Discover the results of solar battery autopsy . We shed light on the mechanisms of its internal degradation to understand its end of life.
My fascination with solar energy is not new. Clean, abundant and increasingly accessible , this energy source has incredible potential. But for the sun to become a true source of autonomy, we must be able to store electricity . This is where solar batteries come into play. True energy reservoirs, they ensure stability and availability , even when the sun disappears behind the horizon. Without them, the energy produced would be ephemeral, lost if it is not consumed immediately.
Huawei LUNA2000-10-S0
Overall rating: ⭐ 5 / 5
✅ Positive points
- Modular design allows for easy expansion of storage capacity.
- High capacity of 10 kWh, ideal for self-consumption and reducing electricity bills.
- Optimal integration and communication with Huawei inverters.
- Lithium Iron Phosphate (LFP) technology for high safety and long life.
- Compact and neat design for easy installation and integration.
❌ Negative points
- Very high initial investment, typical of energy storage systems.
- Requires a compatible Huawei hybrid inverter.
- Technical installation which must be carried out by a qualified professional.
💬 Reviews & Ratings
- ⭐ 5/5 : Good value for money compared to other batteries (like Tesla Powerwall), but Huawei customer service is difficult to reach and not always effective in case of software bugs.
Oasesenergy Battery
Overall rating: ⭐ 5 / 5
✅ Positive points
- Modular and stackable design for custom installation.
- High quality cells, guaranteeing long life (more than 6000 cycles).
- Reliable performance for increased home energy autonomy.
- Compact, lightweight and easy to integrate into a technical room.
- Compatible with many hybrid inverters on the market.
❌ Negative points
- High initial acquisition cost, as with any high-performance storage system.
- Requires installation by a qualified professional for commissioning.
- The case, although compact, can take up a significant amount of space if several modules are stacked on top of each other.
💬 Reviews & Ratings
- ⭐ 5/5 : Good value for money. The after-sales service is very accessible and available to answer questions and even provide additional parts. Use it every day to really benefit from it. Otherwise, if you leave it on standby, the energy is wasted on heating and cooling. Or turn it off if you want to store it for a long time.
Table of Contents
The idea for this “ solar battery autopsy ” came to me from a deep curiosity . These often discreet boxes can store and release astonishing power , but for many remain “black boxes.” How do they actually work? Why do they sometimes break down? This opacity limits our understanding of their performance and lifespan.
By opening these batteries and explaining what's inside, I want to not only impart technical knowledge , but also give you the tools to interact intelligently with your equipment : better choose, maintain and replace your batteries. This approach allows for more informed adoption and optimized management of solar systems.
So I invite you to take a journey to the heart of a solar battery . We will disassemble it, piece by piece, understand the function of each component and demystify the electrochemical processes that transform electricity into stored energy and then release it.
We will focus on the most common batteries for solar: lead-acid and lithium-ion , those which represent the best compromise between performance and accessibility.
But beyond the technical aspect, this exploration is above all a process of popularization and empowerment . Understanding these technologies means reducing the barrier to entry, allowing non-experts to acquire complex knowledge and become an informed actor in their own energy consumption .
Safety first
Before diving into the guts of the beast, I wanted to emphasize the most important aspect: safety . Even a “dead” battery can be dangerous. That's why I followed a rigorous protocol , step by step.
My first step was to check the battery voltage with a multimeter . Even when discharged, a residual charge can still be risky. Then I put on my personal protective equipment (PPE) :
Heavy duty safety glasses to protect the eyes.
Chemical resistant gloves , essential for dealing with sulfuric acid in lead-acid batteries.
Long-sleeved clothing to limit accidental contact.
Ventilation of my workspace was also essential, especially with a lead-acid battery that could release explosive gases like hydrogen .
I then prepared a set of insulated tools : screwdrivers of various sizes, pliers, a cutter, and a container to collect any liquid. Caution was exercised at every step to avoid any short circuits . I made sure to work in a well-lit, clean space away from any sources of ignition . These precautions are not optional; they are absolutely essential , especially with high-voltage batteries or those containing corrosive chemicals.
