No juice left in this ruined AA Alkaline battery

Two NiCds leak better than one (times two)

One AA leaked, the other didn’t but just wait until 2014

A quartet of leaky clock batteries

Data might still be safe? Nah!

A little NiCd battery juice makes for a lot of aged circuitry

Bad battery ends the games for this Game Boy cartridge

This Macintosh battery holder is one rotten apple

The battery’s gone but the destruction remains in this HP 35 calculator

Of course, the culprit is you. You didn’t properly maintain the device by instituting a program of regular maintenance and periodic battery checkups. How could you? The device was tucked away on a shelf, perhaps years ago, and you forgot all about it. After all, batteries aren’t the most important thing in your life. You’re a busy person.

This same scenario applies to batteries in all sorts of embedded equipment and servers. As little electrochemical electricity factories, batteries need to be maintained or they will eventually give you a nasty surprise. It’s that simple.

Over the last 10 years or so, ultra-capacitors have started to replace batteries in a variety of electronic applications where large amounts of energy storage are needed. One of the primary uses for ultra-capacitors is memory backup. A more conventional approach to memory backup employs ultra-capacitors to provide backup power to SRAM or DRAM subsystems in the event of a power outage. However, even large banks of ultra-capacitors cannot back up memory for years. A different sort of approach to preserving data in the event of a power mains failure is to draw energy from ultra-capacitors just long enough to move critical data from volatile SRAM and DRAM into non-volatile Flash memory. Then the Flash memory can retain the data for ten years or more with no power at all.

Ultra-capacitors get their high capacities from porous carbon electrodes that provide massive amounts of surface area in tiny spaces. As nanotech research delves into the mysteries of carbon-based nanostructures such as nanotubes, ultra-capacitor storage capacities improve. Coincidentally, the number of ultra-capacitor vendors has recently been increasing and therefore the effort required to evaluate the various offerings has also been increasing.

Characterizing an ultra-capacitor isn’t simple. For long-term use in critical embedded and server systems, you need to know how an ultra-capacitor’s electrical storage abilities change over time, temperature, and voltage. It turns out that the long-term characteristics of these low-voltage devices are extremely sensitive to temperature and to operating voltage. They’re also sensitive to the way they’re charged and discharged, so the design of charging and discharging circuitry is critical to the safe, long-term use of ultra-capacitors in multiple-device banks.

If you’re designing memory subsystems and wish to use ultra-capacitors for power backup, you have two choices. On the one hand, you can mount your own ultra-capacitor characterization program and develop your own charging and discharging circuitry. Alternatively, you might choose to use a pre-designed, pre-characterized power module based on ultra-capacitors that’s specifically designed for memory-backup applications such as the PowerGEM offered by AgigA Tech. Either way, ultra-capacitors offer a good alternative to backup batteries, one well worth investigating.

References:

Energy Storage Industry Needs Novel Circuits And Semiconductors, Bobby Maher, http://electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=21973&bypass=1

Ultracapacitors Challenge the Battery, John M Miller, http://www.kilofarad.org/files/Ultracap-%20World%20&%20I%20-%20June%202004.pdf

1. October 10, 2009. T-Mobile Sidekick owners found that they’d lost their contacts, calendar entries, to-do lists and photos when Microsoft subsidiary Danger suffered a technical glitch. At first, the news was very bad. The lost data looked unrecoverable. Then, it looked like some of the data might be recovered. Then most. If you are or were a T-Mobile Sidekick user, what would you be thinking about the service right now?

2. September 24, 2009. Google’s Gmail blows up, again. Only a “few” users are affected, but it’s the fourth time in two years that Gmail has made the news because of service loss.

3. September 6, 2009. Twitter fails for hours. Sure the Twitter Fail Whale shows up regularly, but Twitter is a high flyer with huge visibility.

4. August 3, 2009. eBay’s PayPal crashes for five hours. PayPal loses millions of dollars in transactions that don’t happen. PayPal’s merchant customers lose more.

5. June 29, 2009. Rackspace loses power in its Dallas data center and ends up rebating customers millions of dollars in usage credits for lost service.

6. January 6, 2009. Salesforce.com’s servers crash for about half an hour. One blogger notes: “Salesforce demonstrates how (un)reliable SaaS really is.”

This sort of press is a server provider’s worst nightmare. One of the missions of this blog will be to propose approaches to improving server reliability. Please feel free to contribute your ideas.