How to Find the Right Solar Battery Bank for You

How to Find the Right Solar Battery Bank for You?

It can be challenging to decide which features and technical requirements are most important when comparing quotes for various solar battery systems, and for good reason: the home energy storage market is so new that you probably don't know anyone who has a battery whom you can ask about their experience. While all batteries must abide according to certain reliability and safety regulations in order to be marketed and installed in the US, there is very little standardization of specifications and features among the batteries that are currently on the market. In order to help you compare various battery quotes, we've provided some recommendations on what to look for.

What exactly is a Solar Battery and How Do They Work?

A solar battery is a device that stores electricity for later use, allowing you to use more of the solar energy you generate at home, keep appliances running during a power outage, and in certain situations, even save money on electricity. Due to their greater capacity to charge and discharge power than something like a vehicle battery, they are sometimes referred to as "deep cycle batteries."

Should I get battery storage?

From financial savings to emergency backup power, energy storage devices provide a variety of advantages. But they also bring a new set of unfamiliar terminology and technological intricacy. What should you concentrate on and search for in a deep-cycle solar battery?

Power rating

The number of kW that a battery can deliver all at once is referred to as the battery's power rating. In other words, a battery's power rating informs you of both the number and kind of appliances it can power simultaneously.

Different appliances require different amounts of electricity, which is measured in kilowatts (thousands of Watts) or amps. For instance, while a 3-ton AC unit will consume 20 Amps, or 4.8 kW, a typical compact fluorescent lamp will only need 12 Watts (or 0.012 kW). The majority of batteries on the market today provide electricity continuously at a rate of about 5 kW.

The fact that solar batteries sometimes have two separate power ratings—a continuous power rating and a 5-minute or instantaneous power rating—means they can deliver more power in brief bursts, which is noteworthy. This is crucial if you have a device, like a sump pump, that uses a lot of electricity to start up but uses less power once it is running.

Battery size

The amount of power that a battery can store and provide to your house is referred to as the battery's capacity (or size). Power is measured in kW, but battery size is measured in kWh, or power multiplied by time. The length of time a battery can power different components of your house is therefore determined by its storage capacity. Always check for a battery's usable capacity, which indicates how much of the battery's stored energy you can really access.

The more power you use, the faster your stored electricity will run out since electricity use is just power multiplied by time. On the other hand, you may leave them running for a longer period of time if your battery is just being used to back up a few appliances that use a little amount of power. Given that the amount of power a battery is producing directly affects how long it will keep a charge, the size of a battery can be slightly deceiving.

Consider the differences between a light bulb and an AC unit in the previous example. You can only operate your AC unit for two hours if you have a 5 kW, 10 kWh battery (4.8 kW * 2 hours = 9.6 kWh). On the other hand, the same battery could power 20 lights for two full days (0.012 kW x 20 lights x 42 hours = 10 kWh).

Roundtrip efficiency

The ability of your energy storage system (battery + inverter) to convert and store power is measured at the system level by a parameter called roundtrip efficiency. Any electrical operation involves losses, thus when you go from direct current (DC) power to alternating current (AC) electricity or recharge a battery, you lose a certain amount of kWh of energy. The roundtrip efficiency of a solar battery indicates how many units of power you will receive out of the battery for each unit you put into it.


Every solar battery that you get a price from Forme Solar is secure and complies with the safety regulations that must be met in order for it to be approved for installation in homes and businesses. However, certain battery chemistries have undergone safety testing that goes above and above the standards set by the government, indicating that some are somewhat safer than others. The fact that all batteries installed in the US are quite safe is what you need to keep in mind most.


The main substance utilized to store energy inside a battery is referred to as the chemistry of the battery. Since chemistry eventually impacts many of the features of batteries described above, it may be the most crucial factor to compare.

For instance, some lithium-ion chemistries may be more power dense, which means they store more electricity in less amount of space, or may do a better job of cycling, which means they are capable of performing at a higher level for longer periods of time. 

And that's just among lithium-ion chemistries, let alone between lithium-ion batteries and lead acid batteries, vanadium flow batteries, or other experimental battery chemistries. Various solar battery chemistries have (often dramatically) different pricing points, as with most things.

How long do Solar Batteries Last?

Three metrics are used to calculate battery lifetimes: estimated years of operation, expected throughput, and expected cycles. The estimated throughput and cycles of a battery are similar to the mileage warranty on a car. Throughput compares how much power can be moved through your battery during its lifespan. Cycles are the number of times a battery may be charged and discharged.

