I Fixed My 10-Year-Old Bike Lights for $20
Replacing the old battery on rechargeable bike lights
After a decade in a drawer, my rechargeable bike lights only held a charge for five minutes. At my local makerspace, I desoldered the old battery, identified it with help from an LLM, and soldered in a $3 replacement from AliExpress. The lights work again—and I learned that even with minimal electronics skills, repairing old gear is possible.
I thought it was really cool that I was able to do this with extremely minimal electronics skills!
- layer8
> I wasn’t sure how to find out what an “LI????77” was […]. I would be interested to learn non-LLM ways to figure this out though. There must be a way.
Reading https://en.wikipedia.org/wiki/Button_cell#Type_designation would have indicated a solution: The third character must be an R (for rechargeable), the “77” would be the height in tenths of millimeters (which makes for a good plausibility check), and then you can measure the cell’s diameter to obtain the remaining digits in the middle.
- MrGilbert
> I wasn’t sure how to find out what an “LI????77” was […]. I would be interested to learn non-LLM ways to figure this out though. There must be a way.
Back in my days I simply googled my way through the nomenclature of batteries. I feel pretty old, somehow.
- robot_jesus
Love this. I have a pile of nice Cygolites (both front and tail) that my whole family uses that are maybe 8 or 9 years old. Their capacities have largely dropped to the point that I need to charge them every ride or two. Maybe get about 90 minutes of use, down from 3-4 hours previously.
They're not user-serviceable by design but I've been pondering cracking them open and having a go at swapping the batteries. This post may inspire me.
I've got a pile of new 18650s lying around and hopefully the front lights use those!
- dragontamer
I wouldn't worry about matching the exact model number of the battery. Instead, it's more important to get roughly the same chemistry and a capacity equal or maybe a touch greater (if technology improved in the last 10 years, capacity could be greater with modern parts).
Specific batteries go in and out of production. But as long as it's the same CHEMISTRY, voltage, and capacity, it's likely compatible. Chemistry tends to set the voltage, size sets the capacity.
Charge/discharge controllers and algorithms are based on these three bits of info.
In some cases, some chemistries are actually compatible with other chemistries. NiHM cells are largely backwards compatible with Ni-Cd chargers (but not vice versa). It's not good for the NiHM but they will actually take the charge.
- esquire_900
In the Netherlands many people use these kinds of detachable bike lights. I've never came across soldered batteries in the dozen or so I've replaced batteries for. Not always cheaper, but just tossing the whole thing seems like such a waste.
Well done!