Blog, Preparedness / Self-Reliance

Emergency Preparedness: Build your own backup solar generator!

Excerpted from “Tactics for Tough Times” by Dustin Hollis. Used with permission.

You can put together a simple, portable solar “generator” for charging small batteries, electronics, or directly powering lights and small appliances for under $500 with a bare minimum of technical know-how. This power pack can be used as an easy to use, self sustaining power source during emergencies, camping, and outdoor events. It’s a great alternative to a noisy portable generator that requires fuel. Our family uses it a base for charging all manner of electronics, including a radio, laptop, cell phone, GPS, flashlights, battery charger (AAA/AA/C/D cells), and LED or fluorescent shop lights for area lighting instead of bringing noisy and (and possibly dangerous around small children) breakable Coleman propane lamps we used to use.

The core of the system is a portable battery pack, usually sold under Xantrex or Durcell brand. (Links to sources are included at the end.) This power pack is a durable plastic enclosure with a handle containing a sealed lead acid AGM 28 amp-hour battery. Built into this enclosure are indicators to tell you how much power you have left and how much power you may be using, as well as AC and DC inputs. It is usually equipped with some or all of the following, depending of the model: inverter with one to three AC output plugs, a female DC plug, a jump start cable, an emergency light, an AM/FM radio, a clock, and possibly a mini-compressor.

To charge the portable power pack during a power outage or emergency, you need a source of power. The best portable solution for this is a folding solar panel. Solar panels are quiet, simple and easy to use, requiring only to be placed in front of a strong light source to function. For an emergency situation, CIGS military surplus folding solar panels are your best choice. These panels cost more than traditional bulky, heavy, breakable panels, but are well worth the cost considering they are lightweight, folding, flexible, durable plastic covered in a nylon cloth backing (with a storage pocket for cables) to keep them from damage.

While there are several models of panels with different wattage outputs, in my opinion, 25 watt panel offers the best balance between cost and efficiency. I have tested a 25 watt panel (3.4 amps) to fully charge an average power pack within 5-7 hours in full sun. If you feel you need more wattage, other models are available, but I would recommend getting two smaller panels over one high wattage panel for redundancy. If you purchased another power pack, you can then have two power packs charging at the same time.

The panels come with a standard set of trailer plugs and several modular cables with different interfaces, depending on what you want to charge. The cables included are a male DC plug, a female DC plug, a cable with a set of spring clips for charging an auto battery, and a 2.5 mm plug barrel connector.

Two – four identical panels can be daisy-chained together to generate more power with an available SAE “Y” accessory cable.

You can use the barrel connector cable to charge the power pack directly in place of the AC plug provided with your power pack. The power packs have a built-in charge controller that stops the battery from over-charging when at full power. When charging an automotive battery with spring clips, you might want to consider purchasing an inexpensive charge controller to prevent damage from over-charging. It is suggested to use a charge controller when daisy-chaining panels as well.

Some hints and tips for using your panel and power pack:

Panels can be used to charge devices directly if you have a corresponding plug.

A 25 watt panel is 8″x”10″ spread out and will fold up to the size of a hardback book, perfect for fitting into a backpack. They have eyelets at each corner for positioning and mounting. It can just be spread out on the ground or attached to any flat or curved surface facing the sun. I pack a set of small bungee cords with the panel to secure it at each corner, especially if it is windy. As the position of the sun will slowly change throughout the day, you might want to check on the panel periodically and re-position it to make sure that no part is blocked by shadow to make sure you are getting the most from your panel.

In order to best conserve your limited power, try not to plug in AC devices into the power pack’s inverter for a long period of time unless you have to. Converting DC power (what the battery stores and outputs) into AC (what the built-in inverter pumps out) is less efficient than running DC directly to the battery. The inverter uses power when switched on, so make sure it is switched off when not in use. Most small electronics like laptops, cell phones, and small battery fast chargers have DC “car chargers” available for purchase. Use these instead of the AC adapters. You will waste considerably more power converting from DC to AC then AC to DC rather than just using DC directly.

You can often find DC models of your favorite small electronic appliances at your local truck stop or RV supply store, but don’t use appliances whose main purpose is heating or cooking. They often draw way too much power for the power pack to handle for long. Another good purchase is a DC “splitter” that will allow two or more devices to plug into the power pack at the same time.

Keep your usage small and efficient. For example, for lighting, use LED over fluorescent and fluorescent over incandescent. LEDs might use less than 5 watts to produce as much light as a 100 watt bulb.

Several retailers have recently started to sell LED shop lights. These are very efficient area lights with different power options, AC, DC or rechargeable with AC and DC input. The rechargeable units are usually smaller than the direct AC or DC lights. My suggestion is to buy a larger DC direct unit and a smaller rechargeable unit that you can charge and take with you while you perform other activities.

Buy some LED flashlights that run on AA batteries. Purchase a a supply of rechargeable batteries and a small battery charger with a DC accessory plug. The most efficient small batteries available today for the price are Hybrid AA/AAA rechargeable batteries. You can find these at most electronics stores, including Wal-Mart and Costco, though you might find a better deal on-line. Common brands are Eneloop, Hybrio, Rayovac I-C3, and E8DE brand batteries. These “hybrid” NiMH batteries can be recharged up to 1,500 times. The self discharge is very minimal and they have no “memory effect”. You can store them for 3 years and still they will retain 75% of their power capacity.

