Batteries are typically identified by their chemistry and voltage. “5V” stands for 5 volts, which is a measure of the electrical potential difference or voltage that the battery can deliver. Batteries with a 5V output are commonly associated with USB (Universal Serial Bus) power, and they are often used to charge or power various electronic devices.
The physical appearance of a 5V battery would depend on its specific form factor and type. Here are some diverse form factors and types:
Cylindrical Batteries
Some devices use regular AA or AAA batteries, typically delivering 1.5 volts each, but they include internal boost converters to increase the voltage to 5V. Through battery holders, innovative configurations, and the application of boost converters, these familiar cylindrical cells become essential building blocks for customized power solutions.
Coin Cell Batteries
Like the CR2032, coin cell batteries are flat and round. These batteries usually provide 3 volts, and a boost converter can be used to increase the output to 5 volts.
USB Power Banks
USB ports on the power bank indicate the 5V output. They often have a rectangular or cylindrical shape, similar to a small brick or tube. USB power banks commonly provide 5 volts for charging electronic devices.
Custom Battery Packs
For those seeking a tailored approach to portable power, custom battery packs come into play. Devices with unique form factors or specific power requirements often rely on custom-designed battery solutions. These can vary widely in shape and appearance based on the application and design specifications.
Rechargeable Lithium-ion Batteries
As we delve deeper, rechargeable lithium-ion batteries take the spotlight. Renowned for their energy density and versatility, these batteries come in various shapes and sizes, often cylindrical, and have a label indicating the voltage. A voltage regulator or booster might be used to achieve a 5V output.
Remember, achieving a 5V output might involve additional circuitry or combining multiple batteries, as many standard batteries provide lower voltages. From USB power banks to custom packs and beyond, the options are as varied as the applications they serve. As technology continues to advance, the quest for portable power solutions will undoubtedly lead to even more innovative form factors.
HIMAX can provide customized 5v rechargeable battery packs according to your needs. If you have any question, please feel free to contact us:
Name: Dawn Zeng (Director)
E-mail address: sales@himaxelectronics.com
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The energy density of li ion customized battery packs is 48% higher than that of Ni-MH batteries. And its cycle life of charge and discharge times can reach more than 600 times.
Advantages of li ion customized battery packs: small self-discharge, no memory effect, small size, light weight, green and environmental protection.
Application fields: transportation power supply, energy storage power supply, mobile communication power supply, new energy energy storage power supply, aerospace special power supply, electric vehicle applications.
Ni-MH battery is a battery with excellent performance. As an important direction of hydrogen energy application, hydrogen energy has attracted more and more attention.
Advantages: low price, strong versatility, large current, strong reliability, good over-discharge performance, overcharge protection, high charge-discharge rate, no dendrite-formation, good low-temperature performance, no significant change in capacity at -10 °C.
In recent years, more and more Ni-MH batteries are used. The capacity is getting larger and larger, chargers are becoming more and more advanced, and the charging time is greatly shortened.
Uses: electric toys, electric bicycles, power tools, digital products.
Conclusion: In terms of daily charging, li ion customized battery packs have no memory effect and are easy to use. In addition, li ion customized battery packs are light in size and weight, making them easy to carry on mobile devices. The working voltage of the Ni-MH battery is 1.2V~1.5V, and the series voltage of the two batteries is 2.4V~3.0V. Most electrical appliances already have this operating voltage standard, such as walkman, radio, etc. Therefore, in the civil battery, lithium-ion batteries cannot replace Ni-MH batteries. However, in the later development of new electrical appliances, such as mobile phone batteries, camera batteries, mobile power supplies, etc., li-ion battery is more popular now.
If you have any question, please feel free to contact us:
Name: Dawn Zeng (Director)
E-mail address: sales@himaxelectronics.com
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By now, the winter has been successful in many areas. Climate experts predict that the cold air may hit us frequently this winter, and we have ourselves prepared to prevent the cold. Will the batteries, the essential energy supply, and the energy storage device that we live in, also be prepared for the cold days?
For example, in terms of the necessary phone, a fully charged cell phone flies from a warm place to the cold north, when off the plane its power drops sharply or immediately shows “low power for low temperature, automatic shut”. Not only unpaid but also the temperature defeats it. when the phone battery encounters a low temperature beyond its acceptable range, it stops running (also phone freezing phenomenon) so that the mobile phone powers down or automatically off. Knowing the temperature accepted by our batteries is necessary.
Picture 1: Batteries power our life.
Battery classificationon the temperature
Normal temperature battery
This kind of battery is just like humans who enjoy the temperature indoor. Its operating temperature range is generally 0℃~60℃. Under normal circumstances, the temperature is about 45℃, if it exceeds 50 degrees, it will be very hot, and the battery will be easy to age and scrap, such as our commonly used mobile phone battery, mobile power supply, etc. If below minus 20℃, the device with it can’t work normally and it easily ages too.
High-temperature battery
The High-temperature battery uses a solid and inactive electrolyte at a normal ambient temperature. It can only become active at high temperatures by heating from the outside, which is used almost exclusively for military applications.
Low-temperature battery
A low-temperature battery is a battery with strong freezing capacity by adding resistance to the conventional ones and production research and development of technology. Because of the performance advantages of lithium-ion itself, it has become the protagonist in both the institute and the market.
