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  1. #1
    Join Date
    Jan 2008
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    Battery replacement

    The battery in my Therm-ic boot heater died. (I hope itís the battery and not the circuit board).
    It works charge overnight, show full bars, turn on, and run out of juice in a matter of minutes.
    Before I buy a new battery unit from Therm-ic at $130, I figured Iíd try to replace the battery for $8.00 from Battery Junction.
    I ordered the correct battery, and now that it has arrived, Iím not sure how to connect these terminals.
    I assumed I was going to solder them, but the terminal tails look like itís just a crimp and heat shrink?
    And suggestions, or expertise?
    Iím not afraid to buy some new tools if needed
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  2. #2
    Join Date
    Sep 2018
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    5,577

    Battery replacement

    I have the older thermics, but I fixed them the exact same way. You are essentially just splicing wires. I just covered the splice with heat shrink.

    Edit: Ah, see now that the battery has flat tabs. Applying heat to battery terminals is bad news (easy to fry or explode said battery) so I think you are looking at a mechanical connection that you heat shrink over top of.

    But if you really want to buy one of those tiny spot weld tools I think you could do that.

  3. #3
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    Jan 2008
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    Battery replacement

    Soldered in the new battery, and covered the connection with heat shrink.
    The unit powered up right away, connected to Bluetooth, and took a full charge in the typical 4hr charging cycle.
    I left them charging in a room I was in, with the fire extinguisher on the counter beside them.
    After a full charge I plugged them into a spare insole element and ran them on high for 5+ hrs until the battery drained. Run time was longer than I typically get typical on my other battery pack.
    I have it charging again this morning beside the fire extinguisher.
    I think after this next charge/drain cycle I can stop worrying about burning down my house with a dodgy soldering job with an internet battery.

  4. #4
    Join Date
    Sep 2018
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    5,577
    Nice. I think those long tabs disperse heat enough to not screw up the battery if you are quick. Iíve had some mixed results. Fried a battery about a month ago but was connecting directly to the terminal, but pre is oily had not had problems.

  5. #5
    Join Date
    Mar 2005
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    Dystopia
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    18,804
    Nice work.

    FYI. They make fireproof bags for rc car batteries if you’re worried.

  6. #6
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    Jan 2008
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    Quote Originally Posted by Core Shot View Post
    Nice work.

    FYI. They make fireproof bags for rc car batteries if you’re worried.
    Thanks, but I'm over it now, 3 full charges and discharges, I can sleep soundly at night not thinking about my house burning down.
    Plus warm feet again today on the hill.

  7. #7
    Join Date
    Jan 2021
    Location
    Idaho
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    128
    Wow, that runtime is a huge success!

    I think you figured it out... soldering on the end of those tabs is OK and not risky for the battery. Soldering directly to the cell is where spot welding is advised.

    If you do it again maybe consider a tad more for a name brand 18650 cell such as a Panasonic/Sanyo NCR18650GA, Samsung INR, or Sony VCT6. The battery life should be even greater since you could got with a 3500mAh instead of 2500mAh. That is another 40% runtime! Based on your runtime the draw is probably about 0.5A so they should all handle it.

    You can also order cells from MTN Electronics. But they probably don't have those helpful strips already spot welded on.

  8. #8
    Join Date
    Jan 2008
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    livin the dream
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    Dorkey corner of the internet: https://www.reddit.com/r/18650masterrace/


    Sent from my iPhone using TGR Forums
    Best Skier on the Mountain
    Self-Certified
    1992 - 2012
    Squaw Valley, USA

  9. #9
    Join Date
    Jan 2008
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    BC to CO
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    Quote Originally Posted by m5d5cb View Post
    Wow, that runtime is a huge success!

    I think you figured it out... soldering on the end of those tabs is OK and not risky for the battery. Soldering directly to the cell is where spot welding is advised.

    If you do it again maybe consider a tad more for a name brand 18650 cell such as a Panasonic/Sanyo NCR18650GA, Samsung INR, or Sony VCT6. The battery life should be even greater since you could got with a 3500mAh instead of 2500mAh. That is another 40% runtime! Based on your runtime the draw is probably about 0.5A so they should all handle it.

    You can also order cells from MTN Electronics. But they probably don't have those helpful strips already spot welded on.
    I looked for a 3600mAh, but the only option with tabs was that generic 2600 option from BatteryJunction.com.
    If I ever have to do it again, Iíll check some other sites for a better battery.
    Therm-ic sells a 1300, and 1700 battery pack, so I assume the 1300 model has a 2600mAh battery at 0.5A draw.
    And the 1700 model has a 3600mAh battery pack.
    So Iím sure I could just do the 3600.

    The fawking local news has had stories about 2 e-bike fires, a hoverboard fire and last night an consumer warning expose about lithium-ion battery fires.
    Now we canít leave the house without my wife asking me if my ski boot batteries are plugged in.
    Both of our ski boots have had boot batteries plugged in and charging every winter day for 10+ years.

  10. #10
    Join Date
    Sep 2018
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    5,577
    Quote Originally Posted by Dee Hubbs View Post
    I looked for a 3600mAh, but the only option with tabs was that generic 2600 option from BatteryJunction.com.
    If I ever have to do it again, Iíll check some other sites for a better battery.
    Therm-ic sells a 1300, and 1700 battery pack, so I assume the 1300 model has a 2600mAh battery at 0.5A draw.
    And the 1700 model has a 3600mAh battery pack.
    So Iím sure I could just do the 3600.
    I just replaced another battery pack with 2,000mAh. Third party tests have shown this one to come in around 2,100 in actuality. A lot of the generics test far lower than what they say they are, so watch out for that. If you're getting a true 2,000 it should be more than enough to make it through a day - or two.

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