I hate this scale, it says low battery and shuts off after just 3 months of sitting in the drawer. It infuriates me that there’s still a lot of energy in the battery, I can use that in remote controls with no issues
If there’s enough battery to say “low battery”, then there’s enough battery to show the measurements!
That’s because of the way these scales work. They use a material that deforms under stress and when it deforms the resistance changes. By putting current through this material and measuring the voltage drop, it can be mapped to how much stress the material is under and thus how much weight is on the scale.
This is a pretty roundabout way and has a lot of caveats, but it is very cheap. So cheap scales always work this way. That’s why they aren’t super accurate and have deviations depending on things like temperature. Another big downside is any permanent deformation ruins the calibration, giving incorrect results. That’s why you never put more weight on kitchen scales than it says, it will break them.
The issue you are running into is the way it measures. It applies a very specific voltage and current in order to get the result. The lookup table it uses is only valid within a narrow range. When the battery voltage goes outside that range, it can no longer perform the measurement. Even though there’s plenty of juice for things like the little processing chip and the LCD display. They don’t need a lot of power and can do with low voltages. But it can no longer weigh anything so it just errors out with a low battery warning.
Mighty informative, thank you
Look up piezolectric materials if you wanna know more
The GP is not describing a piezoelectric scale. And you won’t be able to find any piezoelectric scale that is anything similar to “cheap”.
Well which principle do the cheap ones operate on?
It’s actually a plastic ribbon with a metallic foil in a zigzag pattern on top of it. It’s extremely cheap and does a pretty good job. It usually sits on top of a metal bar that can deflect a tiny little bit.
You can read all about it here: https://en.wikipedia.org/wiki/Strain_gauge
The main effect is that the resistance depends on the geometry. So as that changes, the resistance changes as well.
Ah okay.
All of which is fixed by a voltage regulator
Except the cheap part. But likely not by much.
You can order 3000 3.3V low drop out (LDO) voltage regulators on LCSC for $25.50. That’s less than a penny each.
Yeah, but it’s more than 0 pennies each.
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Absolutely, My kitchen scale remains accurate and can use the same battery for years.
No, not voltage, current.
This is probably not what you wanna hear, but when the battery gets low, the current gets weaker. If the current gets too weak, the scale becomes more and more inaccurate. Like, wildly so. In other words, the alternative is to lie to you. Badly.
Agree. For clarity, the circuits that show the low-voltage status are much less hungry for current than the circuits that measure weight. So no, having enough battery to report low voltage does not imply that there is enough to make an accurate weight measurement.
I have the same scale and bought a few rechargable ithium-Ion AAAs and they work line a charm having a constant voltage until empty.
Only downside is that you don’t get any warning when they are about to run.
(Something like that: https://www.mediamarkt.de/de/product/_verico-verico-li-ion-akku-loop-energy-aaa-mit-usb-c-buchse-2er-pack-lithium-ionen-akku-109861637.html )
Edit: nvm, just saw your comment about yours usung a coin cell it seems like there are some deviations between different models of the scale.
Normal AA or AAA battery, or a CR<something> button? If it is a button cell, try wiping it with alcohol before you insert it. Many modern button cells have a coating that tastes horrible to prevent people (children) from taking them into the mouth. I’ve noticed that on some brands, this coating measurably increases the resistance of the cell, not only reducing the the power it can deliver, but als making it appear “emptier” than they are ofor the measuring circuits. Wiping off the coating with alcohol (90% isopropanol) expanded the cells’ life (in a kitchen scale to boot!) significantly.
It’s a cr2032 from Duracell with that coating, later I’m going to try that
I wonder if this is why my car’s key fob never works well even with fresh batteries
Could be. Key fobs use button cells.
I know this isn’t helping but your scale is saying “ok lol”
For decades scales worked just fine without any electricity. Maybe get one of those.
There’s also the option of electronic scales which are rechargeable via USB
CR2032 batteries are hit and miss in my experience. Sometimes my car FOB burns through one a month2 and other times they’ll last years.
Get brand name CR2032, the cheap stuff doesn’t supply enough voltage and electronics don’t like em.
In my experience you can feel how good they are by how heavy they weight in your hand.
I actually just bought some Panasonic CR2032 and opened the packaging yesterday and I did notice they were heavier 😁
Funny that you mention Panasonic, because that’s the brand I noticed it first with.
The Panasonic cells that come with a device are usually garbage, also the stuff you get on flee markets and cheap packages on the Internet.
They apparently have cells that hold up and weight noticeably more.
For the standard sizes like AAA, AA and D cells there’s only Duracell for me. They’re still miles ahead of their competitors imo.
It’s my first time getting name brand in a while, but it’s possible it’s like OEM tires, where the tires that come with your car don’t have as much tread as a new tire you bought yourself, even of the same model.
Exactly. They don’t want to provide them at all, but customers would get furious, so they cheap out as much as they can.
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My scale looks similar to this. If I leave it on it goes into sleep mode which still drains power slowly but turn on instantly as soon as there is weight on it. If I hold the power button when I’m done it turns off and makes a beep and then I have no issues turning it back on months later. Still on original batteries after 2 years.
I replaced mine with a usb cable. No batteries.
Didn’t think you were going to get a bunch of nerds telling you exactly why it works this way 🙄
“Bruh just use the finger scale to weigh out your weed. 1 finger = 1.7g and 2 fingers = 3.5g”
I believe I have this exact same scale, and I also hate it. My main problem is that those capacitative buttons sometimes refuse to work, and it’s real nice when I’m trying to measure something in grams and it randomly gets stuck in pounds.
