Battery systems are an excellent addition to any Solar PV or renewable energy setup. They not only allow you to store energy for use when the sun isn’t shining but also enable you to purchase energy from the grid at its lowest cost per kWh and store it for later use. A common question we encounter is: which type of battery is the best?
Our Solar PV systems often come with either high voltage (HV) or low voltage (LV) batteries. But what does that mean exactly? Today, we will explore the differences between HV and LV batteries and help you determine which option is right for you.
What is Voltage?
Voltage, also known as electric potential difference or electric pressure, is the difference in charge between two points in an electric field. The greater the difference in energy between these two points, the higher the voltage. Voltage is measured in volts (V), named after the Italian physicist Alessandro Volta, who is credited with inventing the electric battery.
Higher voltages result in more electricity flow to an electronic device. However, electronic devices are designed to operate at specific voltages. Too much voltage can damage circuits, while too little voltage can hinder performance.
The Voltage Analogy
A common analogy to explain voltage, current, and resistance is a water tank in a loft connected to an outside hose. In this analogy, charge is represented by the amount of water in the tank, voltage by the water pressure at the end of the hose, and current by the water flow.
The more water in the tank, the higher the charge and voltage. If the tank is full, turning on the hose initially results in a burst of water due to the higher pressure. This pressure decreases as the water level in the tank drops. If we think of the tank as a solar battery that stores and releases excess solar energy, draining the tank or using a certain amount of energy reduces the pressure at the end of the hose, which corresponds to a decrease in voltage. This also results in a decrease in charge for your battery. As the water level decreases, so does the pressure and flow of water through the hose, which brings us to current. Make sense yet?
Low Voltage Batteries
Low voltage batteries typically have a voltage below 100V, most commonly at 48v. Due to their lower pressure, they also have less power. As low voltage batteries discharge energy more slowly, these systems often struggle to cover start-up loads, requiring additional assistance from the grid or solar to supply instant power. This is one of the major drawbacks of low voltage systems. However, low voltage systems are much easier to install and upgrade. You will often see multiple batteries linked together in parallel (if the rated voltage is compatible with the inverter) or in series to increase the overall voltage. They tend to have a smaller physical footprint, are cheaper to manufacture, and are in some ways safer. As LV batteries have a higher current, they can continuously run without exceeding temperature limits, resulting in a cooler power supply and optimal charge time.
Although LV batteries need more connections to provide more power, low voltage battery systems are great for off-grid systems and users looking for large capacity potential with medium to low energy demand.
However, choosing between a low voltage and high voltage battery system isn’t just about the battery itself. The inverter also plays a vital role. Each inverter comes with a battery voltage range [V], indicating whether it can manage a high or low voltage battery. Typical battery inverters rated at 48V or above can handle both HV and LV batteries.
LV Batteries are Compact and Scalable.
Examples are
- PowerPlus 48v 3.8kWh
- Pylontech US5000 48v 4.8kWh
High Voltage Batteries
High voltage batteries are a recent phenomenon in the solar industry. Compared to LV batteries, high voltage solar batteries offer a higher discharge rate to support higher load demands. High voltage battery systems are usually rated around 400V. These systems can charge and discharge faster than low voltage batteries and can cover quick demand surges from starting equipment. Returning to the water tank analogy, a high voltage battery is like a high “pressure” battery. This means that as soon as the battery is switched on, there is a burst of initial energy, resulting in a quicker discharge of energy or water from the hose. Because the voltage is so high in an HV battery, they do not require larger conductors.
In a high voltage battery system, the inverters tend to allow for fewer battery connections (around 3 batteries), but the individual batteries themselves have much larger capacities. Additionally, when commissioning a home solar PV system with a high-voltage battery, you can increase the efficiency of the entire system. This is because the DC bus voltage is normally around 300-500V, and the current running to the inverter from the battery is significantly lower. In contrast, when you choose a low-voltage battery, the inverter needs to work harder to reduce the input voltage of 300-500V to below 100V. This results in energy loss and a less efficient system.
High voltage batteries are perfect for households or commercial properties with exceptionally large energy demands. If you are looking for faster charging and discharging, an HV battery is the right choice for you.
Examples of High Voltage Battery Systems
Here are a few examples of the HV battery systems we install at Solar & Batteries Online:
• The 8kWh High Voltage Sigenstor Battery with one of their many inverter options.
• The 2.76kWh BYD HVM battery.
HV Batteries have Higher Charge and Discharge Rates.
More Efficient System.
So, Which Solar Battery is Right for Your Project?
Hopefully, this blog has provided you with a more in-depth understanding of the differences between high voltage and low voltage batteries. In the solar industry, you will see that even though there is a rise in HV batteries, most solar brands offer both options. Ultimately, the best solution depends on your specific needs and circumstances.
I hope this version is more comprehensive and clear! If you have any more questions or need further assistance, feel free to ask.