I tried mine some time ago Eve Thermo heating thermostats to operate with rechargeable batteries. Unfortunately, the app then constantly reports that the battery in the device is empty and in some cases it does not accept the batteries at all and you get no further in the setup process of the app. Without switching to batteries here, nothing worked.
The same game is probably known to users of tado radiator thermostats, because these also report with NiMh batteries that the inserted "battery" is empty.
Chapter in this post:
- 1 Update: Lithium batteries are the best choice
- 2 Update 03.02.2021/2/2019: tado VXNUMX from XNUMX recognizes batteries
- 3 NiMH rechargeable batteries as a battery replacement only possible to a limited extent
- 4 nickel-zinc batteries as an alternative to batteries
- 5 Stable discharge curve: a curse and a blessing at the same time
- 6 Set up a calendar entry for the exchange
- 7 Which NiZn batteries should I use?
- 8 Bad product reviews due to misuse
- 9 List of NiZn batteries for the Eve Thermo and tado thermostats
- 10 best (!) Alternative with deep discharge protection: lithium batteries
- 11 lithium batteries (AA) for Eve Thermo and tado
- 12 Similar posts
Update: Lithium batteries are the best choice
While I was writing the article, I came across a better alternative to NiZn batteries, namely lithium batteries. The electronics built into the batteries prevent deep discharge, which permanently damages many NiZn batteries. In addition, they have about 1200 charging cycles, while the NiZn batteries only manage about 500 charging cycles.
For these reasons, my recommendation is that you get lithium batteries. In order to save you the long reading of the article, you will find the right batteries for Eve Thermo and tado thermostats here, whereby I chose the cheap and well-rated variant with EBL:
You don't need a battery charger for the lithium batteries, since they are equipped with a Micro-USBcable can be charged using a standard USB power pack. With the supplied charging cable, you can charge all 4 batteries at the same time using a USB-A port. The charging time is about two hours.
If you are still interested in the background of my battery selection and a few technical information about lithium and NiZn batteries, you can now read on.
Note from my reader Wolf:
Lithium batteries are good, but they have one disadvantage: they deliver a constant 1,5 V. The cell voltage of 3,7 V drops slightly. And the battery suddenly switches from 1,5 V to 0 V. The thermostat cannot tell whether the battery is empty. And overnight the thermostat switches off in the last position - if you are unlucky, it is just at 0%. Or 100%.
The problem is actually also with the NiZn batteries, because they are reported quite abruptly as empty and stop working. The disadvantage is that the NiZn batteries are then deeply discharged and often break. This no longer happens with lithium batteries.
Update 03.02.2021/2/2019: tado VXNUMX from XNUMX will recognize batteries
In the support area of tado I was just able to read that the newer devices (V2, which will be on sale from 2019) also recognize NiMH batteries from eneloop and adjust the battery warning accordingly. Here is the note from the side:
- For VA01 Smart Radiator Thermostats: two alkaline AA batteries (LR6)
- For VA02 Smart radiator thermostats (available from 2019): two alkaline AA batteries (LR6) or two rechargeable Panasonic Eneloop AA 1900mAh NiMH batteries (the use of other types of rechargeable batteries is not recommended)
To what extent the devices can also handle other NiMH batteries, I cannot say, but eneloop batteries are just simple NiMH battery types.
NiMH rechargeable batteries as a battery replacement only possible to a limited extent
Now, of course, one wonders why the device thinks that the battery is empty when the battery is fresh. The reason for this lies in the different voltages used by alkaline or zinc-carbon batteries and nickel-metal hydride batteries.
While alkaline and zinc-carbon batteries have a cell voltage of 1,5 volts, nickel-metal hydride batteries only achieve 1,2 volts per cell. The electronics in the Eve Thermo or in the Tado thermostat therefore consider the battery to be a fairly empty battery and report this in the app.
One way would be that you could simply say in the Eve app that you have a NiMh battery in it, so that the lower voltage is correctly interpreted. However, the programmers have not yet implemented this, so you have to take a different path.
Nickel-zinc batteries as a battery alternative
The second - more elegant - way is to switch to a different battery technology - namely to NiZn batteries. These nickel-zinc accumulators have a cell voltage of 1,6 volts and are therefore not recognized as an empty battery, but act on the electronics like a very well-filled battery.
Stable discharge curve: a curse and a blessing at the same time
They also have a very constant voltage curve during discharge and only lose a massive amount of voltage when they are really empty. Basically this is an advantage, because the supplied devices have a constant performance for a very long time.
However, this creates the following disadvantage: The electronics in the Eve Thermo consider the battery to be full even when it is almost empty. This means that you will only be warned that the charge of the battery is on "reserve" when it is actually already empty. If you do not take care of the replacement and charging immediately, you run the risk of the battery being deeply discharged and damaged as a result.
Set up calendar entry for exchange
To prevent the batteries from being deeply discharged and thus permanently losing a large part of their capacity, I always make a calendar entry for 2 to 3 months and then walk around the house to charge all Eve Thermo batteries and equip the devices again .
Which NiZn batteries should I use?
If you look around on Amazon for NiZn batteries, you will quickly notice that you will find very mixed reviews and that there is virtually no manufacturer whose NiZn batteries only have 4 or 5 stars. Why is this so?
It's simple: People use NiZn batteries in devices that are designed for batteries or NiMH batteries. The result is that the message "Battery weak" in the devices comes much too late and the voltage of the NiZn batteries has already reached such a low value due to the strong discharge that the cell is permanently damaged because it has been discharged too far .
Bad product reviews due to misuse
All the Amazon customers, who are screaming that the batteries hardly have any capacity after a short time, have probably killed them themselves by removing the batteries from the devices too late and plugging them into the charger.
