What Can I Do To Give Second Life To Half Drained

What are the basic applications of capacitors in daily life?

These are the basic applications of capacitors in daily life. Thus, the fundamental role of the capacitor is to store electricity. As well as, the capacitor is used in tuning circuits, power conditioning systems, charge-coupled circuits, coupling, and decoupling circuits, electronic noise filtering circuits, electronic gadgets, weapons, etc.

How do capacitors work?

Capacitors are connected in parallel with the DC power circuits of most electronic devices to smooth current fluctuations for signal or control circuits. Audio equipment, for example, uses several capacitors in this way, to shunt away power line hum before it gets into the signal circuitry.

What are capacitors & why are they important?

Along with resistors and inductors, capacitors are one of the "Big Three" passive components that make up fundamental electronic circuits. In order to filter out erroneous electric impulses and stop harm from electric surges to delicate parts and circuits, capacitors play another more crucial function.

Do capacitors store energy?

Since the 18th century, Capacitors have been storing electrical energy. They generally do not hold a great deal of energy. However, they provide enough power for electronic devices to use when they need additional power or during temporary power outages.

What is a capacitor (C)?

The capacitor (C) is an electronic component that is capable of storing charge. In electrical and electronic circuits, the capacitor is a very crucial part to store energy in the form of electrical charges. In other technical words, the capacitor is known as the ' Condensor '.

What is a capacitor used for in a power supply?

Capacitors are widely used in electronic devices like smartphones, computers, televisions, and air conditioners to regulate power supply, filter noise from signals, and smooth out electrical currents. How do capacitors work in power supply applications?

How many power plants are in Costa Rica?

Costa Rica has 27 utility-scale power plants in operation, with a total capacity of 1968.4 MW. This data is a derivitive set of data gathered by source mentioned below. Global Energy Observatory/Google/KTH Royal Institute of Technology in Stockholm/Enipedia/World Resources Institute/database.earth

Is biomass a source of electricity in Costa Rica?

Traditional biomass – the burning of charcoal, crop waste, and other organic matter – is not included. This can be an important source in lower-income settings. Costa Rica: How much of the country's electricity comes from nuclear power? Nuclear power – alongside renewables – is a low-carbon source of electricity.

How is electricity used in Costa Rica?

Electricity can be generated in two main ways: by harnessing the heat from burning fuels or nuclear reactions in the form of steam (thermal power) or by capturing the energy of natural forces such as the sun, wind or moving water.

How much power does Reventazón provide in Costa Rica?

Reventazón Hydropower Plant in Siquirres with a generation capacity of 305.5 MW; this plant can supply power for 525,000 Costa Rican households. ICE provides power service for 94.4% of households, businesses, and industries in the country. This numbers are huge if we compare them with the average 14% percent coverage in 1949.

Does Costa Rica have low-carbon electricity?

Costa Rica has made remarkable strides in embracing low-carbon electricity, with over 94% of its electricity generated from clean sources. This exceptional achievement is primarily fueled by hydropower, which accounts for more than two-thirds of the electricity.

What is Costa Rica's energy policy?

Costa Rica's energy policy aims to move from a fossil fuels based energy system towards renewable energy sources and to expand its power generation capacity, replacing old power generating stations and developing new projects.

Why do batteries need foam?

Foams also act as thermal and electrical conductors, depending on their material and the compression amount within the battery. An extra layer can be added to the foam to make it more suitable for EMI shielding. Battery components need protection from electromagnetic waves due to their high frequencies and small size.

Why do EV batteries use foam?

Regarding EV battery production, foam ensures optimal performance and longevity. Foam is widely used as an insulation material within battery packs, protecting the cells from extreme temperatures and vibrations. This insulation not only enhances safety but also helps maximise energy efficiency.

What materials are used to make EV batteries?

One plug-in hybrid EV built in China is already using a thermoplastic polypropylene compound instead of aluminium for its battery case cover, providing savings in weight. Other EVs now in production around world are using several thermoplastic materials for components such as cell carriers and housings, battery modules and battery enclosures.

What type of foam is used for EV batteries?

Polyurethane foam, silicone foam, and Ethylene-Vinyl Acetate (EVA) foam are commonly used foams in EV battery manufacturing. Each type serves specific purposes, such as thermal, electrical, and shock absorption. What are some advancements in foam technology for EV batteries?

