For that reason, unless it is anticipated that the CR2032 battery will need to be replaced during the lifetime of the device it services, manufacturers will avoid this step if it is practical to do so. The alternative is to employ a battery holder, but that, of course, involves extra expense for the OEM. For that reason, manufacturers offer coin cell batteries with solder tabs attached, so heat is not directly applied to the battery. It is important to note that any overheated lithium-ion battery poses a very serious explosion hazard. Soldering a CR2032 battery to a PCB presents some problems because the amount of heat needed is more than the battery can take. It can be seen that over a wide range of the battery’s operating range, from -10 ✬ to +60 ✬, the unit will last almost the same amount of time before the output voltage decreases from 3 V down to 2 V. The chart above shows a continuous draw of 190 microamps. This unit has an operating temperature range of -30 ✬ and +60 ✬.įigure 3: Temperature characteristics of the Panasonic CR-2032L/BN. The datasheet for this battery reveals that this device weighs a scant 2.9 grams, typical of a CR2032 battery. Panasonic battery CR-2032L/BN is available from Arrow Electronics. On the other hand, these CMOS batteries hold up quite well against significant variations in temperature. This can be a major pitfall, and designers must seriously consider its ramifications. This can be a significant problem for Bluetooth-enabled devices. If the CR2032 battery must contend with a pattern of pulsed demand for current, that, too will cause a derating of the optimal 225 mAh figure.
Of course, if a circuit can’t function below 2.0 or 2.4 volts, the added drain makes an even starker reduction in useable battery capacity. So, it can be seen that not only will the battery last only 0.5/3.0, or 17 percent of the time as expected, but there will also be an unexpected 155/240 reduction beyond that, based on the higher drain. If on the other hand, it must provide 3.0 mA, it can only provide 155 mAh. Here we see that if the CR2032 battery is tasked with providing 0.5 mA (500 microamps) continuously, its output voltage will not deteriorate to 1.6 volts until it has provided 240 mAh.
This might actually be true in a case where the battery is powering computer BIOS, but in most cases, the battery must supply more current continuously or in pulses.įigure 2: The capacity of a CR2032 battery versus continuous current demand. In an application drawing a constant 1 microamp or less, this comes out to over 10 years. The simplest way to look at battery life is to look at the total charge in milliamp hours, and divide it by current consumption.īattery Life = 225 milliamp hours/current Thus, in practice, the device is usually taken out of service for reasons such as obsolescence long before the CR2032 battery is depleted. Furthermore, when the device is turned on, the unit should be specifically designed to refrain from drawing power from the CR2032 battery, and subsystems like RTCs are powered from the unit’s main power supply for as long as the device is operational. The CR2032 battery is often used to provide power for ultra-low power subsystems such real-time clocks and oscillators, which must stay operational even when system power to the overall device is shut off. These batteries can lay dormant for years and lose very little of their original charge.įigure 1: Construction of a CR2032 battery button cell. A long storage life is made possible by the typically low self-discharge rate of LiMn02 batteries. The construction of a typical CR2032 battery features a stainless steel case to prevent any leakage of the non-corrosive electrolyte.
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