Embedded batteries: Evil master plan, or elegant solution?

When Ming Yu and David Maxwell of TI wrote a how-to article on the importance of highly accurate fuel gauges in battery packs for smart phones and tablets, I asked if they could also write a sidebar discussing the pros and cons of using an embedded battery in a mobile handheld design. There’s been a spirited discussion over at the Brian’s Brain blog on Apple’s embrace of embedded batteries in its laptops, iPhones and iPads which are so beloved by consumers. Apple is allegedly using built-in batteries, which are difficult for the average consumer to replace, because they guarantee that the purchaser will be ponying up for a new phone or tablet as soon as the battery starts to lose its charge capacity – usually after about 18 months.

But is using an embedded battery really about Apple’s greedy desire to lock us poor consumers into the throw-away phone cycle – or is it because consumers lust after Apple’s design ethos, which is all about thinner and more elegant hand-held devices, while concurrently demanding longer talk times? I’m thinking the latter.

Here’s the sidebar: I’ll also post a discussion thread over in the Forum.

Sidebar: Pros and cons of embedded batteries

Excerpted from Select the right battery fuel-gauge for smart phones and tablets

By Ming Yu, Business Development Manager, and David Maxwell, Application Engineer, Texas Instruments

A debate continues over removable versus embedded battery packs. Let’s look at some considerations, both good and bad, that are driving the trend towards embedded batteries.

The benefits are considerable and include:

• Product designers can design a more aesthetic form without concerns about battery position, compartment, and cover. Smaller form factors can be achieved by avoiding the standard connectors and thick battery case required for removable batteries.

• It’s less likely the user will toss out an expired embedded battery as it could be replaced at a service center, or the entire device could be recycled. Additionally, during the life of the product, fewer batteries will be produced overall, using fewer resources.

• The embedded fuel-gauge is always in-sync with an embedded battery. Swapping batteries can be a challenge for some gauging solutions when profiles or ages are different. It can require cycling for some system-side gauges to “learn” the newly inserted battery and for state-of-charge (SOC) and state-of-health (SOH) predictions to become fully accurate. This is avoided by either embedding the gauge in a removable battery and/or embedding the battery in the system with the gauge.

• Embedding the battery increases overall safety since cheap aftermarket batteries are less likely to be inserted. These cheap aftermarket batteries often skimp on quality and protection features, making them more likely to catch fire and “vent with flame.” Many device makers are now turning to higher voltage (4.3V or 4.35V max) batteries. At least one case of fire was reported when a user introduced a low-voltage (4.2V max) aftermarket battery into a system designed to charge to 4.35V. Unfortunately, the equipment maker usually takes the blame and gets the tarnished image. Embedding authentication into a removable battery pack is another solution to this problem.

There are also several drawbacks for embedded batteries:

• First, it requires a robust system design with fail-safes to prevent or recover from system lockups. Users are practiced at rebooting frozen phones by re-inserting the battery, but this is not possible with an embedded battery.

• Users want to go all day without the need to recharge. Carrying a spare battery is no longer an option with embedded batteries. Shrinking the internal battery to meet marketable size specs means accurate gauging is a must in order to utilize the entire available capacity.

• Users who want extra run-time must use an external battery pack, making the phone bulky.

• If the battery wears out, replacing an embedded battery usually costs more and is difficult to replace, versus simply buying and swapping out an accessible batteries.

Despite the drawbacks of embedding batteries, the general trend that started with tablets is moving to smart phones, and users are becoming accustomed to the idea of non-removable batteries in their consumer electronics.