Thursday, July 26, 2012

Garmin Forerunner 305 battery replacement

The battery in my Garmin Forerunner 305 got to the point where it wouldn't hold a charge long enough for a 6 mile run.  A Google search at first didn't result in much, but finally I came across a couple pages that looked promising.  One guy used a phone battery with success, but I don't have any phone batteries lying around.  Another site I came across indicated that a replacement battery for an iPod Mini is the same voltage (3.7V), about twice the capacity (1300mAh instead of 750mAh), and very similar in size.  I bought an iPod Mini battery on eBay for $4.21 including shipping.  A couple days later it arrived and I went to open my Garmin.  I had read that sometimes the watch pops open of its own accord because the battery swelled, but even if it doesn't you should be able to open it by prying with your fingernails.

I went to pry mine open and realized it was already swelled open, so I just opened it the rest of the way with my fingers.










There were no wires to be careful with...the top just came completely off.











I clipped the black and white wires connecting the battery as close to the battery as I could to leave as much wire to work with as possible.















I cut the connector off the end of the new battery's wires, stripped the black and white wires at the ends, twisted the wires together, and soldered them.  I just left the white wire alone.








After wrapping the exposed wires with electrical tape, I put the battery into the watch and pushed the wires out of the way of the button on the left.









I glued it back together with epoxy since that's what I had on hand.  I hope I don't have to open it again!  I pressed on the watch to keep it snug while the epoxy hardened.  The connectors won't make good contact unless the pieces are snugly together.

When I plugged it into the charger, it started charging normally.  An hour or two later it said battery charging was complete.









It got satellite reception and appeared to be working properly.










I went to the menu to see the battery symbol which indicated it is fully charged.










And Kim tried it out on her run this morning.  It's working well!
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26 comments:

  1. jaknudsenAugust 23, 2012 at 1:46 AM

    Thanks for a great tutorial, just did the same with mine.

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  2. FraserSeptember 5, 2012 at 10:06 AM

    worked perfectly, nice and easy thanks!

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  3. UnknownSeptember 27, 2012 at 11:36 AM

    I want to do this but know nothing about soldering. Is there a soldering kit I should buy or something?

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  4. RandySeptember 28, 2012 at 2:00 PM

    You'll need a standard soldering iron and solder. All you need to do is touch the soldering iron tip to the wires that were twisted together to heat them up and then while the iron is still touching the wires, touch the solder to the wires. Some solder should melt onto the wires and then you can remove the solder and the soldering iron from the wires to let the solder cool on the wires.

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  5. Abhijith RaoOctober 4, 2012 at 1:41 AM

    How long is the battery lasting once you made the change? Does the battery last twice as long (or some where close) as the original? I bought the batteries, but no soldering kit at the moment. So, planning to get it done over the weekend.

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  6. RandyOctober 4, 2012 at 9:03 PM

    I haven't tested to see just how long it lasts, but I never see the battery meter go down below full during my 7 mile runs. In theory it should last almost twice as long. Since it's been so long since my watch battery was holding a full charge, I don't even know how long a full charge on the original 750mAh battery was supposed to last.

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  7. Abhijith RaoOctober 5, 2012 at 4:02 AM

    Thanks Randy for writing this article up. Hopefully I will get mine working again. Cheers!

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  8. AnonymousOctober 16, 2012 at 4:37 PM

    I did this to mine. The original used to last 13 hours. Mine dropped down to 3 hours which is not enough for ironman triathlon bike and run. I have let it stay on to see how long it lasts with this new battery described here. It only lasts 10 hours which is much better than before but not as good as new. It will not last for the ironman since I am slow and it takes me 11 hours for the bike and run. It is close enough that I will probably use it though.

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  9. Boulder BillNovember 28, 2012 at 12:33 PM

    This comment has been removed by the author.

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  10. RandyNovember 30, 2012 at 2:10 PM

    The soldering iron doesn't melt the wires. It just heats them up so the solder will melt onto them.

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  11. AnonymousDecember 6, 2012 at 10:44 PM

    I can get about 4.5 - 5 + hours for sure on my Forerunner 305 now with the original battery probably more because I still had two bars left after I finished. I have been careful to not let my battery discharge completely. One thing to remember about Lithium Ion batteries is that they really "prefer" to stay charged up. When this type of battery discharges fully it makes a salt and it swells up and does not work right (just like this nice man's unit did). NiMH (Nickel Metal Hydride) batteries have the exact opposite "preference" and must be discharged fully before charging or the get a "memory" and the charge life decreases if it is not discharged fully before charging because of a similar corrosive phenomenon.

    I charge my watch after nearly every run. I have had no real battery life issues, unlike my spouse whose need for a battery in hers led me to this wonderful instruction.

    Thanks for sharing, I appreciate the time you took to make this up!

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  12. E.S. KraayDecember 8, 2012 at 4:03 PM

    Randy, Like everyone else, I wasn't so upset that after two years the battery was shot. What ticked me off was Garmin's incredible price to replace it. Fortunately, I found your discussion... I gave it to an 80-year old friend who loves to tinker. He got the thing opened and went down to Battery Plus or whatever it's called. They quoted him $40 for the battery and $20 for handling. NOT! I ended up buying the battery on Amazon.com for $1.14! During the repair, we found that one of the metal contact tines at the top was broken off. My friend wedged a toothpick beneath the panel to insure good contact. Voila/Wa-La or however you spell it.... I am back in business with a 1350 mAh! Great post, and thanks for helping out all of us Garmin 'customers.'

