What’s the Best Battery?

We’re often confused by announcements of new batteries, which not only offer very high energy density but can also do 1,000 charge and discharge cycles as thin as paper. Are these features of the new battery real? Maybe, but these features don’t come together in the same battery. Although a type of battery may be designed to be small in size and capable of running for a long time, the pack will not wear out continuously and prematurely. Another type of battery might have a longer life but would be bulky because of its size. A third battery offers all the desired features but is prohibitively expensive for commercial use.

Fully aware of their customers’ needs, battery manufacturers have responded by providing them with packs best suited to specific applications. The most clever example is the mobile phone industry, which focuses on the small size, high energy density, and low cost, and comes second in longevity.

Engraving NiMH on a battery pack does not automatically guarantee high energy density. For example, prismatic nickel-metal-hydride batteries with slender geometric shapes are used in mobile phones. This type of pack has an energy density of about 60Wh/kg with about 300 cycles, compared to 80Wh/kg or more for cylindrical NIMH batteries. However, the cell cycle count is medium to low. Nickel-metal hydride batteries with 1000 discharge resistance are usually packaged in cylindrical batteries with large volumes. And these cells have an energy of 70Wh/kg, which is a moderate level.

There are some problems with lithium-ion batteries, which are used in defense construction and have an energy density that far exceeds commercial equivalents. Unfortunately, lithium-ion batteries are considered unsafe by the public, even though their high capacity and high price prevent them from entering the commercial market.

In this article, we look at the advantages and limitations of commercial batteries, and wonder batteries are excluded only in a controlled environment. We examine batteries not only from the perspective of life, load characteristics, self-discharge, maintenance requirements, and operating costs. The standard for comparison with other batteries is still nickel-cadmium batteries. We evaluate alternative chemistry with this classic battery type.

Nickel-cadmium (NiCd) has the advantage of being mature and easy to understand but has the disadvantage of having a relatively low energy density. Nickel-cadmium batteries are used in applications requiring long life, high discharge rate, and economic cost. It is mainly used in two-way radios, professional cameras, power tools, and biomedical equipment. But because nickel-cadmium contains toxic metals, it is not friendly to the environment.

Compared with nickel-cadmium batteries, nickel-hydrogen alloy (NiMH) has a higher energy density than nickel-cadmium batteries, but the cycle life is reduced. Nimh batteries are widely used in laptop computers and mobile phones because they do not contain toxic metals.

Lead-acid batteries are a prime choice for emergency lighting, UPS systems, wheelchairs, and hospital medical equipment.

Lithium-ion batteries are the fastest growing battery type in battery systems. Lithium-ion batteries are mainly used in important places with high energy density and lightweight. Because the technology is fragile, a protective circuit is needed to keep it safe, and it is mainly used in laptops and mobile phones.

Lithium-ion polymers are mainly used in mobile phones due to their properties of simplified packaging and ultra-thin geometry.

Figure 1 compares the characteristics of the most common rechargeable battery systems in terms of recycling life, cost, energy density, and motion requirements. These numbers are based on current market ratings of available batteries.

  NiCd NiMH Lead Acid Li-ion Li-ion polymer Reusable
Gravimetric Energy Density(Wh/kg) 45-80 60-120 30-50 110-160 100-130 80 (initial)
Internal Resistance
(includes peripheral circuits) in mΩ
100 to 2001
6V pack
200 to 3001
6V pack
12V pack
150 to 2501
7.2V pack
200 to 3001
7.2V pack
200 to 20001
6V pack
Cycle Life (to 80% of initial capacity) 15002 300 to 5002,3 200 to
500 to 10003 300 to
(to 50%)
Fast Charge Time 1h typical 2-4h 8-16h 2-4h 2-4h 2-3h
Overcharge Tolerance moderate low high very low low moderate
Self-discharge / Month (room temperature) 20%4 30%4 5% 10%5 ~10%5 0.3%
Cell Voltage(nominal) 1.25V6 1.25V6 2V 3.6V 3.6V 1.5V
Load Current
– peak
– best result
0.5C or lower
1C or lower
1C or lower
0.2C or lower
Operating Temperature(discharge only) -40 to
-20 to
-20 to
-20 to
0 to
0 to
Maintenance Requirement 30 to 60 days 60 to 90 days 3 to 6 months9 not req. not req. not req.
Typical Battery Cost
(US$, reference only)
Cost per Cycle(US$)11 $0.04 $0.12 $0.10 $0.14 $0.29 $0.10-0.50
Commercial use since 1950 1990 1970 (sealed lead acid) 1991 1999 1992

