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Comment by klooney | Hacker News Reader

> run at a nominal 1.2V instead of the 1.5V of alkaline batteries.

I've suddenly figured out why so many toys don't work with rechargeable batteries

That's not the reason.

Alkaline batteries only have 1.5V for a short time. In practice, toys are designed to opeerate off of 1V to 1.5V, because Alkalines vary _wildly_ in voltage during use.

NiMH at 1.2V _STAYS_ at 1.2V, even when drawing 1Amp or more (under these conditions, Alkaline would have long dropped below 1V).

EDIT: This is also a problem because "nicer toys" will measure the voltage assuming an Alkaline is "full" at 1.5V and dies at 1.0V. However, NiMH starts at 1.35V, then "plateau" at 1.2V, and stays there for most of its life, before rapidly falling off to 1.0V or .8V like a cliff at the end of its life. So NiMH life "cannot be predicted" by any simple metric.

I had an issue with the original Apple Magic Mouse that would not work correctly with NiMH batteries but work fine with disposable AA. The mouse would be fine for a few days then randomly stop working; using fresh NiMH would revive it again. I assumed it was due to 1.2v vs 1.5v but perhaps that particular mouse (or all Magic Mice) was just bad.

I have an acurite 5in1 weather station running on eneloops/laddas. It whines about the batteries being low but runs for about a month in any conditions. I just rotate and recharge them at the start of the month.

Looking at the discharge curve for an alkaline, much of the energy is below 1.2V even under light load. A device that works with alkaline and not NiMH due to voltage is broken as designed.

https://lygte-info.dk/review/batteries2012/Duracell%20Ultra%...

If you need 1.5V / 3V for some reason, you could maybe insert a tiny boost converter from AliExpress (1€, less than 1 cm in all dimensions). I have done that for a string of fairy lights.

Apple sold their own NiMHs (actually rebadged Eneloops) along with their own AA charger to go along with the Magic Keyboard/Mouse, so my bet would be on a faulty device. https://en.wikipedia.org/wiki/Apple_Battery_Charger

You can now find 1.5V Li-on AA batteries with, and that's a game changer, built-in charger and a type-C port!

I have one in my wireless mouse. If it dies, I change it to a spare and charge it right from my laptop (and the battery that was empty becomes the spare)

Came here to post this. I'm 100% agreed with Mr. Geerling.

For a fun challenge try to find a non-built-in-battery arc lighter (eg: candles, grills, etc). When I found one I bought four (think camping/disaster bag... if everything is AA/AAA then having a shelf-stable fire starter is easier/safer than lighter fluid).

For a fun sidebar check out the "Panasonic BQ-CC87AKBBA" which is effectively a combo "in/out" battery charger OR USB battery pack(!). It'll suck in (unfortunately) Micro-USB and charge your AA's, then switch a button and it'll spit that power back out as a battery bank. When I find one like that for USB-C, it's going on my christmas list.

Look up plastic battery holders that hold 8-10 along with a 4x charger and I just swap batteries out and recharge them into that buffer/holding cell. I'll have to look into the Eneloops as I've been working with the Amazon Basics and generally have 1-2 batteries fail out every few months (and am specifically looking for heat-resistant / outdoor applications).

Last one: Lots of cheap solar products have cheap rechargeable AA batteries inside... you can generally open them up and swap the battery out if they're not working any more (and/or potentially scavenge the charging panel if you think about it!).

I had this charger once! Really cool with the powerbank option. Although, these days, 5V@1A with no PD is probably something to use maybe in emergency, it's too slow for modern devices.

The NITECORE UM10 is an "in/out" charger too - it handles various sized LiIon batteries one-at-a-time. A switch on the end determines if it is charging or discharging. Their site says it's discontinued, but I thought I recently saw them at a shop in Seattle. Time to pick up a spare.

https://charger.nitecore.com/product/um10

I haven't used them, but IIRC they maintain a constant voltage until they're discharged, when it instantly drops to 0. That may be a problem, because if your device has any battery indicator, it will show the battery as full until the end. Nothing will tell you that you need to replace the battery before the device powers off. That's why I decided not to buy them. My mouse knows when my alkaline AA battery is low and gives me a warning.

You can get them with different voltage drop-off curves

E.g., this battery is 1.5V for ~70% of the capacity, before it gradually reduce to 1.0 V

https://www.xtar.cc/product/xtar-1-5v-aa-clr-3300-lithium-ba...

edit: And one with USB-C and linearly decreasing voltage curve https://www.xtar.cc/product/xtar-aa-lithium-lr-2000mah-usb-c...

That's cool, thanks for the links.

I use rechargeable CR123 batteries in my August smart lock that face this issue. The solution is to have a spare set and rotate/charge on a fixed schedule before they die. I have a quarterly calendar reminder to do so.

