Build Your Own Emergency Power Kit

Full-function off-grid solar charging station
100w rig with car battery

This will get you through in a pinch, and it relies on old-faithful 12V car batteries with relatively inexpensive 12v power inverters.  We always keep a few sets of 12v equipment around just for emergencies.  But with more time to prepare and more money to spend, we’d jump straight into a 36 or 48 volt inverter with the insight that you will need at least 3 car batteries connected in series to make your 36v inverter work, or 4 car batteries in series for the 48v inverter.  So simplicity vs complex.  We lean on simplicity in emergencies, and thus we focus on 12v systems for this tutorial.  Future projects go into higher voltage setups.


If you need emergency power for whatever reason, you either crank up a gas/diesel generator, or you pull out your solar panels and batteries.  There aren’t many other solutions.

If your plan is to depend on gas generators, prepare for the noise, fumes, and recurring need for ever more gas. If power is out for an extended period of time, buying more gas will become impossible unless you pay black-market rates.  Many people turn them off even before they run out of gas due to their noise and fumes.

If you build an emergency rig like we describe here,  wait for the wind and rain to calm down, and then deploy your kit in the sunshine.  Set it up in your yard, on your balcony, or on your roof.  Chain it down, and bring it in at night.  Set it back up during daylight. Sound dire?  It will be, and people will steal it, so lock it down with a chain and padlock if there’s any chance vandals and looters will be roaming around (they will).  Now let’s get you ready for the inevitable.

In an emergency, you are going to need batteries.  I’m talking about big ones like car or boat batteries.  Most people won’t be thinking about car batteries, but you will.   They are your fuel and eventually your currency.  At the outset of a disaster though, nobody cares about things like car batteries.  People scramble for basic necessities like water, eggs, milk, bread, and gas for their generators.  The eggs, milk, and everything else in the fridge will go once they run out of gas.  The gas will go in 24 hours;  48 if they’ve filled a few 2-gallon containers.

Car batteries are heavy 12 volt blocks of energy just waiting to be put to a new, good use.  In a really bad crisis, you can pull batteries from abandoned vehicles.  And people will barter their car batteries in exchange for a hot-cooked meal or two.   Offer to store their frozen (but thawing) food in exchange for loaning you their car battery until the grid is back up.  You’ll make a lot of friends fast.  As you read this, if you are thinking about going out now and buying a few car batteries, DON’T.  There’s much better technology around in the form of lithium packs.  For now, focus on emergency conditions and the fact that car batteries will be all around you, and stationary.  All you need is a way to charge them and use them.  Ready? Here’s how you do it:

  • Solar Panels.  One 100 watt panel is all you need to scrape through.  Three will allow you to do all sorts of things.  We recommend three 100 watt panels for emergencies and as the modular foundation for all the higher voltage projects we’re going to teach you about later.  But alas, one will do.  These are about $130 per unit most places.

  • Solar Charge Controller.  This is the electronic component that stands between your panels and your batteries.  It regulates how much power gets pushed into your batteries.  You only need one or two of the cheap 12/24v models with a 5v usb port for your phone.  There are other, more sophisticated models for managing higher voltage lithium battery setups, but we’ll get to those later.
Grid Vision 12/24v 20A Solar Controller
  • DC to AC inverter.  A 1000 watt inverter will run a small to medium refrigerator.  You’ll need a 2000 or 3000 watt inverter for a big fridge.  The data specs are on a label inside the fridge.  It will state the watts needed to run your fridge.  If it says 900 watts, you can get by with a 1000 watt inverter, but you are better off at least doubling the wattage of your inverter.  If you are going to be running your microwave oven or firing up your hair dryer, you’ll need a big 3000 watt inverter.  We recommend 1000W Pure Sine Wave inverters for about $160 each to power things requiring 500-600 watts or less, and a 3000W Pure Sine Wave inverter for about $350 to handle your microwave oven, hair dryer, and other temporary power hogs (including big refrigerators).  Just remember, splitting the loads up onto individual inverters makes everything more stable, and allows you to manage battery charging in a more modular fashion.  You can get by on just one 1000W inverter, but if you have more than one you can start pairing those with additional batteries to power more stuff.
12v 1000w Pure Sine Wave Inverter
  • Batteries.  Like we said, car batteries are your friend in an emergency.  Connect them together in parallel to increase your capacity for running things longer.
You what?  You want my car battery?  Sure, take it.
  • A few connectors, switches/breakers, and wires.  If you are prepared, you’ll have a kit of connectors, wires, tools, controllers, breakers … ready to go.  But in an emergency, all bets are off, and you sometimes just have to make do with the cards you are dealt.  In an all-out Armageddon, strip wire from a car along with the battery.  The only things you absolutely need to have stashed is a solar panel and a solar controller.  Everything else is just flavor.  We recommend stranded 12AWG wire, red for positive and black for negative to keep everything straightforward.  We use DIN Rail mounted circuit breakers between our panels and the batteries, and also between the batteries and the inverter. Use circuit breakers if you have them.  Hot-wire everything together directly if not.

How to wire everything up:

Connect the battery to the solar controller first.  Then connect the solar panels to the controller. Use breakers in between each piece if you have them.

If you have more than one car battery you can wire them together in parallel to increase your capacity to run things longer.  Connect the inverter directly to your battery, and plug your fridge into the inverter.

If you have access to a lot of batteries, you can rotate batteries outside to your solar charging station and back inside to your inverter which is running your stuff.  Obviously, the more batteries and inverters you own, the more freedom you have to wire up and run lots of stuff.

How to charge the battery:

Follow the instructions specific to your controller, but generally, most step-down controllers require the battery side of the circuit to be connected first.

Flip the breaker between the battery and the controller.

Once the controller boots up, flip the breaker between the controller and panel.  You should now have juice flowing from the sun into your panel into your controller, and into your battery.

We’ve seen a few step-up controllers that want you to connect the panel side first.  Step-up converters take a low voltage and step it up to a higher voltage.  So check your controller’s documentation carefully.  You can fry the controller if you connect the wrong side first.  We only sell step-down converters, and they all require that you connect the battery to the controller first.

How to Disconnect it:  Disconnect the system in the opposite order that you connected it.  For most step-down controllers that means disconnecting the panels first.  Then disconnect the battery.  Just use the circuit breakers as switches.  It saves time, and that is what makes them so perfect for these applications.

Variations on the Setup

You can combine batteries in parallel and/or solar panels in parallel to increase the ampacity of your system.

Wire batteries together in parallel by wiring all the negative terminals together, and similarly wire all positive terminals together.  You will then have one negative lead from the battery pack to the controller and one positive lead from the pack to the controller.  You now have one very big 12v pack.

You can connect solar panels in parallel to increase the amperage delivered from the panels into your batteries.  If your panels already have MC4 connectors attached, get some MC4 parallel connectors so you can wire them together properly.  It never feels good to have to clip a perfectly good MC4 connector off a panel, so get yourself a few different connectors.  We offer both the Y2 and Y3 connectors.  With three panels that gives you the ability to wire them in series, or two in parallel or three in parallel.  Lots of combinations for the price of a few connectors.

Congratulations.  You’ve now got a sun-powered source of energy as the foundation for your emergency kit.  You are most likely going to want to start running something off it full-time, so go ahead.  Find something to plug into it, and welcome to the world of energy freedom. FYI, Home Depot offers a setup similar to what you just built (but with a few batteries included) for $1999.

Home Depot Kit you just built for about $475