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How much energy can you really get from a coin cell?
If a system, when awake, draws just 10 mA, 88% of the battery’s capacity is available before the voltage delivered to the load drops to 2.0. It’s pretty hard to build a useful system that needs only 10 mA. Some ultra-low-power processors are rated at 200 uA/MHz with a 48 MHz max – almost 10 mA just for the CPU.
How to calculate the VCC of a battery?
Once VIN is determined, the VCC can be calculated by the formula: = × 1 + 2 / 2 However, ignoring the influence of a temperature drift to the resistances, there is one significant disadvantage in this approach: it will constantly consume power.
What makes a lithium coin battery more efficient?
The capacity of a battery in an application will depend on the device drain rate and the cutoff voltage. In general, lithium coin cells are more efficient at lower drain rates. Device circuitry that has a high cutoff voltage (i.e. greater than 2 volts) will leave capacity unused in the battery when the device stops working.
What’s the life expectancy of a coin cell?
Conservative design means recognizing that ten years is the max life one can expect from a coin cell. In practice, even that will not be achievable. There’s also a war raging about which MCUs have the lowest sleep currents. Sleep current is, to a first approximation, irrelevant, as I showed last year .
How much current does a lithium coin cell draw?
Lithium coin cells are rated for fairly low standard current draws, on the order of 1 to 5 mA. Also, while they allow greater pulsed current draws (i.e., periodic bursts), this appears to be detrimental to cell capacity (and also can cause a drop in the voltage during the pulse).
What can a CR2032 coin cell be used for?
CR2032, and coin cells in general, are meant for low current, long life applications, like real time clocks or battery backups of data. They are not meant for powering heavy loads.
What makes a capacitor suitable for a pulsed load?
As explained by @stevenvh, a capacitor parallel to the load is suitable for pulsed loads. The important characteristic of the capacitor (apart from its capacitance C) is its insulation resistance (IR). The insulation resistance determines the leakage of charge from the capacitor while waiting between pulses.