Testing High Voltage Ev Components Assembly

What is a lithium ion battery charge voltage?

Charging Voltage: This is the voltage applied to charge the battery, typically 4.2V per cell for most lithium-ion batteries. The relationship between voltage and charge is at the heart of lithium-ion battery operation. As the battery discharges, its voltage gradually decreases.

What is the ideal voltage for a lithium ion battery?

The ideal voltage for a lithium-ion battery depends on its state of charge and specific chemistry. For a typical lithium-ion cell, the ideal voltage when fully charged is about 4.2V. During use, the ideal operating voltage is usually between 3.6V and 3.7V. What voltage is 50% for a lithium battery?

What is a safety circuit in a Li-ion battery pack?

Fig. 1 is a block diagram of circuitry in a typical Li-ion battery pack. It shows an example of a safety protection circuit for the Li-ion cells and a gas gauge (capacity measuring device). The safety circuitry includes a Li-ion protector that controls back-to-back FET switches. These switches can be

What is a cut-off voltage for a lithium ion battery?

Cut-off Voltage: This is the minimum voltage allowed during discharge, usually around 2.5V to 3.0V per cell. Going below this can damage the battery. Charging Voltage: This is the voltage applied to charge the battery, typically 4.2V per cell for most lithium-ion batteries.

Why is voltage important in a lithium ion battery?

In simple terms, voltage is the electrical pressure that pushes electrons through a circuit. For lithium-ion batteries, voltage is crucial because it directly relates to how much energy the battery can store and deliver. Think of voltage like water pressure in a hose. The higher the pressure, the more water (or in our case, energy) can flow.

What is a normal battery voltage?

Nominal Voltage: This is the battery's “advertised” voltage. For a single lithium-ion cell, it's typically 3.6V or 3.7V. Open Circuit Voltage: This is the voltage when the battery isn't connected to anything. It's usually around 3.6V to 3.7V for a fully charged cell. Working Voltage: This is the actual voltage when the battery is in use.

How does energy storage work at high voltage?

considerably depending on specific system requirements. Energy storage at high voltage normally requires the use of electrolytic capacitors for which th ESR varies considerably, particularly over temperature. These variables need to be conside

What is high voltage energy storage (hves)?

high-voltage-energy storage (HVES) stores the energy ona capacitor at a higher voltage and then transfers that energy to the power b s during the dropout (see Fig. 3). This allows a smallercapacitor to be used because a arge percentage of the energy stor d choic 100 80 63 50 35 25 16 10 Cap Voltage Rating (V)Fig. 4. PCB energy density with V2

Which electrolytic capacitor is best for energy storage?

r losses with PHT4NQ10T (Q ),SUD15N15-95 (QD) and ES3C.operate at 50 V or higher. This leaves the aluminium electrolytic capacitor as the f rst choice for energy storage, based on volume and cost. On the bus side, depending on the operating voltage, additional selection includes tantalu

What is a L VBUS level with and without an energy-storage system?

l Vbus levels with and without an energy-storage system. For example, in telecommunications applications, the PICMG® AdvancedTCA® specification requires continuous operation in the presence of a 5-ms,0-V input-voltage transient (the total d rat

How many volts does a solar cell produce?

Most common solar panels include 32 cells, 36 cells, 48 cells, 60 cells, 72 cells, or 96 cells. Each PV cell produces anywhere between 0.5V and 0.6V, according to Wikipedia; this is known as Open-Circuit Voltage or V OC for short. To be more accurate, a typical open circuit voltage of a solar cell is 0.58 volts (at 77°F or 25°C).

What is the voltage output of a solar panel?

The voltage output of a single solar cell under Standard Test Conditions (STC) is approximately 0.5 volts. To increase the overall voltage, these cells are connected in series within a solar panel. Solar panels generate Direct Current (DC) power, whereas most household appliances operate on Alternating Current (AC) power.

What is a typical open circuit voltage of a solar panel?

To be more accurate, a typical open circuit voltage of a solar cell is 0.58 volts (at 77°F or 25°C). All the PV cells in all solar panels have the same 0.58V voltage. Because we connect them in series, the total output voltage is the sum of the voltages of individual PV cells. Within the solar panel, the PV cells are wired in series.

How many volts does a solar panel have?

