Fitbit One battery replacement walk-through with photos

[PureEvil]

Hi everyone,

My beloved Fitbit One (bought it on July 2013) has stopped taking a charge well (I now need to recharge every two days), so I decided to replace the battery to give it some new life.

Note:  Though the Fitbit One tracker has been off the market for a couple of years (so your warranty has likely elapsed), this will definitely void your warranty.  Also, this is not endorsed by Fitbit; I'm just an avid user with some electrical know-how... So keep that in mind before you proceed.

I found the replacement battery on ebay.  You can find one by searching for "fitbit one replacement battery".  The one I got was listed for a Fitbit Charge HR as described as "3.7V 80mAh" for voltage and charge capacity respectively.  It seems to work just fine.

These are the tools used:

1. Clamp - Smaller clamp that I use for hobbies.
2. Bondic - This is a plastic that hardens with a particular light frequency.  It works well for both holding the wires together and insulating wires.
3. Gorilla glue - used to seal the Fitbit One back together after replacing the battery.
4. Utility knife - something with hard blade, used to open the Fitbit One.
5. Soldering iron - this one is a low heat version for hobbies.
6. Solder - Thin and low heat, used for hobbies.
7. Wire clippers - To cut out battery and strip wires.
8. Cotton swab - apply glue (and water) to seal the Fitbit One.
9. Replacement battery.
10. Fitbit One.

Open the Fitbit One - Use the utility knife to pry open the Fitbit One.  I wedged the sharp end of the blade between the plastic and metal and pried the two apart, much like you'd pry a clam or oyster open when you shuck one.

Remove the battery - Once opened, remove the battery.  You can lift the battery; there may be some adhesive to hold it in place, you can still safely lift it and separate it carefully.  Use the wire clippers to cut the wires as close to the battery as possible; this will give you the most remaining wire with which to work.  You'll have significantly more red wire than black wire.

Examine the wires - The convention for wires is red for power and black for ground and with Fitbit this is also the case.  As mentioned before, you'll end up with a longer red wire and a shorter black wire.  Using the wire clippers carefully strip the plastic insulation off each wire so that you may solder them to the replacement battery.  Alternatively, you may solder the black wire directly to the terminal.  I did the former. 

Solder the wires - Solder the wires, one at a time to minimize the possibility of short-circuiting (and thus damaging) the battery.  Cover the soldered connection completely with Bondic; you may apply multiple layers.  This will serve to both hold the wires together and to electrically insulate them (much like you would with electrical tape).  Be sure to use the included light to harden the Bondic material after each application as per their directions.

Install battery - Once you have soldered and insulated the two sets of wires together you may tuck the battery and the wires into the Fitbit One.  This is a good time to make sure the battery works by pressing and holding the button to turn it on.  Keep in mind that the battery may be discharged; if so, you may need to plug in the Fitbit to charge before it turns on.  Here's a picture with the old, removed battery.

Apply glue reseal the Fitbit - Use the cotton swab to apply Gorilla Glue to the inside of the Fitbit unit just below the lip around the entire perimeter.  Gorilla glue requires water to bond, so use the other end of the cotton swab to apply a little bit of water to the metal cover.

Clamp the unit and allow to set - Once glue is applied to the unit, hold the Fitbit firmly together with the use of a clamp.  I also took an opportunity to wipe off any excess glue with a paper towel dampened with some alcohol.  It takes 24 hours for gorilla glue to fully set, so leave it clamped during that time.

The whole process, from beginning to end, took around an hour, but I was taking pictures.

With the new battery the charge lasts for 4-5 days.  This is great improvement over the 2 days before the battery replacement.

I ordered the replacement battery months ago and allowed it to sit before I did the replacement.  I imagine that had I installed it sooner (or perhaps ordered from a different vendor), it would last even longer.

I hope this helps and let me know if you have any questions.

[WendyB]

Wow looks scary to me 😁

[Lorikb_00]

Yea, can I send mine to you to fix it?   🙂

[PureEvil]

@WendyB and @Lorikb_00,

It's actually not that bad.  I just took lots of pictures.  Sure, I'm a geek and had all this stuff already, except the battery, of course.

I imagine that you could find a friend to do it with this walk-through.

[WendyB]

I know mine will die at some point but it's still going strong right now 😂😀🤗😮

[WendyB]

My DH could do it. I still have one I haven't used that I'm worried if it will work or not. But quite frankly the inspire with clip will do me

[PureEvil]

Yes, I got an Inspire as well, but I want to have a clip-on and the Versa 2 on my account and right now I can't with the Inspire.  😢

[Williger]

@PureEvil Interesting approach! Kudos for outlining steps and taking pictures along the way. I'd only taken a couple when installing mine, and it seems several people need to replace theirs. One important note, there are two models of Fitbit Ones. One, like yours, opens at the metal/plastic seam, the other kind (like I have) looks identical but is an entire piece (it won't separate at the seam, it's merely aesthetic). I'd approached mine differently (I'm not an engineer nor electrician, I'd purchased a soldering iron specifically for this project). I'd gotten my battery on eBay for ~$11 with shipping, opened the tracker by prying with a pocket knife following warming the case with a heat gun, removed the guts, heated the point on the circuit board where the wires were attached, leaving the existing solder, placed the new wire leads in their appropriate spots, quickly heated to reattach, and closed case with enough time that the glue was still tacky enough to hold. Getting around 10 days between charges. Cheers!