It is crucial to understand that neglecting safety protocols not only puts the operator at risk , but can also distort the autopsy. An inadvertent short circuit could alter the internal state of the battery and mask the true causes of its failure. Safety therefore guarantees both the integrity of the person and the validity of observations and diagnoses .
This emphasis on safety in a solar battery autopsy reflects a broader trend in the renewable energy : increased awareness of the risks associated with high-voltage, high-energy . Solar batteries, and particularly lithium-ion , store significant amounts of energy and pose thermal, chemical, and electrical risks.
Strict adherence to safety protocols underscores the industry's growing maturity : performance is no longer the sole criterion; reliability and safety have become essential pillars for widespread adoption. This translates into stricter manufacturing standards and more rigorous training for all stakeholders.
Disassembly: layer by layer, my observations
I began with a visual external examination of the battery. Were there any bulges, leaks, or corroded terminals ? These signs, even superficial ones, can already provide valuable clues about its history and the cause of its failure.
The opening process varies depending on the battery type. For a lead-acid battery (often a Gel or AGM model for solar), I removed the vent caps where present and sometimes sawed or drilled through the sturdy plastic casing to access the cells. This is delicate work, where damage to internal components or electrolyte spillage must be avoided.
For a lithium-ion battery , the case is often more complex, with hidden screws or welds, and usually contains cell modules rather than individual cells. Accessing the battery management system (BMS) is often the initial and essential step.
Once the case was opened, I was able to observe the general layout : the connection terminals, the external case, and inside, the arrangement of the cells.
In a lead-acid battery, we distinguish the plates immersed in the electrolyte .
In a lithium-ion, we find “packs” or modules of cylindrical, prismatic or pocket cells, connected in series and/or in parallel, and the famous BMS .
The structural differences between lead-acid and lithium-ion batteries are not arbitrary; they directly reflect their chemistries, energy densities, and safety requirements .
Lead-acid batteries require a sturdy casing to contain the sulfuric acid, but their structure remains relatively simple.
Lithium-ion batteries, with higher energy density and sensitivity to overcharge, discharge and temperature, require sophisticated modules , a precise BMS and a complex casing to ensure safety and performance.
These design choices reveal engineering tailored to the risks and benefits of each technology.
The external examination and initial internal observations are essential for diagnosis. They transform the autopsy from a simple dissection into a true forensic investigation of the battery. Each visual anomaly becomes a “piece of evidence” :
Swelling may indicate overheating or gasification.
Corrosion of the terminals may signal an electrolyte leak.
A swollen cell in a lithium-ion can indicate overcharging or a BMS problem.
sulfation on lead-acid plates points to chronic undercharging.
These clues help us understand why the battery stopped working , not just what's in it . This is the first step in decoding its past and anticipating its future behavior.
At the heart of the battery: the key components and their secrets
This is where the autopsy reveals its greatest secrets . Each component tells a part of the battery's story, from its design to its eventual failures. I meticulously examined each element , noting its materials, structure, and role . To better understand, here is an overview of the main components and their functions:
1. Cells or modules
At the heart of any battery are the cells , the true energy storage units.
lead-acid battery , these are lead plates immersed in a sulfuric acid electrolyte. Each positive and negative plate participates in chemical reactions that store and release energy.
lithium-ion battery , cells are often grouped into modules : cylindrical, prismatic, or pouch. They are connected in series and parallel to achieve the desired voltage and capacity. Lithium-ion chemistry allows for higher energy density and reduced weight compared to lead.
2. The housing and the insulation
The casing protects the battery from shock, dust, and leaks. In lead-acid batteries, the sturdy plastic contains the corrosive acid. In lithium-ion batteries, the casing is more sophisticated: it must withstand overheating and internal pressure while protecting the sensitive modules and circuits. Insulating materials inside prevent short circuits and keep the battery safe.
