garmin vector battery doors – version 3!

If you have a pair of Garmin Vector 3 pedals you will be more than aware of the issues relating to the battery doors.

Shortly after their initial release users of the Vector 3 pedals suffered regular data drop outs and pairing problems with their pedals. Garmin traced these problems to the battery doors and updated the design.

As you may have read from my previous post I eventually bought some of these pedals but waited a while until Garmin seemed to have resolved the issue and the chat about it on the forums died down.

However despite that I too had problems shortly after purchase and Garmin promptly sent me a replacement set of battery holders and doors. That solved the problem and I have had no issues since.

Then last month ago, completely out of the blue, I got this email from Garmin;

Since I had only upgraded these parts from Garmin a few months ago I wondered if this was just the same parts. Perhaps by writing to Garmin I had received the update ahead of their general release and this was just a wider distribution to all owners. Or was this a completely new design? Well since the upgrade was “free” to existing owners I had nothing to loose so I went ahead and ordered some. I was however staggered to see that the replacement battery door kits normally retail at £25.99 per pedal!

A few weeks later 2 packets arrived and side by side with the packets from the last update they looked identical, the labels having the same bar code and part numbers;

However on opening them up and checking against the existing parts they were clearly different. Below is a photo of all 3 of the battery holders and door parts I have had. On the left are the original parts supplied with the pedals, in the middle the replacement parts I received shortly afterwards and finally on the right the parts I have received most  recently.

As you can see all 3 of the sets of parts are very similar. I would say that the plastic battery holders and metal door parts are identical. The only differences I can see are in the metal battery contacts.

Between the first and second set of parts the only difference appears to be in the colour of the metal battery contacts, the physical design appears to be the same. The set supplied with the pedals have contacts with a “silver” finish, the replacement parts have a “gold” finish. I cannot say if this is due to a change in material or just the surface coating. However it did make a difference and solved the performance problems I was having.

The design of the contacts for the parts I have just received however is completely different.

Again I cannot say if there is any change to the materials used but the additional sprung tabs should make the contacts more robust in the long term.

Lets hope this is 3rd time lucky for Garmin. I think these pedals are a great product and it is a shame they have been let down by something as basic as the battery contacts. However this does seem to follow the “normal” pattern for Garmin of releasing products before they are fully tested.

All this “taking apart” of the pedals did however get me wondering as to why Garmin were having a problem with something so fundamental. I mean what other electronic device do you have where the battery contacts are so apparently weak that you have power drop outs? None right?

I suspect the issue here relates to the way the batteries are inserted into the rotating pedal assembly. The strain gauges and electrical components are fixed to the pedal spindle along with one half of the battery holder which is fixed in place with 2 screws. The other half of the battery holder is attached to the metal battery compartment cover (or door as Garmin calls it) which is fixed to the pedal body. This means that there is a rotating interface between the outer part of the batter holder and the metal battery compartment cover. Since there is no ‘bearing” here, just a plastic part that is free to rotate against the metal part, there is clearly some free movement in the system. That slack has to be taken up by the sprung contacts in the battery holder, something that is not common.

Now I understand the design better my concern for this product is its longer term reliability. The rotating interface between the metal battery compartment cover and its attached half of the battery holder will undoubtedly wear over time and the additional slop in the system that will generate will result in a reduction in the security of the connection between the battery and the battery contacts.

It would have been more secure to have a separate screw down cap to hold the batteries in place that was connected to the inner rotating assembly  only. The metal battery door would only then have one function, that of providing a water tight seal, thus keeping the rotating parts and static parts separate.  This does seem like a fundamental design flaw to me that will plague users of these pedals for the life of the product.

On reflection I wonder if this is the real reason for the recent design update, not this story that Garmin have concocted about “swelling of batteries”. It would be interesting to cut some of these parts open to see how the interface between the metal battery compartment cover and its attached half of the batter holder is designed. However for £26 I am not that interested!