What is the best insulation for a battery pack?

Additionally, polyurethane foam provides structural support, reducing the risk of damage due to shocks or vibrations. Silicone foam, another popular choice, excels in maintaining electrical insulation. Creating a barrier against moisture and dust ingress ensures the battery pack's long-term reliability.

Why should you use a dielectric battery foam?

These foams are built with fire-resistant materials, ensuring if something such as thermal runaway occurs in the battery, the foam will be an essential factor in reducing the chances of spreading. Dielectric foams and insulation are critical components to protecting the battery cells as they expand and contract while in use.

What is a ceramic capacitor used for?

The easy-to-mold feature of ceramic material is the reason for the production of precise and larger forms of ceramic capacitors for high-voltage, high-frequency (RF), and power applications. Multilayer ceramic (MLCC) and ceramic disc capacitors are the two forms of ceramic capacitors used in modern electronics. Are ceramic capacitors AC or DC?

What are the different types of ceramic capacitors?

Ceramic capacitors are divided into two application classes: Class 1 ceramic capacitors offer high stability and low losses for resonant circuit applications. Class 2 ceramic capacitors offer high volumetric efficiency for buffer, by-pass, and coupling applications.

What is a ceramic disc capacitor?

Due to their compact size and cost-effectiveness, ceramic disc capacitors are used in various electronic circuits. They are suitable for filtering and coupling applications, offering reliability in a concise form factor. Multi-layer ceramic Capacitors (MLCCs) are a more advanced and widely used form of ceramic capacitor.

Are ceramic capacitors suitable for high voltage applications?

Ceramic capacitors, while versatile, are not suitable for applications requiring extremely high voltage or large capacitance values. Their physical construction and material limitations restrict their ability to handle very high energy storage needs or operate reliably in circuits with noteworthy voltage demands.

What type of dielectric does a capacitor use?

They use ceramic materials as the dielectric, which allows them to function efficiently across various electrical environments. These capacitors are categorized based on the type of ceramic dielectric they use, which determines their suitability for either low-frequency or high-frequency applications.

Can a ceramic capacitor be used in AC circuits?

Since a ceramic capacitor is a non-polarized capacitor, it can be easily used in AC circuits. Ceramic capacitors are produced with a capacitance ranging from 10pF to 100F with DC operating voltages ranging from 10 volts to 5000 volts. To reduce RF noise. These capacitors are connected in parallel with a DC motor to reduce interference and noise.

Can liquid-cooled battery thermal management systems be used in future lithium-ion batteries?

Based on our comprehensive review, we have outlined the prospective applications of optimized liquid-cooled Battery Thermal Management Systems (BTMS) in future lithium-ion batteries. This encompasses advancements in cooling liquid selection, system design, and integration of novel materials and technologies.

What is a liquid cooled battery system?

Immersed liquid-cooled battery system that provides higher cooling efficiency and simplifies battery manufacturing compared to conventional liquid cooling methods. The system involves enclosing multiple battery cells in a sealed box and immersing them directly in a cooling medium.

Do lithium ion batteries need a cooling system?

To ensure the safety and service life of the lithium-ion battery system, it is necessary to develop a high-efficiency liquid cooling system that maintains the battery's temperature within an appropriate range. 2. Why do lithium-ion batteries fear low and high temperatures?

Are lithium-ion batteries temperature sensitive?

However, lithium-ion batteries are temperature-sensitive, and a battery thermal management system (BTMS) is an essential component of commercial lithium-ion battery energy storage systems. Liquid cooling, due to its high thermal conductivity, is widely used in battery thermal management systems.

Are lithium-ion batteries a new type of energy storage device?

Under this trend, lithium-ion batteries, as a new type of energy storage device, are attracting more and more attention and are widely used due to their many significant advantages.

What is an immersion cooling system for lithium ion batteries?

An immersion cooling system for lithium-ion battery packs that uses glycol-based coolant and a sealed case to cool the batteries uniformly and efficiently. The battery pack has cells held by cell holders inside a sealed case filled with coolant. The coolant surrounds the cells and circulates to extract heat.

What type of batteries are used in electric vehicles?

There are four main types of batteries that are used in electric vehicles, namely ultracapacitors / supercapacitors, lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries. In the ultracapacitor polarized liquid is stored between an electrode and an electrocyte.

Which battery is best for electric cars?