3. Terminals and connectors
Terminals provide electrical connection to the outside world. Corrosion or oxidation is a classic sign of electrolyte leakage or poor maintenance. In lithium-ion batteries, connectors may also include fuses or thermal shunts , protecting the battery from overcurrent.
4. The Battery Management System (BMS)
In lithium-ion batteries, the BMS is a central component, often invisible to the user. It monitors voltage , current, temperature, and cell balancing , preventing overcharging, deep discharge, and overheating. It ensures the safety and longevity of modern batteries.
5. Electrolyte and separators
In lead-acid batteries, the liquid or gel electrolyte allows the passage of ions between the plates, activating the chemical reaction.
In lithium-ion batteries, microporous separators keep the electrodes apart while allowing lithium ions to pass through. This discreet component is crucial for preventing short circuits and thermal incidents .
6. Protections and accessories
Some batteries contain fuses, temperature sensors, safety valves , or explosion-proof devices. These often-overlooked features are essential for managing chemical, thermal, or electrical hazards. They reveal how safety is built into every layer of the design .
Exploring these components, it becomes clear that every detail has been designed to optimize performance, safety, and lifespan . The autopsy isn't just about looking at things: it's about understanding how and why each element works , and how these design choices influence battery behavior and potential failures.
| Component |
|---|
| Anode — Site of the oxidation reaction, release of electrons (Lead Pb, graphite carbon) |
| Cathode — Site of the reduction reaction, accepting electrons (Lead dioxide PbO2, lithium metal oxide LFP/NMC) |
| Electrolyte — Transport of ions between the anode and the cathode (Sulfuric acid H2SO4, lithium salt in organic solvent) |
| Separator — Porous membrane preventing short circuiting while allowing the passage of ions (Polymer, fiberglass, polyethylene, polypropylene) |
The anode and the cathode: the reactive souls
At the heart of every battery are the electrodes electrochemical reactions take place . Understanding their nature and how they work unlocks the secret of the energy contained within the battery.
Lead-acid batteries
The cathode (positive) consists of lead dioxide (PbO₂) plates , often dark brown in color. Their porous structure maximizes the contact surface with the electrolyte, facilitating chemical reactions.
The anode (negative) is made of spongy lead (Pb) plates , gray in color. Its porosity is equally crucial, allowing better interaction with the electrolyte and efficient diffusion of ions.
Lithium-ion batteries
The cathode (positive) is usually a lithium metal oxide , such as LFP (lithium iron phosphate) or NMC (nickel manganese cobalt) . These materials are chosen for their ability to intercalate and deintercalate lithium ions , and I was impressed by the finesse and precision of their manufacture .
The anode (negative) is most often made of graphite (carbon) , capable of accommodating lithium ions in its layered structure, thus ensuring the flow of ions during charge and discharge cycles.
Electrolyte: the blood of the battery
The electrolyte is the vital medium that allows the transport of ions between the anode and the cathode. Without it, there is no movement of ions, no current , and therefore no operation.
Lead-acid batteries : I identified dilute sulfuric acid (H₂SO₄) as the electrolyte. In Gel or AGM models, it is immobilized in silica gel or absorbed in fiberglass separators, reducing the risk of leakage.
Lithium-ion batteries : The electrolyte is a solution of lithium salt (such as LiPF₆) dissolved in an organic solvent. This liquid is flammable , raising the risk of failure or overheating.
The Separator: The Silent Guardian
The separator is a porous membrane that plays a crucial role: it prevents direct contact between the anode and the cathode (thus avoiding short circuits) while allowing ions to pass freely.
In lead-acid batteries , it can be made of polymer, fiberglass (AGM), or rubber.
In lithium-ion batteries , it is often a microporous polymer film (polyethylene or polypropylene). Its thinness and strength particularly impressed me.