[JEH1]

This is amazing! Thank you! 

[PureEvil]

@Williger,

Nice!  The battery I used was labeled for a Charge HR, I believe.  I may track one like yours to try to get up to the 10 day between charges.

Thanks!

[WendyB]

@PureEvil  I did it! I didn't even give it to my DH

I washed and dried my One for about the 5th time. I guess it didn't like be washed for the 5th time and decided to die even after being in rice. 🤔 But now its happy and alive again 😁

[PureEvil]

@WendyB,

Nice!  High Five!

[theguru1974]

How is it that you folks haven't been affected by the dreaded issue where the One turns itself off over and over again and doesn't track anything? I assume we have all been forced to upgrade the software to version 6.64? As soon as a unplug my fully charged One from the PC, I try to press the button and it won't come on at all. 

[Williger]

@theguru1974 because we have replaced our batteries. The problem you describe is what happens with a functioning tracker with a dead battery. Firmware updates aren't mandatory AFAIK, but I'd recommend them for reliability and battery life optimization. Replace with the tips above, or buy a newer model. They're amazing little devices and it's great they've lasted as long as they have.

[theguru1974]

Thanks for your reply! That actually makes sense. My first Fitbit One worked well but eventually had to be recharged every 2 days. I never had the issue with it refusing to turn on, it was just annoying that the charge didn't last. So about 2 years ago I bought a new One off ebay. It was fine until a few weeks ago. I guess battery life is limited even when sitting in a package unused for years. Difference is this time, it holds a charge for longer than the old one, but has the won't wake up issue. I guess attempting the battery replacement is a fairly cheap prospect.

[WendyB]

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I guess battery life is limited even when sitting in a package unused for years.

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Yes this will cause problems. Sad but true.

Try Battery replacement and  Keep us posted!

[Saratheone]

@PureEvil  @WendyB My One was working great until I took it to the beach in a ziplock :-).  a tiny bit of water got in the bag and now it doesn't hold a charge.  used to last 7-10 days and now maybe 3 hours.  I am so angry with myself!  ugh, I am an avid user of the one since 2012 and would have bought another in a minute even for $50.00 or so.  Its so accurate and has that amazing display.  I use the display all of the time to see where I am.  Anyway, Ive been hoping that it would eventually get back to its full charge but so far, not happening. I may have to try this since my husbands father was an electrician and we probably have all of the supplies.  Fitbit really needs to bring back the One!!

[WendyB]

I would try it @Saratheone  it's worth it

[ekrub]

Thanks @PureEvil for giving me the detailed instructions and confidence. My FitBit One has changed my life; I've gone from a couch potato to someone who exercises every day thanks to the FitBit One (... and maybe a little OCD). Unfortunately, my FitBit One's battery was lasting about a week and recently dropped to lasting less than 2 days (I'd charge it and be down to 20% the next day). That got me to this page.

After reading your post, I purchased this replacement battery (along with wire cutter, Gorilla Glue*, and a heat gun). I heated my FitBit One (mine looked like the version in @Williger's post) and, once warmed, the covers easily separated from the center board using little effort with the blade of a mini Swiss army knife. After pulling up the existing battery – still attached  – I took a couple of pictures to make sure I didn't forget which wire went where, tinned my soldering iron, and then heated the solder for each of the battery's wires until I could pull the wire out of the solder. I cut the wires on the new battery to the same length as the old one and used the hot soldering iron to melt a few millimeters of insulation off the end of each (exposing clean wires without the risk of trying to strip them manually). I tinned my soldering iron again and attached each wire by placing it on top of the existing solder on the board and holding the soldering iron on top of the wire until the solder melted and the wire dropped into it. With its wires soldered to the board, I put the new battery back in position, moistened one side of the cover with a wet Q-tip and applied a tiny string of Gorilla Glue* to the other side using a toothpick. Then I clamped the case shut with the small bar clamp and left it for several hours.

I charged my FitBit One with its new battery and am pleased to say it lasted two weeks (exactly 14 full days) before it dropped to 25%. Woohoo!

Not everyone wants their tracker on their wrist. And not everyone wants to have to remember to charge their tracker every week. Maybe FitBit will make a replacement for the FitBit One some day (a clip-on that measures floors & steps and lasts at least 2 weeks between charges). Until that day, it's nice to have this option! Thanks again!

___

*Instead of Gorilla Glue, consider using a glue like B-7000 adhesive

[theguru1974]

Great post, very detailed and appreciate the advice. One question though, will the Gorilla Glue prevent the One from ever opening again, when the battery needs replacing again?