For an off-grid PV system, a battery bank is necessary for providing power at night and on cloudy days. With a grid-tied solar array, batteries aren’t necessary. However, a growing number of homeowners are choosing to invest in storage banks so they can have electricity during utility grid outages.
A solar battery bank can help put you on the path toward energy independence, and having all the facts will allow you to make the best choice.
Choose from Two Types of Solar Battery Technology
A PV system requires deep-cycle batteries — these are more tolerant of constant charging and discharging. But you have to choose between flooded lead acid (FLA) and valve-regulated lead acid (VRLA).
FLA battery storage is the more common choice for residential solar. These batteries work well when partially or fully charged, and they are built to have a long life span. However, FLA batteries require regular attention. The liquid they contain evaporates over time, so you have to monitor and maintain the water level for each one.
VRLA battery banks don’t require routine maintenance, because they internally convert hydrogen and oxygen into water to maintain liquid levels. These batteries also maintain higher voltage levels and dispense charges faster than FLAs.
Two Factors Affect Solar Battery Storage Costs
Although VRLA batteries don’t require regular maintenance, their initial cost is higher than that of their FLA counterparts. That said, two other factors play a role in determining the actual lifetime cost of a solar battery bank.
The first consideration is the cycle life of the batteries. The more charges and discharges they provide before the storage capacity drops below 80 percent, the lower their lifetime costs.
The second factor affecting lifetime battery cost is the depth of discharge (DoD), which refers to the percentage of the storage capacity used. For example, if a 10kWh capacity battery has 5kWh of stored energy, the current DoD is 50 percent.
Solar batteries are rated for a maximum depth of discharge for their cycle life. Generally speaking, as the DoD increases, battery cycle life decreases. Draining more energy results in higher overall storage bank costs and more frequent battery replacements.
Size Matters in Solar Battery Cost
The most important consideration in selecting a solar battery storage system is size, because your batteries must be sized to meet your energy needs.
An off-grid solar energy system requires sufficient battery storage capacity to hold two to three days’ worth of power. Grid-tied solar arrays can often get away with smaller banks, as stored electricity isn’t needed on a daily basis.
Ultimately, the type of battery storage system you choose for your system will depend on your energy needs, your budget, your preferences for maintenance and whether your system is tied to (or independent of) the utility grid.
The professional team at Intermountain Wind & Solar can help you maximize the return on your photovoltaic investment. Serving commercial and residential solar customers throughout Utah, Wyoming, Nevada, Colorado and Idaho, we can help you determine which type of solar battery bank is best for you. Contact us today to learn more or to schedule a personal consultation.