Product Design Short: To Battery, or Not to Battery?

You’re building an electronics product. Do you do the dirty deed of powering it by battery?

Many great options for device power exist, and you may have a method in mind. Some choices, although they provide a seamless user experience, have significant drawbacks. Others have fewer shortcomings but will make your end user completely miserable.

Before starting your printed circuit board (PCB) layout or mechanical design (or any design for that matter), I recommend taking some time to assess your user’s needs to determine what’s right for your application. Even if your team, your client, or your user has come up with a wish list for their prototype or product, it’s important to give your solution set a critical eye while you still have time. Prototypes deserve consideration before building as well. Take this lesson from my experience: trade shows don’t change dates because you picked a tricky power solution!

I’m going to lay out some reasons when you DEFINITELY want to use a battery, as well as some reasons to skip it — maybe for now, maybe for good.

If you’re here for information only about batteries, I implore you to consider some things in this article to reaffirm it’s the right choice — before it’s too late to go back. However, the following articles provide more in depth information on battery basics: specifying and sourcing, primary vs. secondary).

With that out of the way, let’s start with some key questions.

Does the device need a battery?

First, determine that your product or prototype needs a battery. This seems very basic, but question your own understanding of the user’s needs and make sure you do not add unnecessary complexity.

You need a battery if your device must function away from other sources of power or in transport. If you need 100% uninterrupted power, a battery is also wise.

This reason applies when your product or device must operate while not connected to grid or bus (USB, car, etc.) power, or when it temporarily loses power. If your user will rely on its function while it is in transit and cannot rely on external, portable, or back up power supply methods, a battery is a good choice. In many situations, alternative power sources like an internal combustion engine or fuel cells are impractical or undesired making the use of batteries optimal.

Examples: implanted medical devices, emergency equipment, wearables, communication devices, shipment trackers, electric vehicles

A slightly less common reason for needing a battery that may apply: your device needs to store energy for use or transmission at a later time (solar power, etc.)

Why might you decide against a battery in your design?

• Batteries are bulky, take up space, and need breathing room.
  Batteries are heavy, space-hogging, and must be given room to expand (for safety!). If you’re tight on volume, especially for a prototype, using a plug to power your device saves significant bulk.

Not an unusual sight . A necessary, but large battery contributes to a lot of weight and volume in a laptop.

• Batteries are restricted to standard shapes and sizes.
  Batteries come in only a few shapes and there may not be many suited to the application with respect to electronics and industrial design. Custom batteries are rarely an option without incredibly high-volume production and long R&D cycles, so most applications need to use existing and readily-available battery shapes.
• Designed improperly, device batteries are unsafe.
  Charging batteries inside your device generates heat, which, if done incorrectly, can cause fires. For many common chemistries, impact and puncture can cause fire or explosion.
• Shipping is restricted, and the product may not be able to be checked when flying.
  Li-ion batteries can be shipped in the devices they operate as of the time of writing, but the supply chain for this particular battery type can be complicated. Further, aircraft passengers cannot check lithium batteries due to safety reasons.

Goodness gracious, luggage on fire!

• Disposing of batteries is complicated and bad for the environment.
  All products are disposed of, and even if battery recycling programs exist, consumers may not use them. Only 5% of Li-ion batteries are recycled globally. Batteries become landfill where they leach into groundwater or even start fires that can last for years. Improper disposal of lithium batteries was responsible for 65% of California waste fires in 2017 and those numbers continue to rise.

Be nice to your trash collectors: recycle your batteries, and don’t inappropriately include them in your designs!

• Making batteries is far from environmentally sustainable.
  The mining and processing of raw materials used in batteries do significant environmental harm.
• The battery and charger increases cost.
  The additional cost to include a battery and potentially a charging device can significantly increase a bill of materials (BOM) cost, which may be prohibitive. Many toys are sold “batteries not included” due to the fact that higher sticker prices on the toys reduces the number of buyers. Even though they have to purchase those batteries separately, they don’t associate it as strongly with the cost of the toy purchase. A DC power supply and AC cable can be a cheaper alternative.
• Increase in design time and industrial design impacts.
  Providing for the increased safety risks and environmental considerations listed above requires additional resources during the development phase. Balancing all product needs can prove more difficult with the addition of batteries.

Prototypes can benefit from being built with a plug, and I highly recommend this for your first build. It saves space, circuitry, weeks, and headaches. A wall or USB plug could be sufficient to run your product or demo. Get power at your trade show booth (or bring your own battery device like this one), and a powered demo can sell your product, be made quickly, and be much lighter/smaller.

When it comes to VR headsets, batteries in the headset would weigh on the user’s face and require them to charge the device. Since users typically remain tethered to a high power, graphics card-equipped device via an A/V cable anyway, many VR headsets skip batteries completely.

Robotics engineering teams often power their prototypes and devices via a cable tether, which saves weight and allows for faster development in the lab.

So, if you’ve decided to stick to cables, that’s awesome — you’ll need to pick a power supply and cabling method, and save yourself a bit of headache which you trade for a bit of portability.

However, there’s always times and reasons when a battery makes sense. If you’ve decided a battery is right for your device and your user, you’ve got a few more questions to answer, such as: how does the battery get recharged or replaced?

It’s up to you and your product team to figure out what’s best for your product. However, if you’d like feedback on how to power your device or prototype, feel free to reach out!

If you’ve got a topic related to product development that you’d like to read about, please let me know in the comments, or drop an email to steph {at} swopedesignsolutions.com