Generally, solar panels intended for residential or commercial installations typically have voltage outputs ranging from 12 volts to 48 volts. These panels are designed to meet the voltage requirements of common off-grid and grid-tied systems, ensuring compatibility with standard electrical components and appliances.

How many volts is a 36 cell solar panel?

36-Cell Solar Panel Output Voltage = 36 × 0.58V = 20.88V What is especially confusing, however, is that this 36-cell solar panel will usually have a nominal voltage rating of 12V. Despite the output voltage being 18.56 volts, we still consider this a 12-volt solar panel.

What is the maximum voltage of a solar panel?

: The maximum voltage of a solar panel is the panel's open circuit voltage (VOC) plus the voltage increase due to the temperature coefficient. What Are Some Solar Cells Examples?:

How to analyze voltage and current in a battery system?

Various measurement techniques and tools can be used for analyzing voltage and current in battery systems. These include multimeters, power analyzers, and data loggers. Each method has its advantages and limitations, and the choice depends on the specific application and requirements.

What is a battery current control system?

The current control system is commanded by a superimposed battery voltage controller aimed at bringing the battery terminal voltage to the fully-charged state while also limiting the maximum battery charging current.

How many volts does a battery have?

Battery A has a voltage of 6 volts and a current of 2 amps, while Battery B also has a voltage of 6 volts and a current of 2 amps. When connected in series, the total voltage would be 12 volts, and the total current would remain at 2 amps. Advantages and Disadvantages of Series Connections

Why is balancing voltage important in a battery connection?

In series connections, maintaining balanced voltages across all batteries is important to prevent overcharging or undercharging. In parallel connections, equalizing currents among the batteries is necessary to prevent imbalances and avoid premature failure of individual batteries. Importance of Proper Battery Maintenance and Monitoring

How do you analyze a complex battery configuration?

Analysis of Voltage and Current Behavior in Complex Battery Configurations Complex battery configurations require careful analysis of voltage and current behavior. This includes considering the total voltage and total current, as well as understanding how series and parallel connections impact the overall performance of the system.

What happens if a battery is connected in series?

When batteries are connected in series, the voltages of the individual batteries add up, resulting in a higher overall voltage. For example, if two 6-volt batteries are connected in series, the total voltage would be 12 volts. Effects of Series Connections on Current In a series connection, the current remains constant throughout the batteries.

What is a cut-off voltage for a lithium ion battery?

Cut-off Voltage: This is the minimum voltage allowed during discharge, usually around 2.5V to 3.0V per cell. Going below this can damage the battery. Charging Voltage: This is the voltage applied to charge the battery, typically 4.2V per cell for most lithium-ion batteries.

What is a lithium ion battery charging cut-off current?

This point is commonly referred to as the “charging cut-off current.” II. Key Parameters in Lithium-ion Battery Charging Several crucial parameters are involved in lithium-ion battery charging: Charging Voltage: This is the voltage applied to the battery during the charging process.

What is the difference between charging voltage and cut-off voltage?

Charging Voltage: This is the voltage applied to the battery during the charging process. For lithium-ion batteries, the charging voltage typically peaks at around 4.2V. Cut-off Voltage: The cut-off voltage is the minimum voltage at which the battery is allowed to discharge during charging. Going below this voltage can damage the battery.

What happens if a lithium battery charger fails?

The voltage output of the charger must meet the voltage requirements of the lithium battery pack to ensure safe and efficient charging. Using a charger with incorrect voltage output will result in overcharging or undercharging, which may damage the battery and shorten its life.

What parameters are involved in lithium-ion battery charging?

Several crucial parameters are involved in lithium-ion battery charging: Charging Voltage: This is the voltage applied to the battery during the charging process. For lithium-ion batteries, the charging voltage typically peaks at around 4.2V.

What happens if you charge a lithium ion battery below voltage?

Going below this voltage can damage the battery. Charging Stages: Lithium-ion battery charging involves four stages: trickle charging (low-voltage pre-charging), constant current charging, constant voltage charging, and charging termination. Charging Current: This parameter represents the current delivered to the battery during charging.

What voltage should a lithium battery be?

It is recommended to maintain the battery within the voltage range of 3.0V to 4.2V per cell to ensure optimal performance and avoid permanent damage to the cells. Lithium battery voltage is essential for understanding how these batteries operate.