Wide temperature battery
Wide temperature battery with a larger operating temperature range always over 100℃ （like -40℃-80℃ Ni-MH battery）can be applied to other harsh environmental fields such as petroleum drilling and aerospace.
Treat the effect of temperature on the battery
How to maintain the mobile phone in winter?
We have no idea to replace the battery of our mobile phones. But we have some tips to protect it from cold damage:
Before being out
Equip the phone with a thicker and warmer phone case (Picture 2 ).
Stick the mobile phone membrane for anti-static electricity.
Prepare a charging bank and the line.
Picture 2: Equip our electronics against this winter.
When staying outdoor
Put it into a pocket (inside the clothes) or bag to keep warm.
Use the headphones instead of releasing the sound out and shorten the outdoor-use time.
No mobile phone for a large temperature difference.
Do not start it up immediately after an automatic shut down until the temperature of the phone becomes normal.
Choose the correct battery to avoid unnecessary trouble
The battery activity is reduced for the low temperature, which affects charging and limits the use of electricity. If we are going to have a new product. the battery choosing must be taken seriously. When we have to get outdoor to a temperature under 40℃， low-temperature polymer lithium batteries can be your best choice. Maybe you need a battery for your device to climb a mountain or other unique demand. Specializes in battery solutions against different temperatures. There are more suggestions for you, just click here to know more or contact us.
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Learn about the revival of the fuel cell for transportation
The fuel cell as a propulsion system is in many ways superior to a battery because it needs to carry less energy storage by weight and volume compared to a vehicle propelled by batteries only. Figure 1 illustrates the practical driving range of a vehicle powered by a fuel cell (FC) compared to lead acid, NiMH and Li-ion batteries.
Figure 1: Driving range as a function of energy storage.
The logarithmical curves of battery power place limitations in size and weight. The FC has a linear progression and is similar to the ICE vehicle.
Note: 35MPa hydrogen tank refers to 5,000psi pressure; 70MPa is 10,000psi. Source: International Journal of Hydrogen Energy, 34, 6005-6020 (2009)+
One can clearly see that batteries simply get too heavy when increasing the size to enable greater distances. In this respect, the fuel cell enjoys similar qualities to the internal combustion engine (ICE) in that it can conquer great distances with only the addition of extra fuel.
The weight of fuel is most critical in air transport. Airlines only carry sufficient fuel to safely reach their designation, knowing that the airplane becomes more fuel efficient towards the end of the journey as the weight eases. A study group calculated that if the kerosene in an aircraft were replaced with batteries, the flight would last less than 10 minutes.
Although the fuel cell assumes the duty of the ICE in a vehicle, poor response time and a weak power band make on-board batteries necessary. In this respect, the FC car resembles an electric vehicle with an on-board charger that keeps the batteries charged. This results in short cycles that reduces battery stress over the EV; a propulsion system that bears a resemblance to the HEV.
The FC of a mid-sized car generates around 85kW (114hp) to charge the 18kWh on-board battery and drive the electric motor. On start-up, the vehicle relies fully on the battery; the fuel cell only contributes after reaching a steady state in 5–30 seconds. During the warm-up period, the battery must also deliver power to activate the air compressor and pumps. Once warm, the FC provides enough power for cruising; however, during acceleration, passing and hill-climbing both the FC and battery provide throttle power. Braking delivers kinetic energy to the battery.
Hydrogen costs about twice as much as gasoline, but the higher efficiency of the FC compared to the ICE in converting fuel to energy bring both systems on par. The FC has the added benefit of producing less greenhouse gas than the ICE.
Hydrogen is commonly derived from natural gas. Folks might ask, “Why not burn natural gas directly in the ICE instead of converting it to hydrogen through a reformer and then transforming it to electricity in a fuel cell to feed the electric motors?” The answer is efficiency. Burning natural gas in a combustion turbine to produce electricity has an efficiency factor of only 26–32 percent while a fuel cell is 35–50 percent efficient. That said, the machinery required to support the FC is costlier and requires more maintenance than a simple burning process.
To complicate matters further, building a hydrogen infrastructure is expensive. A refueling station capable of reforming natural gas to hydrogen to support 2,300 vehicles costs over $2 million, or $870 per vehicle. In comparison, a Level 2 charging outlet to charge EVs can easily be installed by connecting to the existing electric grid. The benefit with FC is a quick refill similar to filling a tank with liquid fuel.
Durability and cost are further deterrents for the FC, but improvements are made. The service life of an FC-powered car has doubled from 1,000 hours to 2,000 hours. The target for 2015 is 5,000 hours, or a vehicle life of 240,000km (150,000 miles).
A further challenge is vehicle cost as the fuel cell is more expensive to build than an ICE. As a guideline, an FC vehicle is more expensive than a plug-in hybrid, and the plug-in hybrid is dearer than a gasoline-powered car. With low fuel prices, alternative propulsion systems are difficult to justify on cost alone and the environmental benefits must be considered. Japan is making renewed efforts with FC propulsion to offer an alternative to the ICE and the EV. Toyota plans to phase out the ICE by 2050 and other vehicle makers are observing the trend.
