Backup plan: Best solar batteries in 2024
- 08 Jun 2023
- 10 min
To gain true energy freedom and autonomy, you have to get a battery bank for your solar system. Choosing one isn’t easy, especially since the energy storage system can account for more than 50% of the PV system’s total costs. That’s why we’ll be looking at the best solar batteries in this article to help you separate the wheat from the chaff and save money.
What is a solar battery: The basics
Solar batteries store excess solar energy produced by solar panels during the day. You can use it at night when the sun isn't shining, during power outages or at the hours of peak electricity demand to save money.
The decision of whether or not to add energy storage is not to be taken lightly because of the high solar battery cost. A simple grid-tie system without batteries provides better ROI than an off-grid installation or even a hybrid one in some cases. However, for homeowners in areas with frequent power outages, solar batteries are a smart investment. They become essential if you go for complete energy independence.
The number of batteries needed for your home depends on your energy consumption and why you need them. The optimal size of a battery bank is going to be different in off-grid and hybrid systems.
DC and AC batteries: Lower costs vs. easier setup
DC and AC batteries differ in how you add them to your system. DC-battery systems are less confusing but AC-systems are surprisingly easier to implement.
DC batteries are cheaper
Solar panels produce direct current by themselves and they can directly charge a DC battery. There always should be a charge controller in between to make the voltage from panels safe for the battery. The DC from the battery and panels then goes to an inverter, turns into AC and flows into the grid or to the appliances. A DC-coupled system is a low-cost setup for mobile installations and residential systems under 6-7 kW in size.
Standard grid-tie inverters cannot be paired with DC batteries. You need a hybrid or an off-grid inverter to pair it with DC energy storage.
AC batteries are easier to add to a system
AC batteries, on the other hand, require a separate inverter that is connected to your electric panel. The inverter draws AC from the grid, converts it to DC and sends it to the battery. When extras are needed, it draws energy from the battery, converts it back to AC and sends it elsewhere. The most notable examples are Tesla Powerwall 2 and Enphase Encharge.
Multiple conversions mean energy losses and this makes AC battery system less efficient. Besides, an extra inverter makes it more expensive. However, an AC battery is much easier to add to an existing system even if you have a grid-tie inverter. AC-coupled systems are a better option for large houses, heavy loads and EV charging. Read more in our article on AC and DC energy storage systems.
Types of solar batteries: From lead-acid to lithium
For a long time, lead-acid batteries were the most popular type of energy storage. They are still widely used because these are the cheapest batteries for solar systems. The downside is how vulnerable they are. Overheating, extreme cold, overcharging, deep discharge — all of these things shorten the lifespan of a lead-acid battery drastically. A lead-acid battery can be safely discharged only by 50% which means that only half of its capacity is actually usable.
There are three most common subtypes of lead-acid batteries that are used in solar systems:
• Wet cell or flooded batteries. A wet cell battery consists of cells filled with electrolyte: water and sulfuric acid. You’ll have to check its level from time to time and add some distilled water. The safe DOD of wet-cell batteries is around 50-60%. All wet cell batteries are afraid of extreme climates: water can either evaporate in hot areas or freeze when it's cold.
• Gel batteries. A silica additive in gel batteries makes the electrolyte stiff, so it doesn't have a risk of spilling. They withstand extreme temperatures better. Gel batteries are particularly vulnerable to overcharging. Their safe DOD is at around 75%.
• Dry cell or absorbed glass mat or AGM batteries. AGM batteries safe DOD reaches 80%. They are vulnerable to overcharging, plus AGM batteries cost twice as much as wet cell batteries.
With all the downsides of lead-acid energy storage, it’s not a surprise that lithium batteries take over the market. Their efficiency is higher: 85-95% compared to 60-80% of lead-acid ones. They last longer: most come with warranties for 10 years. Their acceptable depth of discharge (DOD) reaches 100%. They charge faster, they are lighter and take up less space. The only downside is their higher price.
There are three most common types of lithium batteries that are used in PV systems:
• Lithium Cobalt Oxide or LCO battery. LCO batteries are most common in smartphones, tablets et cetera. You rarely see LCO batteries in solar systems because of their relatively short lifespan. They last for 700 to 1,000 cycles.
• Lithium Nickel Manganese Cobalt Oxide or NMC. NMC batteries last for 2,000-2,500 cycles. They are among the more affordable lithium-ion batteries. They also do well at low temperatures. The problem is toxic components which make NMC batteries harder to recycle.
• Lithium Iron Phosphate or LFP battery. LFP batteries can withstand from 3,000 to 6,000 cycles. They are more expensive than NMC batteries but they last longer. However, they are more vulnerable to cold and their energy density is lower. If you have an NMC battery and an LFP one of the same capacity, the NMC battery is going to be smaller.
Top 3 solar batteries for home and business
Let’s look at a few batteries that can be used at home in combination with solar panels. We based the rankings in this article on expert opinions, customer reviews and technical details of the products.
Generac PWRcell: Modular flexibility
- TypeLi-Ion batteries
Delivery on Mar 06–11
The Generac PWRcell is a high-capacity DC solar battery designed for residential and commercial use. With a storage capacity ranging from 8.6 kWh to 17.1 kWh, the PWRcell can provide backup power during outages and reduce reliance on the grid during peak hours.
PWRcell features a modular design. The number of battery modules can range from three to six. As power needs grow, you simply add new modules to the cabinet. Lithium nickel manganese cobalt (NMC) battery chemistry provides long-lasting and reliable power storage with a 10-year warranty. A great battery for solar panel systems, PWRcell can be controlled through a mobile app that lets you monitor your energy consumption.
Enphase Ensemble Encharge: All-in-one storage system
Enphase Ensemble Encharge is a high-performance solar battery designed for residential and commercial use. Lithium iron phosphate (LFP) cells offer a longer lifespan and better performance compared to other types of lithium batteries.
The Enphase Ensemble Encharge also employs modular design. The storage can be expanded by adding additional units. Each battery module has a storage capacity of 3.4 kWh. The units come with Enphase microinverters, turning a battery into an AC one, and you can simply connect it to your electric panel.
Strong software is what stands out with this model. You can track their energy production and storage in real time and adjust it to your needs.
LG RESU Prime: Trusted manufacturer
LG RESU Prime is a high-performance solar lithium battery designed for residential and commercial projects. It has a capacity range from 8 kWh to 16 kWh. A battery management system (BMS) monitors the battery's performance and protects it from overcharging, overheating, and other potential hazards.
LG RESU Prime can be easily installed indoors or outdoors and is compatible with a wide range of inverters and solar PV systems. It also comes with a 10-year warranty, retaining at least 70% of its capacity by the time the warranty runs out.
How long do solar batteries last? Depends on you
The lifespan of solar batteries depends on type and brand, as well as on how you treat it. A lithium-ion battery lasts between 10 to 15 years on average while the lifespan of a lead-acid battery ranges from 2 to 8 years.
To prolong the lifespan of a solar battery, it is essential to maintain it properly. Keep it away from extreme cold or high temperatures. Always add a charge controller in between the panels and the battery. It protects your energy storage from the high voltage of solar array and prevents overcharging and deep discharge. Using a battery management system can help optimize the battery's performance and increase its lifespan.
This article has been updated as of January 2024
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