Two CR2032 batteries read 5.97V but Kitchen Scales show 'LO'

Hysteresis or viscoelastic effects on the strain-gauge mounting changing with the increasing age of the scales, or the current cooler temperatures affecting the same?

Aging batteries affected by the lower temperatures?

Combination of both?

Electrode passivation in the batteries. Try shorting them for a couple of seconds and retesting. John

I usually find brand new CR2032s reading about 3.2V open circuit. By the time they are down to 3.0V they are getting quite old?

nib

I bought a new radio moyse and fitted the old mouse batteries to it. After a month it started drifting. The mouse pointer would move without any movement of the mouse. I measured the battery. 0.9V...

Easy enough to change the batteries.

My kitchen scales are old and mechanical. I picked them up at an 'antique' shop for a fiver..

In my experience many batteries can register close to their stated voltage when measured open circuit but will show a rapid drop off in voltage as soon a load is applied a drop off in open circuit voltage only occurring when when the battery is almost exhausted.

Rise in internal resistance. Absolutely typical of a car battery. They test by applying a small load and extrapolating to how much current will drop the volts to some arbitrary value like 6V, that wont turn the starter.

Cold Cranking Amps. Needs to be about 500 IIRC

The CR2032 in my car keyfob last one hell of a long time. So much so that when the battery died a couple of days ago I had no recollection on how to open the thing up. I had to watch a Youtube video to remind me of the steps. That's the second time I've replaced the battery and we've had the car for 8 years.

The CR2032 in my car keyfob last one hell of a long time. So much so that when the battery died a couple of days ago I had no recollection on how to open the thing up. I had to watch a Youtube video to remind me of the steps. That's the second time I've replaced the battery and we've had the car for 8 years.

Needs an impedance test.

Pulse Drain: 2 seconds X 12 times/day 400 ohms ~6.8 mA @ 2.7V # Voltage drops to 2.7V when you draw 6.8mA # And that is when the battery is new.

# The other test they do is with 15,000 ohms as a resistor load.

By pulling datasheets from some other companies, additional test cases may be extracted.

Normally, there isn't a lot of "other chemistry" behaviors, such as charging up an onboard capacitor to near ideal voltage. Usually a CR2032 sags in both voltage and increased internal impedance, and once approaching the knee voltage, a CR2032 is usually flat in an additional 3 weeks or so (at 10uA).

The shelf life on CR2032 is only ten years.

The LR2032 are rechargeable, and last for about three days, and are intended for mains powered devices that need a bit of backup for settings when mains go off. When you find these in devices, you may not place the alter-ego in the slot. You cannot replace a CR2032 with an LR2032, nor replace an LR2032 (in a laptop) with a CR2032.

CR2032 are not a rechargeable cell type, and truth be told, their allowed charging current is 0 uA. However, for real world circuits, and using Schottky diodes, some amount of charging-leakage current needs an allowance, and consequently the datasheet was "adjusted" to make certain applications of CR2032 possible. But a CR2032 can explode if abused (at much higher abuse-currents), a 1uA current flow makes this mostly unlikely (the gas would likely escape as soon as it is made).

A digital watch would draw 2uA from a CR2032. A computer draws 10uA from a CR2032 (RTC and CMOS RAM locations as a load).

While they can be pulsed at larger currents than the datasheet suggests, they're not going to last all that long while doing that.

Paul

What sort of watch takes a CR2032 ?

I have one - displays the time in binary on LEDs!

nib

I have a watch that runs off two penlight cells.

You've heard of bodges I suppose :-)

The RTC in a computer, uses the same circuit as a digital watch, and a crystal at 32768Hz (inaudible). The digital watch draws 2uA doing that, the computer draws 10uA. That's one reason the battery is larger.

An older Mac used a cylindrical battery for its timepiece, but the thing still did not run forever. You might get a dozen to fifteen years out of that setup. It's unclear why they thought such a power source was required for the job.

Before the CR2032 era came along, the timepiece was a taller epoxy package Dallas Semi time piece. The battery was underneath the epoxy out of sight. (You were given no way to access the battery and change it.) And the battery in that was a bit smaller than a CR2032. And when the battery was worn out, you had to take a Dremel and grind off some epoxy and make bodge connections to power it and keep it going. Using whatever battery you thought appropriate.

Mine takes a CR2025. It is advertised as having a 10 year battery life, and I've changed the battery twice in mine, which is rather more than

In message <10jane5$14oph$ snipped-for-privacy@dont-email.me, at 04:27:30 on Sat, 3 Jan

Meanwhile, the RTC battery in an Amstrad PC1512 was four AA cells (in a holder in the plastic lid). Keep it simple, stupid.

I've a Lidl watch that takes one. And if there's space, so it should.

My pet hate is devices that use AAAs when AAs could easily have been used in the case space.

I've always wondered why computers didn't use a low-capacity rechargeable battery so it never runs out of charge, even after 10 years or so, and is kept topped up all the time the computer is powered on (either booted up for an old-style PSU or trickle charged from a modern PSU with standby power), so it only needs to power the RTC for the fairly short times that the PC is off or unplugged from the mains?

Some motherboards I've used in the past (like 20 ore more years ago) had small NiCd cells for the RTC.

However all modern ones seem to have non-rechargeable button cells.

Cost, I would think

In message <10jb0kq$17bvh$ snipped-for-privacy@dont-email.me, at 12:04:41 on Sat, 3 Jan

Mainly because they never expected the machines to have an operating life of even five years, let alone ten.