Form Factors and Voltage
It’s hard to imagine life without AA and AAA batteries. They power everything from TV remotes and portable milk frothers to tons of small IoT sensors.
Standard AA/AAA batteries use alkaline chemistry and are rated at 1.5 V. You might also have heard of rechargeable batteries in the same size. Those usually work, but they’re typically Ni‑MH and rated at 1.2 V.
That voltage difference matters a lot for smart devices that report battery status. Many are hard‑wired for 1.5 V, and using 1.2 V rechargeables can trigger false low‑battery warnings. Some sensors are also voltage‑sensitive, so I wouldn’t recommend rechargeables unless you’re sure the device supports them.
So we know AA and AAA sizes don’t define chemistry, or even expected voltage. And it gets even more mixed up. I recently ordered two other varieties:
- AAA Li‑ion 3.7 V
- AAA LiFePO4 3.2 V
Self-Discharge Rate
Batteries aren’t perfect, they can’t hold a charge forever, even if you don’t use them. That’s why some people have a bad experience with rechargeable batteries in their remotes. Remotes are low-power devices, and most of their power draw can come from the battery’s self‑discharge. Some cheap Ni‑MH batteries lose 10% or more of their charge per month. Putting those in a remote is a terrible idea, because you’ll have to recharge them every few months.
My rechargeable batteries are IKEA LADDA, which are high‑quality and rumored to be rebranded Eneloops. They’re supposed to last for years, but I wanted to test that myself. I’m also adding Li‑ion and LiFePO4 batteries to the mix to compare self‑discharge rates between different chemistries. Both of those are made by Soshine, which is a solid brand.
Initial Measurements
Tested Batteries:
- IKEA LADDA AA 2450 mAh, 1.2 V | Voltage: 1.44 V (100% charge)
- IKEA LADDA AAA 750 mAh, 1.2 V | Voltage: 1.47 V (100% charge)
- Soshine AAA LiFePO4 280 mAh, 3.2 V | Voltage: 3.39 V (100% charge)
- Soshine AAA Li‑ion 350 mAh, 3.7 V | Voltage: 4.17 V (100% charge)