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. Oct 6, 2020 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, 2020 at 19:33
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    Take the light/battery to a local shop that does small battery replacements. "Batteries Plus" is one option in our neck of the woods. Oct 6, 2020 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, 2020 at 15:24
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    Did anyone on this thread find a replacement battery for the Fortified Boost Bike Lights? I haven't had any luck. Oct 31, 2021 at 16:39

2 Answers 2


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, 2020 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, 2020 at 8:27
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    @Criggie that's not optimism, that is simply fraud.
    – user253751
    Oct 7, 2020 at 11:23
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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, 2020 at 15:19
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    Lets be honest - the specs on batteries are frequently overstated and sometimes outright fabrications. If your battery is suspiciously lightweight, it will have rubbish capacity. And the price should reflect their quality, so avoid cheap ones.
    – Criggie
    Nov 1, 2021 at 0:04

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, 2020 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, 2020 at 20:28
  • Just a note to emphasize that not all similar-looking batteries are safe for your use (as mentioned above). Aside from chemistries, in your case it's likely important that the new batteries be "protected", which means they've got a small disc PC board stacked on top of the battery under the colorful shrink wrap, which prevents overcharging and other dangers that could start a fire.
    – Armand
    Oct 31, 2021 at 18:17

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