One of the two rechargeable batteries that go with my Fortified Bicycle's lights appears to have started to die permanently. (The other remains in good condition.) I have looked through eBay and found nothing there. Can I get usable replacements from another manufacturer via an online battery story or bike store?

I do not know much about bikes but I can tell you that these batteries recharge using ports. Printed on the battery: 18350 950 mAh 3.7 Li-Ion. These connect via port to a computer or charger for recharging.

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    Add pictures of the battery and electric parts, especially brand names. – Nathan Knutson Oct 6 '20 at 15:54
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    @NathanKnutson: my clumsiness makes it tough for me to take photos. (seriously.) I can, however, tell you that Fortitude made its own batteries and that they have two round points for connection with their lights. – Ria Oct 6 '20 at 19:33
  • Take the light/battery to a local shop that does small battery replacements. "Batteries Plus" is one option in our neck of the woods. – Daniel R Hicks Oct 6 '20 at 20:21
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    Regarding why the battery might have gone bad: if your country sees freezing temperatures, make sure to let the battery warm up before charging. – jpa Oct 8 '20 at 15:24

If your light is not sealed, and you can see a battery that looks like this


(the colour/color does not matter) then you can pop out all the old batteries and fit new ones. Replace all the batteries in one light together, don't mix and match. The old ones should be recycled properly.

If the current batteries are soldered in, then its still possible to swap them, just takes more effort.

Aside, "18350" is a dimension, being 18mm across, 35mm long, and 0 means a round/cylindrical casing. 18mm diameter is slightly thicker than a common AA battery which is a 16mm diameter.

Matching the voltage and chemistry is important - you can't put a 1.5V battery in place of a 3.7V battery, because it probably won't work and it definitely won't charge safely. Matching the size helps stop things from rattling about and becoming loose.

Additionally there is another size of battery called a 16340, which is 2mm smaller in diameter. This is also known as a CR123A, which might be an acceptable fit if you add some tape around the outside as packing. Note this battery can come as a disposable or as a rechargeable lithium-based chemistry. Don't recharge a disposable.

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    And the 700 mAh (as shown) has only the ~75% of the capacity of the original 950 mAh battery. The 700 mAh will work but just won't last as long. – D Duck Oct 7 '20 at 8:13
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    @DDuck excellent point - thank you. I'd extend that to say there's a lot of optimism in those capacity ratings too. I've had one battery pack rated at 4800 mAh when inside were two 1200mAh batteries in series, which is still only 1200 mAh. – Criggie Oct 7 '20 at 8:27
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    @Criggie that's not optimism, that is simply fraud. – user253751 Oct 7 '20 at 11:23
  • @user253751 Or, whoever calculated the number didn't understand the difference between mAh and mWh and therefore got the answer wrong by a factor of 2. Definitely incorrect labelling, but committing fraud requires intent, not just incompetence. – alephzero Oct 7 '20 at 15:09
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    @alephzero Except they actually got the answer wrong by a factor of 4. You can blame one factor of 2 on incompetence but the other factor of 2 is fraud. – user253751 Oct 7 '20 at 15:19

First, hello, and welcome to Bicycles SE. Sorry to hear about your manufacturer collapsing... that's really unfortunate, particularly for a higher-cost item like an e-bike. My guess is that 18350950 mAh 3.7 Li-Ion is actually "18350 950 mAh 3.7 Li-Ion", meaning that the pack is comprised of 3.7 volt 950 mAh 18350-type lithium ion battery cells. This is valuable information, but also somewhat general. There are services that will open up battery packs like that and replace the dying cells with new ones. Batteries Plus in my area is an example.

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    thanks for the information. I gave the impression that I had an e-bike, when in fact, I have a regular bike, with chargeable bike lights. I have changed my original question to make this clear. – Ria Oct 6 '20 at 19:31
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    Ah, got it. Thanks for the clarification. As it happens, the solution remains the same, but probably for a much lower cost. That's a relief! – Andrew Oct 6 '20 at 20:28

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