Determine all the devices you want to power and how many batteries you need and then buy at least twice that number of batteries. You will then always have one set of batteries charged while you use the others. Hybrid C and D cell batteries are not quite available yet, but will be soon. In the mean time, adapter sleeves are available from Sony for AA batteries that allow you to convert an AA battery into the same size as a C or D battery to fit and power whatever device you need.

Expansion:

You can expand and upgrade the system by purchasing additional redundant sets of power packs and panels, or larger battery packs and higher wattage panels.

Lithium Ion rechargeable battery packs are just coming on the market and may prove to be a better solution to your portable power needs. Lithium power packs are considerably lighter in weight than similar wattage lead-acid or gel battery systems. They do not yet have the same range of features as more mature traditional power packs, but more than make up for it in considerable size and weight savings. You can easily fit a lithium battery pack in your backpack along with a folding solar panel and add only a few pounds, as opposed to the average Durcell power pack coming in at close to 40!

As with most technology, smaller, lighter and more efficient equals more cost. Today, expect to pay 3 to 6 times the cost of a regular battery system. As these technologies become more popular over time and manufacturers produce more of them, the prices will eventually come down.

Resources:

Suggested Power Pack model:

(Amazon.com often has sales on these. There are several similar models with similar functionality, shop around for the best price, and consider these are heavy units, so free shipping is a good deal)

Duracell DPP-600HD Powerpack 600 Jump Starter & Emergency Power Source with Radio, available for between $100-150.

Features:

  • Three three-pronged AC outlets to power multiple loads
  • One DC outlet
  • Built-in 600-watt inverter
  • Sealed, non-spillable 28 amp hour AGM battery (replaceable)
  • AM/FM radio and digital alarm clock
  • Jump Start cables

Specifications:

  • Dimensions (L x W x H): 19.25 x 8.25 x 11.25” (48.9 x 21 x 28.6 cm)
  • Weight: 32 lb
  • Warranty: 6 Months
  • AC output power (continuous): 480 Watts
  • AC output power (10 minutes): 600 Watts
  • AC output surge capacity (peak): 960 Watts
  • AC output voltage: 115V
  • AC output frequency: 60 Hz
  • AC output waveform: Modified sine wave
  • Internal battery capacity: 28 Ah
  • Internal battery type: Sealed lead-acid, AGM
  • DC output: 12 Vdc

Folding Solar panels:

These military grade units use non-silicon based, CIGS (Copper Indium Galium di-Selinide) panels backed with nylon and nylon cloth.

Cable pack with 4″ trailer cable 12V female socket, cigarette lighter adapter, 8″ cable with alligator battery clamps, 4″ cable with 2.5 mm plug barrel connector, quick-connect components and 8′ extension cable.

SAE Y-Cable to connect two or even four solar panels together.

Charge Controller

iPod charging cable

Specifications:

  • Dimensions Folded: Length 11″ x Width 8″ x Thickness .7″
  • Dimensions Deployed: Length 41.25″ x Width 21.5″ x Thickness .03″
  • Weight: 1.80 lbs

Power:

  • Voltage: 12 Volts
  • Wattage: 25 Watts
  • Amperage: 1500mA or 1.5 Amps

Search for “Foldable Solar Panel” in Google for the best price. Ebay has a few reliable inexpensive sources. “Sunlinq” and “Global Solar” are common brand names. Look from the type backed with nylon camo pattern cloth. This will protect your panel from damage. Average prices run between $225-350.

I suggest looking for panels in the 25-30 watt range for the best price/performance. This level of power will charge the Duracell/Xantrex power pack in 5-7 hours, depending on sun.

Lithium Ion power packs:

Due to the extreme cost and limited availability, I have yet to review the few types available as of yet.

Rechargeable Lithium Ion power packs are a new technology.

Brunton, Tekkeon and APC make some units. Batteryspace.com sells some solar kits that come with a bag, inverter, charger and cables. The units are a collection of pieces and not as integrated as the solutions from Brunton or others. They may, however, be the least expensive solution until Lithium power packs become more available.

Here are some web links to Lithium Ion rechargeable battery packs and folding solar panel solutions:

http://www.brunton.com

http://www.tekkeon.com/products-mobile-pwr.html

http://www.batteryspace.com

http://www.powerenz.com

http://www.readymaderesources.com

http://www.21st-century-goods.com/product/Sunlinq-25-Watt-Solar-Panel.html

Rechargeable batteries:

For the best prices on hybrid NiMH batteries, Google search for “hybrid rechargeable batteries”. Common brands are Eneloop, Hybrio, Rayovac I-C3 and E8DE brands. Costco often carries Eneloop brand at a good price.

Take a look at this excellent review from Metaefficient on hybrid low self-discharge (LSD) batteries and various chargers online:

http://www.metaefficient.com/rechargeable-batteries/best-rechargeable-batteries-battery-chargers.html