If you’re a prepper, you’ve probably seen all sorts of products that claim to be “solar powered generators”. There are tons of YouTube videos about how to make your own and there are plenty of companies that will gladly sell you one.
Heck, you may even have one that you put together yourself. In this article, I’ll be explaining 5 reasons that these products may not live up to your expectations when it comes to providing you with the amount of electricity that you might be expecting to have in a survival situation.
The main problem is that people have unrealistic expectations of how the solar powered generators will actually perform in a GDE (grid down event).
A well designed solar powered generator will consist of several basic components. I’ve listed them below for your convenience.
- Solar Panel(s)
- Charge Controller
- Battery or Battery Bank
- Voltage Meter
- Power Inverter
- 12 Volt Power Outlets
- Heavy Gauge Wire
One might think that making homemade solar generators would be as simple as ordering up the parts and slapping them together but the key to a system like this working efficiently is in the proper selection of each component so that they will all work in harmony. If they aren’t sized properly, the components themselves could be very high quality but the sum of the components, being the “end product” won’t perform as you would have expected it to.
Without further ado, let’s get started and I’ll explain why all you preppers who have solar panels stashed away in your basements may find that they won’t be as useful as you had hoped they would be.
Why a Solar Generator Might Not Meet Your Expectations
- Many people don’t realize that not all solar panels are created equally. If you’ve never lived off the grid or you’ve never had to rely on solar panels, you might think that any old solar panel that you pick up from your local discount catalog will be sufficient, but that’s just not the case.
Solar panels are rated by the amount of “watts” that they put out under ideal conditions. Many of the solar panels that I’ve seen on DIY solar powered generators are inexpensive 15 watt panels. The problem with these panels is that they won’t produce enough electricity to recharge the batteries that people plan on using. If you plan on connecting your homemade solar power charger to a 100 amp hour 12 volt deep cycle battery, you’re going to be quite surprised when you learn exactly how long it will take to charge it up.
Let’s take a minute and do the math using the formula that is used to figure out how many amps a 15 watt solar panel should “theoretically” be able to produce. The formula that we’ll use is Amps = Watts/Volts. So, in this case 15 watts / 12 volts = 1.25 amps. If the 15 watt solar panel actually produced 1.25 amps, it would take Approximately 72 hours of direct sunlight to recharge your battery if it had been depleted down to 10% of its capacity (90 amp hours / 1.25 = 72 hours).
Now, for the sake of keeping things simple, let’s assume that you have 10 hours of good sunlight per day. This would mean that it would take just over seven days to recharge your battery! Now let’s throw some real world variables into the mix. I just did a quick Internet search for 15 watt solar panels and in less than five minutes I looked at three different models that were being sold online. They all claimed to be “15 watt” panels but one claimed that it would output 1 amp, another claimed that it would output .85 amps, and the third claimed .83 amps.
Keep in mind that these ratings are under ideal conditions when the solar panel is perfectly aligned with the sun and there are no clouds in the sky. If you don’t take the time to turn the panel throughout the day so that it continually gets direct exposure to the sun, the output will be lower and if clouds pass by, the output will also be lower.
So, based on the three examples that I found in less than five minutes on the Internet, let’s do the math again using the one with the highest rating. Just like before, we’ll assume that the battery has been depleted to 10% of its capacity meaning that we will need to put 90 amp hours back into it for it to be fully recharged.
In this case, 90 amp hours / 1 amp per hour = 90 hours to fully recharge the battery. If we again assume that we will have 10 hours of good sunlight per day and that we’ll be diligent enough to turn the solar panel so that it is always facing the sun as it moves across the sky, it will theoretically take 9 days to charge the battery! You read that right, NINE DAYS!
- The second reason that a solar powered charger might not meet your expectations is because of the way 12 volt deep cycle batteries actually take a charge. It’s not like filling up a bucket with water. If you have a 5 gallon bucket and you add 1 gallon of water per minute, it would take you 5 minutes to fill the bucket.
