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Table of Contents: 12 and 24-Volt Solar Systems
12 vs 24-Volt Solar System
If you’re only just beginning to learn about batteries and solar systems, and you only want to know the bare-bone basics of the difference between 12 and 24-volt solar systems, then you’re in the right place!
Let’s look at the pros and cons of choosing a 24-volt solar system and when it’s appropriate to use a higher voltage battery bank in this easy-to-read post!
Please Note: If you don’t know the basics of a solar system yet (as in you don’t know what a solar charge controller or inverter is), I highly recommend you read my post: Solar Power for Beginners
Then, come back to EASILY understand the bare bone basics of the differences between 12-volt 24-volt solar systems.
Cost of Copper Wires & Lugs
One of the main pros to having a higher voltage solar system is that 24-volt systems are always cheaper.
The cost of the wire in your solar system can be pricey, especially if you’re building a large system. And if you have a 12-volt system the number of amps going through that wire is going to be double compared to a 24-volt system.
So that means that the wire needs to be twice as thick to carry that load. Copper wire is not cheap at all, and copper lugs (especially big ones) are really expensive as well.
What Are Copper Lugs?
In a solar system, copper lugs (Amazon) give you the best performing electrical connection between your copper wires and battery/inverter/charge controller (etc.) and are made of pure copper.
Cost of Solar Charge Controller
Solar charge controllers are rated in amps and a lot of solar charge controllers are rated for 12 and 24-volt systems.
If you have a 24-volt system, you can get away with half the size of a solar charge controller as you would a 12-volt system.
For example, if you have a 20 amp charge controller and you’re using it on a 12-volt system, you can only hook up around 260 watts of solar panels to it. But, if you have that same 20 amp charge controller on a 24-volt system, you can hook up around 520 watts of solar panels to it.
Without going into too much math, just know that having a 24-volt battery doubles the wattage of solar panels that you can use on your system. And this is a good thing because solar panels are actually one of the cheapest parts of a solar system.
But the recommended MPPT solar charge controllers (Amazon) are not cheap, and you’ll be spending double the money on a 12-volt system compared to a 24-volt system.
Cost of Inverter
On the other hand, whether you buy a 12-volt or 24-volt inverter, they’re gonna typically going to be around the same price.
The only advantage of having a 12-volt system is that 12-volt inverters are readily accessible in local stores. Actually, it’s much easier to find all parts for a 12-volt system in a local store than it is for a 24-volt system.
However, this isn’t such an issue because many people are now comfortable with shopping online for 24-volt inverters (Amazon).
Parallel vs Series
Please Note: If you don’t know what connecting batteries in parallel or in series, I recommend you quickly check out my post: Wiring in Parallel vs Series (Easy, Simple Definition)
If you’re using batteries connected in series to create a 24-volt battery bank (for example, you’re using four 6-volt batteries or two 12-volt batteries), this is considered to be a better setup than having your batteries connected in parallel.
When your batteries are connected in parallel and you have more than 3 batteries, one battery can start feeding on another battery. This can cause one of the batteries to die sooner than the others and you’ll have to remove it.
Basically, batteries don’t like to be connected in parallel, especially if there are more than 3 batteries connected together. It’s just better to have them connected in series or to have bigger batteries.
Another advantage of the 24-volt system is that all of the solar system components like to be at a higher voltage.
If you have high volt solar panels and you have a higher voltage battery or battery bank, the solar charge controller will need to do less work and the system will probably be a little more efficient (although this isn’t always the case).
You’ll also have less wire loss. Wires like to heat up when they carry power and if you’re running everything at a higher voltage, there will be some improvement in the efficiency there as well.
Solar Panel Array
One thing you need to keep in mind when designing your off-grid solar system is that your solar panel array needs to produce a voltage that is larger than your battery banks’ voltage.
A solar panel array just means a collection of multiple solar panels.
For example, you cannot use a 12-volt solar panel array with a 24-volt system. However, you can use a 60-volt or a 100-volt solar panel array with a 24-volt system (as long as your solar charge controller can handle it).
In a 24 volt system, the real volts in the battery system can actually be 32 volts (most batteries actually have a voltage that’s slightly higher than what you see on its label). So, that means that your solar panel array should be at least 40 volts or more. But, this is usually not a problem because you can take 12-volt solar panels and connect them in series to increase the voltage.
One big drawback in using a 24-volt system is that you can’t run 12-volt appliances unless you buy a 24V to 12V converter (preferably one with overload, over-current, over-temperature, short-circuit, and over-voltage protection).
Then you put up your own little fusebox and you can still use 12-volt appliances. (A post on how to do this is coming soon and I’ll link it here!)
Even though you might need to buy a 24V to 12V converter for a 24-volt solar system, a 24-volt solar system is still cheaper than a 12-volt system overall.
Charging With Your Vehicle’s Alternator
The next drawback to using a 24-volt system is that you can’t charge it with your car’s alternator.
If you have a big van, RV, or bus, and you want to charge your 24-volt battery with your alternator, you can’t do it easily without some special equipment.
Overview: 12 or 24-Volt Solar System
If you want a small solar system (like if you’re camping), then a 12-volt system will be fine because you don’t really have to worry about wire loss as you won’t have many wires, to begin with, and you’ll probably only have 1 or 2 batteries.
And, really, if you’re just looking for a solar system to go camping, you can really get away with a portable power station (Amazon). They’re super easy to use, portable, and nowadays you can find really great prices for these.
But if you want a medium-sized system (for something like a tiny home, or a large RV), you should think about building a 24-volt system (or buy a portable power station like the EcoFlow Delta Max on Amazon… if it’s not sold out. They sell out fast!)
Building a 24-volt solar system will save you money and it’s still pretty safe for a DIY solar system. For me, 30-volts is considered the threshold for a DIY solar system, especially if you don’t know what you’re doing.
And, if you’re looking to continuously power something big like a house or an off-grid cabin, you should be thinking of running 48-volt batteries. But, please keep in mind that you definitely need to know what you’re doing at 48-volts! It’s best to get a professional to help you out at this point, especially if you’re just learning this stuff.