Repairing a Wii Balance Board

In an age of cost cutting on products to compete in a very competitive market place, some producers seem to go too far. Reducing the quality of the product to the very edge in order to shave a few pennies. One consequence of this has been more battery leaks, with Duracell being by far the worst offender. Seriously, why does anyone still buy Duracell products! This time it was a friend who brought me the latest corrosive disaster, a Wii Balance Board with a mess in the battery compartment.

Wii Battery Compartment Repairs
The battery compartment of a Wii Balance Board after the repair
At least the balance board was easy to get apart, just a mess of screws on the back to remove, a few minutes with a phillips screwdriver. First remove the feet with three screws each, then the backplate with another ten screws. The unit is essentially a fancy bathroom scale with load cells in each foot. Rather nicely made, the engineers did a good job here.

Opening the case reveals the good news and the bad news. Good… The battery compartment is removable with just another couple screws. Bad… The damage here is severe, the small circuit board under the battery compartment is heavily corroded, traces and components destroyed. Good… The complex circuits for the unit, the processor and transmitter, are on another circuit board on the other side of the balance board and are untouched. Bad… The battery contact plating is gone, these are unusable. Even the wiring harness is damaged.

Damaged and replacement battery contacts
Damaged and replacement battery contacts for the Wii Balance Board
First to clear away the damaged bits and clean everything thoroughly. The battery compartment is dismantled and into a bowl of hot water to soak away the corrosive leakage from the batteries. Some folks panic at the idea of putting electronics into water. Truth is that most electronics components are rated for resistance to water and other solvents as washing is standard in many electronics manufacturing processes. As long as there is no power present you can wash most circuit boards. There are some exceptions here, I would not submerge an LCD display or any sort of battery. You must thoroughly dry everything before applying power.

Wii Battery Compartment Repairs
Repairs to the circuit board under the battery compartment
A little gentle toothbrush action is required to remove some of the corrosion deposits on the little circuit board. As I do more damage becomes apparent… I will have to patch an number of traces with wire. Also being replaced is the sync switch. The wiring will have to be cut away and re-soldered after the last inch of damaged wire is trimmed back. A number of the pads are also in bad shape.

The battery contacts are replaced with some contacts out of some inexpensive AA battery holders I had on-hand. Not quite the neat spring arrangement of the originals, but they will work. A little RTV is needed to hold the new contacts in place, but I did not modify any plastic to make them fit.

All repairs complete, back together, and put some batteries in… It works! Well at least it powers up and the power LED flashes. I do not have a Wii to test it and will have to await news of proper testing after the unit has been returned.

Update: The unit is reported as working fine when returned to the owner.

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on the island of Hawaiʻi.

28 thoughts on “Repairing a Wii Balance Board”

  1. Thanks a lot, i repaired my wii balance board with the help of your blog post, i have only to clean all the mess with lemon and patch a pair of cables everything else was good.

    1. I assume the original solder pad has been destroyed. In this case follow the cooper trace that went to the pad and solder along it somewhere. If necessary you can remove the green layer, the solder mask, with a sharp tool by gently scraping it away to expose the copper, then solder to that.

  2. The circuit board under the battery compartment of mine doesnt have the blue cables you show. Could it be that corrosion ate them away perhaps? My board has a 7 instead of a 4 , could it be different?

    What type of cables are the blue ones and can i replace then and solder new ones?

    1. The blue wires were added by me. They bypass traces on the circuit board that were damaged by the corrosion, completing the circuits. You need to carefully inspect the circuit card once you have it cleaned off. If the copper traces appear to be damaged you can repair by using a bit of fine wire. If you are unsure the trace is damaged check it with an ohmmeter.

  3. Thanks Andrew, i guess mine was damaged by corrosion but i will clean it up to see if for any chance it works.

    Could you please tell me if the fine wire has any denomination so i can buy it in a hardware store please? i dont have any equipment so i will have to go to some circuit repair shop and bring the cables and tell them what to do because my local video game store doesnt repair these boards.

    1. The wire most of the industry uses to do this sort of patch is Kynar wire (try googling Kynar wire). Originally developed for wire wrap construction the wire has outlived this use as it is very useful for many tasks. I have rolls of the stuff, thousands of feet, use it for electronics construction. It is solid core and quite fine, about 30 or 32 AWG. Are you in the US? E-mail me a mailing address (see my about page) and I will slip a little in an envelope and send it to you.

    1. You can either make your own (there are multiple ways to do this), or look for another Wii balance board for parts. I see that a new balance board is about $30 from a few online retailers, probably your best bet.

  4. Hello! Just have the same issue I will appreciate some assistance I have that copper trace it suppose to connect with something? Also I think the sync button is damaged

  5. Hello!! I checked all contacts for connectivity from the power pcb to the main pcb which has connections for the weights. They all seem to be fine. I even replaced the sync switch with the one from an old remote that was heavily damaged. I still can’t get the unit to power on. I checked voltage between the power pcb and main pcb and there’s a significant drop from 6v to something in 0.5V range. I have a feeling the resistor on the power pcb is damaged. I tried checking for resistance but my meter shows no result. The resistor has a label of F 0.50 on it. It’s been ages since I studied resistors, so I’m ashamed I cannot recollect what the resistance in this case. Do you think the resistor is damaged and could be causing my unit to not function? Can I get a replacement resistor from somewhere and if yes, what value of resistance should I be looking for? Many thanks!!

    1. Not sure that is a resistor, I do not have a Wii board to check, but that may just be a fuse you are looking at, they often come on the same packages as resistors. F0.5 suggests a 0.5A fuse.

      1. Thanks, Andrew for your quick response. Is there a way I can send you a picture of that via email? Can I try and short/bypass the fuse?

        1. I am exactly in the same situation. I measured the fuse/ resistor and I have the same values. What did you do next? Did you manage to fix it?

  6. Hi, is there a way to activate the sync function manually just by using wire? The sync button is broken on my board but everything else is working. Thanks

  7. Many thanks for your blog post. I am hoping mine is just a case pf replacing one of the corroded battery holders…. fingers crossed… it would be amazing if I can get it working again 🙂

    1. Mate, 8 years on and your post is still heaping people out. Broke the wii out after years of being in a box. Ahhh, left batteries in it. Cleanes it up and I got as far knowing it was the copper under battery pack. Came across your photo with the new wires soldered on while doing a google search to find what the part was called so I could buy a replacement. Reading the comments you say what gauge you used. Gave it a crack and it worked a treat. Cheers from Australia.

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