Divide the throughput (expressed in kWh) by the battery's usable capacity to estimate how many full cycles you'll get from the battery, and then multiply that number of full cycles by the number of days in the year. For example, a battery with a 20,000 kWh throughput warranty would have 2,000 expected cycles, or one cycle per day for 5.5 years.

Divide the number of cycles by the number of days in the year to get the projected lifespan of a battery. For example, a 4,000-cycle guarantee is equivalent to one cycle every day for 11 years.

Choosing the Right Battery Specifications for Your Needs

When assessing your energy storage options, there are several possible decision criteria and comparative points to consider. Here are some of the most typical selection criteria and which battery specifications are most crucial if they apply to your circumstances:

  • You should seek a solar battery with a high power rating if you want to power more of your house at once.
  • Look for a battery with a high instantaneous power rating if you wish to be able to power a more power-hungry item (such as a sump pump).
  • Look for a battery with a larger usable capacity if you want to use your solar battery to power your house for longer.
  • Look for batteries with a greater roundtrip efficiency if you want to get the most out of every kilowatt-hour of power you put into your battery.
  • Look for lithium-ion nickel manganese cobalt (NMC) solar batteries if you have a limited amount of space and want to maximize storage while using the least amount of space possible.
  • Lithium iron phosphate (LFP) batteries are the best choice if you want a battery with the longest life and the ability to be cycled the most.
  • Look at LFP solar batteries if you want a battery with the exact best safety rating available (don't worry, they're all safe!).

What is Battery Bank Sizing?

Solar battery sizing, also known as battery bank sizing, is one of the most vital to take into account when designing your solar power system.

The main goal when sizing a battery bank is to acquire one that can take the load from your PV panel array and supply enough stored power for your needs without having to drain to an unhealthy level on a frequent basis. By connecting many batteries in various wire configurations, you may create a battery bank that is appropriate for your solar power system and so accurately executes solar battery sizing.

Factors Affecting Battery Bank Sizing

The amount of batteries in your solar system is determined by numerous factors.

The amount of money that you should invest in this solar project. Part of solar battery size is ensuring that you can purchase enough solar batteries to meet your power storage requirements.

You must also consider how many days you want to be able to travel before needing to recharge your batteries. If you need to run particular appliances for a set number of days without interruption, you'll need extra batteries to carry a heavier load. This is influenced by the number of batteries you use and how you wire them to affect the overall amp hours of your battery bank (storage capacity).

Another aspect influencing solar battery sizing is the quantity of electricity used by all of your gadgets. If your appliances demand a lot of watts (electricity), you'll need a lot of batteries to store the power so you can use them.

The voltage produced by your solar system is another aspect that influences the size of your battery bank. If your system generates 48 volts, you'll need enough batteries in your battery bank to hold 48 volts. Actually, a little less is ideal, such as a 36-volt system with a 24-volt battery bank, to ensure that your system can charge the battery bank even if the power drops suddenly.

Always size your solar panels larger than your battery bank when sizing a battery bank to be able to account for problems like voltage drop, power fluctuations, and energy loss due to typical system wear.

A generating device must supply a higher voltage to a battery than what is currently present in it in order to charge it. Because of this, the majority of PV modules are designed at 16–18V peak power points. This essential voltage differential will be reduced by a voltage drop of more than 5%, and it may also result in a significantly bigger reduction in the charge current to the battery. Our typical advice is to size for a voltage drop of between two and three percent. In order to account for an unexpected power decrease, a 16–18V solar panel should be utilized with a 12-volt battery bank.

The amount of storage space your battery bank will need is another crucial factor to take into account when sizing one. You'll need additional batteries if your region has shorter daytime daylight hours so that you can store more "amp hours" of power in your reservoir and survive the lengthy night's stretch. The more amp hours you have when sizing a battery bank, the longer it will take for your entire power reserve to run out.

The desired rate of discharge must be taken into consideration while sizing solar batteries. Remember that you'll get more use out of your batteries if they can drain more slowly. A battery's rate of discharge may be determined by glancing at it and locating the value designated as (C-?). If you see (C-10) it implies the battery needs 10 hours to fully drain; if you see (C-5) it means the battery needs 5 hours to fully discharge.Finally, you must take into account the depth of drain you intend to reach before recharging when sizing a battery bank. Your individual power requirements and capacity, which have an impact on battery life, determine this.