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Governments are asking the public to reduce fuel consumption and lower pollution. They do this without imposing a change in driving habits and the HEV fits the bill. Japan is leading in adapting the HEV because of high fuel costs and environmental concerns.
The purpose of the HEV is to conserve fuel without sacrificing performance, and the HEV achieves this by using one or several electric motor to assist the ICE during acceleration and to harness kinetic energy when braking. The ICE turns off at traffic lights and the electric motor propels the car through slow-moving traffic. On full power, both the ICE and electric motor engage for optimal acceleration.
The HEV uses a mechanical powertrain to transfer power from the ICE to the wheels. In this respect, the HEV resembles an ordinary vehicle with a crankshaft and a clutch, also known as parallel configuration. Fuel savings are achieved by the use of a smaller ICE that is tuned for maximum fuel efficiency rather than high torque. Toyota claims a thermal efficiency of 40 percent for the new Prius. Peppy driving is accredited to the electric motor as this propulsion system delivers far better torque than a sluggish ICE of the same horsepower. Figure 1 illustrates the different modes of an electrified powertrain in in an HEV.
Figure 1: Basic function or an electrified powertrain in an HEV.
Battery power is only used for short durations. The HEV battery seldom encounters full charge-discharge cycles that are common in the electric vehicle. Source: RWTH Aachen University, Germany
Most batteries for HEVs are guaranteed for 8 years. To meet this long service life, the cells are optimized for longevity rather than high specific energy as with consumer products. The battery maker achieves this in part by using a thicker and more durable separator. To reduce stress, the battery operates at 30–80 percent state-of-charge (SoC), or roughly 3.5–4.0V/cell for Li-ion, rather than the customary 3.0–4.20V/cell.
HEV batteries operate momentarily and share similarity with a starter battery by applying short power bursts for acceleration rather than long, continuous discharges as with the EV. Rarely will an HEV battery discharge to a low 20 percent state-of-charge (SoC). Under normal use, a parallel HEV consumes less than 2 percent of the available battery capacity per mile (1.6km). Capacity fade goes unnoticed, and an HEV battery still works well with less than half the original capacity.
Figure 2 shows the battery capacity of six hybrid cars at a 256,000km (160,000 miles). The test was done by the US Department of Energy’s FreedomCAR and Vehicle Technologies Program (FCVT) in 2006 according to SAE J1634 practices and it included the Honda Civic, Honda Insight and Toyota Prius.
Figure 2: End-of-life battery capacity of HEVs. At 256,000km (160,000 miles), the two Honda Civic vehicles had 68% capacity, the Insight had 85% and the Prius had 39%. The capacity fade did not affect the fuel efficiency by much. Source: FreedomCAR and Vehicle Technologies Program
The hybrid battery of the two Honda Civic vehicles had 68 percent remaining capacity; the Insight had 85 percent and the Prius 39 percent. Even with lower capacity at the end of life, the fuel efficiency was not severely affected. The Insight showed a 1.2mpg (0.12L/km) decrease in fuel economy during the test, while the Prius reduced the fuel efficiency by 3.2mpg (0.33L/km). Air-conditioning was off in both cases.
Stringent battery demands are needed for hybrid trucks with a gross vehicle weight of 33 tons (73,000 lb). The battery must be able to continuously charge and discharge at 4C, deliver 10kW (200hp) for up to 10 minutes, operate at –20°C to 40°C (–4°F to 104°F) and deliver 5 years of service. Supercapacitors would provide the required durability but high cost and low energy density are against this choice. Lead acid has good discharge characteristics but it is slow to charge. Li-ion, especially LTO, would be a good choice but high power draw requires active cooling. Second generation NiMH is being tested; the rugged NiCd may also be tried.
Paradox of the hybrid vehicle
As good as a hybrid may be, the car is not without ironies. At a conference addressing advanced automotive batteries, an HEV opponent argued with an HEV maker that a diesel car offers better fuel economy than a hybrid. Being a good salesman, the HEV maker flatly denied the claim. Perhaps both are right. In city driving, the HEV clearly delivers better fuel-efficiency while diesel consumes less on the highway. Combining both would provide the best solution, but the high cost of a diesel-hybrid solution might not pay back with low fuel prices, although such vehicles are available in Europe.
High-end HEVs come with a full-sized ICE of 250hp and an electrical motor of 150–400hp in total. Such vehicles will surely find buyers, especially if the government assists with grants for being “green.” It’s unfortunate that consumers who walk, cycle or take public transportation won’t get such handouts. Common sense reminds us to conserve energy by driving less, or using smaller vehicles when driving is necessary.
Wolfgang Hatz, the then head of powertrain for Volkswagen Group, said that hybrid technology is a very expensive way to save a small amount of fuel and states that Volkswagen only makes hybrids because of political pressure. He supports diesel as the most energy-efficient motor, especially on highways.
Volkswagen may have a solution — the 1-Liter Car (Figure 3). It is called the 1-Liter Car because the concept vehicle burns only one liter of fuel per 100km. To prove the concept, the then VW chairman Dr. Ferdinand Piëch drove the car from their headquarters in Wolfsburg to Hamburg for a shareholders meeting. The average consumption was just 0.89 liters per 100km (317mpg).