The case and the terminals: the skin and the veins
The casing , usually made of sturdy plastic (polypropylene) for both types of batteries, protects the internal components from shock and the environment, while containing the electrolyte. I carefully examined its integrity, looking for deformations or cracks .
The terminals provide the external electrical connection:
Lead for lead-acid batteries.
In copper or aluminum for lithium-ions.
I noted the absence of excessive corrosion , a sign of either good maintenance or early internal failure , revealing clues about the condition of the battery before its “death”.
Battery Management System (BMS): The Electronic Brain
Inside a lithium-ion battery , I discovered a complex circuit board : the BMS, or Battery Management System . This component is essential for the safety and longevity of the battery.
Its key functions include:
Protection against overcharge , deep discharge and overcurrent.
Monitoring extreme temperatures to avoid any risk of thermal runaway.
Balancing voltages between all cells in the pack, extending lifespan.
battery state of charge (SOC) and state of health (SOH)
I examined the electronic components of the BMS: microcontrollers, MOSFETs, and temperature sensors. A faulty BMS is often the main cause of lithium-ion battery “death,” even when the cells themselves are still functional.
Thermal management system: keeping the battery at optimal temperature
I also looked at thermal management elements , such as cooling plates or additional sensors. These devices are essential to keep the battery within its optimal temperature range , prevent thermal runaway, and ensure safe and efficient operation.
Essential sophistication
The increasing sophistication of materials (LFP or NMC cathodes, microporous polymer separators) and the integration of electronics (BMS and thermal management) in lithium-ion batteries are not simply aesthetic improvements: they address the fundamental limitations of older batteries such as lead-acid and modern requirements for energy density, safety and durability .
Lead-acid batteries are simpler structurally and chemically, but limited in energy density and prone to degradation such as sulfation.
Lithium-ion batteries offer higher energy density but are inherently more volatile (risk of thermal runaway, formation of dendrites).
The development of stable cathodes , safe electrolytes , high-performance separators , and above all the integration of BMS and thermal management , have made it possible to unlock the potential of lithium-ion batteries compact, efficient and safe storage solutions .
Read the history of the battery
The condition of the internal components sulfation, dendrites, integrity of the separator acts as a logbook , revealing past usage and root causes of failure.
Sulfation in a lead-acid battery often indicates chronic undercharging or prolonged discharge .
The presence of dendrites or an SEI layer on the separator of a lithium-ion battery suggests excessive overcharging or fast charging .
A damaged separator can cause an internal short circuit.
The status of the BMS shows whether it has correctly fulfilled its protective role.
Thus, the examination of the components is not only descriptive: it is diagnostic , allowing the history of the battery to be reconstructed and the factors which contributed to its failure to be identified.
| Battery Type | Anode (material) | Cathode (material) | Electrolyte (composition) | Separator (material) |
|---|---|---|---|---|
| Lead acid | Lead (Pb) | Lead dioxide (PbO2) | Dilute sulfuric acid (H2SO4) | Polymer, fiberglass, rubber |
| Lithium-ion (LFP) | Graphite | Lithium iron phosphate (LFP) | Lithium salt in organic solvent | Microporous polymer film (PE/PP) |
| Lithium-ion (NMC) | Graphite | Nickel manganese cobalt (NMC) | Lithium salt in organic solvent | Microporous polymer film (PE/PP) |
How does it really work? Energy in motion
After identifying the components, it's time to understand how they work together . This is the most fascinating part of the autopsy: the magic of electrochemistry . The key idea is simple and powerful: the movement of ions in the electrolyte and electrons in the external circuit . It's this flow that transforms chemistry into usable electrical current.
Simplified explanation of charges and discharges
Discharging (the battery provides energy)
Lead-acid battery:
At the anode (lead) , the lead oxidizes and releases electrons. The sulfate ions (SO₄²⁻) in the electrolyte then combine with the lead to form lead sulfate (PbSO₄) .