Figure 1: Characteristics of commonly used rechargeable batteries

  1. The internal resistance of the battery pack varies with the battery class, the number of batteries, and the type of protection circuit, with 100m ω added to the protection circuit for lithium ion and polymer.
  2. The cycle life is because the battery needs to be maintained regularly, and the cycle life is reduced by three times if the complete discharge cycle is not adopted periodically.
  3. The length of cycle life depends on the depth of discharge, which does not provide as many cycles as shallow discharge.
  4. Recharging immediately after the discharge will reach the highest and gradually decrease. The capacity of NiCd reduces by 10% in the first 24 hours and by about 10% every 30 days after that. The strength of self-discharge depends on temperature and increases gradually with temperature.
  5. Internal protection circuits typically consume 3% of stored energy per month.
  6. The slotted voltage is 1.25V, where the standard value is 1.2V, but there is no difference between cells.
  7. Be able to withstand a high current pulse.
  8. Only suitable for unloading goods, and the charging temperature range is small.
  9. Fees are usually “balanced” or “top.”
  10. Battery cost for commercial portable devices.
  11. The price of a battery is divided by its cycle life, which excludes the cost of electricity and charging equipment.

Observation: It is worth noting that nicDS have the highest load current with the shortest charging time and the lowest total cost per cycle, requiring the highest maintenance requirements.

The Nickel Cadmium (NiCd) battery

NiCd doesn’t like slow charging, prefers fast charging, and doesn’t like dc charging. Prefers pulse charging. Other types prefer shallow discharges and medium-load current types. NiCd can be likened to a silent but stern worker, for which complex labor is not a problem. Only NiCd batteries can maintain good performance under harsh environmental conditions. And they don’t like to be cuddled in a charger and are used only occasionally and briefly. It is important to note that periodic total discharges, if ignored, will form large crystals on the panels, and the lithium ion battery will lose the NiCd performance.

For applications such as unlimited dual-wire power, power tools, and emergency medical equipment, Nickel-cadmium batteries are preferred in rechargeable battery types. But the trend toward less toxic, energy-dense batteries is shifting away from nickel-cadmium batteries towards newer technologies.

Advantages and Limitations of NiCd Batteries
Advantages It can also be quickly and easily recharged after long storage.

Properly maintained, the NiCd can provide more than 1000 cycles of high charge status.

NiCd can be charged at lower temperatures, so it has good load performance.

It has a long shelf life in any state.

It can carry out simple storage and transportation, therefore, meet the conditions of the vast majority of air cargo companies.

Good performance at low temperature.

NiCd is robust.

The price is lower.

There are more performance and size choices.

Limitations Have lower energy density and more novel system.

Regular use of NiCd can prevent memory.

Nickel-cadmium batteries are restricted in some countries because they contain toxic metals and are not friendly to the environment.

High degree of self-discharge so storage needs even after charging.

Figure 2: Advantages and limitations of NiCd batteries.

The Nickel-Metal Hydride (NiMH) battery

Research on NiMH systems began in the 1970s to explore ways to store hydrogen in NiMH batteries. Nickel-metal hydride batteries are widely used in satellite applications today. Nickel-metal hydride batteries are bulky, contain high-pressure steel tanks, and cost thousands of dollars each, making them very expensive.

In early experiments with NiMH cells, metal-hydride alloys in the battery environment were extremely unstable and failed to achieve the desired performance characteristics. As a result, NiMH’s development was prolonged until the 1980s, when new cyanide alloys were developed that were stable enough to be used in battery environments. Meanwhile, NiMH has been in a steady state of development since the late 1980s.

NiMH’s success is due primarily to its high energy density and its simultaneous use of environmentally friendly metals. Although the energy density of modern NIMH batteries is higher than that of NiCd batteries, and the energy density of current NIMH batteries is about 40% higher than that of NiCd batteries, it does not mean that NIMH batteries do not have any adverse effects.

The durability of nickel-metal hydride batteries is not as good as that of nickel-metal hydride batteries. Recycling and storage at higher temperatures will reduce the durability of nickel-metal hydride batteries. At the same time, nickel-metal hydride batteries have the advantage of high self-discharge, which is much greater than the self-discharge strength of nickel-metal hydride batteries.

Nickel-metal hydride batteries replace Nickel-cadmium batteries in wireless communication and mobile computing. In many other parts of the world, too, consumers are encouraged to use nickel-metal hydride batteries rather than nickel-cadmium batteries because of the environmental problems caused by the careless disposal of used batteries.

Although NiMH has made great strides over the past few years, it still has limitations, which experts agree on. However, most of the shortcomings and problems are inherent in nickel-based technology, so NiCd batteries also have the same weaknesses and problems. It is believed that the lithium battery technology of nickel-metal hydride batteries is in a transitional stage.

Advantages and Limitations of NiMH Batteries
Advantages The NiMH has 30-40% more capacity than the standard NiCd, thus achieving higher energy densities for thousands of miles.

It’s not as easy to remember as NiCd, so periodic motion cycles are less frequent.

As transport conditions are not subject to regulatory control, simple storage and transport can be carried out.