What is the nominal voltage of a lithium ion battery?

The nominal voltage of lithium-ion cells is typically around 3.6V to 3.7V. This is the average voltage when the battery is in a stable state, neither charging nor discharging. State of Charge (SOC) is crucial for monitoring battery health. For best performance, lithium batteries should be within specific voltage ranges:

What is a lithium ion battery charge voltage?

Charging Voltage: This is the voltage applied to charge the battery, typically 4.2V per cell for most lithium-ion batteries. The relationship between voltage and charge is at the heart of lithium-ion battery operation. As the battery discharges, its voltage gradually decreases.

What should you know about lithium ion batteries?

The most important key parameter you should know in lithium-ion batteries is the nominal voltage. The standard operating voltage of the lithium-ion battery system is called the nominal voltage. For lithium-ion batteries, the nominal voltage is approximately 3.7-volt per cell which is the average voltage during the discharge cycle.

What is a lithium battery voltage chart?

A lithium battery voltage chart is an essential tool for understanding the relationship between a battery's charge level and its voltage. The chart displays the potential difference between the two poles of the battery, helping users determine the state of charge (SoC).

What is a cut-off voltage for a lithium ion battery?

Cut-off Voltage: This is the minimum voltage allowed during discharge, usually around 2.5V to 3.0V per cell. Going below this can damage the battery. Charging Voltage: This is the voltage applied to charge the battery, typically 4.2V per cell for most lithium-ion batteries.

How a distributed energy storage system is connected to a photovoltaic system?

The distributed energy storage and photovoltaic are connected at the same node. The total load of the system and the active output of photovoltaic are shown in Figure 8. Figure 6. Schematic of distribution network structure and distribution of photovoltaic-storage system. Figure 7. Installed capacity of PV vs. peak load power. Figure 8.

Is distributed photovoltaic a fixed power source?

The above methods have mainly focused on consideration of distributed photovoltaic as a fixed power source, and the uncertainty has not been fully considered. In response to this, reference proposed a dynamic voltage control method for a distribution network based on distributed model predictive control.

Does PV access affect distribution network voltage?

First, the impact mechanism of PV access on the distribution network voltage needs to be further investigated; second, the regulation costs of photovoltaic and energy storage are different, and the effects of the control by different node powers on node voltage are also different.

What is the voltage control strategy of a distribution network containing PV?

Therefore, it is of great significance to study the voltage control strategy of a distribution network containing PV. The most traditional reactive power voltage control in distribution networks is to use reactive power resources such as transformer taps and capacitor banks [6, 7] for regulation.

Where is the feeder current distribution when the photovoltaic-storage system discharges?

where is the feeder current distribution when the photovoltaic-storage system discharges during peak period, and x1 is the ratio of the distance between photovoltaic-storage system location and the start of the feeder line to the total length of the feeder line. Figure 4. Current distribution during discharge of photovoltaic-storage system.

How much voltage does a solar farm need?

If the nearest transmission line to your property has a voltage of, say, 115 kV (115,000 volts), the output voltage from the solar farm needs to “step up” to 115 kV to feed power into it. Likewise, the power that line carries to a neighborhood 50 miles away eventually needs to “step down” in voltage so that homes can use it.

How many batteries are in a series lithium battery pack?

Batteries 1–4 in the series lithium battery pack correspond to the four lithium batteries shown in Figure 8. The charged charge SOC, voltage and current collection in the battery information acquisition board correspond to SOC, voltage and current modules shown in Figure 8.

What is the maximum voltage difference between battery pack cells?

The equalization voltage threshold set was 10 mV. After active equalization, the maximum voltage difference between the battery pack cells was reduced to 9 mV, a relative decrease of 96.2%, which met the requirements of the equalization study.

What happens if a lithium battery is overcharged?

When the terminal voltage of a LIB increases from the lower limit cutoff voltage to the rated voltage, the operating voltage will plummet, resulting in battery overdischarge; when the SOC is high, the lithium battery increases from the rated voltage to the upper cutoff voltage, resulting in overcharge of a battery with a high charge.

How accurate is a LiFePO4 battery pack?

Good measurement accuracy is always required, especially the cell voltage, pack current, and cell temperature. Precision is necessary for accurate protections and battery pack state of charge (SoC) calculations. This is especially true for LiFePO4 battery pack applications because of the flat voltage.

