Rechargeable batteries and solar cells may be older than you realize.
Gaston Planté invented the first lead-acid rechargeable battery in 1859.
The discovery of solar electricity goes back considerably deeper.
Edmond Becquerel demonstrated the photovoltaic effect with an electrochemical solar cell in 1839.
Needless to say, solar cell and rechargeable battery technologies have advanced significantly since then.
Nonetheless, lead-acid batteries are still widely used in solar systems today.
Here are today’s most popular solar battery types, ranked from lowest to maximum performance.
Flooded Lead Acid Batteries
The oldest rechargeable battery technology is Flooded Lead Acid (FLA), which is still frequently used today.
All lead-acid batteries, including Sealed Lead Acid (SLA) batteries such as AGM and Gel Cell, charge and discharge DC current using electrolysis.
They also use many of the same raw components, albeit the battery cell design differs greatly between varieties.
Unless you’ve moved to charging a Tesla or another EV, you most likely have a FLA battery in your car or truck.
FLA batteries are affordable and effective in providing short bursts of high-current electricity.
The key components of a FLA battery are:
Cathode (positive electrode): Lead dioxide plate
Anode (negative electrode): a metallic lead plate.
The electrolyte is sulfuric acid diluted with distilled water (H2SO4 + H2O).
FLA batteries’ capacity to generate quick surge power makes them ideal for starting engines in automobiles, trucks, and other vehicles.
However, FLA batteries are inefficient in providing a continuous supply of electricity and have a very shallow depth of discharge (DoD).
FLA batteries can be utilized in a compact solar panel system that requires little power.
However, they are rarely the best option.
FLA solar batteries may be inexpensive, but they will cost you more in the long run.
Pros
Lowest upfront pricing
Suitable for starting motors and engines.
May be appropriate for low-current solar applications.
Cons
Short cycle life (300-1000 charges/discharges at no less than 50% state of charge).
Shallow discharge.
High vulnerability to harsh temperatures—particularly cold.
Requires regular maintenance and refilling with distilled or deionized water.
To prevent hazardous leaks and spills, it must be installed or stored upright.
Offgassing of harmful vapors needs working in a well-ventilated location.
Sealed lead acid batteries (SLA/VRLA).
Sealed lead acid (SLA) and valve-regulated lead acid (VRLA) are equivalent terminology for a newer, less volatile version of old FLA battery technology.
VRLA batteries reduce the difficulties of wet cells by “starving” or immobilizing the liquid electrolyte solution used in FLA batteries, while also improving performance significantly.
SLA batteries are commonly marketed under the following terms:
Dry batteries
Deep cycle batteries
Acid-starved batteries
Maintenance-free batteries
There are two types of VRLA solar batteries: absorbent glass mat (AGM) and gel cell.
Many consumers do not distinguish between the two types of SLA (dry) cells since their performance and marketing are so similar.
AGM and Gel Cells differ greatly in design and materials, although they share many of the same advantages (and problems) as “wet” FLA solar batteries.
Pros
Faster charging.
Increased cycle life.
Lower self-discharge rate.
Depth of discharge up to 80%— But make sure to read the fine print. Many SLA manufacturers propose maintaining a 50% state of charge (SoC), rather than repeated discharges to 80% DoD.
There is no need to install upright.
Operate in an unventilated environment for less risk of harm to the case.
No refilling or watering.
Less sensitive to excessive heat and cold.
Resistant to vibration
There are no spills or leaks.
Cons
Higher pricing.
Lower surge power (beginning wattage)
Use less electrolyte by volume and avoid overcharging or charging at higher current/voltage than suggested.
AGM and Gel Cell solar batteries outperform FLA in high-wattage solar applications such as whole-home generators.
But how do they compare to one another?
Let’s have a look.
Absorbent Glass Mat Batteries (AGM)
AGM battery cells are made of fibreglass mats that absorb (starve) the liquid electrolyte solution.