So my recommendation is: It's better to change and charge the batteries too early than too late. A recurring reminder under macOS or iOS can be created quickly and may save one or the other battery.
For this reason you can use all NiZn batteries equally, because the ratings simply say nothing.
List of NiZn batteries for the Eve Thermo and tado thermostats
Here is a list of NiZn batteries of the size AA, as they fit into the Eve Thermo and tado thermostats. Please consider: you need two batteries per device.
I have read the Ansmannbatteries and am quite happy with them. I have to admit, though, that I've already shredded a few of them because I loaded them too late.
Best (!) Alternative with deep discharge protection: lithium batteries
Actually, it is almost a bit of a shame that I only discovered these batteries when the article was almost finished, because ultimately this type of battery is the best solution, as they have built-in protection against deep discharge - one thing that many NiZn batteries do saved life.
But now to these great things: There are lithium batteries that actually have a cell voltage of 3,7 volts. However, built-in electronics reduce the voltage to the 1,5 volts that we need to replace batteries.
It should be noted here that this type of battery is not filled with conventional chargers, but rather via the supplied USB cable with four micro-USB outputs that are plugged directly into the batteries.
The advantage of the deep discharge protection and the built-in charging electronics is bought at a slightly higher price and less capacity, since the electronics naturally cost money and also require space. Nevertheless, the investment seems more sensible to me than having to buy new NiZn batteries every few months because they had been forgotten.
Here is a short selection of the products for you:
Lithium batteries (AA) for Eve Thermo and tado
I hope I was able to help you a little with these tips when converting the tado and Eve Thermo devices. Of course, the mentioned battery types also work with all other devices that insist on batteries and do not want conventional batteries: flashlights, remote-controlled cars, remote controls and many more.
I would be happy if you write me in the comments where you use or want to use these batteries.
Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.
14 comments on "NiZn and lithium batteries as battery replacement for Eve Thermo and tado thermostats"
the Tado radiator thermostat uses 2x AA instead of 4x AAA.
As far as I know, the room thermostat needs 3x AAA. But I'm not sure because I only have the one for the radiator.
Hello Florian! Thank you for your hint. I don't use a tado and actually made a mistake in the device on the support page. You're right with 2x AA. The newer models also seem to recognize eneloop batteries and accept them. I'll rewrite that in the article.
My Eve thermostats were fed with Eneloops the first time the battery was changed.
Eneloops are the best NiMH batteries. Not the ones with the greatest capacity, but those with the lowest self-discharge. Can also be used 1 year after the last charge. Other NiMH are already empty. This is one of the reasons why they are used as a standard by professional photographers.
Lithium batteries are good, but they have one disadvantage: they deliver a constant 1,5 V. The cell voltage of 3,7 V drops slightly. And the battery suddenly switches from 1,5 V to 0 V. The thermostat cannot tell whether the battery is empty. And overnight the thermostat switches off in the last position - if you are unlucky, it is just at 0%. Or to 100%
Hello wolf! Thank you for your hint. I add that again with the lithium batteries. I also have Eneloops, but my Eve Thermo doesn't like them. Do you have the new version of Eve Thermo, where you can set the temperature yourself on the Eve Thermo? I still have the old version, where everything is only possible via Home or Siri. Maybe you have built in a battery detection in the newer version, like tado? Also, and most of the time the thermostat is not set to 0 or 100%, but somewhere in between. It only readjusts very finely when I look at the curve. But of course ... it could be that the room is cooler or warmer than it should be.
Interesting tech approach. Unfortunately, I just ordered and received AA-size lithium batteries 3 days before via an instagram advertisement. Just have their own charger, which can also charge NiMh.
Hi Peter! Have your batteries also built in the electronics? Probably not with a charger, right? LG
Not recognizable, but probably not. The company produces models for different voltages. https://www.xtar.cc/product/XTAR-AA-1.5V-Li-ion-Battery-137.html
Yes, the specifications say 3,6V, regulated to 1,5V
Hello Jens, are you still using the Eve Thermo without a temperature display on the thermostat? I have these and recently bought the EBL lithium batteries recommended here. Even when the battery is 100% charged, the Eve app complains that the battery will soon have to be changed. Don't you have the problem?
Hi Michael! I didn't have any problems back then, but the Eve people always make adjustments with the firmware, it's possible that the situation has changed. Unfortunately, when I moved, I messed up my box with the Eve thermo-thermostats and currently, because of a new heater, I don't really need to always use the thermostats. That's why I didn't research any further. So I can't give you a current status. :(
Thanks anyway for the quick reply.
I'll keep an eye on it, the charge level is 100%, but the Eve app still says (I assume because of the voltage) that the battery will soon have to be replaced.
It's a shame that Eve doesn't offer better support for rechargeable batteries here.
I can only explain this by wrong evaluation. In principle, lithium batteries offer the same (or even slightly higher) voltage as normal alkaline batteries. It can only be that the slightly increased voltage may confuse the evaluation in the Eve Thermo. And yes, I agree with you: Better support for rechargeable batteries would be nice - this is the case for many devices.
Hi Jens, I can't explain it, but the Eve app no longer says that the batteries need to be replaced. Since I have screenshots, I know it wasn't my eyes ;)
I push the behavior to a faulty display in the app after replacing the battery. The message to change the battery only disappeared after three days.
Thanks for the tip about the EBL!
Yes, that is also a problem I had. Sometimes I had to reset the Eve Thermo for the battery warning to go away. Overall, I'm not so convinced of these parts. If I had to decide on something at the moment, it would probably be tado... but of course they also have a few disadvantages with their subscription model.