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Solar batteries come in different voltages, the most common being 12V and 24V. The question many new users ask is, is there a significant difference between the two? Take a 12V 200ah and 24V 200ah battery. They have the same amp hours, but what difference do the voltages make? And which should you use?
The difference between a 12V 200ah and 24V 200ah battery are the voltage and the amount of energy stored in watt hours. A 12V 200ah battery holds 2400 watts while a 24V 200ah battery has 4800 watts. The amps drawn in a 24V battery is also half that of a 12V system.
Which is Better 12V or 24V?
No type is better than the other. Some devices and appliances are designed for 24V batteries like the 24V Ampere Time which can run a variety of off grid applications. Others are for 12V like the Renogy Hybrid Gel and others work for both. To better understand the difference between the two, we have to take a look at their different properties.
Volts, Amps and Watts Comparison
Using our examples of two 200ah batteries, there are three things you need to be aware of, the amp hours, watts and volts.
- The amp hours is the capacity of the battery
- The watt hours is used to determine the power usage of an appliance or device.
- Voltage can be 12, 24, 36 or 48. In this case we are comparing 12 and 24V.
Both batteries have the same amp hours (ah), 200 in this case. To find its watt equivalent, multiply the amp hours by the voltage. With a 12V battery it looks like this:
12V x 200ah = 2400 watts
With a 24V battery the watts are doubled:
24V x 200ah = 4800 watts
If you connect a load to both batteries , the 24V has greater capacity. You can run more appliances on it compared to the 12V. Whether your battery will be fully discharged or at 50% only, the watt hour load capacity is double on the 24V.
Another way to think of this in the amps drawn. The higher the voltage, the lower the amps required. For instance, an Engel 40l can be powered on a 12V and 24V battery. If you connect it to a 12V system it will draw 3 amps. But on a 24V battery the draw drops to 1.5 amps.
The lower the amps drawn, the longer the battery will last. If your load pulls 100 amps an hour a 12V 200ah battery will last just under two hours. But if you opt for a 24V, the draw drops to 50 amps and the battery can last for 3 and half to 4 hours.
Which Battery Should I Use with My Solar Panels?
It depends on what type of solar system you have and what appliances you will run. The solar panel voltage must be equal or higher than that of the battery at all times.
If you have a 24V battery, your solar panels have to be at least 24 volts. With a 12V battery you should use a 12V solar panel too. You can use a 24V solar panel with a 12V battery, but you have to use an MPPT charge controller, otherwise the extra power from the solar panels will be wasted.
If you have two or more 12V batteries, you can connect them in a series to increase the voltage to 24V, matching them with your 200ah battery. Connect the positive and negative terminals of the solar panels and it is good to go.
A series connection only increases the voltage, not the amps. If you have 24V panels and want to boost the amps, connect them in parallel instead. Just connect the positive terminal of the panel to the positive terminal of another panel. Repeat with the negatives and you have a parallel connection.
How Batteries, Charge Controllers and Solar Panels Work Together
Solar panels convert the energy of the sun into direct current (DC). if your device runs on DC, you can connect it directly to the solar panel . The device or appliance will run as long as there is power in the panels.
The purpose of a battery is to store the power the panels produce. As the sun sets and solar production stops, there is solar energy stored in the battery you can use to run appliances. With an inverter the DC power is converted into AC so it is compatible with appliances.
A charge controller regulates the charging of the battery to prevent overload. If the battery and solar panel voltage are a match, for example both 12V or 24V, you can use a PWM charge controller. It is the most basic controller and works fine for small panels and batteries
If you have a 24V 200ah battery and a 48V solar array, an MPPT controller is recommended. With a PWM the solar panel voltage is reduced so it matches the battery, wasting the power. With an MPPT system, the solar panel can produce at its maximum voltage.
If you have a large solar array and several 24V 200ah batteries, use an MPPT controller. The higher the voltage, the more power will be wasted if you use a PWM controller. Your solar panel kit will have information that tells you what battery voltage works best with it.
24V vs. 12V Battery – Which Lasts Longer?
A 24V battery has a greater capacity than a 12V, so it will last longer. In this example we are using 200ah, but the following are applicable to any battery of any capacity, whether it is lithium, gel, AGM or gel.
Suppose you have a 200ah 12V lithium battery. It has a 100% depth discharge so you can use the full capacity. You want to run a laptop, a fan, a mini fridge and some lights. Solar appliances consume different amounts of power, but let us assume the following.
- Laptop 200 watts
- Fan 60 watts
- Mini fridge 100 watts
- Lights 100 watts
The total power consumption is 460 watts. If you run these appliances off a 12V 200ah battery they will draw 38 amps an hour. The battery can run for about 5 hours before it is drained. If you have an AGM or FLA battery the runtime will be 2.5 hours due to the lower discharge rate.
If you use these same appliances on a 24V battery the runtime will be 10 hours. Power consumption will still be 460 watts / 38 amps an hour. But the higher voltage capacity allows the battery to handle more energy / watts.
The biggest benefit of a 24V battery is that it reduces the amps pulled per hour. Deep cycle batteries lose power the more amps are drawn, so it really helps if you have a 24V system.
The math is not as simple as 200ah is good for 1 hour, 100ah for 30 minutes and so on. The higher the amps pulled, the faster the battery drains. With a higher voltage system this is exactly what happens. A 12V and 24V battery can have the same load, but the 24V will last longer.
When to Use 12V or 24V Batteries
So should you always use a 24V battery? The one disadvantage of a 24V battery is the cost. They are more expensive. Also some appliances and electronics only run on a 12V battery. If that is the case you should stick with a 12V.
If you have a 12V solar panel and want to use a 24V or higher battery, you have to either switch to a 24V panel or connect two or more 12V panels in a series to increase it to 24 volts. You also have to make sure your inverter and charge controller is compatible with the higher voltage.
In the end it comes down to what devices and appliances you will be using. if they can run on a 24V battery and you are willing to pay the extra cost, then go for it. If the appliances are only for 12V or you are happy with 12V systems in general, stick with it.
As should be clear by now, a 24V battery is not necessarily better than a 12V. There are some cases where a 24V is more suited but in other times you should get a 12V. By assessing your power requirements you will know which is more appropriate.