I believe I have zero Alkaline batteries left in my house and I'm relatively surprised that pretty much everything works fine. If anything, I suspect the only problem is that some devices have an inaccurate account of how dead the batteries are. But I use Eneloops on everything, even things surely not designed at all to run on them. (And I reckon you could probably make more devices work if you really wanted to; adding an additional cell or two in series would surely give you a voltage that's in range, if you can figure out a good way to do it.)

Of course not all rechargable batteries are the same; there are a few different rechargable battery chemistries in the AA form factor. I like Eneloop Pros, though; they've been very reliable for me. I've been using them for years and I've never had to throw one out yet; supposedly they last over a thousand cycles with most of their capacity.

I think I have only one device that uses AA - my central heating's radio thermostat. This thing has caused me untold hassle, which is only partially down to the batteries, but still...

Totally OT, but does anyone have a good link on how the thermostat gets paired with the boiler? I'm thinking of getting replaced and would like to talk to the gas fitter from a vaguely informed point of view.

Personally, I keep things simple. Got a new (pretty basic) Honeywell thermostat after a kitchen fire; thermostat was pretty old anyway. For wiring, you mostly have 2-wire and 3-wire although there are a lot of variations as you get fancier: https://nassaunationalcable.com/blogs/blog/a-full-guide-to-t...

Number of zones in the house may affect things as may boiler only or AC being in the picture as well.

> good link on how the thermostat gets paired with the boiler?

You should have a book with the boiler that says how your system is setup. They nearly always include schematics and are very helpful. Typically you can open a cover and see the wiring details as well.

Forget about web sites, there are too many different ways a system can be setup, so even if they are not slop they can still be inapplicable for you. Once you know what you are looking at you can sometimes get useful information from the web, but until then you can't sort out what is useful for you.

Yeah. Have your manuals handy if you get a furnace guy/electrician in. My electrician actually wired up my thermostat wrong when I got a new thermostat in.

Thanks, and to the other guys. But I am asking about a remote wireless thermostat. How does it know to talk to my boiler, and not her next door's?

As I said totally OT, and I do have a couple of good C/H firms I can get in to sort it.

Sounds like an awful idea in general. Think KISS concept. But you'd have to look at manuals. There's probably no single answer. (I was thinking of wireless control of the thermostat itself.)

I'd add that, where I live (New England), furnace failures can be basically catastrophic so any theoretical convenience advantages just aren't worth it.

Wireless thermostats are really common in the UK. I don't know about elsewhere. I'm interested how they pair (like Bluetooth) with the boiler.

Basically, the thermostat is in a living area and you set the temperature(s) to what you want, it senses them, and then talks to the boiler (in my case in the roof-space) to heat up (or not, via radio) the water in the radiators to satisfy that. It's a feedback loop.

I'm maybe just a fuddy duddy but relying on wireless tech for critical systems unnecessarily seems like asking for trouble. Running wires to a boiler isn't generally that complicated and it's just one less point of failure.

That depends. Sometimes because they have encryption. It isn't hard to have shared keys of some sort. If there is no internet connection on the link (which is possible - I've never seen where both systems connect to wifi, but if they do worry!), and so you don't have to worry about malicious hackers and in turn the encryption is good enough even if done somewhat wrong.

Sometimes they are just send a radio signal and hope nobody else in range is using that frequency.

So again, there are too many different ways this is done to guess. Unfortunately they probably don't put this in the manual.

Thermostats (aka space temperature sensors) can have between two and eight wires. A boiler will usually have three: 24V power, call for heat, and common.

If your boiler has inputs on the terminal block for a thermostat, I would highly recommend buying a wired one, the 24V constant power removes the need for batteries.

If you can provide a link to your boiler’s installation and operations manual, I can tell you.

Three things prevent me from eliminating all alkalines:

* smoke and CO detectors with low-battery voltage sensors calibrated to alkaline

* some older electronics (e.g. multimeters) using 9V batteries

* my non-contact voltage tester refuses to turn on using NiMH, for safety reasons presumably

There are 9V NiMHs, too. They just need dedicated charger.

Yeah, most of the devices using 9V are smoke/CO detectors which only accept alkalines. I don't use the few remaining 9V devices enough to justify buying a new charger.

I have a weather station that takes two 1.2 V. The LCD screen is a bit dim compared to when used with fresh 1.5 V alkalines. Other than that, most things take the 1.2 V well. But they better do because alkalines reach 1.2 V with >50% capacity left.

If they don't work at 1.2V they weren't very good quality to begin with. AAs are dead at 1.0 or 0.9V.

There are a lot of low–quality toys.

A weird flipside is things like... the IKEA Zigbee devices. Many of these do not work right at all with 1.5V batteries and basically require rechargables.

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