Figure 3: Volkswagen’s 1-Liter Car. The 1-Liter Car is said to be the most economical car in the world but it never made it into production. Source: Volkswagen AG
Aerodynamics and weight help to achieve the low fuel consumption. While a typical car has a drag coefficient of 0.30, the 1-Liter Car is only 0.16. Carbon fiber and a magnesium frame reduce the weight to 290kg (640lb). The one-cylinder diesel engine generates 8.5hp (6.3kW), and the 6.5-litre (1.43-gallon) fuel tank has a range of 650 kilometers (400 miles). The average fuel consumption is 0.99 liter per 100km (238mpg).
Although the 1-Liter Car did not go into production, VW demonstrated that fossil fuel could be stretched should the cost rise or should frivolous consumption create unsustainably high pollution levels. Point-to-point personal transportation could be made possible with a light carrier that weighs only 290kg, a weight that is less than the 540kg Tesla S battery. Rather than consuming 150–250Wh per kilometer, as with an electric vehicle, the 1-Liter Car would only use about 40Wh/km. Even though it burns fossil fuel, the environmental impact would be less than an EV propelled with electricity, which is mainly produced by fossil fuel.
Plug-in Hybrid Electric Vehicle (PHEV)
Most PHEVs use a fully electrified powertrain in a series configuration with no mechanical linkage from ICE to wheels. The system runs solely on the electric motor for propulsion, and the ICE only engages when the batteries get low to supply electricity for the electric motor and to charge the battery. The driving range of a fully charged battery is about 50km (30 miles).
The PHEV is ideal for commuting and doing errands. No gasoline is consumed when driving on batteries and the highways are tax-free. However, there will be an increase in the electrical utility bill to charge the batteries at home.
Unlike the parallel HEV that relies on the battery for only brief moments, the PHEV battery is in charge depletion mode, meaning that the battery must work harder than on an HEV. This adds to battery stress and reduces longevity. While a capacity drop to 39 percent will affect the performance of the Toyota Prius HEV only marginally, such a loss would reduce the electric driving range of a PHEV from 50km to 20km (30 to 12 miles).
The Chevy Volt carries a 16kWh Li-ion battery that weighs 181kg (400 lb) and powers a 149hp (111kW) electric motor. The temperature of the prismatic cells is kept at 20–25C (68–77F) during charging and driving. An 115VAC outlet fills the battery in 8 hours; a 230VAC reduces the charging time to 3 hours. The driving range is 64km (40 miles) before the 1.4-liter four-cylinder ICE kicks in to activate the 53kW AC generator that powers the electric motors.
Economics
As good as the PHEV sounds, the long-term savings may be smaller than expected, especially if a battery replacement is needed during the life of the car. Battery aging is an issue that car makers avoid mentioning in fear of turning buyers away. A motorist used to driving ICE cars expects ample power at hot and cold temperatures and minimal performance degradation with age. The battery cannot match this fully, and the owner will need to tolerate a decrease in driving range during the winter, as well as accept a small reduction in delivered mileage with each advancing year due to battery aging.
Modern cars do more than provide transportation; they also include amenities for safety, comfort and pleasure. The most basic of these are the headlights and windshield wipers. Buyers also want cabin heat and air-conditioning, services that are taken for granted in a vehicle that burns fossil fuel. Heat is a by-product in the ICE that must be generated with battery power in a PHEV, but the larger concern is air-conditioning, which draws 3–5kW of power. Comforts might need to be provided more sparingly when running on a battery.
Many PHEV buyers value the environmental benefit and the pleasure of driving a quiet vehicle powered by electricity. This has a large buyer appeal because electric propulsion is more natural than that of an ICE. Drivers must adapt to the new lifestyle of charging the vehicle at night when electricity is cheap and then driving measured distances. Users of these cars will also appreciate new charging stations at workplaces and shopping malls.
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Capacity alone is of limited use if the pack cannot deliver the stored energy effectively; a battery also needs low internal resistance. Measured in milliohms (mΩ), resistance is the gatekeeper of the battery; the lower the resistance, the less restriction the pack encounters. This is especially important in heavy loads such as power tools and electric powertrains. High resistance causes the battery to heat up and the voltage to drop under load, triggering an early shutdown. Figure 1 illustrates a battery with low internal resistance in the form of a free-flowing tap against a battery with elevated resistance in which the tap is restricted.
Low resistance, delivers high current on demand; battery stays cool.
High resistance, current is restricted, voltage drops on load; battery heats up.
Figure 1: Effects of internal battery resistance.
A battery with low internal resistance delivers high current on demand. High resistance causes the battery to heat up and the voltage to drop. The equipment cuts off, leaving energy behind.
Lead acid has a very low internal resistance and the battery responds well to high current bursts that last for a few seconds. Due to inherent sluggishness, however, lead acid does not perform well on a sustained high current discharge; the battery soon gets tired and needs a rest to recover. Some sluggishness is apparent in all batteries at different degrees but it is especially pronounced with lead acid. This hints that power delivery is not based on internal resistance alone but also on the responsiveness of the chemistry, as well as temperature. In this respect, nickel- and lithium-based technologies are more responsive than lead acid.
Sulfation and grid corrosion are the main contributors to the rise of the internal resistance with lead acid. Temperature also affects the resistance; heat lowers it and cold raises it. Heating the battery will momentarily lower the internal resistance to provide extra runtime. This, however, does not restore the battery and will add momentary stress.
