Batteries for energy storage
The function of a storage battery is to provide electricity, instead of always drawing directly from the grid. Most solar/battery systems are “grid-tied,” meaning that some power still comes from the grid, but the battery helps offset the amount of grid electricity used. How this works is that solar panels generate electricity from sunlight, and the batteries store excess power that is not used immediately. During the night or when there is not sufficient sunlight, the battery can provide electricity to the house. A battery can also act as a backup generator if power goes “out”. When the grid goes “out”, as in a storm, the power from your solar panels is automatically cut off, ensuring that line workers remain safe. But if you have a storage battery, your system can switch to the battery for energy, much in the same way as you would use a generator.
In the diagram below, the example storage battery is being charged from the electricity being generated by the solar panels on a very sunny day. If there is insufficient electricity coming from solar, then the power from the grid would come in and make up the difference. However, if the batteries are already charged completely, then they can serve as a means to provide electricity to the home during the night.
Figure 1: During the day, batteries charge themselves from the solar panel. Whereas, during the night or in case of power outage, batteries act as a backup generator and provide electricity to the house
Inverters and capacity
All batteries are Direct Current (DC) based and need an inverter to interact with the Alternate Current (AC) power that comes from the power grid. Most of the batteries being offered on a 48-volt platform can be paired with many solar hybrid or battery-capable inverters. When selecting batteries, apart from the cost and reliability, an important factor is the usable capacity, as some batteries can have high usable capacity (95%) while others may have as low as around 50% usable capacity. Vendors often recommend installing solar panels along with these batteries systems to get the maximum benefit from the system, while also taking advantage of the current federal tax incentive.
Pricing and Vendors
The following table lists the above-mentioned batteries systems, the list of vendors providing these systems, and vendors starting price (including installation) for a single battery system.
|Battery system/Vendor||Michigan Solar Solutions||Oak Electric Services Inc.||Modern Mill Solar||Solar King, LLC||Distributed Power||Sumpter Solar Services|
|LG Chem high voltage||X||$10,800||$12,400||$12,500||$11,500||X|
|LG Prime|| X||X||X ||X ||X ||$11,000|
The following outlines the current most accessible types of batteries on the market.
This is a 14kWh battery + inverter system with a usable energy of 13.5kWh. It is a lithium ion battery. A single battery system can be used to offer partial home backup (for emergency loads only) whereas two (2) or more Powerwalls can be used for full backup. Additional batteries can be stacked to provide more output, as well as more capacity. They can also be programmed for self-consumption and emergency backup. It can interface with most home generators but is only designed to be charged from a generator when used for off-grid power. A separate solar inverter is required to utilize solar modules and to generate continuous backup power. Tesla Powerwalls must be connected to the internet for remote monitoring, software updates, and warranty purposes.
LG Chem and LG Prime
LG Chem is a 9.8 kWh battery system out of which 9.3kWh is usable whereas the LG Prime (RESU Prime) is a 16-kWh battery system with the rated power of 7kW and peak power of 11kW. Their Battery Management System (BMS) allows installers to measure battery state information such as voltage, current, and temperature. Their in-depth diagnosis monitoring capabilities assist in troubleshooting abnormal symptoms that lead to energy losses over time. Users are further able to control temperature and cell balancing of the battery. Their high voltage (400V) battery system is compatible with inverter brands such as SMA, SolarEdge, SUNGROW, GOODWE, and Solis.
The Sol-Ark hybrid inverter can be paired with their 48-volt battery banks. A single extended lead life AGM battery consists of approximately 2.76 kWh. When stacked together, four of these make 11 kWh, out of which 5.5 kWh is usable. Their inverter can be programmed for no battery operation, off-grid, self-consumption and/or emergency backup. It can integrate with most home generators for charging batteries and supporting large loads. Sol-ark offers a unique feature, optional EMP hardening of the complete system and backed up circuits. If a customer wants long term off-grid/ survival this is a great option. A separate solar inverter is not required to utilize solar modules, but the Sol-ark can also interface with existing solar inverters. The Sol-ark inverter may be connected to the internet to enable remote monitoring and software updates.
The Outback Skybox or Radian hybrid inverters can be paired with 48-volt battery banks. Outback batteries are high tech versions of the AGM technology, starting with a valve regulated lead acid (VRLA) AGM 2.4KWH battery. Four (4) 12-volt VLRA AGM batteries make up one 9.6KWH battery bank, out of which 4.8kWh is usable. They can be stacked in sets of four to achieve more storage. The Skybox inverter can be programmed for no battery operation, off-grid, self-consumption and/or emergency backup. It can integrate with most home generators for charging batteries and supporting large loads. If a customer wants long term off-grid/ survival, then this is a good option. A separate solar inverter is not required to utilize solar modules, but the Skybox and Radian can also interface with existing solar inverters. Outback Skybox inverter may be connected to the internet to enable remote monitoring and software updates.
The Fortress battery is a 48-volt lithium ferro phosphate battery with a built-in battery management system (BMS) with capacity starting with the eFlex 5.4KWH (4.8KWH usable) and eVault 18.5KWH (16.6 usable). They are stackable for expanded storage. It can also pairs with the Sol-Ark and Outback inverters. The eFlex and eVault may be connected to the inverter for battery monitoring and software updates.
Below are the contact details for battery storage vendors who provided information for this page. Individuals are encouraged to contact these individuals for more details and/or estimates.
Special Thanks to Mr. Mark Hagerty, President Michigan Solar Solutions for providing very detailed information for the batteries systems.