High Voltage or Low Voltage what is right for Home Energy Storage?

High voltage and low voltage lithium battery systems are both popular choices for Solar PV systems. But which one is the best choice for your needs? In this article, we will compare and contrast High Voltage (HV) and Low Voltage (LV) lithium battery systems, so you can decide which one is right for you.

Battery systems are a great addition to any Solar PV or Renewable energy system. Not only do they allow you to store your energy to use when the sun isn’t shining, but they also allow you to buy energy from the grid to store when the cost per kWh is at it’s lowest. But a common question we get asked is which type of battery is the best.

Many of our Solar PV systems come with either high voltage or low voltage batteries, however what does that mean exactly? Today we will look at the difference between HV and LV batteries and which option is right for you.

WHAT IS LOW VOLTAGE BATTERY SYSTEM?

The voltage of low-voltage home battery backup is typically less than 100V. As these types have less voltage, they also provide less power than high voltage battery system would do.

Low-voltage home battery backup offer a number of advantages. For starters, they are easier to install and upgrade. For example, connect multiple batteries together in parallel or series. Additionally, low-voltage Home Solar Battery Backup have a smaller physical footprint. This makes them ideal for applications where space is limited. Furthermore, low-voltage batteries are cheaper to manufacture than high-voltage batteries. Finally, low-voltage batteries are in some ways safer. But low voltage home energy storage systems have trouble with start-up loads, this can be resolved by hooking up your system temporarily using grid or solar energy – but this takes time!

Low-voltage solar batteries for home are often used in off-grid systems where customer demand for medium to low energy is high. But inverters play a crucial role in choosing what’s kinds of batteries. Each inverter has a battery voltage range [V], which indicates whether the inverter can manage a high or low voltage battery. Typical battery inverters are rated at 48V or above and can handle both high and low voltage batteries. When choosing an inverter for a low-voltage home energy storage systems, it is important to select an inverter with a voltage range that includes the nominal voltage of the battery.

WHAT IS HIGH VOLTAGE BATTERY SYSTEM?

The high voltage battery systems are usually rated at more than 100V. These powerful batteries can charge and discharge faster than low-voltage ones, making them ideal for covering those quick demand surges from starting equipment that might not be able to stay running without power immediately. The increased volts also mean smaller conductors.

High-voltage battery systems are a more recent development in the world of home solar battery backup. These higher voltage models can provide increased energy output to support heavier loads, making them perfect for homes with electricity consumption rates that exceed what is typically seen at lower voltages

Commissioning a home battery backup with an high-voltage battery not only increases efficiency but also saves energy. The DC bus voltage normally varies between 300 volts and 500 V, so when you choose this option your inverter has less work to do. When you choose a low-voltage home battery backup, the inverter needs to work harder and reduce an input voltage of 300 -500V below 100 V. This results in less energy efficiency for your home or business’s power requirements.

High voltage battery systems are perfect for properties with commercial energy storage demands and home battery backup use. They offer a number of advantages over other types of batteries, including longer life and higher discharge rate. In addition, high voltage battery systems are less likely to overheat, making them safer to use. With their many benefits, it’s no wonder that high voltage home battery backup are becoming increasingly popular.

HIGH VOLTAGE HOME BATTERY BACKUP ARE MORE EXPENSIVE TO INSTALL?

Generally speaking, the price of high-voltage batteries in the market is higher than that of low-voltage batteries. The main reason for this is the high manufacturing cost of high-voltage batteries and the brand premium. However, there are a number of factors that can affect the price of lithium batteries, including the type of battery, the size of the battery, and the quality of the battery. In addition, lithium battery prices can also vary depending on the supplier. As a result, it is important for buyers to compare prices from different suppliers before making a purchase.

FIND THE BEST HOME SOLAR BATTERY BACKUP FOR YOUR NEEDS

So, what is the takeaway from all of this? First and foremost, it’s important to understand that there is a big difference between high voltage and low voltage battery systems. Secondly, inverter brands are starting to provide more high voltage battery system options for their customers; however, both types of batteries still have a place in the market. If you’re looking for the best price on a home solar battery backup battery, contact COREMAX Battery today.