Crystalline formation, also known as “memory,” contributes to the internal resistance in nickel-based batteries. This can often be reversed with deep-cycling. The internal resistance of Li-ion also increases with use and aging but improvements have been made with electrolyte additives to keep the buildup of films on the electrodes under control. With all batteries, SoC affects the internal resistance. Li-ion has higher resistance at full charge and at end of discharge with a big flat low resistance area in the middle.
Alkaline, carbon-zinc and most primary batteries have a relatively high internal resistance, and this limits their use to low-current applications such as flashlights, remote controls, portable entertainment devices and kitchen clocks. As these batteries deplete, the resistance increases further. This explains the relative short runtime when using ordinary alkaline cells in digital cameras.
Two methods are used to read the internal resistance of a battery: Direct current (DC) by measuring the voltage drop at a given current, and alternating current (AC), which takes reactance into account. When measuring a reactive device such as a battery, the resistance values vary greatly between the DC and AC test methods, but neither reading is right or wrong. The DC reading looks at pure resistance (R) and provides true results for a DC load such as a heating element. The AC reading includes reactive components and provides impedance (Z). Impedance provides realistic results on a digital load such as a mobile phone or an inductive motor.
Figure 2 illustrates the internal resistance of an 18650 Li-ion cell when exposed to 1,000 full cycles at 40ºC (104ºF). The AC readings in the green frame do not reflect the true resistive state of a battery; DC method provides more reliable performance data with loading.
Figure 2: Rise of internal resistances of 18650 Li-ion cell measured with AC and DC methods when cycled.
AC resistance readings in green frame stay low; DC method gives true state. Source: Technische Universität München (TUM)
Pack Resistance
The internal resistance of a battery does not consist of the cells alone but also includes the interconnection, fuses, protection circuits and wiring. In most cases these peripherals more than double the internal resistance and can falsify rapid-test methods. Typical readings of a single cell pack for a mobile phone and a multi-cell battery for a power tool are shown below.
Internal Resistance of a Mobile Phone Battery
Cell, single, high capacity prismatic
50mΩ
subject to increase with age
Connection, welded
1mΩ
PTC, welded to cable, cell
25mΩ
18–30 mΩ according to spec
Protection circuit, PCB
50mΩ
Total internal resistance
ca. 130mΩ
Internal Resistance of a Power Pack for Power Tools
Cells 2P4S at 2Ah/cell,
18mΩ
subject to increase with age
Connection, welded, each
0.1mΩ
Protection circuit, PCB
10mΩ
Total internal resistance
ca. 80mΩ
Source: Siemens AG (2015, München)
Figures 3, 4 and 5 reflect the runtime of three batteries with similar Ah and capacities but different internal resistance when discharged at 1C, 2C and 3C. The graphs demonstrate the importance of maintaining low internal resistance, especially at higher discharge currents. The NiCd test battery comes in at 155mΩ, NiMH has 778mΩ and Li-ion has 320mΩ. These are typical resistive readings on aged but still functional batteries. That demonstrates the relationship of capacity, internal resistance and self-discharge.)
Figure 3: GSM discharge pulses at 1, 2, and 3C with resulting talk-time
The capacity of the NiCd battery is 113%; the internal resistance is 155mΩ. 7.2V pack.
Figure 4: GSM discharge pulses at 1, 2, and 3C with resulting talk-time
The capacity of the NiMH battery is 94%, the internal resistance is 778mΩ. 7.2V pack
Figure 5: GSM discharge pulses at 1, 2, and 3C with resulting talk-time
The capacity of the Li-ion battery is 107%; the internal resistance is 320mΩ. 3.6V pack
Notes: The tests were done when early mobile phones were powered by NiCd, NiMH and Li-ion. Li-ion and NiMH have since improved.
The maximum GSM draws is 2.5A, representing 3C from an 800mAh pack, or three times the rated current.
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Learn how certain discharge loads will shorten battery life.
The purpose of a battery is to store energy and release it at a desired time. This section examines discharging under different C-rates and evaluates the depth of discharge to which a battery can safely go. The document also observes different discharge signatures and explores battery life under diverse loading patterns.
The electrochemical battery has the advantage over other energy storage devices in that the energy stays high during most of the charge and then drops rapidly as the charge depletes. The supercapacitor has a linear discharge, and compressed air and a flywheel storage device is the inverse of the battery by delivering the highest power at the beginning. Figures 1, 2 and 3 illustrate the simulated discharge characteristics of stored energy.
Most rechargeable batteries can be overloaded briefly, but this must be kept short. Battery longevity is directly related to the level and duration of the stress inflicted, which includes charge, discharge and temperature.
Remote control (RC) hobbyists are a special breed of battery users who stretch tolerance of “frail” high-performance batteries to the maximum by discharging them at a C-rate of 30C, 30 times the rated capacity. As thrilling as an RC helicopter, race car and fast boat can be; the life expectancy of the packs will be short. RC buffs are well aware of the compromise and are willing to both pay the price and to encounter added safety risks.
To get maximum energy per weight, drone manufacturers gravitate to cells with a high capacity and choose the Energy Cell. This is in contrast to industries requiring heavy loads and long service life. These applications go for the more robust Power Cell at a reduced capacity.