Because AGM batteries are sealed, they do not require watering and require minimal maintenance other than keeping the battery contacts clean.
The primary components of an AGM battery are:
Cathode (positive electrode): Lead dioxide plate
Anode (the negative electrode): Metallic lead plate
The electrolyte is sulfuric acid diluted with distilled water (H2SO4 + H2O).
Absorbent Glass Mat (AGM)
AGM battery cells employ the same raw materials as FLA batteries, with the exception of absorbent glass mats placed between the positive and negative lead plates.
The mats absorb and immobilise the liquid electrolyte of sulfuric acid.
The AGMs stay wet, but there is no free-flowing acid in the cell.
As a result, AGM batteries are often described to as “acid-starved.”
Trapping the electrolyte in fibreglass mats does not prevent the battery from being charged and discharged via electrolysis.
On the contrary, most essential indicators indicate that it improves performance.
One historical advantage of FLA batteries over SLA cells is their ability to generate more precise (or immediate) power.
That is one of the reasons why FLA has traditionally been utilized in automobile batteries.
AGM batteries have long been found in golf carts and motorbikes.
AGM batteries are gradually taking the place of FLA batteries in cars and trucks due to advancements in technology. They survive longer and are less vulnerable to severe cold.
However, what are the benefits and drawbacks of AGM batteries in comparison to Gel Cell batteries?
Advantages
Quick charging
Charge parameters that are more lenient
Reduced vulnerability to overcharging
Elevated density of energy
Increased production of surge power
More effective at starting mechanical motors
Reduced susceptibility to intense heat
Greater variety in applications
Drawbacks
shallower discharge depth
More prone to undercharging
At lower charging rates, less effective
Average lifespan is somewhat shortened because of stratification and dendrites.
Gel Cell Batteries
At this point, you might have noticed that FLA and AGM batteries share primary ingredients.
Additionally, gel cells use diluted sulfuric acid as the electrolyte and lead plates as electrodes.
The technique and materials used to lower volatility and enhance the performance of the liquid electrolyte used in all lead-acid batteries are the primary distinction between AGM and gel cells.
The following are the main parts of a gel cell battery:
Lead-dioxide plate cathode (positive electrode)
Metallic lead plate serves as the anode (negative electrode).
Electrolyte: Distilled water diluted with sulfuric acid (H2SO4 + H2O)
To immobilize the liquid electrolyte and give it a gel-like consistency, silica dust is added.
Performance-wise, there aren’t many changes between Gel Cell and AGM battery cells.
These are the most important benefits and drawbacks.
Benefits of deeper cycles
More appropriate for gradual and consistent charging and draining
Reduced vibration sensitivity
Drawbacks
might be little more costly overall.
More prone to excessive charges
Increased susceptibility to changes in voltage and current
A little more sensitive to temperature, especially in intense heat
The decision?
In the majority of photovoltaic applications, gel cell batteries may outperform AGM batteries by a small margin.
The inherent intermittency of solar power may be slightly mitigated by reduced vulnerability to harm from low current and undercharging.
Gel cell solar batteries, however, are typically a little more expensive.
Lithium-ion solar batteries are superior to both varieties of SLA batteries.
Lithium-ion and LiFePO4 solar batteries outperform both AGM and Gel Cell SLA batteries in terms of performance.
Price will probably be the most important deciding factor if you are determined on a VRLA solar battery.
After that, we’ll discuss LFP.
Advantages
Greater power output rating
Greater density of energy
Enhanced cycle efficiency
Cycle life is extended (1000-2000).
Reduced vulnerability to thermal runaway
Mechanical abuse is less likely to occur (Nail test).
less cobalt is needed (the normal cathode composition is 10% cobalt, 10% manganese, and 80% nickel).