If you are worried about the high price of high-voltage home solar battery backups. COREMAX Battery is here to help. We offer home battery backups at an affordable price, and we even have a factory direct program that can save you even more money.

With our high quality products and low prices, you can’t go wrong with COREMAX Battery. Plus, our batteries are backed by a 5-years warranty so you can be sure you’re getting the best possible product.

But what about the costs of the batteries?

There are many ways to do storage and the answers are rarely ‘black and white’, SMA argues. Image: SMA.
Battery

Let’s start with the appropriate battery capacity which would perfectly fit the residential system needs. There are several factors to be considered, such as depth of discharge (DOD), energy consumption, PV profile, backup functionality etc. However, let’s assume that the typical usable battery capacity will range between 2kWh and 8kWh. If you want to realise a 2kWh with 48V, the battery cell size will be approximately around 42Ah. If one wants to have it on the 400V-level, the cell has to shrink to 4Ah. Doing the same calculation for the 8kWh, the cell size would be approximately 170Ah for lower and 20Ah for higher voltage.

Now it is time to have a look on the cell availability and the system costs. Generally, the cells with the lower size are the xx650-round type cells, highly commercialized, typically offering lowest costs/kWh. The cells in a range of 40-60Ah are well known and used in the automotive world, so yes, these are also highly commercialised and competitive cells in terms of costs. Now, if the cell costs are not the issue, what else could it be? Most reasonably, it will be the question of the definition of the smallest battery unit, the question of flexibility – fixed pack size or modularity, the retroactive extension of the battery, battery technology and synergies with other markets.

48V-Modules are available and accepted as standard for the telecommunication market – the modules can be found from different manufacturers in different sizes, ranging from somewhere around 5kWh to 10kWh – if Li-Ion Batteries are used. And the 48V are certainly more adequate if you want to use different battery technologies. With a parallelization either on cell or module level, basically all required storage sizes can be covered (but this might be accompanied by higher costs). On the other hand, other technologies can cover a very broad range of storage sizes without any additional system costs. The flexibility of the high voltage system is more limited – the coverage for the smaller storage sizes will result in a very specific design and the voltage level will probably not be at 400V, but lower. High voltage in residential systems somehow seems to be a lithium ion-specific topic, and most other technologies will have difficulties in following that trend.

System technology – power electronics

To connect a DC battery to an AC distribution grid, power electronics is needed, regardless of the question of AC- and DC-coupling. Turning a blind eye to the battery technology, and anticipating a standard PV inverter with MPP-Trackers (maximum power point), a DC link and a semiconductor bridge on the grid side, the lowest system costs for battery integration will be achieved with the least sophisticated topology engineers can imagine.

Asking experienced power electronics engineers, the results will most likely be that coupling a battery to the DC link of a standard PV inverter with a state-of-the-art buck-boost-converter looked most promising. With a minimum effort on windings and switches (only two are needed), this topology is unbeatable regarding costs.

To allow the utilisation of this technical approach, the voltage-level difference between the DC link and the battery should not exceed a ratio of 4:1 to allow acceptable efficiencies. As a practical example, a battery to be connected to a 400V DC link should not provide a minimum voltage below 100 V. Lower battery voltages would require galvanic separation, and this means a transformer and more switches, and thus higher costs. So in general, high voltage batteries allow for lower system costs – if the system integration is done properly and some mandatory degrees of freedom in the design are available.

Conclusion

It seems that in each blog article we have to emphasise that, even though the marketing campaigns of various providers are claiming that they found the one and only right way to do residential storage, it is not a simple black and white issue that we are talking about.

From an academic level, lower battery voltages offer better battery costs at higher system integration costs, whereas higher voltages turn that comparison the other way round. In the end, only accurate and diligent system integration can cut costs. To close, allow us one final commonplace observation: the more battery prices decrease, the more system costs move into focus and correspondingly, more accuracy has to be invested in the system design.