The most recent manufacturing run of Mooshimeters has battery contacts that weren’t deburred properly. This has created a very frustrating problem where the burr (rough edge) of the battery contact cuts through the label of the AA battery, short circuiting the battery and causing it to heat up. It’s not a fire hazard but it’s alarming to users and it kills the battery. Even worse, failure is not immediate so it didn’t get caught during the manufacturing process, as it usually takes several physical impacts on the meter for the rough edge to saw through the label.
The battery contact manufacturer has offered a refund for the contacts and future Mooshimeter will be made with contacts from a different supplier. The contacts themselves are not a big part of the manufacturing costs though, the time and energy supporting users who receive meters with a flat battery or have one heat up when they replace it is a far greater cost.
The battery contact in question is manufactured by Memory Protection Devices (MPD) and the same model been in every Mooshimeter since production started almost 2 years ago. The part in question is here if you’re interested. MPD said a bad batch was released last year. The contacts that made it on to this manufacturing run of Mooshimeter were from that bad batch. Here is a picture of the offending battery contact in context. This is a board from the most recent manufacturing run.
The rough lip is extremely hard to see but it’s there. If you run your fingernail along the inside lip of the battery contact, you can feel it. Our friends at ESI have already found compatible replacement contacts from another manufacturer. They sent me some samples. Below are microscope images of the two side by side so you can see the difference.
The burr becomes more clearly visible when the light is positioned to reflect off of it. Please excuse my fingerprint in the background. Hardware work is never clean.
I also photographed the kind of damage these contacts inflict upon the AA batteries over time. There seem to be two failure modes, which I dub slicing and gouging.
How to know if you’ve been affected
- One battery became hot after placing it in the meter
- You found your Mooshimeter with a single dead battery
- Your Mooshimeter was fine until you dropped it, then one of the batteries went flat
In all of these cases, examine the dead battery near the negative terminal. You will probably see a spot where it looks like the label has been scratched down to the metal.
How to fix the issue
In the cases so far, the failure has always occurred at the negative AA battery terminal closest to the corner. This is where mechanical shock is most directly transmitted to the battery contact. The failures documented so far also happen at the edge closest to the corner.
Fortunately the battery contacts are not hardened and deburring is quite easy. If you have a deburring tool, running it over the inside lips of the battery contacts should fix the issue. If you don’t have a deburring tool, almost any steel implement with a corner will do. Just take the corner and scrape it along the burr a few times while applying pressure. Since the contacts are springy, you will have to hold the contact directly to get enough force
As a test, I used a phillips head screwdriver on the meter photographed above. Here’s the same contact, before and after deburring:
Since we’re switching battery contact manufacturers, this should not be a problem on future manufacturing runs. For meters that are already in the wild and affected by this issue, your meter should be fine once you push down the rough edge.
We work hard to build a reliable product and every meter is tested before it leaves the factory, unfortunately this issue only manifests once the meter is bounced around in a truck for a few days. I apologize for any inconvenience or scare this issue has caused.