Li-ion batteries are the preferred choice for modern electric cars due to their advanced rechargeable battery technology. However, they are relatively expensive to produce compared to other battery types. Nickel-Metal Hydride (NiMH) batteries gained commercial use in the late 1980s.

What are electric car batteries used for?

Beyond their 1500 charges and useful lifespan in a vehicle, electric vehicle batteries can be used for energy storage where performance isn't so important. For example, they can be used in motorhomes to store solar power, or as a backup for a power cut in our homes. Why are electric car batteries so expensive?

What is an electric vehicle battery?

An electric vehicle battery is a rechargeable battery used to power the electric motors of a battery electric vehicle (BEV) or hybrid electric vehicle (HEV). They are typically lithium-ion batteries that are designed for high power-to-weight ratio and energy density.

Which battery is best for an EV?

NiMH batteries are known for their recyclability and are proven to be a suitable option for EVs, with an average battery life of 5-7 years. Lead-Acid batteries, formulated in 1859, are the oldest type of battery still in use. They are known for their low cost but have a shorter lifespan of around 3 years.

What type of battery should I use?

Nowadays, Lithium-ion batteries are by far the most widely used, this is due to them recharging quickly, being robust against temperature changes, and being able to maintain power for long durations, with bursts of very high power.

What is energy storage?

Energy storage is defined as the capture of intermittently produced energy for future use. In this way it can be made available for use 24 hours a day, and not just, for example, when the Sun is shining, and the wind is blowing. It can also protect users from potential interruptions that could threaten the energy supply.

How do energy storage technologies work?

Energy storage technologies work by converting renewable energy to and from another form of energy. These are some of the different technologies used to store electrical energy that's produced from renewable sources: 1. Pumped hydroelectricity energy storage

How do we store energy to keep our lives powered?

Here's a look at how we store energy to keep our lives powered. Battery energy storage: Think of battery storage systems as your ultimate energy ally. They can be charged by electricity from renewable energy, like wind and solar, storing it away for cloudy days.

Should energy storage be a solution?

Energy storage offers a solution. Capturing and storing excess renewable energy when it is plentiful and releasing it as needed could solve both problems. On sunny and windy days, renewable energy sources can supply energy storage systems, which can be deployed at night, on cloudy days, or when there's less wind.

What is chemical storage?

Chemical storage refers mainly to hydrogen, which can be produced from renewable energy, but also from nuclear power, and fossil fuels. Converting energy from those sources into chemical forms creates high-energy density fuel.

What is battery energy storage & how does it work?

Battery energy storage: Think of battery storage systems as your ultimate energy ally. They can be charged by electricity from renewable energy, like wind and solar, storing it away for cloudy days. When demand peaks – like during that evening dinner rush – they spring into action, releasing energy to keep our homes and businesses buzzing.

What is the voltage of a lead acid battery?

The 24V lead-acid battery state of charge voltage ranges from 25.46V (100% capacity) to 22.72V (0% capacity). 48V Lead-Acid Battery Voltage Chart (4th Chart). The 48V lead-acid battery state of charge voltage ranges from 50.92 (100% capacity) to 45.44V (0% capacity). Lead acid battery is comprised of lead oxide (PbO2) cathode and lead (Pb) anode.

What is a 6V lead acid battery?

Here we see that a 6V lead acid battery has an actual voltage of 6V at a charge between 40% and 50% (43%, to be exact). The voltage spans from 6.37V at 100% charge to 5.71V at 0% charge. It is also important to note that lead batteries have a depth of discharge (DoD) close to about 50%.

What is a 12 volt lead acid battery?

For example, a 12-volt lead acid battery has a nominal voltage of 12 volts. However, the actual voltage of a lead acid battery can vary depending on its state of charge, temperature, and other factors. The state of charge (SOC) of a lead acid battery refers to the amount of charge remaining in the battery.

What is a 48V lead acid battery?

The 48V lead-acid battery state of charge voltage ranges from 50.92 (100% capacity) to 45.44V (0% capacity). Lead acid battery is comprised of lead oxide (PbO2) cathode and lead (Pb) anode. The medium of exchange is sulphuric acid. Most common example of lead-acid batteries are car batteries.

What is the float voltage of a 12V lead acid battery?

