Electronics > Power/Renewable Energy/EV's

Any use for old 3G flip-phone batteries?

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Rick Law:
Probably like many of you, I have a collection of old cell phone batteries.  For example, my 3G flip-phone are long since useless but the batteries are still somewhat good.  Throwing them out seem such a waste.

Looking for ideas to put them to some use.

So far, I "repurpose" a couple of my decade old (razr v5 3G flip phone) 800mAH range lithium battery as emergency (power outage) lighting.  Most of my flip phone batteries are down to 50% to 80% of capacity.  Still, 600mAH flip-phone lithium battery would give hours of lighting running at say night light level.  That little light is such a calming thing not to have to deal with complete darkness during occasional power outage.  But, I don't need half a dozen more of such emergency lamp and I still have more than a handful of old flip phone (<1000mAH) batteries...

Have you guys "repurposed" old lithium batteries?  Suggestions?  I like to explore what can I do with them other than using them to fill up unused capacity of my garbage can.

Andy Chee:
I also have a handful of random phone batteries, alongside my collection of vape batteries.

Unfortunately I also have yet to find a use for them :P

Yes, I repurposed a few phones, too.

Sometimes the entire phone can be reused as it is, for example:
- as a dedicated audio player (I use to play audiobooks in the background while doing house chords), or as a FM radio
- have a more recent phone as a photo camera, it sits on the lab workbench at all time (in airplane mode, so the phone won't waste battery trying to detect the radio networks around), and use it to quick take snapshots of the tech gadgets I might open and their PCBs because it takes good close-up photos and can be transferred to PC by Bluetooth, so no cable needed
- used an old Nokia as a battery holder, for its battery contacts, to test/charge Li-Ion batteries with the same step between battery terminals
- once desoldered and reused an oscillator
- there are drivers for the displays from Nokia 5110 and similar models, to reuse the display in other microcontroller projects
- some electronic gadgets made for working with a 3V button cell like CR2032 might run just fine with a rechargeable Li-Ion.  A Li-ion has max 4.2V instead of 3V, but if you suspect this might be too much, you can charge the Li-ion to only 3.8V, because not much energy is stored above 3.9V anyway.  A Li button cell, single use CR2032, may have as much as 3.3V when new, so you won't probably damage anything at the 3.8V from a rechargeable Li-ion.

It's nice that Li-ion rechargeables have very low discharge rate, one charge can last for years.  My weighting scale has more than a year with a 4.2V charged Li-ion instead of a 3V CR2032, and still working fine.  Never recharged it in the last 1.5 years, and it should probably last a few more years before needing a recharge.  After one year the voltage went from 4.19V to 3.96V:  https://www.eevblog.com/forum/beginners/li-ion-cell-instead-of-a-cr2032-for-a-domestic-wight-scale/msg5339312/#msg5339312  Calculated time to last on one charge was about 20 years.  ;D

I have noticed that lots of batteries that you don't use for a while are prone to be almost dead ...
check your batteries with a tester, I'm sure half of them don"t hold a charge anymore ...

I've repurposed one of my old phones as a dash cam. The free software to support that is out there if you look for it.


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