Depth of Discharge
Lead acid discharges to 1.75V/cell; nickel-based system to 1.0V/cell; and most Li-ion to 3.0V/cell. At this level, roughly 95 percent of the energy is spent, and the voltage would drop rapidly if the discharge were to continue. To protect the battery from over-discharging, most devices prevent operation beyond the specified end-of-discharge voltage.
When removing the load after discharge, the voltage of a healthy battery gradually recovers and rises towards the nominal voltage. Differences in the affinity of metals in the electrodes produce this voltage potential even when the battery is empty. A parasitic load or high self-discharge prevents voltage recovery.
A high load current, as would be the case when drilling through concrete with a power tool, lowers the battery voltage and the end-of-discharge voltage threshold is often set lower to prevent premature cutoff. The cutoff voltage should also be lowered when discharging at very cold temperatures, as the battery voltage drops and the internal battery resistance rises. Table 4 shows typical end-of-discharge voltages of various battery chemistries.
End-of-discharge
Nominal
Li-manganese
3.60V/cell
Li-phosphate
3.20V/cell
Lead acid
2.00V/cell
NiCd/NiMH
1.20V/cell
Normal load
Heavy load or
low temperature
3.0–3.3V/cell
2.70V/cell
2.70V/cell
2.45V/cell
1.75V/cell
1.40V/cell
1.00V/cell
0.90V/cell
Table 4: Nominal and recommended end-of-discharge voltages under normal and heavy load.
The lower end-of-discharge voltage on a high load compensates for the greater losses.
Over-charging a lead acid battery can produce hydrogen sulfide, a colorless, poisonous and flammable gas that smells like rotten eggs. Hydrogen sulfide also occurs during the breakdown of organic matter in swamps and sewers and is present in volcanic gases and natural gas. The gas is heavier than air and accumulates at the bottom of poorly ventilated spaces. Strong at first, the sense of smell deadens with time, and the victims are unaware of the presence of the gas. (See BU-703: Health Concerns with Batteries.)
What Constitutes a Discharge Cycle?
A discharge/charge cycle is commonly understood as the full discharge of a charged battery with subsequent recharge, but this is not always the case. Batteries are seldom fully discharged, and manufacturers often use the 80 percent depth-of-discharge (DoD) formula to rate a battery. This means that only 80 percent of the available energy is delivered and 20 percent remains in reserve. Cycling a battery at less than full discharge increases service life, and manufacturers argue that this is closer to a field representation than a full cycle because batteries are commonly recharged with some spare capacity left.
There is no standard definition as to what constitutes a discharge cycle. Some cycle counters add a full count when a battery is charged. A smart battery may require a 15 percent discharge after charge to qualify for a discharge cycle; anything less is not counted as a cycle. A battery in a satellite has a typical DoD of 30–40 percent before the batteries are recharged during the satellite day. A new EV battery may only charge to 80 percent and discharge to 30 percent. This bandwidth gradually widens as the battery fades to provide identical driving distances. Avoiding full charges and discharges reduces battery stress. (See also BU-1003: Electric Vehicle.)
A hybrid car only uses a fraction of the capacity during acceleration before the battery is recharged. Cranking the motor of a vehicle draws less than 5 percent energy from the starter battery, and this is also called a cycle in the automotive industry. Reference to cycle count must be done in context with the respective duty.
Reference to discharge cycle or cycle count does not relate equally well to all battery applications. One example where counting discharge cycles does not reflect state-of-life accurately is in a storage device (ESS). These batteries supplement renewable energies from wind power and photovoltaic by delivering short-term energy when needed and storing if in excess. The time duration between charge and discharged can be in milliseconds; a typical battery state-of-charge is 40–60%. Rather than cycle count, coulomb counting may be used as a means of measuring wear and tear.
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Nickel-based batteries dwell between lead acid and Li-ion.
They are safe, economical and long-living but are increasingly being assigned to niche markets. Table 1 summarizes the characteristics of present, past and future nickel-based batteries.
