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Replacing the old battery on rechargeable bike lightsjvns.ca
207 points•surprisetalk•4 days ago•130 comments•
#battery#rechargeable#replacing#bike#lights#old battery#rechargeable bike#bike lights

130 comments

layer83 days ago
> 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.

artisinal3 days ago
And this is why you don't ask an LLM such questions. An LLM will give you a random battery type as it doesn't have calipers nor hands to measure the size of the battery.
tialaramex3 days ago
An LLM might know there's a system to this, but equally depending on training material it might not. If you find a battery nerd they will know. For a whole bunch of topics there will be a nerd who cares a lot about that topic and knows the answer, and one of the lovely things about having connected ~all the world's humans is that you could find that nerd.

The nerd, unlike an LLM is clear on the difference between reality and imagination and where exactly the grey areas are. They can tell you whether your question just has an answer like this one (measure the battery, now you know) whether it has an accepted canonical "answer" but it's made up so if you hate that just make up your own canon, or whether it's absolutely MST3K Mantra material ("repeat to yourself it's just a show, I should really just relax").

Tade03 days ago
Word of warning: batteries from AliExpress might not be the size it says on the tin.

Also: not all lights require soldering to change the battery. Some brands, like Fenix, offer lights where you can change the battery on the go.

I had a light from a lesser known Taiwanese brand - an INFINI Lava 500. At some point it stopped working, so I took it apart with my iFixit kit and inside was a 102660 battery (1700mAh instead of the advertised 2600mAh), so I bought a 102560 unit - 10mm thick, 25mm wide and 60mm long (supposedly).

It was a good few millimetres longer and didn't fit. What's worse - AliExpress stopped shipping batteries to my address, because due to safety regulations you can't ship batteries via airmail, it's just that one vendor who chanced it, so now I couldn't even buy a smaller replacement.

Local vendors didn't have anything nearly the same format, so I gave up and bought a LEZYNE LED Macro Drive 1300XL. Inside there are two 18650s wrapped in a pack that has a plug, so should they die, you can replace the battery without soldering.

phyzome3 days ago
Yeah, I really like that Fenix lights just take a Li-ion 21700 or 18650 (and they have a little caddy to adapt the latter for the former).

However, the manual is very specific about only using their specific batteries and not just arbitrary batteries of matching size and chemistry (generic 18650s). I'm currently trying to get some information out of the manufacturer about whether there is risk of damage or they're just trying to avoid people using shitty batteries and blaming them for a bad experience.

(The manufacturer is fenixlight.com, but the seller is fenixlighting.com. It's kind of confusing.)

phyzome3 days ago
OK, got a response back, although it was possibly slightly AI flavored? But they said no, a good quality 18650 shouldn't harm the light. It just might not power the top modes.
nom3 days ago
Was it a protected cell? They have a little circuit board on one side, sometimes you can see it through the shrinkwrap.
Tade03 days ago
Both were protected - it's just that the battery I bought was genuinely the wrong size - it wasn't 60mm in any axis.
dragontamer4 days ago
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.

bestham4 days ago
The chemistry set the voltage and the voltage and the size set the capacity. Everything else equal, a larger capacity battery is often compatible with an original smaller capacity battery in a given device because the charge current will be lower in relation to the capacity.
dghlsakjg3 days ago
The corollary to this is that if you choose a smaller capacity battery, you run the risk of charging at too high of a current possibly leading to fire.
robot_jesus4 days ago
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!

Rebelgecko3 days ago
Depending on your lifestyle, IMO the USB-C cygolites are worth the expense vs dealing with old ones
MrGilbert3 days ago
> 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.

sublinear3 days ago
I'm pretty sure that's what most people would do now and the AI summary would still be wrong half the time anyway.

I don't think much has changed at all. The LLMs don't magically have new information that didn't already exist out there.

zdragnar3 days ago
In recent months (I don't use it enough to confidently state when the change occurred) Google's LLM summary more often answers the wrong question rather than confidently answering the question wrong.

If it answers and the answer is for what I asked, it is right much more often than not. With that said, "trust but verify" is more like "don't trust and also verify" anyway, which is the same metric that should be used for most websites.

artisinal3 days ago
That is why I turned off the AI summary on Google. Useless 90% of the time, takes up space on my screen.
ivanjermakov3 days ago
> googled

Could've been a trip to a local library!

NooneAtAll33 days ago
> google

he specifically asked for non-LLM, tho :)

crossroadsguy3 days ago
> he

I prefer "they". It's just too much work trying to find out someone's preferred pronouns on the Internet, unless they have somewhere specifically asked not to be mentioned as "they" on the Internet, and that is also too much work, but anyway, in that case I may also indeed have to answer to fellow Internet strangers. But in this case the title says "Julia" so should have easily been "she" (in my defence I am from a region where these kind of names are not very common, so I may be wrong).

doubled1123 days ago
Back in my day, Google wasn’t an LLM. And we liked it!
tantalor3 days ago
Julia = she

Read the full thread on Hacker News →

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