I bought a bunch of eneloop pro, but using them in connected thermostats is always displaying “low battery” even after just fully charged. This is when I discovered that they are actually 1.2V
It really came as a surprise, is there a catch? Are they only good for low power stuff like remote controls?
Edit: it seems they do exist in lithium. Question remains why are the NiMH only 1.2v and why are they the most widespread?
The voltage of a battery is dependent on what materials it’s made of and their electrical properties. So because of quantum physics and shit, a cell made of different materials will have a different voltage. The only real ways to change the voltage is to put multiple batteries in series like how there’s six little batteries in a nine-volt battery (but two NiMH cells would give 2.4 volts and overvolting can cause even more problems than undervolting), or have some kind of active circuitry to adjust the voltage (which adds a significant amount of inefficiency and therefore reduces the effective capacity of your battery, not to mention the cost of having a circuit board with many components embedded in the battery).
It really came as a surprise, is there a catch? Are they only good for low power stuff like remote controls?
Most AA battery powered devices are designed to accept a fairly wide range of voltages because the raw voltage from a battery is inherently variable, and 1.2 is almost certainly within tolerance (depending on how reputable the manufacturer is, there’s a good chance the engineers specifically tested it with rechargeable batteries to ensure they work, since it would be a really bad customer experience if they didn’t work) Besides, for high power stuff, usually it’s the current rating that matters, specifically, something called equivalent series resistance AKA how much the voltage drops when under load. High quality NiMH batteries can deliver a lot more current than alkalines so depending on what kind of load you have on it, the voltage of a NiMH might even be higher than alkaline when the voltage drop is factored in. I’ve personally never had any issues with NiMH’s in high draw devices.
There are rechargeables with integrated buck converters that can provide 1.5V, but they have their own issues.
my understanding is that the nominal voltage you get out of a cell is always dependent on the chemistry it’s using. alkaline battery cells are always 1.5V until they run down. even a 9V battery is actually six little 1.5 V cells in series in its little rectangular box. NiMH cells are 1.2V. Lithium batteries are actually a variety of different chemistries, but i think all of them have upwards of 3V nominal voltage, so they wouldn’t make a good drop in replacement either without some kind of voltage regulation circuitry.
Different chemistries produce different voltages per cell. Alkaline produces 1.5v, NiMH produces 1.2v, Li-Ion produces 3.6v. These are averages, the actual voltage varies over the current charge level of the cell. This variation in voltage is how the low battery alarm actually works, although Alkaline cells produce 1.5v initially, once they are nearly empty they are producing 1.1-1.2v. Your thermostats will likely work fine on NiMH batteries, if you can live with them continually complaining about the batteries being low.
There are, or at least were, rechargeable alkaline batteries, but they don’t last many cycles.
The 1.5v Li-Ions have a tiny circuit board on them that regulates the voltage down to 1.5v, which takes up space so the capacity is reduced. You could do that with NiMH, but it would have less capacity than the Li-Ion version, so there’s little point.
Eneloops are about the best rechargable AA and AAAs you can buy, they last close to forever. I’ve got some that are a decade old and still in use after thousands of uses and still about 80% of original. You chose well.
And it’s fine. I used to use them a lot for GPSrs. A pair of eneloops lasts about 8 hours in an Oregon. A pair of decent branded Alkaline AAs lasts about 7-8.
The voltage is not an indicator of charge life when you’re comparing different chemistries. The reason you’re seeing low charge is that your device is not calibrated for rechargables. In things that are, they have settings for both so you can select which you use. If your thermostats don’t, then they’ll always removed about anything other than Alkalines.
Always removed about anything else?
A consumer advice study in the UK actually found Ansmann batteries to be the best by quite a bit, with Eneloops in second
Never heard of those or seen them for sale, and I’m in the UK
Not your fault, but doesn’t mean it’s incorrect. I used to work in procurement, so I keep up with this stuff.
The consumer organisation is which.co.uk, well worth the subscription price
Ansmann are so popular, you can’t buy them from Amazon or they’ll be fakes. Stick to places like cpc.co.uk
It boils down to chemistry. The nickle-metal-hydride chemistry used in rechargeable batteries just don’t produce 1.5V (explaining why is a lot more complicated), while the alkaline chemistry in non-rechargable batteries produces slightly more volts.In the same vein, lithium-ion batteries produce around 3.6V, while lead-acid produce about 12.4V.
To answer your other question, they should be able to power most things that aren’t an analog clock (which might run slightly slow).
Lead acid is actually closer to 2v/cell. Car batteries are 6 cells in series.
But there are 1.5v rechargeable AA batteries out there.
Yeah but they’re a cheat. They’re lithium cells regulated down to 1.5v. Good ones are rare, when you find good ones they’re generally expensive and because they’re regulated down you generally get 100% battery showing until just before they fail.
I used them for some voltage sensitive stuff, but finding a brand that held a good charge for more than even 50-100 charges was hard.
