The sense charging cable

[PaPaRJW]

Another cable failure. Two now since I bought it 6 months ago.  Fitbit are sending another one.  I’m told it is the same design, so not confident of it lasting, they are.

Anyone have success with other ways to charge.?

[Guy_]

Hi @PaPaRJW - you could try sourcing a non Fitbit charge cable but how it is used may be an issue.

Do you always connect the watch to the cable before plugging it in and remove the cable before taking the watch off?

[PaPaRJW]

The manual says to to plug the cable in first then attach the watch.

[Guy_]

@PaPaRJW - it does, though still not a good idea due to a risk of shorting, also as the magnets can attract paper clips etc, it's never a good idea to leave it plugged in as a short circuit can arise, in both cases the charge cable and even power source can be damaged.

See these tips

Tips when using the Sense or Versa 3 charging cable

Tips for charging your Sense

The importance of cleaning

How best to get the maximum longevity from the watch battery?

[PaPaRJW]

So why does the pin not pop up any more? 
Is the spring just broken.? Doubt that because it always appears to be the same pin.

If the spring is part of the charging circuit, is it because the circuit shorts and “breaks/melts(as in a fuse)” the spring.

Is it due to wear and the pin touches the watch body and shorts etc.etc.

Something else?

It appears a lot of people have this problem.  Not sure I would have bought it if I knew this first. (Lemon laws apply).

[Guy_]

@PaPaRJW - yes it would seem the spring is broken, so the pin doesn't pop up anymore.

It does seem to be the same pin.

It would seem that a short circuit may have fused it but disassembly would be required to verify.

Yes it does seem to happen often, due to design or use, or over use. For example, I charge once every 5 days or so which means it has only been attached 160 times in 18 months and the charge cable might last longer than someone who has attached it 630 times during that time.

Good to ask these questions.

[PaPaRJW]

So after some investigation my hypothesis for the failure reason is this.  The pogo pin used in the charger is under rated for the force that is exerted on it when the charger base snaps on to the watch. So….

1. Increase the rating of the pogo pin strength.

2. Decrease the magnetic attraction force between the charging base and the watch.

3. Try not to let the charger base “snap” on to the watch.

I noted that even though the pin has retracted into the base it can be gently tapped out and it still shows an active voltage (5.4V) using my charger block.  I will try superglue to keep the pin out and if not solder it in the out position.

I hope Fitbit take this on board to improve their product. 

[Alecalok]

Hi - I think I have solved this problem.

The top left pin got stuck inside - signature move by fitbit charging system. I checked through all the posts here and everybody said I will have to buy a new charger (either original fitbit or those replacement ones).

I took a small scalpel and a pair of tweezers. Scratched away the little ring of plastic around the sunk pin, and using the tweezers, pulled out the sunk pin. Then with the help of the tweezer, I pushed it half way in and then applied superglue carefully.

Lo and behold the charger is working like magic again. Now it is resting on the springs of the three pins. It looks ugly but working alright. Happy to assist anybody trying this. It is totally risky and you may end up damaging your device (both charger and watch). So proceed at your own risk.

[Guy_]

HI @Alecalok - an interesting solution but not to be recommended for the long term. The springs ensure even seating of the contacts. Once it is glued in position it may harm the watch anytime. It would be much cheaper to buy a new one online [rather than a new watch] if you are out of warranty, they only cost a few dollars. Follow the charge cable photo links in How to check charge cable - Sense/Versa 3 won't charge, won't start or blank screen 

[PaPaRJW]

Well done. My heavy handed application of araldite didn’t work to well. It is probably too fiddly of an operation for my hands.

Fitbit will hopefully improve the situation.

[wmccharles]

I've had 3 fail in 3 months...I thought it was my power so I brought a new cord to my gf house and the same happened there

[PaPaRJW]

The pin is still active, that’s why I suspect it is the pins spring that has failed. Just be very gentle putting the charger on the watch.

Sent from my iPad

[Stebit]

I have a tons of chargers all over the place thrown in boxes because they stop working. The solution is to make the holes for the pins slightly larger and the spring slightly stronger. The problem is, no one will do this because the neither Fitbit nor the manufacturer (I doubt Fitbit is the manufacturer) will admit there is a problem. There is hardly anything about this on Google but I suspect there are lots & lots people with this issue. Fitbit's solution is to clean the contacts. While this CAN be a problem it is ALWAYS the pins that fail (at least one will get stuck in and not make contact) after so many uses - in my case, it's about 20 uses, give or take. That is for every single one of the many, many chargers I have purchased in the last two years, regardless of who the seller was - there may be only one or two manufacturers anyway.

If I knew how to go about it, I could easily redesign it and have it manufactured to my specs and guarantee the product - probably make a bundle.

I got so pissed this last time, I drilled a small hole next to the pin and inserted a tiny piece of aluminum foil rolled into the shape of a pin. I'll bet it lasts longer than the original, provided a different pin doesn't fail. LOL

[Stebit]

Good suggestion, Alecalok. I actually tried this on several different chargers over the past year. I was unsuccessful. I couldn't get the pin to come out. But congrats on your success.

[Alecalok]

Thanks Stebit. I guess the difference is using a super fine tweezer (I used the ones that come with swiss knives) and a metal scalpel/ paper cutter. This does scratch the surface of the charger, but then - it was anyway a garbage with a sunk pin. One week of regular usage and the contraption is still working. Charging a little slowly, but cant complain.

[KB9WNS]

Use a current limited power supply with the limit set to 325 milliamps. A 500 milliamp USB charger will suffice for those who don't have an electronics lab. Best not to use any charger power supply that has a higher current rating.  Attach the charger to the watch prior to connecting to the power supply.  The internal spring can only handle about that much current.  I took one apart and found that the springs are heating up to the annealing temperature.  If for any reason the pins short out against the watch back while using a 2 amp charger the springs will overheat and anneal. Also keep the contacts on the watch clean.  Again, disconnect the cable from the charger power supply PRIOR to attaching to the watch.

Aerospace electrical engineer with 40 years of experience and a HAM radio operator.

[Andyroo2au]

Same issue to both my charge cables, as an electrical engineer my view is the issue is a design flaw and latent defect that fitbit should fix and compensate

[PaPaRJW]

Hi “Hillrunner” I tested the pin after failure and it was still active. This suggests the spring is not in the circuit for charging.
I haven’t pulled it apart as far as you have and only offer this information to the root cause.
If the spring has been “annealed” in the compressed position but not fractured I would still expect it to work as it is supplying enough pressure to push the pin against the watch.
In my experience the failure includes failure of the spring to push the end out for charging.

Russell. (Metallurgist)

Sent from my iPad

[Guy_]

See More on the pin stuck 

[Stebit]

So that’s the problem! The heat from using a power supply with too much amperage. If i understand you correctly. 
Good to know. Thanks for this, KB9WNS. 
It does beg the question: why doesn’t Fitbit put that in the accompanying literature?