At the cathode (lead dioxide) , PbO₂ reacts with sulfate ions and protons (H⁺) from sulfuric acid. This reaction consumes electrons and also produces lead sulfate and water.
Electrons released at the anode flow through the external circuit to the cathode, generating the electric current we use to power our devices.
The overall reaction can be summarized as follows:
Pb + PbO₂ + 2 H₂SO₄ ↔ 2 PbSO₄ + 2 H₂O
Lithium-ion battery:
At the anode (graphite) , lithium ions (Li⁺) deintercalate from the layered structure of the graphite and migrate to the cathode through the electrolyte.
Simultaneously, electrons leave the anode and flow to the cathode via the external circuit, producing the current.
At the cathode (lithium metal oxide) , lithium ions intercalate into the structure of the material and combine with electrons arriving through the external circuit.
The overall reaction boils down to an intercalation/deintercalation movement of lithium ions between the electrodes:
Li_anode + cathode ↔ anode + Li_cathode
The fascinating thing is that all of these reactions are reversible . When charging, the process reverses: the ions and electrons return to the anode, storing the energy for future use.
Understanding this dance of ions and electrons transforms a “black box” into a living, coherent system , where each component plays a precise role. The movement of ions in the electrolyte and electrons in the external circuit is the heart of the energy stored and released , and it is this subtle mechanics that makes solar batteries so essential for energy autonomy.
When charging, the battery receives energy
The reactions reverse. The electrons are forced back to the anode, and the ions move in the opposite direction, reconstituting the original materials.
Each component is essential: the anode and cathode as reactors, the electrolyte as a highway for ions, the separator as a safety filter, and the BMS as the conductor (for lithium-ion batteries). Solar panels generate a direct current that forces the battery to charge, storing chemical energy. When the sun sets, this chemical energy is converted into electricity for our needs.
Degradation mechanisms (sulfation, dendrites, SEI growth) are not isolated defects but direct consequences of electrochemical reactions and operating conditions, revealing the intrinsic limitations of each chemistry. For example, sulfation is the formation of PbSO₄, which is the normal discharge reaction of lead-acid. Dendrites are the growth of metallic lithium on the anode of lithium-ion batteries. SEI is a layer that forms at the electrolyte-anode interface. These “problems” are actually manifestations of the chemical reactions themselves, exacerbated by suboptimal operating conditions. Sulfation becomes problematic when PbSO₄ crystallizes and can no longer be converted back into charge, often due to chronic deep discharge or undercharge. Dendrites form during fast charging or at low temperatures, when lithium ions do not intercalate uniformly into the graphite and are deposited in metallic form. Excessive SEI growth consumes active lithium, reducing capacity. Understanding normal operation helps us better understand the root causes of degradation, not just its symptoms.
Understanding electrochemical reactions is the key to extending the lifespan of solar batteries, transforming users from mere consumers into informed managers of their energy systems. Understanding that sulfation is related to deep discharge can help avoid completely draining their lead-acid batteries. Knowing that dendrites are related to fast charging can help adjust charging profiles for their lithium-ion batteries. This knowledge goes beyond generic recommendations (“do not deep discharge”). It provides an understanding of the “whys” and “hows” that allows users to adapt their behavior to optimize the performance and longevity of their solar batteries. This is a step toward proactive energy management, where system sustainability is maximized through intelligent use, reducing the need for costly replacements and environmental impact.
My discoveries and reflections: what the autopsy reveals
This is the part where I share my most striking observations and what they mean.
For the lead-acid battery (if it is the one I “autopsied”), I have often noticed visible sulfation on the plates , a whitish or gray layer that indicates capacity degradation. The extent of this sulfation can give an idea of the severity of the undercharge or deep discharge. Sometimes I have been able to observe deformed plates or sludge deposits at the bottom of the case , signs of overcharging or advanced degradation. The condition of the electrolyte, if I had been able to test it, with too low a specific gravity, would indicate a charging problem or acid loss.
