Stretch Battery Life on Your IoT Pilot with A One-Minute Calculation

Stretch Battery Life on Your IoT Pilot with A One-Minute Calculation

It would be quite the understatement to say that battery-powered Internet of Things (IoT) devices have permeated almost every aspect of our lives over recent years.

From wearables such as fitness trackers and medical devices, right through to smart home devices like smart thermostats, locks, and sensors – to say nothing of the industrial applications, too – great numbers of us have witnessed the transformative impacts of these technologies across our homes and workplaces alike.

However, when you are looking to optimise your company’s own IoT pilot, there are all manner of aspects of your solution that you will need to learn about, consider, and refine. The given device’s battery life, and the matter of how to stretch it, will be just one of those areas of focus.

Key Things to Know About Battery-Powered IoT Devices

IoT devices can vary greatly in the amount of battery power they use. Simple sensors, for instance, which collect and transmit minimal data, will use very little power. On the other hand, IoT solutions with cameras or extensive local processing tend to drain batteries quickly.

One of the important things to know about battery-powered IoT devices is that they often operate in cycles. This entails brief active periods of the sensing, processing, and transmission of data being followed by long sleep modes to conserve energy.

A 60-Second Calculation That Could Lead to Much-Enhanced Battery Life

Ultimately, to stretch the battery life of your IoT pilot, you will need to minimise average power consumption. You can estimate and optimise this by rapidly calculating the average current draw – and when we say “rapidly”, we do mean in less than a minute, if you have the basic specifications of the device to hand.

Performing this calculation will help you predict runtime and identify tweaks you could make to your IoT pilot, such as the use of lower-power components or longer sleep intervals.

How To Carry Out the Calculation to Estimate Battery Life

The formula for battery life, or t, in hours, can be expressed as t = C / I_avg. C refers to the battery capacity in milliamp-hours (mAh), while I_avg is the average current in milliamps (mA).

Let us, then, take you through the steps of the calculation:

1. Gather the specifications (10 seconds)

After noting the capacity of your battery (C) – for example, 2000 mAh if it is a common LiPo – estimate the:

• Active current (I_active) – for example, 100mA during sensing and transmission
• Sleep current (I_sleep) – such as 5 µA = 0.005 mA
• Active time per cycle (t_active), such as 10 seconds
• Total cycle time (t_cycle) – for example, 600 seconds = 10 minutes, including sleep.

1. Compute the duty cycle (10 seconds)

This part of the calculation, with the duty cycle expressed as D, is D = t_active / t_cycle.

So, plugging in the aforementioned example figures, this would be 10 / 600 = 0.0167 or 1.67%.

1. Calculate the average current (20 seconds)

The relevant formula here is I_avg = (I_active x D) + (I_sleep x (1 – D)).

Introducing the relevant numbers, this would therefore work out as I_avg = (100 x 0.0167) + (0.005 x 0.9833) ≈ 1.67 + 0.005 = 1.675 mA.

1. Estimate battery life (10 seconds)

This simply leaves you with the task of calculating t = 2000 / 1.675 ≈ 1194 hours (~50 days).

Well, of course, your work isn’t strictly “done” here, because you would then need to consider potential means by which you could stretch that battery life.

This might entail selecting more efficient components like low-power sensors, or you may consider reducing the duty cycle. The latter could involve the given IoT device transmitting less frequently, such as every 30 to 60 minutes, or using event-triggered wakes.

Various Online Tools Can Help You Extract More from Your IoT Device’s Batteries

You do not, of course, always need to depend on manual calculations as a means of figuring out likely battery performance and considering how this can be improved.

A range of calculators and similar tools exist across the web, including on reputable sites such as that of the electrical component supplier, RS.

That particular site, for example, offers an intuitive RC time constant calculator. Tools like these can support the optimisation of battery life, by revealing the rate at which a battery (or its associated circuitry) charges or discharges. This enables engineers, in turn, to predict and manage performance.