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  13. Brother ADecember 30, 2012 at 1:22 AM

    I am reading this from Israel and planning to try the same. I guess the 305 was never waterproof, so getting the thing closed and watertight is not an issue here.

    Just one question. I see that you wrote this in July and now we're at the end of December. Is your watch still operational? Have you ran many hot, sweaty miles with it, and did it withstand the use? I just wanted to make sure that this is a long-term solution, not a quick fix. Thanks for putting this post up - much appreciated.

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  14. RandyDecember 31, 2012 at 10:04 PM

    Yes, my watch is still working great. I've run in the snow and rain with no problems. It still has great battery life. I get about 6 hours of usage before a battery low message, and 9 before it actually runs out of power.

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  15. UnknownJanuary 14, 2013 at 1:54 AM

    Thanks for the DIY. Just completed the job and blogged it, and am hoping for some extended battery life.

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  16. UnknownJanuary 25, 2013 at 1:04 PM

    Hope this works. Thanks for the info

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  17. Boulder BillJanuary 27, 2013 at 11:44 AM

    Worked like a charm! Never soldered before, so feeling like quite the electrical engineer. :)

    Thanks for the helpful and detailed post.

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  18. WazzupFebruary 22, 2013 at 7:17 AM

    Thank you... Who would have thought I would be buying an apple (well battery anyways :))

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  19. ChrisMarch 23, 2013 at 2:52 PM

    Just wanted to thank you. It was also my first time soldering and it worked perfectly. Thanks!

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  20. UnknownMay 15, 2013 at 10:00 PM

    After more than three years of having given up on my Forerunner 305 I'm pleased to find several people have had success (I searched when it first failed but found nothing).
    Now I'm happy to see there's hope for it... I just ordered an iPod mini battery and it will take several days to get here.
    With the 5V source hooked up to the cradle I get current on the board inside the watch (where the contacts from the cradle) so I know the path into the battery is good, but I'm wondering if I should be able to turn it on with a faulty battery while it's plugged in.
    When you were testing- were you able to turn the unit on while it was plugged in? Or does it need a good battery to turn on even when plugged in (as if it were being charged)?
    Thanks....

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  21. The_MickMay 22, 2013 at 2:56 PM

    SILICONE SEALANT AND ADHESIVE!
    I would recommend to people that there are water-proofing silicone sealants/light [but strong enough] adhesives available (Permatex Clear RTV Silicone, Loctite Clear Superflex RTV Silicone Adhesive Sealant, etc.) in small tubes that I would use rather than something as strong as epoxy.

    A similar website on replacing the battery used Permatex Clear RTV Silicone on the 305 with good results and says: "The original adhesive is some kind yellow, slightly stretchy stuff. I’ve seen it before, but I don’t know what it is. After reading others’ posts, I decided to go with silicone adhesive, which I found at the auto store for a few bucks. We want a watertight seal, but nothing so permanent that we can’t reopen the case.

    I applied a little to the edges of both the top and bottom of the case with a toothpick.
    The whole thing is wrapped in a cocoon of tightly stretched electrical tape and left for a day. The edge came out looking pretty good."

    Source: http://www.jimandkatrin.com/CodeBlog/post/Forerunner-305-Battery-Replacement.aspx

    He used a Samsung battery he happened to have around, thanks for the information on the higher capacity iPod Mini battery!

    Thank's so much for the detailed procedure. I hadn't used my 305 for a year and now am finding I'm getting low battery warning within 2 hours after charging, though it may not be smart to leave the battery on my USB charger after it's removed from the computer.

    If things don't improve, I'll follow your directions with the exception of resealing and waterproofing with a silicone sealant.

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  22. AndrewJune 1, 2013 at 6:42 PM

    This was fantastic, thanks so much. As mine was still intact, I used a small putty knife to open the case starting from the bottom "GARMIN" side and working my way around, and it opened up quite easily. My eyes aren't what they used to be so soldering was a bit slow, but all in all it took maybe 15 minutes. Best $5 spent in a long time. Thanks for the post.

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  23. Fancy Dress To ImpressJune 2, 2013 at 4:11 AM

    361-00026-00 Garmin Battery

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  24. Caroline DunnJune 5, 2013 at 1:37 PM

    Thanks for the tutorial. I made a video of my Garmin 305 battery replacement - http://youtu.be/8vQTHF76B6A
    I put a link in the description field to your blog post here.

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  25. Andre BretonAugust 7, 2013 at 7:15 AM

    Thanks to this post my Garmin Forerunner 305 is ready to roll in the Leadville Trail 100 Mountain Bike Race on Saturday. Thank you for posting the solution to my failing battery!

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  26. AnonymousJanuary 3, 2015 at 5:46 PM

    Thanks for the instruction, I just ordered a battery on Ebay $5.19 w/shipping. I was ready to shop for used 305's since they are not made any more. My eyes aren't getting any younger and I love the big display. It seems like all the new models are getting smaller.

    ReplyDelete

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