pop up when you push it down from the air trapped inside. To make sure it stays down all the way use a weight on the cover to press it into the cutout. We aware that you don't want it to stick to the sealant. I use a small spring clip to hold the cover down.

NOTE: if the light up cube doesn’t light up it may not be the battery (yet). In my case 1/3rd of the cubes had corrosion covering the electrodes. When the corrosion was cleaned off the LED illuminated as usual.

The warning here is to dry the cubes after they’ve been in water or at least lay them down so that the water runs off the electrodes. They have a small voltage between them which will cause some electrolytic activity causing corrosion products to build up.

To clean the electrodes, use a cotton swap (Q-tip) that has been immersed in vinegar or water. If you use vinegar, wash it off the electrodes after the corrosion has been removed.

PRINTING

PLA is OK, clear would be best but you can match the cube you are working on.

Settings: I used 0.16mm layer height with adaptive height and Arachne wall generator for the thin areas.

If you were a bit too enthusiastic with the cutter, scale X and Y as you need it. Don’t scale the Z dimension, it is designed to hold the batteries in place and mustn’t be thicker than the original.

This is a very small print so print a few at a time to save time for next time you need to replace a battery set.

NOTES

1. You don't need to print the part. a small plastic sheet cut from sone packaging may work just as well especially if you glue the piece you cut from the cube to the sheet to act as a centering shape. Don't use PP or PE, nothing sticks to them, use PET or PS (you can usually see the material in the recycling mark). 

2. If you use silicone to seal the cover in, it will be easier to replace the batteries again because it remains flexible and can be pried out easily.

3. Instructables link