Rechargeable coin cells: LIR, ML and VL explained
Three rechargeable families share their cases with ordinary CR cells. Only one direction of the swap is dangerous, and it is not the one people fear.
A rechargeable coin cell belongs only in a device built to charge it: a solar watch, a solar keyboard, a laptop clock backup, a self-charging key fob. LIR cells run 3.6 volts, ML and VL run 3. All three hold a fraction of a primary CR cell's capacity, so fit never means compatible.
The three rechargeable coin cell families
| Family | Chemistry | Nominal voltage | Capacity in our sizes | Where it belongs |
|---|---|---|---|---|
| LIR | Lithium-ion, rechargeable | 3.6 V, charges to 4.2 | 18-25 mAh (LIR2016) to 100-120 mAh (LIR2450) | Hardware designed for Li-ion coins, with a proper charger |
| ML | Lithium manganese, rechargeable | 3 V | 16-17 mAh (ML1220) to 65 mAh (ML2032) | Solar keyboards and watches, laptop and camera clock backup |
| VL | Vanadium pentoxide lithium, rechargeable | 3 V | 20 mAh (VL2020) | Self-charging key fobs, backup circuits |
What is an LIR coin cell?
LIR cells are lithium-ion in a coin case. The LIR2032 is the one most people meet: the CR2032's exact 20 by 3.2 mm case, a nominal 3.6 volts charging to 4.2, and 40 to 45 mAh over roughly 500 cycles. The LIR2016 holds 18 to 25 mAh, the LIR2025 28 to 30, and the LIR2450 tops out at 100 to 120 mAh in a 24.5 by 5 mm case.
Two numbers define the family: voltage above anything a 3 volt circuit expects, and capacity about a fifth of the CR cell in the same case. Our LIR2032 notes add a third: self-discharge of a few percent per month, which rules out backup roles.
What does ML mean on a coin battery?
ML is lithium manganese rechargeable at a nominal 3 volts. It answers a fair question: how can a device recharge something that looks exactly like a CR2032? It cannot. It shipped with an ML cell instead. The ML2032 holds about 65 mAh in the 20 by 3.2 mm case, in Logitech solar keyboards and Casio Waveceptor solar watches. The ML2016 is the 25 mAh slim version for solar movements, the ML2020 holds 45 mAh at 20 by 2 mm for self-charging fobs, and the ML1220, 12.5 by 2 mm and 16 to 17 mAh, is the yellow-wrapped clock backup cell inside ThinkPads, cameras and handheld consoles.
What is a VL2020, and why do BMW keys use it?
VL is vanadium pentoxide lithium, rechargeable, also 3 volts. Our catalog lists one size, the VL2020: 20 mm across, 2 mm thick, about 20 mAh, welded in with angled solder tabs. E-series BMW fobs charged it by induction whenever the key sat in the ignition slot, which is why a worn one works only after a drive. ML and VL overlap in size and role but their charge curves differ, so match the code on the old cell, not its dimensions.
When never to swap one in
Two mistakes, opposite directions. Only one is a safety problem.
Never fit a primary CR cell where the device charges its battery. Our ML2032 record calls charging a non-rechargeable lithium cell a rupture hazard, the ML1220 entry warns of leakage or rupture on a motherboard, and the ML2016 entry notes a CR2016 fits a solar watch perfectly and fails dangerously under charge current.
That covers solar watches and keyboards, laptop and camera clock backup positions, and fobs that charge in a dock or ignition slot. A watch counter offering a CR2016 for a solar movement, or a listing selling a CR1220 for a laptop RTC pigtail, has the wrong cell.
The other direction is not a fire risk, just a fit-versus-function failure, and it is the more common one. An LIR2032 drops into a CR2032 holder and does two wrong things at once. It presents 3.6 volts nominal, 4.2 off the charger, to a circuit designed for 3, and it brings 40 to 45 mAh where the CR2032 offers 220 to 240. Same case, roughly a fifth of the runtime, nothing inside to recharge it. Our CR2032 record is blunt: do not substitute an LIR2032 in fobs, motherboards, AirTags or medical devices. The CR2032 vs LIR2032 page has the rest.
ML and VL are the quieter version of the same error. At 3 volts they are voltage compatible, so the device runs and nothing looks wrong at first. But an ML2032 holds 65 mAh against a CR2032's 220 to 240, and no car fob has a solar panel to top it back up. With no charging circuit, a rechargeable coin cell is just a tiny primary cell that self-discharges. See CR2032 vs ML2032.
One point applies to every cell here. A rechargeable coin cell is the same swallowing hazard as a primary one, and the 20 mm sizes are the worst. Our button battery child safety guide covers the risk and first aid.
How to tell whether your device charges its own cell
Read the old cell first. The letters stamped on it settle the question: CR is single use, LIR is 3.6 volt lithium-ion, ML and VL are 3 volt rechargeables. Buy the same letters back, tabs and angle included if the cell has them.
If the marking is gone, the hardware tells you. A solar panel on the watch face or keyboard deck means it charges. So does a tabbed cell soldered near a clock that survives a power cut, or a fob that revives after a drive or a spell in a dock. A cell behind a coin-slot door you open with a fingernail, in a remote, a scale or an LED tealight, almost never charges. It wants the primary CR cell listed in the battery size chart.
Is a rechargeable CR2032 a real thing?
No, and the phrase does real damage. A CR2032 is single use, and charging one can make it vent or rupture. What sellers mean is a lookalike: an ML2032 at 3 volts, or an LIR2032 at 3.6. Neither belongs in a device built for a CR2032. The letters before the digits carry the whole message, which our battery naming guide decodes.