Monday, December 18, 2017

Guest Post: Laptops and Cellphone Post-Disaster

by George Groot
George is a member of our Facebook Group and has written for us before.

In the event of a major but temporary disruption to normal life, keeping things as “normal” as possible for my children is something that I try to do. Several years ago during a tornado warning we spent a few hours in the basement and a laptop with some videos was enough to keep the kids happy.

But what do you do when a few hours turns into a few days to a few weeks? Assuming that you have some form of alternative energy such as a generator or solar panels, and a battery bank to store electricity, you might be just fine recharging laptops, tablets, or cell phones from that alternative power source. However, if you don’t have a general purpose alternative electricity source, there are a number of portable solar charging options just for portable devices.

Solar Recharging

As a rule of thumb, more surface area for solar panels is better. Anything that is a battery bank with just a single solar panel will be pretty useless as an energy source; battery banks need at least three or four fold-out solar panels in order to get into the “worthwhile” category. For example, this solar battery bank advertises 10,000 milliamps of energy after 20 hours of charging, which is actually useful for a smartphone that uses about 1,800 milliamps of power for a full charge. With 10 hours of daylight, at 100% efficiency and working as advertised, that’s 5,000 milliamps. Even if you drop the efficiency to 50%, that’s still 2,500 milliamps, which is enough to charge up that smartphone or most tablets. 

An even larger option is made by the popular Anker brand, and it comes with an 18 volt outlet, which is enough to charge most laptops (although many are set to receive an input of 19 to 19.5 volts). Not all laptops are great options for solar charging, though; a very high efficiency “ultrabook” style laptop will be a very good option, while a “desktop replacement workstation” will be much harder to keep charged. For example, the 4th generation Core i7 processor has a 47 watt power draw at full power, where a 4th Generation Core i5 is only 15 watts. The Core i5 has half the processing cores as the i7 of the same generation, but less than a third of the power consumption at max load (although the i7 can handle a much larger max load, we are talking playing kids games or movies to keep them out from underfoot). 

This shouldn’t discourage you from getting an i7 based system, though, as many ultrabooks use the i7 processor knowing that it has a variable power requirement based on load, so in practice they can often work on battery power for much longer than “business class” laptops using the same generation i5 processors because the entire package is meant to be more efficient. What you should look for is total battery capacity and advertised usable time under battery power; an ultrabook should be good for over 10 hours on battery power with a new battery. As batteries age, that number will go down.

From Recreation to Communication 

I believe that smart phones are one of the handiest pieces of communications gear that a prepper can have after a natural disaster. While voice telephone calls eat up a lot of bandwidth, SMS messages are tiny and can allow people to communicate in and out of the affected area with reasonable latency. Also, communications apps such as Zello have been used to coordinate local groups of disparate people, such as South American opposition political parties or volunteer search and rescue groups helping in the aftermath of Hurricane Harvey.

Mesh Networks
Even if there is a complete failure of the cellular network, smartphones can be used for local communications via “mesh network” solutions like Serval, and Sonnet is an interesting project that I hope becomes a reality.

If you can find good versions of the Linksys WRT-54G router at thrift stores for a few bucks, you can build mesh net infrastructure. It won’t be as sexy a solution as Sonnet looks like, but as long as you can keep them powered they will keep people connected. Every time I see a version 2 WRT-54G at a Goodwill, I pick it up. They are generally priced in the 5 to 10 dollar range, and even the later version 5 and up models can be useful when loaded with DD-WRT or Open WRT firmware.

Be aware that using WiFi as a primary communications channel will often suck a smartphone battery dry much quicker than the cellular radio connection. This is because the power management for a cell radio is much more “passive” than the WiFi radio, which was designed for computer networking and which keeps the device registered with the Wireless Access Point (WAP) constantly rather than on an “as needed” basis.

I hope this has been an interesting and informative look into how to plan for a power budget in the event of a disaster, although you don't need to wait for an emergency to put them into practice; the concepts are exactly the same as if you were going to do some remote camping and wanted to bring your power source with you.

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