Author Topic: Lithium Batteries Voltage too High?  (Read 1322 times)

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Offline TraderTopic starter

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Lithium Batteries Voltage too High?
« on: July 15, 2020, 09:01:04 pm »
Usually, the (1.5V) alkaline batteries are around 1.62V, I purchased some (1.5V) Bevigor AA Lithium Batteries and they have 1.82V.

I wonder if it is normal, can I use it safely in an expensive multimeter that recommends 1.5V Alkaline batteries?

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Offline amyk

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Re: Lithium Batteries Voltage too High?
« Reply #1 on: July 16, 2020, 01:19:10 am »
To be sure you could trace the circuitry and see where the voltage goes, but I wouldn't risk it --- many devices designed for 3.3V have an absolute max of 3.6, which 1.82*2 will exceed.
 
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Offline cliffyk

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Re: Lithium Batteries Voltage too High?
« Reply #2 on: July 16, 2020, 04:39:28 am »
I suspect those AA LIthium "batteries" are actually lithium-iron/disulfide cells which have can produce 1.8 only with no or very low load. When you tested them was it done with no load other than the meter?

Test them again with a small 50 or even 25 mA load (36 to 72 Ω) on them and see what you get. Batteries should always be tested with some appropriate load--best is the load of whatever device you intend to use them in.

Li-FES₂ cells (from Wikipedia):

« Last Edit: July 16, 2020, 04:46:34 am by cliffyk »
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Online magic

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Re: Lithium Batteries Voltage too High?
« Reply #3 on: July 16, 2020, 05:48:14 am »
A multimeter probably won't draw 25mA, though. You would better test them with something more realistic and consider if the DMM can handle such voltage when it is turned off.
 
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Offline TraderTopic starter

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Re: Lithium Batteries Voltage too High?
« Reply #4 on: July 16, 2020, 06:09:41 am »
When you tested them was it done with no load other than the meter?

I measured the voltage with no load, I'll check with a small load.  Thank you.
 

Offline cliffyk

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Re: Lithium Batteries Voltage too High?
« Reply #5 on: July 16, 2020, 08:21:36 am »
A multimeter probably won't draw 25mA, though.

Absolutely;, Even a very cheap contemporary DVM, like that often given away for free by Harbor Freight has an input impedance of 10 MΩ or better.

I assumed (very often an error) the OP would understand he'd need to use some external load or a real battery tester which if properly engineered would apply appropriate load to the test cell--something often not understood.

In fact a particular inexpensive (which does not always mean bad) digital battery tester offered on eBay was trashed by more than a few reviewers because of it's "inaccuracy". All to a man reported how they had used the tester to test a cell, and then measured the same cell using a DVM--lo and behold, the tester consistently read 0.2 to 0.5 V lower than their, of course perfect, DVMs, proving beyond doubt (in these reviewer's minds) the "inaccuracy" of the tester.

I have that same tester. when testing a 1.5 V cell it places a 47 Ω load (32 mA) on the DUT which of course pulls the no-load voltage down by 0.2 to 0.5 V depending on the condition of the cell.
 
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Re: Lithium Batteries Voltage too High?
« Reply #6 on: July 16, 2020, 08:24:32 am »
No. I mean that when you put the battery in a DMM, the DMM won't draw 25mA from it. The DMM must withstand whatever is the battery voltage at only a few mA load and also the full open circuit voltage when it's off. The latter won't be a problem if there is a physical switch, if there is a physical switch.
 

Offline cliffyk

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Re: Lithium Batteries Voltage too High?
« Reply #7 on: July 16, 2020, 08:44:55 am »
No. I mean that when you put the battery in a DMM, the DMM won't draw 25mA from it. The DMM must withstand whatever is the battery voltage at only a few mA load and also the full open circuit voltage when it's off. The latter won't be a problem if there is a physical switch, if there is a physical switch.

I misunderstood, you meant the DVM the OP intends to run with the lithium-iron cells. If that is a concern just use a larger resistor for a test load to be certain how the cell reacts, a 2.2 kΩ resistor would draw just 82 μA. As I understand it almost any load (other than the piddly 180 nA a 10 MΩ multimeter applies will knock these things down to their nominal voltage. That's why the vendors can tout them as universal replacements for AA alkalines.
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