What is lithium battery pack balancing control?

The lithium battery pack balancing control process needs to detect the charging and discharging state of each individual battery. Figure 11 is the lithium battery balancing charging and discharging system test platform, where Figure 11 (a) is the bidirectional active balancing control integrated circuit designed in this paper.

Why should a battery pack be monitored?

Therefore the pack current, cell temperature, and each cell voltage should be monitored timely in case of some unusual situations. The battery pack must be protected against all these situations. Good measurement accuracy is always required, especially the cell voltage, pack current, and cell temperature.

How to diagnose a battery overvoltage & undervoltage fault?

Threshold-based fault diagnosis methods The battery overvoltage or undervoltage fault can be diagnosed using the threshold-based method. The voltage information collected by the voltage sensor is compared with the preset threshold. When the battery voltage exceeds the threshold, the fault occurrence state and fault occurrence time are defined .

How effective is battery management & fault detection in electric vehicles?

The robustness of the proposed method across varying conditions highlights its potential for effective battery management and fault detection in electric vehicles, ensuring better health monitoring and predictive maintenance. This contributes to extending battery lifespan and enhancing overall vehicle performance.

Can a Bayesian optimized neural network detect voltage faults in energy storage batteries?

Accurately detecting voltage faults is essential for ensuring the safe and stable operation of energy storage power station systems. To swiftly identify operational faults in energy storage batteries, this study introduces a voltage anomaly prediction method based on a Bayesian optimized (BO)-Informer neural network.

Why do EV batteries have voltage deviations?

Voltage deviations are a primary indicator of battery faults and can arise from various causes, including internal short circuits, external short circuits, and capacity degradation 8. These deviations are critical for timely fault detection and prevention, thus ensuring the reliability and safety of EV batteries.

Can segmented regression be used to detect battery faults?

This paper proposes segmented regression to better capture these distinct characteristics for accurate fault detection. The focus is on detecting voltage deviations caused by internal short circuits, external short circuits, and capacity degradation, which are primary indicators of battery faults.

Can a battery model be used to detect voltage anomalies?

Future studies can investigate extensions of the model to diagnose specific types of voltage anomalies, enhancing fault detection capabilities. Additionally, exploring the model's adaptability for voltage prediction in other battery systems can also be considered.

What are the performance requirements of lithium iron phosphate batteries?

Lithium iron phosphate batteries, which use LiFePO4 as the positive electrode, meet the following performance requirements, especially during high discharge rates (5-10C discharge): stable discharge voltage, safety (non-burning, non-explosive), and long life (cycle times).

What is the nominal voltage of lithium iron phosphate battery?

The nominal voltage of the single lithium iron phosphate battery is 3.2V, the charging voltage is 3.6V, and the discharge cut-off voltage is 2.0V. Lithium iron phosphate battery packs reach the required voltage by the equipment through battery cell series connection. The battery voltage is equal to N* series connection number.

What is the difference between lithium ion and lithium iron phosphate batteries?

Both battery charging methods are constant current and constant voltage (CCCV), but the constant voltage point is different. The nominal voltage of lithium iron phosphate battery is 3.2V and the charging cut-off voltage is 3.6V. Conventional lithium ion batteries have a nominal voltage of 3.6V and a cut-off voltage of 4.2V.

How to test a LiFePO4 battery?

Multimeter: This tool will allow you to measure the voltage of your LiFePO4 cells. Battery Capacity Tester: This device will allow you to test the capacity of your LiFePO4 cells. Safety Equipment: When working with batteries, it's important to take safety precautions. Wear gloves, eye protection, and a respirator if necessary.

What equipment do I need for a LiFePO4 battery test?

Here's a list of what you'll need: Multimeter: This tool will allow you to measure the voltage of your LiFePO4 cells. Battery Capacity Tester: This device will allow you to test the capacity of your LiFePO4 cells. Safety Equipment: When working with batteries, it's important to take safety precautions.

What is the capacity of lithium iron phosphate power lithium-ion batteries?

The capacity of a lithium iron phosphate power lithium-ion battery can be divided into three categories: small-scale, which is a few to a few milliamperes; medium-scale, tens of milliamp-hours; and large-scale, hundreds of milliamp-hours. The capacity of individual batteries can vary greatly.

