Lithium Batteries Voltage too High? - Page 1
Forum section: electronics / beginners

author: Trader
author_rank: Frequent Contributor
timestamp: July 15, 2020, 09:01:04 pm
content: 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?Thank you.

author: amyk
author_rank: Super Contributor
timestamp: July 16, 2020, 01:19:10 am
content: 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.

author: cliffyk
author_rank: Frequent Contributor
timestamp: July 16, 2020, 04:39:28 am
content: I suspect those AALIthium"batteries" are actuallylithium-iron/disulfidecells 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):

author: magic
author_rank: Super Contributor
timestamp: July 16, 2020, 05:48:14 am
content: 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.

author: Trader
author_rank: Frequent Contributor
timestamp: July 16, 2020, 06:09:41 am
content: Quote from: cliffyk on July 16, 2020, 04:39:28 amI measured the voltage with no load, I'll check with a small load. Thank you.

author: cliffyk
author_rank: Frequent Contributor
timestamp: July 16, 2020, 08:21:36 am
content: Quote from: magic on July 16, 2020, 05:48:14 amAbsolutely;, 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.

author: magic
author_rank: Super Contributor
timestamp: July 16, 2020, 08:24:32 am
content: 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.

author: cliffyk
author_rank: Frequent Contributor
timestamp: July 16, 2020, 08:44:55 am
content: Quote from: magic on July 16, 2020, 08:24:32 amI 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.