If you were to lose power because of a natural disaster or other event, would you still be able to keep your important electronic devices, such as cell phones and flashlights charged? With catastrophic events such as major hurricanes becoming a more frequent occurrence, it’s not a bad idea to make your own DIY solar charging station for your home, especially if you can’t afford an expensive backup generator.
Our Setup For Emergency Solar Power Charging at Home
When we go camping off-grid somewhere for a few days we take along a portable 12 volt solar charging station to run our Dometic fridge/freezer, as well as for charging our walkie talkies, headlamps and other gadgets. We run everything off of a 114 amp/hour battery that we bought from Walmart, which is charged by two 100 watt Renogy monocrystalline solar panels and using a PWM charge controller.
Our all-in cost for this 200 watt off-grid solar setup was just under $400 and solar panel prices have actually come down from when we first got ours. Together, both 100 watt panels can provide about 800 watt hours or 66 Ah of charging power per day under normal conditions. When we’re at home, we can hook these same panels up to a second deep cycle battery that we keep on our workbench as an emergency 12 volt power supply which can be used to charge our portable electronics and for lighting during an power outage.
What About DC to AC Inverters?
Inverters are devices that convert a 12 volt battery’s DC (direct current) to AC (alternating current) so that you can use things like laptops or even small microwave ovens when off the grid. In terms of using these with a small solar backup charging station for emergency home use, inverters aren’t always practical, since they’re not generally energy efficient and can quickly deplete your power bank.
The typical efficiency of a high-quality pure sine wave inverter ranges from 90% to 95% but these models are quite expensive. For cheaper modified sine wave inverters such as those found in discount stores, efficiency can be in the 75% range – meaning 25% of your power is simply wasted before it ever gets to your appliance. If you’re looking to make an inexpensive backup 12 volt charging station, it’s best to stick with using it to charge 12 volt and 5 volt USB devices to save power.
Determining Your Power Needs from a Home Solar Charging System
The first step when making a DIY solar charging station for your home is to determine how much stored power you’ll need to keep all your devices charged. Charging our Baofeng UV-9G handheld radios uses about 1/2 amp-hours (Ah) and our home system can produce many times that, allowing us to also run our small 12 volt fridge if necessary.
An excellent solar calculator can be found here, which you can use to determine what size of panels and battery might work best for your solar backup system.
Example: A 45 liter 12 volt Dometic fridge will use 4.5 Ah and run about 8 hours out of 24 in moderate weather conditions for about 35 Ah of daily power draw. To allow for occasional cloudy days and other factors, you’ll need a solar power system with a battery capable of storing about twice the fridge’s draw to be on the safe side. Having a larger battery bank can help offset any loss in charging power because of prolonged overcast conditions.
What’s All This Amps and Watts Stuff?
An amp-hour (Ah) is simply how many amps a device draws per hour. Multiply that by 24 and you’ll have the daily power requirement for that device. If your device’s power is only listed in watts, to find power draw in amps simply divide the watts listed by the voltage of the device. A 120 volt fan listed as 100 watts would draw .84 amps for example.
Do I Really Need a Solar Charge Controller?
Some people think solar charge controllers aren’t really necessary. While this may be true when using very small panels, under 10 watts, it’s definitely not the case when using 100 watt solar panels. If an unregulated 100 watt solar panel is connected to a battery it can easily cause “boiling” of water and drying up of the cells, as well as premature failure of your expensive battery.
A 100 Watt Panel Is Enough For Charging Most Devices
For most situations where you only need to keep the most important devices, such as two-way radios, cell phones, camping lanterns and flashlights charged, a 100 watt solar panel should be more than enough. You may have to move your panel during the day to track the sun, but you should be able to collect around 33 Ah or 400 watt hours on an average day to charge a deep cycle battery.
What Can You Power With a 100 Watt Solar Panel Setup?
If you only use one, 100 watt solar panel you can still keep several essential items charged, such as battery powered fans, flashlights, two-way radios and more. You’ll likely have surplus power if only charging small items. Even though they’re not that power efficient, you could also use a system this size to occasionally run a 100 to 500 watt inverter for short-term operation of things like laptops, blenders and other small 120 volt appliances during a prolonged power outage.
What You’ll Need to Make a DIY Emergency Solar Charging Station
Our system uses Renogy 100 watt solar panels feeding a wet cell 12 volt deep cycle battery. We used a plastic battery box costing about $15 to safely hold the battery. Our emergency home solar charging station utilizes a Renogy Wanderer charge controller ($30), along with a fused power distribution hub with cigarette and USB outlets ($20).
We connected the hub to the battery using a 12′ long cigarette lighter extension cord with alligator clips. Using the items in the photo above, our DIY 12 volt solar power setup cost around $260. This is far less expensive than an inverter generator and works just as well – and quieter – for charging important electronics in a disaster scenario.
Keeping it Safe
You’ll want to set up your backup 12 volt solar charging station somewhere out of the way, such as on a garage workbench. It’s important that you use a case for your deep cycle battery and secure it somewhere it won’t be knocked over.
Batteries contain dangerous acid and can also emit explosive hydrogen gas, and must be kept away from anything that could cause those gasses to be ignited. Be sure to use fuses placed at the battery for any extension cords that you use to power USB hubs, etc. When using wet-cell batteries it’s important to regularly check fluid levels and refill with distilled water when necessary.
How Often Do You Need to Add Water to Deep Cycle Batteries?
It’s a good idea to check your solar backup power system’s battery at least once a month and add distilled water if necessary. (Never add tap water, since the chlorine and minerals it contains will damage your deep cycle battery.) Always wear eye protection and gloves when adding water to a wet-cell battery. If you can afford them, fully sealed AGM batteries are a better way to go. These typically cost up to three times more than regular lead-acid deep cycle models.
Disclaimer: The information in this post is correct to the best of our knowledge. Always consult with a licensed electrician first before attempting to permanently install any new electrical system in your home.
This post may include affiliate links to products we recommend.
Resources: Solar and 12 Volt Power for Beginners, by George Ecccleston. The 12 Volt Bible For Boats – Miner K. Brotherton
