Products > Test Equipment
using 3x CR2032 to power a fluke 77 series meter
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robert.rozee:
i was thinking... how practical would it be to power a fluke 77 (or similar) from a stack of 3x CR2032 cells?

1. a stack of 3 would easily fit within the volume of a PP3 battery. indeed, two stacks of 3 would fit along with a couple of schottky diodes and terminal clips;
2. the capacity of a CR2032 is around 250mA/h 250mA.h, versus something like 500mA/h 500mA.h for a PP3;
3. the battery housing could be 3d printed, or made out of a stack of PCB material, or consist of a single PCB with metal holder clips (2 on top, 1 underneath);
4. CR2032 cells are really cheap.

i just did a quick test, with a stack of 3x CR2032 cells totalling 9.3 volts and having no trouble supplying the 500uA or so needed.

an interesting idea?


cheers,
rob   :-)
wasedadoc:

--- Quote from: robert.rozee on October 19, 2023, 12:44:56 pm --- the capacity of a CR2032 is around 250mA/h

--- End quote ---
Minor correction.  Capacity is current multiplied by time.  Hence you should be writing mAh, not mA/h
Fungus:
I'm sure it'll work but what would be the point?
Ian.M:
The Energiser datasheets I have seen differ from your numbers.  Their Alkaline PP3 is about 600 mAH capacity but their CR2032 'falls off the cliff' with rapidly rising internal resistance around 200mAH.  I doubt no-name or off-brand CR2032's will be any better. 

For the same life you'd need 9 cells, and there's only room for 6 so you'll be changing them more frequently.  The only benefit is the reduced risk of leakage, which is pretty low anyway for a branded alkaline PP3, and can mitigated by wrapping the battery in clingfilm after fitting the clip, reducing the potential damage to the fairly simple to replace clip.

TLDR: branded CR2032 cells would need to be more than ten times cheaper than the PP3 alkaline batteries before its even worth considering, if you were given the adapter for free.  Figure in time and materials for the adapter amortized over lets say ten years and I think its not worth it even if the cells are free!
robert.rozee:

--- Quote from: wasedadoc on October 19, 2023, 12:55:18 pm ---
--- Quote from: robert.rozee on October 19, 2023, 12:44:56 pm --- the capacity of a CR2032 is around 250mA/h

--- End quote ---
Minor correction.  Capacity is current multiplied by time.  Hence you should be writing mAh, not mA/h
--- End quote ---

good point - i have corrected the error of my ways   :palm:



--- Quote from: Fungus on October 19, 2023, 01:07:52 pm ---I'm sure it'll work but what would be the point?
--- End quote ---

to avoid a leaking battery destroying your favourite multimeter, or course. the meter i used for testing (above) had itself suffered a battery leak that wrecked it - it no longer zeros.


cheers,
rob   :-)
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