Does battery voltage change during lifecycle?

Yes, the battery voltage changes throughout its lifecycle, most notably during charging and discharging. During Discharge: As a battery discharges, its voltage gradually decreases.

How do I know if I need a voltage change?

Lower voltages can cause sluggish operation. Signs of needed voltage change include reduced battery life and slow charging. Understanding battery voltage empowers you to make informed decisions, ensuring optimal device performance and longevity. Keep an eye on signs indicating a need for voltage change to keep your electronics running smoothly.

How does voltage affect battery capacity?

Generally, a battery's capacity is directly proportional to its voltage. As the voltage increases, the capacity also increases, allowing the battery to store more energy. This is why lithium-ion batteries with higher voltage typically offer longer usage times. 2. The Relationship Between Voltage and Discharge Curve

What happens when a battery is discharged?

During Discharge: As a battery discharges, its voltage gradually decreases. For example, a lithium-ion battery will drop from around 4.2V (fully charged) down to 3.7V, then further to 3.0V (cut-off voltage), after which the device will stop working. During Charging: When charging, the battery voltage increases.

How does battery voltage affect battery life?

Optimal charging practices and usage extend battery life. Advancements in technology could lead to more efficient batteries. At its core, battery voltage refers to the electric potential difference between the positive and negative terminals of a battery. This difference is what drives electric current through a circuit, powering our devices.

What is battery voltage?

At its most basic, battery voltage is a measure of the electrical potential difference between the two terminals of a battery—the positive terminal and the negative terminal. It's this difference that pushes the flow of electrons through a circuit, enabling the battery to power your devices.

What causes lithium batteries to go in protection mode?

Connect with Darren on LinkedIn. The BMS causes lithium batteries to go in to protection mode when overheating, high currents, and high or low voltage. Learn more on how to prevent those and recharge your battery

How to protect a lithium battery?

Use special lithium battery protection chip, when the battery voltage reaches the upper limit or lower limit, the control switch device MOS tube cut off the charging circuit or discharging circuit, to achieve the purpose of protecting the battery pack. Characteristics: 1. Only over-charge and over-discharge protection can be realized.

What are the benefits of lithium battery protection boards?

In addition to basic overcharge, over-discharge, over-current, and over-temperature protection, future lithium battery protection boards will also integrate more functions, such as power estimation, balanced charging, etc. These features will help improve the efficiency and management of lithium batteries. 3. Intelligent

What is lithium battery overcharge protection?

Lithium battery overcharge protection allows the battery to shut off and the current goes away. The battery will cool down but if it goes back into protection mode after the battery turns back on you may have to reduce your load, reduce the charge rate, or improve the ventilation around the batteries. Next is current protection.

What should you know about lithium ion batteries?

The most important key parameter you should know in lithium-ion batteries is the nominal voltage. The standard operating voltage of the lithium-ion battery system is called the nominal voltage. For lithium-ion batteries, the nominal voltage is approximately 3.7-volt per cell which is the average voltage during the discharge cycle.

What is a safe voltage for a lithium ion battery?

Lithium-ion batteries function within a certain range at which their voltage operates optimally and safely. The highest range where the fully charged voltage of a lithium-ion battery is approximately 4.2V per cell. The lowest range which is the minimum safe voltage for lithium-ion batteries is approximately 3.0V per cell.

How do you measure a solar panel voltage?

Measure the open-circuit voltage: Place the solar panel in a well-lit area under the sun and measure the voltage across the solar panel's positive and negative cables using the Multimeter. This voltage is called the open-circuit voltage (Voc), which is the maximum voltage the solar panel can produce under no-load conditions.

How do you test a solar panel?

To quickly test your solar panel, first, check the panel's Voc (open-circuit voltage) and Isc (short-circuit current) from the label. Set your multimeter to DC voltage, then attach the leads to the panel's terminals to measure the voltage. Next, switch to amps to check the current output and compare it to the panel's Isc rating.

How do I test a solar panel with a multimeter?

To accurately test a solar panel, set the multimeter to measure DC voltage and make sure proper lead connections to the positive and negative wires. When setting up your multimeter for testing solar panels, keep in mind the following basics: Select DC Voltage Mode: Set the multimeter to measure DC voltage to assess the output accurately.