For the lithium-ion battery (if it's the one I "autopsied"), I looked for signs of cell swelling , an indicator of gasification due to overcharging or heat, or evidence of short circuiting . Examining the separator might reveal punctures or lithium dendrite deposits , explaining capacity loss or an internal short circuit. The condition of the BMS is crucial: burned components or cold solder joints could indicate an electronic failure that led to the death of the battery, even if the cells were still viable. The presence of a thermal management system and its condition can also give clues about the performance and safety of the battery.
These observations allowed me to better understand the weaknesses of each technology. Lead-acid batteries are robust but sensitive to deep discharge cycles and sulfation. Their lifespan is strongly impacted by maintenance. Lithium-ion batteries offer better energy density and longer cycle life if properly managed by the BMS. However, they are more sensitive to extreme temperatures and overcharge or discharge, which can lead to dendrite formation or electrolyte degradation.
The “death” of a battery is rarely due to a single, isolated cause; it is often a combination of factors: natural wear and tear, operational stress, and failure of a supporting component such as the BMS, which interact in complex ways. Post-mortem examination reveals that battery failure is often multifactorial . For example, a lithium-ion battery may die due to dendrite formation (intrinsic chemical degradation), but this formation can be accelerated by overcharging due to a faulty BMS (electronic failure) or by poor thermal management (environmental stress). Similarly, a lead-acid battery may suffer from sulfation, aggravated by repeated deep discharge cycles (misuse). Post-mortem examination helps unravel this complex web of cause and effect.
The lessons learned from the autopsy of a failed battery are invaluable not only for the individual user, but also for manufacturers and developers, informing future designs and lifespan optimization strategies. The autopsy of a “dead” battery is not just a post-mortem curiosity; it is a source of crucial data for continuous improvement . Manufacturers can use this information to design more robust batteries (better sulfation resistance, more dendrite-resistant separators), smarter BMSs , and more efficient thermal systems . For users, this means more accurate usage recommendations. In short, each failed battery is a case study that helps advance the entire solar energy storage ecosystem.
Conclusion: The importance of understanding our energy sources
This exploration took us from the outer casing to microscopic electrochemical reactions. We saw that behind the apparent simplicity of a battery lies complex engineering and fascinating chemical interactions. I highlighted the importance of safety precautions, the diversity of architectures (lead-acid vs. lithium-ion), the vital role of each component (electrodes, electrolyte, separator, BMS), and how their interaction allows for the storage and release of energy. We also glimpsed the reasons for their "death": wear, sulfation, dendrites, or electronic failures.
The demand for solar batteries will only grow with the expansion of renewable energy. Research continues to improve battery materials, energy density, safety, and lifespan. Innovations such as solid-state batteries and new lithium-ion chemistries promise significant advances.
Incorporating recycling into the conclusion is not a mere environmental formality, but a recognition of the battery's complete life cycle, which must be considered from the design stage for true sustainability. With the proliferation of these technologies, recycling and reuse are becoming major issues to minimize environmental impact and recover valuable materials. For true sustainability of solar systems, it is imperative that batteries are designed not only for performance and safety, but also for ease of disassembly, their materials recoverable and reusable. This involves material choices and architectures that facilitate the dismantling and separation of components, an engineering challenge that influences battery design from the outset.
The autopsy of a battery, by its very nature, is a microcosm of the challenges and opportunities of the energy transition. It reveals the technical complexity, the importance of safety, the need for sustainability, and the imperative of responsible resource management. The solar battery, as a critical component of renewable energy, is an excellent example of the challenges inherent in the energy transition. It symbolizes the need for advanced engineering to maximize efficiency and safety, the management of scarce and toxic resources, and the importance of the complete life cycle (from manufacturing to recycling). This exploration of a single part gives us a window into the full range of issues facing humanity for a successful and sustainable energy transition. As users and citizens, understanding these technologies not only allows us to better use them, but also to participate in more informed choices for a sustainable energy future.
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