What is the Battery Life of your IoT Device?
A question that clients buying battery-operated IoT sensors don’t ask often enough.
Batteries can have such an impact on the product life cycle cost, so why are they often forgot about when evaluating a solution? In this article, we will take a deeper dive into the important questions you should be asking a vendor when it comes to batteries. For example: what type of batteries are being used, how many batteries does the product require and how long is the expected battery life.
Batteries should be top of mind for you as a client. Depending on your agreement with the vendor, you may be responsible to cover the battery cost and the time required to replace them. In some cases, the cost of a battery replacement can exceed the cost of the initial purchase. It is for that reason that you must always ask a vendor the following questions.
Question # 1: What type of batteries are required for this product and are you responsible for providing them?
The type of batteries used in a particular device makes a significant impact on the life expectancy of the product. Below is a table showing the delta in value when a vendor chooses to opt for Option 1, Alkaline 1.5V batteries versus Option 2, Lithium thionyl chloride 3.6V batteries that highlights the key differences between battery types:
Question # 2: Do you have a battery life estimator spreadsheet you can share with me?
When putting together an IoT solution, the manufacturer and/or solutions provider will have established certain “rules” for the device. These parameters include time spent on air, frequency of messages, battery discharge rate, wake-ups per day, and sampling period. This comprehensive assessment gives the manufacturer and/or solutions provide the ability to estimate the life expectancy of the product before it will require replacement batteries. The calculation performed to get an estimated life expectancy takes all the parameters into account, with two valuables standing out above the rest: Self-discharge rate and total energy capacity. The self-discharge rate is the amount of energy that is lost over a period of time due to internal chemistry degradation. Two total energy capacity means that there is more energy available for use by the device. This difference is caused by the battery configuration and voltage of the cells used. The information gathered from the transmission rate and configuration is then used to calculate the “energy used per message”. This number is then divided into the total capacity and self-leakage deducted to get to a total number of messages per battery pack. This number is then divided by the number of messages per day/month to get estimated battery life in years. It is important that you ask for this information to validate and evaluate the life cycle of the product or solution you are looking at purchasing and investing in.
Question #3: Who is responsible to supply and install the replacement batteries on these devices?
More often than not, you the client will be responsible for the battery replacements and the labor involved in replacing these batteries. In the event that this is the case the most important step for you to take is the one that comes next. Making an analysis on what the life cycle cost of your device will look like over time when factoring in battery replacements.
Question #4: What is the product life cycle cost when factoring in battery replacements?
When evaluating the product life cycle cost it is imperative to consider the battery replacement cost. For example, let’s compare Option 1 with (2) AA 1.5V batteries versus Option 2 with (3) AA 3.6V batteries using the same IoT capabilities:
The Delta: Option 1 will cost $33.60 more over the same period of time or 3 times more money than Option 2. You may also need to account for travel costs and access to the tenant or resident’s property.