Meanwhile, the float voltage of a sealed 12V lead acid battery is usually 13.6 volts ± 0.2 volts. The float voltage of a flooded 12V lead acid battery is usually 13.5 volts. It is important to choose a battery with a voltage range that is appropriate for the application in which it will be used to ensure optimal performance and longevity.

What is the state of charge of a lead acid battery?

The state of charge (SOC) of a lead acid battery refers to the amount of charge remaining in the battery. The SOC of a lead acid battery can be determined by measuring its voltage using a multimeter or other device. As the battery discharges, its voltage level decreases. Conversely, as the battery is charged, its voltage level increases.

Who provides UL certification services against UL 9540 requirements?

UL Solutions provides certification services against the requirements of UL 9540 for companies looking to ensure that their energy storage systems are compliant with the standard's requirements. TÜV SÜD provides certification and energy storage testing services against the requirements in UL 9540 and related standards (e.g. UL 1973).

Do energy storage systems need to be listed in ul 9540?

According to UL Solutions, installation codes such as the International Residential Code and the NFPA 855 require energy storage systems to be listed according to the requirements in UL 9540.

Does ul test large energy storage systems?

Research offerings include: UL can test your large energy storage systems (ESS) based on UL 9540 and provide ESS certification to help identify the safety and performance of your system.

What is the energy storage standard?

The Standard covers a comprehensive review of energy storage systems, covering charging and discharging, protection, control, communication between devices, fluids movement and other aspects.

How do I test a solar cell?

You can effortlessly test the efficiency of your solar cell device using the Ossila Solar Cell Testing Kit — which combines our solar simulator with our source measure unit and test board. There are several methods used to characterize solar cells. The most common and essential measurement you can take is the current-voltage (I-V) sweep.

How often should a solar PV system be tested?

A solar photovoltaic (PV) system is required to be rigorously tested as part of the commissioning process and periodically throughout its subsequent lifespan. This is to test both the quality of the installation and the quality of its performance.

Can you test a solar cell using sunlight?

Of coruse, you could use actual sunlight, but this would introduce an uncontrollable variable. To test solar cells reliably, you need to maintain controlled conditions within your lab — and this is impossible to do while allowing direct, unfiltered sunlight onto your testing equipment.

Can solar cells be tested reliably?

To test solar cells reliably, you need to maintain controlled conditions within your lab — and this is impossible to do while allowing direct, unfiltered sunlight onto your testing equipment. Additionally, many potential solar cell materials are unable to withstand weathering effects during the early stages of development.

Why do solar panels need to be tested?

So continuously verifying system performance is essential. But the priority is safety, and because the panels are connected to the electricity grid and generate electricity themselves, maintaining the safety of the system is also essential and strictly regulated. What are the two types of solar PV testing?

Why is a four-wire measurement important in a solar cell test?

The relationship between the two might need to be adjusted for the resistances of the wires, as in the example we described above, but overall the four-wire measurement is a way to accurately get current and voltage information of a device. A Kelvin or four-wire measurement is essential to getting accurate IV data while testing a solar cell.

Why do lead acid batteries have more negative plates than positive?

Lead acid batteries have more negative plates than positive due to the way they are made. The negative plates are made of lead oxide, while the positive plates are made of pure lead. The lead oxide is heavier than the lead, so it takes up more space on the plate. That's why there are more negative plates in a lead acid battery.

What is the difference between battery acid and battery positive plate?

Battery Acid: The acid is a high-purity solution of sulfuric acid and water. Battery Negative Plate: The negative plate contains a metal grid with spongy lead (Pb 2+) active material. Battery Positive Plate: The positive plate contains a metal grid with lead dioxide (PbO 2) active material.

What is the construction of a lead acid battery cell?

The construction of a lead acid battery cell is as shown in Fig. 1. It consists of the following parts : Anode or positive terminal (or plate). Cathode or negative terminal (or plate). Electrolyte. Separators. Anode or positive terminal (or plate): The positive plates are also called as anode. The material used for it is lead peroxide (PbO 2).

What is the difference between positive and negative plates on a battery?

If you're talking about a car battery, the positive plate is usually more in “battery” than the negative plate. The negative plate typically has more sulfate build-up on it, which can reduce its effectiveness. How Many Negative Plates Does a Lead Acid Battery Have? A lead acid battery has two negative plates.

What are the different types of lead acid batteries?