Chemistry
Nickel-cadmium
Nickel-metal-hydride
Nickel-iron
Nickel-zinc
Nickel-hydrogen
Abbreviation
NiCd
NiMH
NiFe
NiZn
NiH
Type
Nickel cathode;
cadmium anode
Nickel cathode;
hydrogen-absorbing anode
Oxide-hydroxide cathode; iron anode with potassium hydroxide electrolyte
Similar to NiCd; uses alkaline electrolyte and nickel electrode
Nickel electrodes, hydrogen electrodes, in pressurized vessel
Nominal voltage
1.20V/cell (1.25)
1.20V
1.65V
1.25V
Charge
Taper charger. Constant current; floating voltage
Taper charger, similar to NiCd
Taper charger, similar to NiCd
Not defined
Full charge
Observing voltage drop; plateau voltage as override
1.9V
Not defined
Trickle charge
0.1C
0.05C
Not defined
No trickle charge
Not defined
Specific Energy
45–80Wh/kg
60–120Wh/kg
50Wh/kg
100Wh/kg
40–75Wh/kg
Charge rate
Can be above 1C
0.5–1C
Not defined
Regular charge
Not defined
Discharge rate
Can be above 1C
1C
Moderate
Relative high power
Not defined
Cycle life
(full DoD)
1,000
300–500
20 years in UPS
200–300
Very long cycle life (>70,000 partial)
Maintenance
Full discharge every 3 months (memory)
Full discharge every 6 months
Not defined
Not defined
Maintenance free; low self-discharge
Failure modes
Memory reduces capacity, reversible
Memory (less affected than NiCd)
Overcharge causes dry-out
Short cycle life due to dendrite growth
Minimal corrosion
Packaging
A, AA, C, also in fractional sizes
A, AA, AAA, C, prismatic
Not defined
AA and others
Custom made; each cell costs >$1,000
Environment
Broad temperature range. Toxic
Considered non-toxic
Poor performance when cold
Good temperature range
Operates at
–28°C to 54°C
History
1899, sealed version made commercial in 1947
Research started in 1967, commercial in the 1980s; derived from nickel-hydrogen
In 1901,Thomas Edison patented and promoted NiFe in lieu of lead acid; failed to catch on for ICE, EV
In 1901, Thomas Edison was awarded the U.S. patent for the NiZn battery
Problems with instabilities in 1967 caused a shift from NiMH to NiH
Applications
Main battery in aircraft (flooded), wide temperature range
Hybrid cars, consumer, UPS
German V-1 flying bombs, V-2 rockets; railroad signaling, UPS, mining
Renewed interest to commercial market with Improvements
Exclusively satellites; too expensive for terrestrial use
Comments
Robust, forgiving, high maintenance. Only battery that can be ultrafast charged with little stress
More delicate than NiCd; has higher capacity; less maintenance
In 1990, Cd was substituted with Fe to save money. High self-discharge and high fabrication costs
High power, good temperature range, low cost but high self-discharge and short service life
Uses a steel canister to store hydrogen at 8,270kPa (1,200psi)
Table 1: Summary of most common nickel-based batteries.
Experimental and less common versions are not listed. All readings are estimated average at time of publication. Detailed information is on BU-203: Nickel-based Batteries.
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Analyze the pros and cons of other battery systems and learn what the potentials are.
The media promotes wonderful new batteries that promise long runtimes, charge in minutes, are paper-thin and will one day power the electric car. While these experimental batteries produce a voltage, the downsides are seldom mentioned. The typical shortcomings are low load capacity and short cycle life. (See BU-104c: The Octagon Battery.)
As a lemon can be made into a battery, so also has seawater been tried as electrolyte, but the retrieved energy is only good to light an incandescent flashlight for a short time before corrosion buildup renders the battery unusable. Many chemical processes are being tried to generate electricity from diverse metals but only a few promise to surpass today’s lead, nickel and lithium systems.
There is much media hype, and this may be done in part to attract venture capitalists to fund research projects. Few products have incubation periods that are as long as a battery. Although glamorous and promising at first, especially if the battery promises to power the electric vehicle, investment firms are beginning to realize the high development costs, uncertainties and long gestation periods before a return can be realized. Meanwhile, universities continue publishing papers about battery breakthroughs to keep receiving government funding while private companies throw in a paper or two to appease investors and boost their own stock value.
Zinc-air (Primary & Secondary)
Zinc-air batteries generate electrical power by an oxidation process of zinc and oxygen from the air. The cell can produce 1.65V; however, cells with 1.4V and lower voltages achieve a longer lifetime. To activate the battery, the user removes a sealing tab that enables airflow. The battery reaches full operating voltage within 5 seconds. Airflow can control the rate of the reaction somewhat and once turned on, the battery cannot be reverted back to standby mode. Adding a tape to stop the airflow only slows the chemical activity and battery will soon dry out.
The Zinc-air battery shares similarities with the fuel cell (PEMFC) by using oxygen from the air to fuel the positive electrode. It is considered a primary battery and recharging versions for high-power applications have been tried. Recharging occurs by replacing the spent zinc electrodes, which can be in the form of a zinc electrolyte paste. Other zinc-air batteries use zinc pellets.
At 300–400Wh/kg, zinc-air has a high specific energy but the specific power is low. Manufacturing cost is low and in a sealed state, zinc-air has a 2 percent self-discharge per year. The battery is sensitive to hot and cold temperatures and high humidity. Pollution also affects performance; high carbon dioxide content reduces the performance by increasing the internal resistance. Typical applications are hearing aids while large systems operate remote railway signaling and safety lamps at construction sites.
Silver-zinc (Primary & Secondary)
The small silver-based batteries in button cells are typically called silver-oxide and are non-rechargeable; the higher capacity rechargeable versions are referred to as silver-zinc. Both have an open circuit voltage of 1.60 volts. Because of the high cost of silver, these batteries come in either very small sizes where the amount of silver does not contribute significantly to the overall product cost, or they are available in larger sizes for critical applications where the superior performance outweighs any cost considerations.
The primary cells are used for watches, hearing aids and memory backup; the larger rechargeable version is found in submarines, missiles and aerospace applications. Silver-zinc also powers TV cameras needing extra runtime. High cost and short service life locked the silver-zinc out of the commercial market, but it is on the verge of a rebirth with improvements.
The primary cause of failure in the original design was the decaying of the zinc electrode and separator. Cycling developed zinc dendrites that pierced through the separator, causing electrical shorts. In addition, the separator degraded by sitting in the potassium hydroxide electrolyte. This limited the calendar life to about 2 years.