Reduced State of Charge (SoC) influence on cycle life
Deeper suggested DoD (operational DoD of 80%–90%)
Drawbacks
More costly
reduced energy density by a little amount
Reduced specific energy
LCO batteries continue to function until 95–100% discharge, however full discharges negatively impact cycle life. Shallower real DoD
Lithium iron phosphate (LFP/LiFePO4)
The benefits of LCO and NCM batteries over lead-acid batteries are combined with special qualities that make lithium iron phosphate (LFP/LiFePO4) batteries perfect for photovoltaic applications.
Although the cathode is composed of lithium iron phosphate (LiFePO4/LFP), the main components are the same as those of other Li-ion batteries.
The graphite anode
Lithium iron phosphate is the cathode.
Lithium salt solution, such as lithium hexafluorophosphate (LiPF6), serves as the electrolyte.
Polyethylene (PE) separators
Collectors of positive and negative current (copper foil and aluminum)
Thermal runaway is virtually nonexistent in LFP batteries, in contrast to LCO batteries.
In high-capacity solar systems, reducing the risk of fire or explosion due to thermal runaway is extremely beneficial, regardless of how distant the risk may be.
EV manufacturers like Tesla are quickly adopting LFP because to its superior safety profile, frequently replacing NMC.
Manufacturers of EV and solar batteries are progressively moving away from NMC to LiFePO4 batteries for reasons other than safety.
Decobaltization: Cobalt is a conflict mineral, as was previously mentioned. There is growing pressure on brands to discontinue its use in their goods.
Declining Costs: NMC is a more well-known technology. Because producers had to make investments in new machinery and procedures, LFP batteries were initially more costly. Nonetheless, the cost of NMC and LFP solar batteries is currently comparable. The cost of LiFePO4 batteries is anticipated to continue declining. Compared to iron and phosphate, nickel and cobalt NMC batteries are much rarer and more costly materials. Prices should keep declining as long as there is a greater demand for LFP. NMC prices are anticipated to either increase or stay the same in the interim.
The safest lithium-ion battery chemistry for high-load applications, such as home solar power and electric vehicles, is LiFePO4. Thermal runaway is almost completely eliminated in LFP cathodes due to their strong covalent bonds.
Greater working temperature range: LFP batteries can run at temperatures ranging from 140°F (60°C) to -4°F (-20°C). The ideal operating temperatures for Li-ion batteries are 32°F (0°C) to 113°F (45°C).
Cycle Life: LFP batteries such as the DELTA Pro Ultra from Maxworld Power
Drawbacks
reduced energy density by a little amount
The average voltage (3.2V vs. 3.8V) is lower than that of LCO and NCM. Solar panels can be linked in series rather than parallel if there are voltage shortages.
Find out more about the advantages and disadvantages of LiFePO4 solar batteries over conventional lithium-ion (LCO) batteries.
New Developments in Solar Battery Technology
Globally, manufacturers, governments, and academics are constantly searching for the next significant development in renewable energy storage.
These new solar battery solutions have showed some promise, but it will probably be years before they are commercially available for domestic use.
Batteries that Flow
Batteries with iron air
Batteries with solid state
ion batteries made with sodium
The Value of Superior Solar Batteries
Solar energy for homes is an investment that takes time to pay off.
Rigid solar panels with high efficiency usually endure more than 25 years before their performance starts to drastically deteriorate.
Compared to LiFePO4 batteries, SLA “deep-cycle” solar batteries have a substantially shorter cycle life and frequently need to be replaced after just a few years of consistent operation.
However, the whole-home generator solutions from Maxworld Power can be used every day for more than ten years.
Investing in high-quality solar batteries and other parts is essential to saving money and getting the most out of your PV investment.
Your solar payback period may be extended, but your long-term return on investment will be improved.
Additionally, government solar rebates can drastically lower your initial outlay of funds.
Concluding remarks
A solar + storage system has several benefits if you’re thinking about using solar energy to power your house.
Although it won’t totally eliminate them, a grid-tied system can help you save money on your electricity bills.
Additionally, during a blackout, you won’t have power.
Maxworld Power’s whole-home generator solutions combine PV modules with premium LFP solar batteries to maximize your solar investment return and provide energy security.