Nimh is much better for anything that won’t be upset about the voltage too much.
There’s a type of lithium batteries that have a fixed voltage drop, meaning it will show the SoC of the lithium cell. I know about a company that just released a charger system meant for professionals that use these cells: https://klvr.no/charger-pro
Thanks, indeed. I was searching NiMH 1.5v, but indeed in lithium there are 1.5v
I have some thermo regulated valves that require 1.5v as well, so for those I decided to go with regular alcaline batteries. Those are still above 80% charge after 1 year of usage, that is why I decided not going with rechargeables for those trvs
Yeah, I have some EBL brand 1.5v rechargeable batteries since the VR handsets I own are pretty sensitive to low voltage. They were unfortunately a bit more expensive than regular 1.2v rechargeables.
The problem with non-rechargeable batteries is how they can easily become e-waste. Yes, there are recycling programs, but I once heard rumors about fake recycling programs that simply dispatches the e-waste to landfills across poor countries, polluting their soils. Rechargeable batteries will eventually become e-waste, too, but it seems to take longer than non-rechargeable batteries… of course it depends on how frequently they are charged and discharged. I have rechargeable batteries (which I use in my wireless keyboard/mouse set, digital hygrometer and a Bluetooth joystick) that have been lasting for years, I even don’t remember when I bought them. It’s worth mentioning that the battery brand I use is known by their poor quality (Multilaser, a Brazilian company that sells white-label electronics under their brand), and yet they’ve been holding charge.
I’ve reached the point of absolutely hating rechargable batteries. Between their ghost discharge, and the fact that I don’t go through as many batteries like I used, using normal alkaline batteries seems to be the best for me anyway.
Huh, I use exclusively rechargeable batteries in everything. Works great.
Except the smoke alarm, that one complains if I don’t use lithium
Google seems to have set their nest protect units to need six lithium AA non-rechargeable cells. Which is 1.8v, not 1.5v. You put in completely fresh batteries verified with a multimeter at above 1.5v (1.58v iirc) and they’ll complain about it.
I bought lithium rechargeable and they’re 1.5v. Which seems reasonable. I wish all of ‘em would be one standard.
Feels instead like we have AA-, AA, and AA+.
Huh yeah, guess I got lucky when I purchased extras for mine.
Same. Temp sensors, flashlights, game controllers, thermostat, whatever. Haven’t had any issues.
The only time they suck is when a device wants an odd number of batteries. And my charger only works with tandem batteries. Not really sure of the implications, but charging two batteries with significantly different charge makes me nervous.
There are battery chargers that allow charging an odd number of batteries, even single batteries. I have a charger that is powered through USB, similar to the following:
The one I have has two power inputs: an USB-C and Micro USB, so it can be powered by any of these.
Idk, I use one that charges 8. Both double and triple A’s
Always have spares in the charger ready to go
I gave up on them as well. They’d always be dead after sitting in a drawer and a lot of devices I use AA or AAA batteries in don’t like the lower voltage. The devices complain about the batteries being low and I could never tell if they were dead from lying around for too long or if the device thought they were dead just because of the low voltage.
yeah when things did not come with their own rechargable integrated battery it was a thing but the few I use at this point it just does not make sense to use rechargables.
“I don’t use enough rechargeables that it’s okay use ephemeral junk cells”? Really?
For me it’s the opposite.
I pretty much only use batteries for my wireless mouse and my Xbox controller. When the batteries die I just recharge them and put them back a few hours later.
I feel like the only batteries I use are for the firealarm and remotes. Oh then I have oddball things with watch type batteries but as far as I know their are no rechargable equivalents.
I finally bought some rechargeables again this year after shunning them years ago but that’s just because I 3D printed a bunch of Christmas lights that have battery powered RGB pucks inside them.
Funnily enough, I started with all alkaline until the rechargables came in the mail at which time I replaced half of them with rechargeables which have already died and needed recharging before the other half with the original alkaline have needed to be replaced.
Previously, the only really good use I had for them was with my old Xbox 360 controllers since I could have a pair on the charger while using the other pair.
classic rechargeable batteries are always 1.2V. That’s due to the chemistry.
The “low power” warning is the reason why a lot of devices will tell you not to use rechargeable batteries, as they will trigger the low battery warning earlier, and the cutoff voltage might be reached earlier.
I think there are modern rechargable lithium batteries with usb ports that will emulate 1.5V batteries and their voltage curve. But they have their own quirks as well
Those USB charging batteries scare the lights from me. I saw one explode once. Not a nice thing.
The light coloured Eneloop ones seem to have the lowest self discharge. I use them in Arlec PIR sensors without issue.
I’ve bought a few of these before (no affiliation) https://www.amazon.com/dp/B0CCL7TJ48
Edit: this is a link to 1.5V rechargeable batteries, which I commented before OP’s edit acknowledging them.
