All the gizmos, gadgets and devices we used today are packed full of amazing technologies, many of which have become extremely small. The A7 chip is smaller than a postage stamp, and it’s probably one of the bigger components in your device. The fingerprint scanner sensor on the iPhone is only 170 microns thick. But all these amazing technologies are totally subservient to the true unsung heroes of the mobile digital age: batteries. If your batteries are no good, all the CPU cores and RAM in the world won’t help you. That said, batteries have come a long way even if they don’t get as much press as a new CPU or touchscreen.
To start at the beginning, you’d have to look at probably the most popular, widely used battery of all time: the lead acid battery. Invented in the mid 1800s, we still use them for our cars, boats, battery backup systems and just about anything else that requires a tough, reliable and durable power source. They’ve even had their own share of improvements, from VRLA (Valve Regulated Lead Acid) designs that are sealed, to AGM (Absorbed Glass Mat) designs that don’t really contain any liquid electrolyte at all (it’s suspended in woven glass fibers). Despite being fairly toxic (lead, sulphuric acid, etc), they’re one of the biggest success stories in all of recycling. Upwards of 97% of the lead and other materials from lead acid batteries are recycled in the US. They truly are some of the most robust batteries too as anyone around here who’s started their car in the past few sub-zero days would attest to.
This all makes lead acid batteries sound pretty great, right up until the big ‘gotcha’ that you’re probably already thinking about: weight. If you wanted to run your iPad Air with a lead acid battery, it would be a battery that weighed about 8.5 pounds, and because there isn’t much flexibility in designing the shape of lead acid cells, it would probably be fairly bulky too. Another drawback with lead acid batteries is their life span. Even deep cycle batteries with thick lead plates shouldn’t be routinely discharged below 50% of their capacity. This means that to get the roughly 33 watt-hours the iPad Air requires, you’d need to use a lead acid battery with double that capacity, meaning even more weight.
Fortunately for us lovers of thin, light and robust technological gizmos like the iPad Air, we don’t need to rely on 150 year old battery technology. Check back next week when I’ll discuss the intermediate stages of battery development in the 20th century including nickel-based batteries.