# Replacing 3S LR44 button cells with li-ion?



## santza (Jul 14, 2008)

Is it possible to use 10180 li-ion cell in a device designed for 3 X LR44 / AG13 in series?

The size is almost the same and voltage too. Opinions?


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## dulridge (Jul 14, 2008)

*Re: Replacing LR44 button cells wit li-ion?*

If I had a 10180 I'd try it given the value of the only device i have that takes three LR/SR44 cells.

I'd like to know too.


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## Illum (Jul 14, 2008)

10180? gee, I never thought of that:laughing:
I'm interested to know too


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## santza (Jul 15, 2008)

Wikipedia states LR44 maximum height as 5,4mm. 5,4x3=16,2mm. 10180 is 18mm. I think it might fit some devices with a loose spring but not ones with a tighter fitting.

Has anyone tried this yet? I just might order 10180 and a nano charger to try out


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## Jarl (Jul 15, 2008)

Internal resistance of the 10180 might be too low, resulting in whatever it is using too much current and breaking. Be interesting to hear the results, though


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## dulridge (Jul 15, 2008)

santza said:


> Wikipedia states LR44 maximum height as 5,4mm. 5,4x3=16,2mm. 10180 is 18mm. I think it might fit some devices with a loose spring but not ones with a tighter fitting.
> 
> Has anyone tried this yet? I just might order 10180 and a nano charger to try out



You get the cell, I'll contribute the Nano (I have more than one) - PM me with your address. 

I'd be a bit concerned that the Nano charging current is rather too high for such a small cell. But then Rob sells them with the Wee lights so presumably he reckons it is safe to charge them in a Nano.


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## santza (Jul 15, 2008)

dulridge said:


> You get the cell, I'll contribute the Nano (I have more than one) - PM me with your address.
> 
> I'd be a bit concerned that the Nano charging current is rather too high for such a small cell. But then Rob sells them with the Wee lights so presumably he reckons it is safe to charge them in a Nano.



PM sent!


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## dulridge (Jul 15, 2008)

santza said:


> PM sent!



Packed up - will post it in the morning


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## santza (Aug 3, 2008)

IT WORKS!! 

:rock::rock::rock::rock:


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## lctorana (Aug 3, 2008)

Good get!

You know you've only gone and made heretofore junk lights suddenly practical...


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## Minjin (Aug 3, 2008)

I've wanted to try this with my HP 32SII calculator but I'm a bit worried about over-voltage in such a valuable piece of gear. Been meaning to take an adjustable power supply and gradually ramp it up to see if it can handle the voltage that the lithium cell puts out.


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## Phaserburn (Sep 14, 2008)

The question is, what is the current draw on the li-ion vs the 3 LR44s?


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## Illum (Sep 14, 2008)




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## TorchBoy (Sep 15, 2008)

*Re: Replacing 3x LR44 button cells with Li-ion?*



santza said:


> The size is almost the same and voltage too.


But as Jarl mentioned, the internal resistance will be much MUCH lower. In some devices it might be fine, while others might go 



Illum_the_nation said:


> If I understand your concern consider that LR44s capacity resides between 150-200mah depending on alkaline or silver-oxide the current draw at the most would still be within the safe level of the 10180...unless of course the capacity of the 10180 is below that of LR44s which I find very unlikely


:huh2: The capacity has nothing to do with the internal resistance. You could use four LR44s and still have less voltage under load than the 10180. Indeed, my latest keyring torch relies on the internal resistance of LR44 cells to limit maximum current.


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## Phaserburn (Sep 15, 2008)

What I want to know is does the lower resistance of the li-ion mean more current than the button cells w/ voltage sag under load.


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## santza (Sep 23, 2008)

I measured capacitity of AW 10180 liIon with a hobby charger at discharge current of 0.1 amp = it was only 65mah 

3XLR44 is around 120mAh at 4,5v
3XSR44 is around 180mAh at 4,65v

so do not discharge more than 130mA!

Is the math done correct?


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