Improvements in the zinc electrode and separator promise a longer service life and a 40 percent higher specific energy than Li-ion. Silver-zinc is safe, has no toxic metals and can be recycled, but the use of silver makes the battery expensive to manufacture.
Reusable Alkaline
The reusable alkaline served as an alternative to disposable batteries. Although fabrication costs were said to be similar to regular alkaline, the consumer did not accept the product.
Recharging alkaline batteries is not new. Ordinary alkaline batteries have been recharged in households for many years. Recharging is most effective if alkaline is discharged to less than 50 percent before recharging. The number of recharges depends on the depth of discharge and is limited to just a few cycles. Battery makers do not endorse this practice for safety reasons; charging ordinary alkaline batteries may generate hydrogen gas that can lead to an explosion.
The reusable alkaline overcomes some of these deficiencies, but a limited cycle count and low capacity on repeat charge are major drawbacks. Longevity is also in direct relationship to the depth of discharge. At a 50 percent depth of discharge, the battery may deliver 50 cycles, but most users run a battery empty before recharging and the manufacturer, including the inventor Karl Kordesch, overestimated the eagerness of the user wanting to recharge early. An additional limitation is its low load current of 400mA, which is only sufficient for flashlights and personal entertainment devices. NiMH in AA and AAA cells has mostly replaced the reusable alkaline.
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Find out how NiCd, NiMH and Li-ion perform when put to the test.
To compare older and newer battery systems, Cadex tested a large volume of nickel-cadmium, nickel-metal-hydride and lithium ion batteries used in portable communication devices. Preparations included an initial charge, followed by a regime of full discharge/charge cycles at a 1C rate. The following tables show the capacity in percent, DC resistance measurement and self-discharge obtained from time to time by reading the capacity loss incurred during a 48-hour rest period. The tests were carried out on the Cadex 7000 Series battery analyzers with a 1C charge and discharge and a 100 percent depth-of-discharge (DoD).
Nickel-cadmium
In terms of life cycling, NiCd is the most enduring battery. Figure 1 illustrates capacity, internal resistance and self-discharge of a 7.2V, 900mA pack with standard NiCd cell. The internal resistance stayed low at 75m and the self-discharge was stable. Due to time constraints, the test was terminated after 2,300 cycles.
This battery receives a grade “A” rating for almost perfect performance in terms of minimal capacity loss when cycling with a 100 percent DoD and rock-solid internal resistance over the entire test. NiCd is the only chemistry that can be ultra-fast charged with little stress. Due to its safe operation, NiCd remains the preferred choice of battery onboard aircraft.
Figure 1: Performance of standard NiCd (7.2V, 900mAh) This battery receives an “A” rating for stable capacity, low internal resistance and moderate self-discharge over many cycles. Courtesy of Cadex
The ultra-high-capacity nickel-cadmium offers up to 60 percent higher specific energy compared to the standard version, however, this comes at the expense of reduced cycle life. In Figure 2 we observe a steady drop of capacity during 2,000 cycles, a slight increase in internal resistance and a rise in self-discharge after 1,000 cycles.
Figure 2: Performance of ultra-high-capacity NiCd (6V, 700mAh) This battery offers higher specific energy than the standard version at the expense of reduced cycle life. Courtesy of Cadex
Nickel-metal-hydride
Figure 3 examines NiMH, a battery that offers high specific energy but loses capacity after the 300-cycle mark. There is also a rapid increase in internal resistance after a cycle count of 700 and a rise in self-discharge after 1000 cycles. The test was done on an older generation NiMH.
Figure 3: Performance of NiMH (6V, 950mAh). This battery offers good performance at first but past 300 cycles, the capacity, internal resistance and self-discharge start to increase rapidly. Courtesy of Cadex
Lithium-ion
Figure 4 examines the capacity fade of a modern Li-ion Power Cell at a 2A, 10A, 15A and 20A discharge. Stresses increase with higher load currents, and this also applies to fast charging. (See BU-401a: Ultra-fast charging of Li-ion.)
Li-ion manufacturers seldom specify the rise of internal resistance and self-discharge as a function of cycling. Advancements have been made with electrolyte additives that keep the resistance low through most of the battery life. The self-discharge of Li-ion is normally low but it can increase if misused or if exposed to deep discharges.
Figure 4: Cycle characteristics of IHR18650C by E-One Moli. (3.6V, 2,000mA). 18650 Power Cell was charged with 2A and discharged at 2, 10, 15 and 20A. The internal resistance and self-discharge are N/A. Courtesy of E-One Moli Energy
Batteries tested in a laboratory tend to provide better results than in the field. Elements of stress in everyday use do not always transfer well into a test laboratory. Aging plays a negligible role in a lab because the batteries are cycled over a period of a few months rather than the expected service life of several years. The temperature is often moderate and the batteries are charged under controlled charging condition and with approved chargers.
The load signature also plays a role as all batteries were discharged with a DC load. Batteries tend to have a lower cycle life if discharged with pulses. (See BU-501: Basics About Discharging.) Do not overstress a battery as this will shorten the life. If a battery must repeatedly be loaded at peak currents, choose a pack with increased Ah rating.