The most common lead acid battery is the flooded lead acid battery, which has two cells with three compartments each. The center compartment is the neutral plate and the outer compartments are the positive and negative plates. The positive plate contains a larger surface area of lead oxide than the negative plate, so it needs more space.

What are the positive and negative sides of a battery called?

The positive and negative sides of a battery are also commonly referred to as the poles. The positive side is often marked with a plus (+) sign or a red color, while the negative side is marked with a minus (-) sign or a black color.

Can micro inverters be used in off grid solar power systems?

With the growth in the use of micro inverters, I'm starting to get more and more emails asking: can micro inverters be used in off grid (or hybrid) solar power systems? The short answer is yes they can! In fact a number of micro inverter battery backup systems are already operating here and abroad.

Can You power micro inverters with batteries instead of solar panels?

To answer your question. Yes, you can power micro inverters with batteries instead of solar panels. I have a IQ7X powered off my 60 volt battery bank to take out my base load that doesn't go through my hybrid inverter. It flashes orange (orange means AC good but not connected to Envoy). It makes a constant 312 watts.

Are microinverters a good option for energy storage?

Until recently, microinverters were not a great option for those looking at energy storage. However, this has now changed with the advanced Enphase IQ8 energy storage system and intelligent controllers designed to seamlessly integrate solar, batteries and even backup generators to provide partial and full off-grid functionality.

Does a micro inverter need a battery?

The micro inverter is designed to be grid tied. It needs to be connected to the grid in order to operate. It won't work. I think they are referring to using the battery on the input side of the microinverter. But I can't say I fully understand. Most batteries would vaporize the circuitry in a micro inverter...

Can a solar inverter be used with a lithium battery?

Integrating a solar inverter with a lithium battery can take your renewable energy setup to the next level. This combination allows for better energy storage, improved efficiency, and greater resilience during power outages. LiFePO4 batteries are particularly well-suited for solar applications because their thermal stability and long cycle life.

Can a micro inverter battery backup system work?

The short answer is yes they can! In fact a number of micro inverter battery backup systems are already operating here and abroad. The longer answer gets a bit technical – but I'll try to keep it as simple as I can!

What are battery cells & modules & packs?

Battery cells, modules, and packs are different stages in battery applications. In the battery pack, to safely and effectively manage hundreds of single battery cells, the cells are not randomly placed in the power battery shell but orderly according to modules and packages. The smallest unit is the battery cell. A group of cells can form a module.

What is a cell in a battery pack?

A cell in a battery pack refers to the individual battery unit that stores and releases electrical energy. These cells are typically cylindrical or prismatic in shape. They are connected in series or parallel to achieve the desired voltage and capacity for the pack. What is a modular battery pack?

How a battery pack works?

In the battery pack, to safely and effectively manage hundreds of single battery cells, the cells are not randomly placed in the power battery shell but orderly according to modules and packages. The smallest unit is the battery cell. A group of cells can form a module. Several modules can be combined into a package.

What is a battery pack?

A battery pack is an integral unit assembled from multiple battery modules. It is used to store and provide electrical energy. It is a higher-level component in the battery system. 1. Battery pack structure It usually consists of several battery modules, connectors, battery BMS, cooling system, electrical interface, and casing. 2.

What is the difference between battery module and battery pack?

The primary distinction between a battery module and a battery pack lies in their scale and functionality. A battery module is a smaller unit that contains a group of interconnected cells, often with its own BMS. It is a component within a larger battery pack, which consists of multiple modules arranged in a specific configuration.

What is the total voltage of a battery pack?

When multiple cells are connected in series within a battery pack, the total voltage of the pack is the sum of the individual cell voltages. What is a Lithium-ion Battery Module? A lithium-ion battery module is a group of interconnected battery cells that work together to provide a higher level of voltage and capacity.

What materials are used in a battery?

Lithium Metal: Known for its high energy density, but it's essential to manage dendrite formation. Graphite: Used in many traditional batteries, it can also work well in some solid-state designs. The choice of cathode materials influences battery capacity and stability.

What are solid state batteries made of?

Solid state batteries are primarily composed of solid electrolytes (like lithium phosphorus oxynitride), anodes (often lithium metal or graphite), and cathodes (lithium metal oxides such as lithium cobalt oxide and lithium iron phosphate). The choice of these materials affects the battery's energy output, safety, and overall performance.

What is inside a battery?