That’s pretty simple math but unfortunately that’s just not the way batteries work when they are recharged. Think of charging a deep cycle battery like water going through a pipe that is slowly getting narrower in diameter. When a battery is deeply discharged, the diameter of the pipe will be very large and it will allow a lot of current to flow into it.
As mentioned above, a charge controller is an essential component to this type of a system. This device regulates the amount of current that is delivered to the battery to prevent it from becoming overcharged and permanently damaged. Charge controllers often have three stages which are “bulk”, “absorption”, and “float”.
During the bulk charging phase, the charge controller allows the maximum amount of current that your solar panel is capable of producing to flow into the battery. This phase lasts for about 80% of the charging cycle.
During the absorption phase, the controller will decrease the amount of current that the solar panel will be able to put into the battery which will prolong the theoretical amount of time that it will take to fully recharge the battery. This is because less current will be flowing into it as it nears the point of being fully charged. This phase of the charging cycle lasts for the remaining 20% of the time.
The third state is called the float stage and during this part of the charging cycle the voltage is reduced or completely cut off to the battery. The purpose of this stage of the cycle is to simply keep the battery fully charged once it has reached its full capacity.
- Now let’s throw another wrench into the mix. If you have a 100 amp hour battery when it’s fully charged, if you connect it to a load that draws 1 amp of electricity per hour, you should be able to use that device for 100 hours, right?
Well, unfortunately that’s not the way it really works. The first reason is that even though you may be using a deep cycle battery, you should never completely deplete the battery before recharging it. Doing this will cause permanent damage. So, your 100 amp hour battery won’t really be capable of providing the full 100 amp hours that it’s rated at.
- The other little hiccup that you may have not thought about is that the temperature of the battery has a direct relationship to its charging rate, as well as to its storage capacity. I don’t want to make this article too complicated so for the sake of simplifying things, I’ll just put it this way.
A cold battery is incapable of holding as many amp hours as a battery that is at its ideal storage temperature. This means that during the colder times of the year, you may think that your battery has the capacity of storing 100 amp hours but that’s just not the case. Just remember that the colder it gets, the less capacity your battery will actually have.
- If I haven’t already complicated things enough for you, there’s more to consider. Deep cycle batteries like to be fully recharged after each discharge cycle. This is where the matter of “balancing the components of the system” comes into play.
If your solar panel isn’t large enough to produce enough current to completely charge your batteries after you use them, they will almost always be only partially charged. Essentially, this means that they will never fully be recharged because before they have a chance to become fully charged you’ll most likely put a load on them and use some of the electricity that they have stored.
Why is this important, you might ask? If your charging system isn’t adequately sized to fully recharge the battery between each use, your 100 amp hour deep cycle battery will lose its ability to be charged to its advertised capacity. Over time, this will result in your 100 amp hour battery being reduced to 90 amp hour capacity, then to 80 amp hour capacity, then to 70 amp hour capacity, and so on.
Is There Really a Place for Solar Power in a Doomsday Scenario?
Solar power is a very complicated matter. The companies that specialize in installing alternative energy systems in people’s homes are very skilled at putting together a well balanced system. They look at the home’s average daily electricity consumption and then they use that information to determine how large the battery bank needs to be as well as how many solar panels will be needed in order to fully recharge the bank on a daily basis.
I’m not saying that solar power doesn’t have a place in prepping. What I’m trying to get across is that it’s much more complicated than simply buying a few solar panels that you have stashed away in the corner of your garage or basement with the plans of hooking them up to a battery when doomsday arrives.
If you plan on using a so called “solar power generator”, look very closely at its specifications to see if the solar panel that it is equipped with will have the capability of charging its battery pack in a reasonable amount of time.
Now, taking into account all that I’ve written in this article, you CAN buy a small scale portable solar powered charging station that may not be as susceptible to these limitations. For example, if the battery pack in your solar power generator is lithium-ion based, my understanding is that these batteries do not develop a memory if they are not fully recharged after each use. If the battery pack is made up of NiCad batteries, it will be susceptible to the same problems that deep cycle flooded lead acid batteries are susceptible to.