How do I measure PV current?

Note: You can more easily measure PV current by using a clamp meter, which I discuss below in method #2. That's right — you can use a multimeter to measure how much current your solar panel is outputting. However, to do so your solar panel needs to be connected to your solar system.

What is a good voltage for a solar panel?

I measured a Voc of 19.85V on my panel. The claimed Voc for this panel is 19.83V, so we're spot on. The voltage you measure with your multimeter should be close to the open circuit voltage listed on the back of the panel. It doesn't have to be identical, though. If they're similar, so far your panel seems to be in good condition.

How do you calculate solar panel wattage?

Calculate the solar panel wattage by multiplying the PV voltage by the PV current. In this situation, 15.2 volts times 4.5 amps equals 68.4 watts. You may measure the output of the solar panels using the manufacturer's app on your phone if your charge controller has Bluetooth functionality.

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 the difference between lithium and lead-acid batteries?

Most common example of lead-acid batteries are car batteries. When compared to the lithium battery voltage charts here, we can quickly see that the lead-acid state of charge and corresponding voltage has a narrower range (12.73V to 11.36V for 12V lead-acid batteries vs. 14.4V to 10.0V for LiFePO4 batteries).

What is a lithium battery voltage chart?

A lithium battery voltage chart is an essential tool for understanding the relationship between a battery's charge level and its voltage. The chart displays the potential difference between the two poles of the battery, helping users determine the state of charge (SoC).

What is the highest voltage a lead-acid battery can achieve?

The highest voltage 48V lead battery can achieve is 50.92V at 100% charge. The lowest voltage for a 48V lead battery is 45.44V at 0% charge; this is more than a 5V difference between a full and empty lead-acid battery. With these 4 voltage charts, you should now have full insight into the lead-acid battery state of charge at different voltages.

What is the voltage of a 24V lead-acid battery?

We see the same lead-acid discharge curve for 24V lead-acid batteries as well; it has an actual voltage of 24V at 43% capacity. The 24V lead-acid battery voltage ranges from 25.46V at 100% charge to 22.72V at 0% charge; this is a 3.74V difference between a full and empty 24V battery.

What is a 12V flooded lead acid battery?

12V flooded lead acid batteries reach full charge at around 12.64 volts and reach complete discharge at about 12.07 volts. Below is a table showing a flooded lead-acid 12V battery chart and it has a lower maximum: Lithium iron phosphate batteries are the most common batteries used in solar systems.

What should you know about lithium ion batteries?

The most important key parameter you should know in lithium-ion batteries is the nominal voltage. The standard operating voltage of the lithium-ion battery system is called the nominal voltage. For lithium-ion batteries, the nominal voltage is approximately 3.7-volt per cell which is the average voltage during the discharge cycle.

What is the difference between a lithium ion and a discharged battery?

The chart displays the potential difference between the two poles of the battery, helping users determine the state of charge (SoC). For example, a fully charged lithium-ion cell typically has a voltage of 4.2V, while a discharged cell may have a voltage of 3.0V or lower.

What does a lithium ion battery voltage mean?

In consumer electronics like laptops and smartphones, the size of lithium-ion battery voltage defines the time of operation between two charges. When the starting voltage (in a single lithium-ion cell) reaches close to 4.2 volts, then the battery is fully charged.

What is the SOC voltage chart for lithium batteries?

The SoC voltage chart for lithium batteries shows the voltage values with respect to SoC percentage. A Li-ion cell when fully charged at 100%SoC can have nearly 4.2V. As it starts to discharge itself, the voltage decreases, and the voltage remains to be 3.7V when the battery is at half charge, ie, 50%SoC.

How do you know if a lithium ion battery is charging or discharging?

The voltage of a lithium-ion battery system always fluctuates during charging or discharging. If you see the voltage during charge or discharge cycles, you will notice that the voltage remains constant initially and then varies over time. In the discharge cycle, initially, the voltage will be 4.2V.

How much voltage should a lithium ion battery have?

As per the table above, for Li-ion batteries, the usual nominal voltage is approximately 3.6V to 3.7V per cell and the fully charged voltage should be around 4.2V. The voltage of the lithium ion battery drops gradually as it discharges, with a steep drop in voltage only towards the end.