Original AirTags use a CR2032 "coin" battery. I would like to replace it with an LiR2032 battery, which is the same size but rechargeable, while CR2032 is not. I thus feel LiR2032 is more eco-friendly.
Is there any risk of damaging the device? And will there a be difference in terms of battery life?
In particular, I noted the following specifications:
| CR2032 | LIR2032 | |
|---|---|---|
| Voltage | 3 V | 3.7 V |
| Capacity | 200 mAh | 40 mAh |
Just looking at the voltage & charge figures alone, the two are in no way cross-compatible.
Voltage must match. The LIR is perhaps only 0.7V over-spec, but as a percentage that's quite a lot. With such a small actual over-voltage, there is the potential that it may just work, all else being equal.
The total charge held by each is considerably different. The CR holds five times the charge of the LIR, meaning it will last five times as long in use.
The CR2032 can last for years, Apple says 1 year for an Air Tag whereas the LIR2032 will need recharging every couple of months.
It's not a 'set & forget' solution like the CR.
The LIRs are designed for entirely different purposes. They are capable of quite high short-term power drain, 8mA vs the CR's 0.2mA, but their shut-off voltage is 3V, meaning the recharge frequency may be even shorter. The CR is designed to run smoothly right down to 2V before shut off.
The LIR, being a rechargeable, also needs support circuitry, as you would find in a phone or laptop, making sure the battery does not over-drain [or over-charge]. This is obviously not available in a device which isn't expected to support it.
Here's an additional warning, from a battery specialist:
For example, you can safely replace most CR2032 coin cell batteries with a BR2032 type lithium battery. You can not, however, always substitute an LiR2032 rechargeable battery for either a CR2032 or BR2032 type, without running safety risks, including overheating and fire.
So, TL:DR - use the battery type specified by the manufacturer.
Battery spec also from CR2032 vs DL2032 vs BR2032 vs ML2032 vs LiR2032 vs LR2032 Lithium Batteries Equivalents and Replacements
Yes, it works without issue.
I too wondered if the AirTag could function with the increased voltage of the Li-Ion based LIR2032 so I just did it, with full knowledge the device may be destroyed. I connected the 4.2v Lithium-Ion battery to the AirTag and then also connected the battery to a small Lithium-Ion battery charger tied to the switched accessory power output of my car. This allows the AirTag to be charged when the vehicle does, allowing the AirTag to function indefinitely without battery replacement. The AirTag (with the speaker physically disabled) is physically hidden deep inside the vehicle along with the Lithium-Ion battery and charger powering it, and has been functioning for 10 months now without fail.
I cannot answer how long the AirTag will function with the LIR2032 alone as my Li-Ion battery is charged every time I start my vehicle, so the answer to that question is left as an exercise for the reader, but I suspect it will be approx 1/3th the time of the CR2032 since it is approx 1/3rd the energy capacity, so ~4 months.
Even if it fits and works at the higher voltage, the battery will need recharging 5x as often.
Apple rates the Airtag as having "over one year" of normal usage. You'll be charging this one every two months.
That may seem acceptable, but part of the point of long battery life is when your item is lost, and you don't get a ping for months. Is the battery dead?
A coworker lost a bike saddlebag with an Airtag inside, and he knew where it was (an office building) but it took ~3 months to remember the tag, and then another month to get access. If the battery only had 2 months of charge from new, it would have been useless.
If it were me, I'd be trying to use two CR2032 in parallel, for 400 mAh of capacity.
That battery is too high voltage and its current (mA) is unknown. mAh (capacity) makes no difference, in regards to suitability for safety/compatibility.
The voltage is wrong: 3.7 V is 0.7 V higher than a standard CR2032. This could cause damage to your AirTag.
Electronic devices operate in a range of voltages. For example when an 18650 battery is fully charged it is at a capacity of 4.2 V. When it is half full it might be at about 3.62 V. When it’s dead it might be at about 2.75 V (these voltages are dependent on the specific model of battery - here I’ve taken the voltages from a Samsung model ICR-18650-22P. Other models of 18650 batteries will have similar voltages but not identical).
Devices account for this by using components which are tolerant of a range of voltages, in this example maybe 3-5 V (cutting off the use of the device at 3 V rather than 2.75 V in order to not drain it too far, which could cause it to explode).
For an AirTag, this voltage range appears to be 2-3 V - which immediately rules out a 3.7 V cell.
As for the mAh rating: the capacity is 5x lower, meaning you will need to remove and recharge the battery 5x as often.
Importantly, mAh is not a measure of the current that the cell can supply - it is a measure of its capacity (how long it will last before needing recharging) - so this does not rule out that cell.
You would however need to check that any cell you wish to use can supply at least the same number of mA of current (not mAh) as an AirTag demands/as a CR2032 supplies. A higher mA is perfectly acceptable, just not anything lower - since the device/AirTag will only draw as much current as it needs.
I tried it and it works.
However: As mentioned in the previous answers, the voltage of the LIR2032 is about .7 Volt higher than the CR2032. So from the circuit that surveys the battery voltage, the battery looks overfull and then suddenly disappears. The discharged curve below 3.5 V drops down very sharply. I have never received any low voltage warning when I used a LIR2032. The dropout also happens much earlier for the LIR2032, since it holds much less energy.
Therefore I will not use LIR2032 batteries in my AirTag and I cannot recommend it.
