Emergency Laptop Power on a Budget!

Have you lost commercial power, can’t get to the office and your laptop’s battery is fading fast?
What can be done to prevent being put in such a position? Good question! We assembled our own emergency power supply from readily available items.  If you want to try it yourself, here’s what we did (and it was easy!)
First, you’ll need a battery with sufficient storage capacity to power the laptop for an extended period. It also must be in an enclosure, for safety reasons. Finally, it must be easily transportable. Fortunately, there is an off-the-shelf item that satisfies this requirement nicely: an automotive jump-start pack.

image4It must have a cigarette lighter type receptacle. This is an example of a Shumacher XP400 unit which we purchased at a local Wal-Mart. It can be acquired for under $40. It is advertised as a 400 Amp jump starter and contains a 5 Amp-hour battery. Since many of the more efficient laptops and netbooks draw much less than 1 Amp to operate when not charging internal batteries, you can see why you’ll get many happy computing hours drawing from a source such as this. The more efficient your netbook, the greater the run time!

Next, you’ll need a voltage level that you can actually USE. The jump-start pack produces a little over 12 Volts, but almost all laptops require something in the 18 Volt range. You’ll need something to convert the 12 Volt supply into the 18 Volts that the laptop needs. As luck would have it, we found a DC-DC converter designed to do exactly that.

image2The one we used for testing is made by Targus and comes with a cable and multiple plugs for the end that fit most laptops and netbooks. It’s called the ‘Targus Laptop Mobile Charger with USB Fast Charging Port’. (You won’t need to use the USB charging port attachment that comes in the box to charge your phone or 4G Wi-Fi device if your jump start pack has a USB charging port.) List price is just under $70. The device is rated at 90 Watts, so check your laptop power requirements.

OK, so now there’s sufficient power at the correct voltage. Let’s add the laptop! But first, keep in mind that in order to get the most out of emergency power, you want it to perform ONE job, not TWO. We want to power the laptop. We DON’T want to power the laptop AND charge the laptop battery. Why? Because of conversion loss. Electricity used to charge a laptop battery is converted from electrical energy to chemical energy as ions are physically moved inside the battery. You do not end up storing anywhere near as much energy as you put in. Additional loss comes from the heat generated in the charging process. When charging from a wall outlet, we don’t even consider this, as electricity is still relatively cheap.

image6But when talking about emergency power, the goal is to minimize loss. To this end, it is recommended that you REMOVE the laptop battery prior to powering up from the emergency supply. If you are already using the laptop running on its internal battery, you can wait until that gets low, plug in your emergency supply, and then remove the laptop battery. In this way, all available power will be used productively; to power the laptop.

The final configuration is small, has very few components and is extremely portable. Power supplies such as these helped Dynamic Strategies remain productive during the relatively long-term power outages that occurred here in the aftermath of Hurricane Sandy.

image8 photo

With the addition of a Wi-Fi cellular internet device such as this one from Verizon (above right), which can also be powered via the USB port on the battery pack or the adapter that comes with the Targus DC-DC converter, we were able to maintain productivity where screens would have otherwise long been dark.

It should be noted that every component in this project is being used well within each manufacturer’s published specs. No modifications are required.

So, if you would like to have a little insurance against power outages, this little project might be just the thing to keep you productive in emergency situations. Just remember to keep the jump start pack charged!*


*Note: Do NOT leave the jump start pack charging all the time, or unsupervised.