Everything You Need to Know About Solar Storage Batteries

What is a solar storage battery?

Solar storage batteries are pretty much exactly what they sound like: rechargeable, deep-cycle batteries that collect excess energy from a solar panel system for future use. Many solar  systems generate more energy than a home can consume. If the local utility company does not have a net metering policy, or if the homeowner prefers to store their own excess energy, solar  storage batteries provide an easy solution. 

We mention “deep-cycle,” but what does that mean? A deep-cycle battery has the ability to be charged and discharged to 50% or more and then recharged to a full 100% charge. Think about  your phone battery as being a deep-cycle battery: you can use and run it down over time before it dies. Your car battery is not a deep-cycle battery: you can only use it when it is powered. Keep  in mind that although deep-cycle batteries are made to lose 50% or more of their retained energy, they must retain some amount of charge at all times. Deep-cycle batteries have what’s  called Depth-of-discharge, or DoD, telling you how low you can run it down safely. Most battery manufacturers will specify a maximum DoD for best performance. As an example, a 10 kWh  battery that has a DoD of 90% means that you should not use more than 9 kWh of energy before recharging.


What is solar battery backup and how does it work?

Solar battery backup is a system and method of storing excess energy created for future use. Solar panels are able to generate energy during the day but at night they cannot produce any  energy. The problem is that, in many homes, there is a great deal of energy needed since that is when most people are home and using things like hot water heaters, TVs, ovens and clothes  dryers.

With a solar battery backup system, a home could be considered truly off the grid since it wouldn’t necessarily need reliance on the utility for its off-peak energy-producing time of the day.  In an off-grid system, there are some special components required in addition to a conventional solar panel system installation. In order to keep the battery from back-feeding power to the  panels which could damage or destroy them, a Schottky Diode is installed between the panels and the battery. There is also a Charge Controller put in place to regulate the charging of the  battery. This helps the even charging of the battery to avoid ruining the battery and causing permanent damage.


Capacity and Power

Most home solar storage batteries are designed and manufactured to be stackable: You can increase the energy capacity by adding more batteries. Batteries can be installed “in-series” to  increase both capacity and performance. Battery storage capacity is measured in kilowatt-hours (kWh). The batteries are then rated in “power ratings” that show the amount they can deliver at  one time. 


What is round-trip efficiency?

To define round-trip efficiency, we need to look at the amount of energy a user can get from a battery with relationship to the amount that was stored. Since it takes energy to store energy,  some amount of power will be lost since a battery cannot deliver 100% of the amount of energy stored. As an example, if a user had stored 5 kWh of energy but was only able to  retrieve 4 kWh of energy from the battery, the round-trip efficiency of the battery is 80%. It goes without saying that the higher the round-trip efficiency, the higher the economic value of the battery.


How long will my battery last?

A solar battery cycle is one day: the time it takes for it to charge and re-drain. Your battery’s ability to continue to hold a charge will decrease over time just like your cell phone battery.  Battery warranties guarantee a certain number of cycles and/or years, and most manufacturers guarantee the amount of capacity during the warranty period. Here’s an example: a battery  covers 5,000 cycles, 10 years at 70% capacity.

So, what’s the bottom line? Do your homework and work with your solar energy team to get the right battery for your system and expected usage. At SAVKAT Solar, we are prepared to match your  system with the right storage battery based on your configuration and expected usage.


Are you ready? To find out how you can go solar and become less energy dependent, request a free quote from us at SAVKAT Solar. Still have more questions? Check out our Solar 101 page or our FAQ page. If that still leaves you unsure, we are happy to answer any other questions by giving us a call at 800-860-6932.


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