Are lithium primaries OK for use in handheld DMMs? - Page 1
Forum section: electronics / testgear

author: knotlogic
author_rank: Regular Contributor
timestamp: August 31, 2015, 05:17:05 am
content: Does anyone have any experience with using lithium primary cells in their handheld DMMs? Energizer has them in AA and AAA sizes (L91 and L92), but although they describe them as having a voltage of 1.5 V, people have measured them at 1.7 V. So for a stack of four, that's 6.8 V as opposed to 6 V.It's less the weight or the longer life I'm interested in as it is the fact that I haven't heard of these lithium cells leaking. (Exploding maybe, but that's a different matter...)I think Panasonic Oxyrides also have a cell voltage of 1.7V, but I don't remember the last time I saw those on the shelves.

author: mariush
author_rank: Super Contributor
timestamp: August 31, 2015, 06:09:14 am
content: Fully charged alkaline (non-rechargeable) batteries have a voltage of around 1.6-1.65v ... doesn't stay there for much time, but pretty much any device should be designed to handle that, so I think it would be safe to use 4x1.7v batteries.If you don't want to risk it, keep in mind that a DMM would most likely have to be designed in a way that accepts regular rechargeable batteries, which have 1.2-1.35v depending on charge, so the meter should also work with 4.8 - 5.4v, therefore the DMM would probably work with just 3 x 1.7v ( total 5.1v) batteries installed and a simple wire connecting the poles of the last battery "compartment" for continuity.I'm not sure it's really worth investing money in such batteries, I would think you can buy 2-3x the amount of regular alkaline batteries for the price of lithium ones, and replacing 4 batteries doesn't take a huge amount of time.If you think about running dmm for long periods of times (for data logging for example), it would make more sense to make yourself an isolated power supply for your DMM, just buy a very small isolation transformer, add a bridge rectifier and a capacitor and a linear regulator and you have 5-6v (and you can just solder a couple of wires to the battery terminals. Perfectly safe and with small wires, unobtrusive, no damage to the meter etc.

author: LaurentR
author_rank: Frequent Contributor
timestamp: August 31, 2015, 07:15:06 am
content: Some HH DMMs specify the supported battery types. For instance, the Keysight U127X series do specify the Lithium batteries. Actually, the U1273AX even ships with them and specifies them uniquely to meet its extreme (cold) temp range.I purchased a new Agilent DMM that had a production date 3 years in the past and turned out to already have leaky alkalines. Since then, I have only be using Lithiums in my HH DMMs. They are not cost effective for this application, but their incredible shelf life is good to prevent any risk of leaky batteries damaging an expensive DMM.Laurent

author: mzzj
author_rank: Super Contributor
timestamp: August 31, 2015, 07:28:46 am
content: Quote from: mariush on August 31, 2015, 06:09:14 amMore like 5-10 times more expensive than alkaline. But worth of it in some cases.

author: Berni
author_rank: Super Contributor
timestamp: August 31, 2015, 07:32:04 am
content: Quote from: LaurentR on August 31, 2015, 07:15:06 am3 Year old brand new alkaline calls can also leak? I thought they only did that if left almost completely discharged for a long time. I have alkalines in my Agilent U1273A to see how long they will last and plan to put NiMH in there afterwards (They seam to last a surprisingly long time for having a OLED screen).

author: knotlogic
author_rank: Regular Contributor
timestamp: August 31, 2015, 07:34:11 am
content: Quote from: LaurentR on August 31, 2015, 07:15:06 amInteresting to know. Actually, I should have specified that I'm specifically looking at at batteries for a Agilent U1242B. Thing is the user guide does specify NiMH or alkaline, but not lithium.Quote from: LaurentR on August 31, 2015, 07:15:06 amAgreed, they're not cost effective, especially since I figure a DMM doesn't count as a high drain device, it's about the leak risk. I had a wireless keyboard where *new* alkalines leaked not long after installing them, though I think those came with the keyboard itself. No telling how long that was sitting in a warehouse. A pain in a keyboard, but would not want it happening in a DMM.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 31, 2015, 07:43:08 am
content: A while ago I bought a lithium 9V, but found the case was slightly big & it didn't fit my Fluke 87!