Products > Test Equipment
using 3x CR2032 to power a fluke 77 series meter
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Fungus:

--- Quote from: mikeselectricstuff on October 21, 2023, 03:15:02 pm ---If you're worried about leakage, wrap the battery in cling film

--- End quote ---

Brilliant!
edavid:

--- Quote from: AVGresponding on October 21, 2023, 03:44:32 pm ---
--- Quote from: edavid on October 21, 2023, 03:12:50 pm ---
--- Quote from: AVGresponding on October 19, 2023, 04:44:14 pm ---
--- Quote from: bdunham7 on October 19, 2023, 01:51:07 pm ---Just use an EBL 6F22 lithium battery, rechargeable or primary.  Coin cells don't sound very efficient, although it's true that type of meter doesn't exactly draw much current.

https://www.eblofficial.com/products/9v-batteries-with-battery-charger

--- End quote ---


EBL, Znter, am currently trying the brand "PUJIMAX" in one of my DMMs, seems fine. Only issue you get with these is they give a constant voltage until the internal cell is empty then just stop, so you don't get a low battery warning.

These are quite a bit less than a tenner these days, I see no good reason to use anything alse (in most use cases, YMMV).

--- End quote ---

It sounds like you are talking about the USB chargeable kind with a built in DC-DC converter.  That is the wrong choice for a DMM.  The EBL batteries that were linked are a 2S Li-ion package.  The voltage drops gradually and the low battery warning works.  The downside is that you need the special charger.

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Wrong how?

--- End quote ---

As you mentioned, the low battery warning doesn't work.  Also they have lower capacity since there is only room for 1 cell, and shorter shelf life due to the self discharge caused by the DC-DC converter.  So they are inferior unless you need the higher output voltage, which you don't for most DMMs.
AVGresponding:

--- Quote from: edavid on October 21, 2023, 05:53:00 pm ---
--- Quote from: AVGresponding on October 21, 2023, 03:44:32 pm ---
--- Quote from: edavid on October 21, 2023, 03:12:50 pm ---
--- Quote from: AVGresponding on October 19, 2023, 04:44:14 pm ---
--- Quote from: bdunham7 on October 19, 2023, 01:51:07 pm ---Just use an EBL 6F22 lithium battery, rechargeable or primary.  Coin cells don't sound very efficient, although it's true that type of meter doesn't exactly draw much current.

https://www.eblofficial.com/products/9v-batteries-with-battery-charger

--- End quote ---


EBL, Znter, am currently trying the brand "PUJIMAX" in one of my DMMs, seems fine. Only issue you get with these is they give a constant voltage until the internal cell is empty then just stop, so you don't get a low battery warning.

These are quite a bit less than a tenner these days, I see no good reason to use anything alse (in most use cases, YMMV).

--- End quote ---

It sounds like you are talking about the USB chargeable kind with a built in DC-DC converter.  That is the wrong choice for a DMM.  The EBL batteries that were linked are a 2S Li-ion package.  The voltage drops gradually and the low battery warning works.  The downside is that you need the special charger.

--- End quote ---
Wrong how?

--- End quote ---

As you mentioned, the low battery warning doesn't work.  Also they have lower capacity since there is only room for 1 cell, and shorter shelf life due to the self discharge caused by the DC-DC converter.  So they are inferior unless you need the higher output voltage, which you don't for most DMMs.

--- End quote ---

A 2S Li-ion is going to have a fair bit of its capacity unused, since the BMS will let the cells go to 2.5v before cutting them off. Pretty sure the DMM will have shut off long before then.

I've had no problems with these 1S w/dc-dc convertor; as I've said I get months between charges on my 87V and I don't let it run out, I give it a charge when I remember, which is usually 2-3 months.
bdunham7:

--- Quote from: AVGresponding on October 21, 2023, 06:48:15 pm ---A 2S Li-ion is going to have a fair bit of its capacity unused, since the BMS will let the cells go to 2.5v before cutting them off. Pretty sure the DMM will have shut off long before then.

--- End quote ---
Most DMMs turn on the low battery warning at about 7.0V, which means 3.5V/cell and the energy left at that point at a low discharge rate is fairly low.  That's not a bad point to make a mental note to charge the battery when you are done with the meter.  I'm not saying the version you use is wrong--unless you don't like surprise shutoffs--but I find the 2S versions to be just about perfect.  Their low internal resistance also helps prevent issues caused by ranges that draw more power (continuity, etc) when the battery is at or below the warning threshold.  Even if the battery warning comes on while you are out at the beginning of your workday, the meter will work fine for the entire day or more.  Other than initial testing, I haven't yet had a meter that actually used up even one charge with the EBL 2S 6F22 600mAh.
AVGresponding:
I only had that happen the once, and it was after such a long time I'd completely forgotten about the battery, probably 6 months or so.

Ultimately the best battery is the one that suits your own use case best.
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