What's inside a battery? A battery consists of three major components – the two electrodes and the electrolyte. But the commercial batteries consist of a few more components that make them reliable and easy to use. In simple words, the battery produces electricity when the two electrodes immersed in the electrolyte react together.

What materials are used in lithium ion battery production?

The main raw materials used in lithium-ion battery production include: Lithium Source: Extracted from lithium-rich minerals such as spodumene, petalite, and lepidolite, as well as from lithium-rich brine sources. Role: Acts as the primary charge carrier in the battery, enabling the flow of ions between the anode and cathode. Cobalt

What raw materials are used in solid-state battery production?

The raw materials used in solid-state battery production include: Lithium Source: Extracted from lithium-rich minerals and brine sources. Role: Acts as the charge carrier, facilitating ion flow between the solid-state electrolyte and the electrodes. Solid Electrolytes (Ceramic, Glass, or Polymer-Based)

Which cathode material is best for a battery?

The choice of cathode materials influences battery capacity and stability. Common materials are: Lithium Cobalt Oxide (LCO): Offers high capacity but has stability issues. Lithium Iron Phosphate (LFP): Known for safety and thermal stability, making it a favorable option.

What is a solar panel monitoring system?

Solar panel monitoring systems keep tabs on your system and its output. As a system owner, you'll find that the monitoring system provides production data that you can access from any internet-connected device like a PC, laptop or mobile device. Each solar monitoring system will work differently, but the objective is the same.

How does solar panel monitoring work?

Solar panel monitoring works by collecting and analyzing production data related to the performance and output of solar panels. There are two main types of monitoring: built-in inverter monitoring and third-party monitoring. Built-In Inverter Monitoring Vs. Third-Party Monitoring

Why do you need a solar panel monitoring system?

By continuously monitoring your solar panel system's performance, you can identify and fix any issues that may affect energy output. The monitoring systems provide detailed insights into the overall health and performance of the solar array, allowing for early detection of potential problems like shading or equipment malfunctions.

How do I monitor solar panel output?

Legacy solar products typically do not have monitoring capabilities, but if you have an older system, there are still ways you can monitor solar panel output. You can add a third-party monitoring system that typically uses current transformers (CTs) to measure the system production. Total Solar Power Production Vs. Module-Level Monitoring

How do I choose the best solar panel monitoring system?

Determining the best solar panel monitoring system is subjective and depends on specific needs, preferences, and the characteristics of the solar installation. Enphase Enlighten is a web-based monitoring system that allows you to track your solar system's performance in real time.

What is total solar power production monitoring?

Solar monitoring systems can track the total solar power production or provide module-level monitoring. Total solar power production monitoring offers an overview of the entire system's performance, combining the data from all the panels. It provides a holistic view of the system's efficiency and energy generation.

How long does a lead acid battery take to charge?

Last example, a lead acid battery with a C10 (or C/10) rated capacity of 3000 Ah should be charge or discharge in 10 hours with a current charge or discharge of 300 A. C-rate is an important data for a battery because for most of batteries the energy stored or available depends on the speed of the charge or discharge current.

How does a lead acid battery work?

A typical lead–acid battery contains a mixture with varying concentrations of water and acid. Sulfuric acid has a higher density than water, which causes the acid formed at the plates during charging to flow downward and collect at the bottom of the battery.

What is a good coloumbic efficiency for a lead acid battery?

Lead acid batteries typically have coloumbic efficiencies of 85% and energy efficiencies in the order of 70%. Depending on which one of the above problems is of most concern for a particular application, appropriate modifications to the basic battery configuration improve battery performance.

What is a lead-acid battery?

The lead–acid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston Planté. It is the first type of rechargeable battery ever created. Compared to modern rechargeable batteries, lead–acid batteries have relatively low energy density. Despite this, they are able to supply high surge currents.

How do you calculate kWh in a lead-acid battery?

Lead-acid batteries, common in various applications, have their unique kWh calculation methods. The fundamental approach involves understanding the nominal voltage and capacity of the battery. The formula for lead-acid battery kWh is: markdown kWh = Voltage x Capacity (in Ah)

Is the capacity of a lead-acid battery a fixed quantity?

The capacity of a lead–acid battery is not a fixed quantity but varies according to how quickly it is discharged. The empirical relationship between discharge rate and capacity is known as Peukert's law.