Because it contains only mild toxins and can be recycled, it is also more environmentally friendly.

Limitations If repeated deep cycles are carried out in a high load current mode, performance begins to deteriorate at 200 or around 300 cycles. Guard point is better than shallow discharge.

At high load current, the cycle life of the battery will be reduced by repeated discharge, and the effect is best only when the load current is 0.2c to 0.5C.

Because nickel-metal hydride batteries generate more heat during charging and require relatively longer charging time, they require more complex charging algorithms, so careful control of trickle charging must be taken.

New chemical additives improve the high self-discharge rate of nimH batteries at the cost of reducing energy density.

Performance degrades in high temperature storage and therefore needs to be stored in a cool environment.

To prevent crystallization, the battery needs to be fully discharged periodically.

Nickel-metal hydride batteries for high current are about 20 percent more expensive than regular nickel-metal hydride batteries.

Figure 3: Advantages and limitations of NiMH batteries

The Lead-Acid battery

A French doctor named Gaston Plante invented the first commercially available rechargeable lead-acid battery in 1859. It is now commonly found in cars, forklifts, and sizeable uninterruptible power (UPS) systems.

In the mid-1970s, researchers developed maintenance-free lead-acid batteries that could work anywhere. Converts the liquid electrolyte into a wet separator while sealing the shell. To make lithium ion battery can release the gas in the process of charging and discharging, the safety valve is added.

Different applications drive two battery models. We were known as Gel cell brand for Small Seal Lead acid (SLA) and Large Valve Regulating Lead-acid (VRLA). The two batteries are technically the same. (Engineers argue that “sealed lead acid” is a misnomer because it is a fully sealed lead acid battery.) But our focus is on portable batteries, so we’re more focused on SLAs.

SLA and VRLA, unlike submerged lead-acid batteries, have lower overvoltages to prevent the battery from reaching gas-producing potential during charging. Batteries will never reach their full potential, given that overcharging depletes gas and water.

Lead-acid is not affected by memory, so lead-acid batteries will not be damaged even if they float for a long time. Lead-acid batteries also have the best charging capacity of any storm. The amount of self-discharge in SLA1 year is the same as that in NiCd in 3 months, about 40% of the energy storage. As a result, SLA is relatively cheap, but NiCd is more affordable to operate in repeating the required complete cycle.

The SLA is suitable for slow charging, with 8-16 hours. The SLA storage state must be powered on. If it is discharged, it acidifies and becomes challenging to recharge.

Unlike NiCd, SLA does not like deep loops. A full discharge causes the extra pressure, and the battery loses a minor capacity with each cycle. Other battery chemicals have similar wear properties. Using SLA batteries with large capacity can avoid repeated deep discharges causing battery stress.

An SLA provides 200 to 300 discharges per cycle. At the same time, the cycle life is short because of the depletion of active material, the expansion of the positive plate, and the corrosion of the positive gate. These changes are most common at higher operating temperatures, and the trend cannot be reversed or stopped by cycling.

SLA and VRLA batteries have the best performance when the temperature is 25℃. Battery life is halved for every eight °C(15°F) increase in temperature. Valve-controlled seals were designed to last at 33°C(95°F) and up to 10 years at 25°C. At 42°C(107°F), it only lasts a little more than a year.

Because the lead-acid battery family has the lowest energy density, it is not suitable for small handheld devices, and performance is poor at low temperatures.

Five hours is the SLA-rated discharge time, but some batteries can discharge slowly for 20 hours. Higher capacity readings are produced at longer discharge times. The SLA performs well at high pulse currents and can be drawn with discharge rates greater than 1C.

SLA is less harmful than NiCd batteries in terms of treatment but is not environmentally friendly due to its high lead content.

Advantages and Limitations of Lead Acid Batteries
Advantages Not only are they cheap, but they are also simple to manufacture, with SLAs being the cheapest in terms of cost per watt-hour.

The technology is mature, easy to understand and open. When used correctly, slAs are persistent and the service is reliable.

Has extremely low self-discharge rate, lowest in rechargeable battery system.

Low maintenance, no memory, no electrolyte to fill.

Has a high discharge rate.

Limitations Do not discharge when stored.

Because of the lower energy density and poor weight energy density, only wheeled and stationary applications can be used.

The number of full discharge cycles is limited and is suitable for backup applications that require occasional deep discharges.

Because the electrolyte and the amount of lead are not environmentally friendly.

Because of environmental concerns about leakage, shipments of saturated lead acid are restricted.

Thermal runaway can occur when improperly charged.

Figure 4: Advantages and limitations of lead acid batteries.

The Lithium Ion battery

G.N. Lewis led the work on lithium-ion batteries in 1912, but the first non-rechargeable lithium-ion batteries came to market in the early 1970s. The lightest of the metals is lithium, which has the highest electrochemical potential, providing the highest energy density.

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