You are here: / Ni-Mh Battery
, ,

Basics about Discharging

Himax - Discharge-Curves-Power（Data trend chart）

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.

Discharge-Curves-Power

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.

,

Summary Table of Nickel-based Batteries

NI-MH-Battery-Pack

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.

,

Alternate Battery Systems

Himax - New-Battery-Technologies

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.

, ,

Cycling Performance

Cycling Performance（Data trend chart）

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.

Performance of standard NiCd

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.

Performance of ultra-high-capacity NiCd

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.

Performance of 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.

Performance of lithium-ion

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.

, ,

Safety Issues When Using Drones

Himax - Drones

Safety Issues When Using Drones

The most common drone safety issues, next to pilot error are related to battery failures. If you’ve ever experienced battery failure during charging, storage, or operation, then you understand how alarming and potentially dangerous it can be.

Over 200 injuries related to drone battery incidents were reported to the U.S. Consumer Product Safety Commission between 2012 and 2017. The reported incidents involved fire, smoke, and even explosions. It’s likely that countless other incidents went unreported because they didn’t end in an emergency room visit.

In order to ensure battery safety, it’s critical as a commercial drone operator to purchase your batteries and battery management systems from a reputable, safety-minded provider. 

Why Do Drone Batteries Fail? 

While some drone battery failures occur for reasons that no one could predict or discover, most incidents could have been avoided with proper care and maintenance of your battery fleet. To reduce your potential risk drone users should be well-versed in battery safety practices.

Manufacturers are also responsible for the safety of each battery. In order to provide reliable performance and increased safety, reputable battery manufacturers employ high-quality materials and precise manufacturing and quality control processes. When manufacturers cut corners, they reduce overall battery safety. Quality costs money, so when a battery price seems too good to be true, it probably is.  

Choosing Batteries for Drone Safety

Know the Manufacturer

Reputable manufacturers are transparent and provide plenty of information about their company and practices. Research the quality of materials and designs used to manufacture their drone batteries. If you’re considering a discounted battery purchase but can’t find much information about the company that makes it, it’s best to reconsider. Make sure that your supplier is located within the United States, if you need support or have a question, you want to have an English speaking support staff to answer your call.

Focus on Safety Features

In the interests of the bottom line, some manufacturers strip away “expendable” safety features to create budget batteries. You might be tempted by those batteries when you’re browsing online, but be careful – always review the product description carefully and note the safety features listed. You’ll probably need to visit the manufacturer’s website to find a complete list of features and related details. 

Choose the Right Charger

A top-of-the-line drone battery plugged into a low-quality charger will inevitably cause headaches and compromise battery safety. It’s best to choose a “smart” or programmable battery charger. You’re better able to manage your drone batteries when you have important charging data at your disposal. It’s also best to use batteries and chargers produced by the same manufacturer. 

Best Practices for Battery Safety

How to Store

It’s recommended that you drain batteries to 40-60 percent of their full capacity before storing them for more than ten days. If you’re planning to store them for fewer than 10 days, drain them to 60-80 percent of their capacity. Partially draining batteries reduces stress on them and extends their working life. Never store your batteries for more than three months without charging them. 

It’s best to store batteries in a dry location at room temperature. Before tucking those batteries away, inspect them for a puncture, puffing, or other abnormal physical features that indicate an unhealthy battery. 

How to Charge

Most incidents occur while the battery is charging, which is why it’s recommended to charge your drone batteries at a 1C charge rate. To find this rate take the milliamp hour capacity rating of your battery divide it by 1000. For example, a 22,000 millamp battery should be charged at 22amps. Always monitor your batteries during the charging process and only charge your batteries on a non-flammable surface located away from any flammable materials. While battery fires are rare, a damaged battery or incorrect charge settings can cause a battery to swell, expand and worst-case scenario catch fire. Being prepared with a suitable fire extinguisher and ready to react if you see signs of trouble is critical.

How to Operate

How and where you fly your drone can impact its battery life. It’s best to avoid flying in extreme temperatures. Refer to the manufacturer’s instructions for specific information about safe flight temperatures for your drone. The generally accepted rule is to fly within the range of 14 °F to 104 °F for optimal drone safety. 

Using an appropriately sized battery for your drone is critical for overall safety. Using a battery that does not provide enough power for your drone will not only adversely affect battery life but can lead to overheating of the pack and thermal runaway, a dangerous process that devours the battery. Thermal runaway is a heat-induced chemical reaction that intensifies and continues to raise internal temperatures until all the reactive agents within the cell are consumed. 

How to Transport

Secure your batteries with padding during transport to prevent them from hitting against other batteries or objects. Also, make sure that any exposed leads or connectors are protected from arcing or shorting. Cover with tape or use specifically designed covers to avoid issues.  You can purchase cases and backpacks designed specifically for this purpose. If you’re taking them with you on a plane, remember to pack your drone and batteries in your carry-on baggage and review the current FAA rules for batteries. Regulations for transportation of batteries are also subject to the carrier by carrier-specific rules. Always check with your airline before you try and fly with your drone or batteries.

Himax Provides Safe, Custom-Designed Batteries for Commercial Use

Himax values safety above their bottom line, which is why they offer custom-designed batteries that are produced with superior materials and high-tech safety features. 

Custom-Designed Lithium-Ion Batteries for OEM Applications

Himax’s custom-designed batteries were created for professional, commercial, and industrial use. Their robust composition will withstand the most rigorous, unmanned applications without compromising on energy density and weight. They offer a wide range of custom battery designs, which ensures that you will receive a product that meets your unique and precise requirements. 

Why does custom design matter for drone safety? Himax’s custom-designed batteries accommodate targeted operating temperatures and discharge voltages. When your drone battery is designed with a specific application in mind, it will operate more efficiently and safely in the conditions under which it will actually be used. 

Battery Safety Certifications

Himax products are produced with high-quality materials that ensure durability, extend battery life, and prevent battery failure. Himax can assist with manufacturing to meet and exceed any required safety compliance schemes. We have experience with UN38.3, CE, RoHS, and FCC. We have multiple NRT laboratories that can provide testing services.

Safety Features

Himax’s commercial series of batteries provides the most advanced battery management system (BMS) available on the market. These “smart” batteries include an embedded BMS. This active BMS system helps extend battery life, tracks, and stores critical battery information. The system also allows for additional safety features include real-time fault detection, battery lockout protocol, five LED Indicators, and the ability to capture and store KPIs, which include:

  • Remaining capacity
  • State of charge
  • Cell voltage
  • Pack voltage
  • Current draw
  • Cell temperatures
  • Faults

In addition to careful construction and critical safety features, Himax inspects all products before they leave the factory to ensure each one meets their quality and safety standards.

,

8 Tips For Using NiMH Batteries(Nickel-Metal Hydride)

2200mah-Nimh

2200mah-Nimh

NiMH is an abbreviation for nickel-metal hydride. Ni-MH batteries are our most common rechargeable batteries in consumer electronics. Due to its superior chemical properties, nickel-metal hydride batteries have replaced nickel-cadmium batteries. Since NiMH does not use cadmium (the use of toxic chemicals in battery use) and also does not have the same memory problems that plague NiCD, NiMH batteries are a better choice. At the same time, portable high-power processing methods are one of the most popular processing methods in battery use. Today, we come to know the techniques of using Ni-MH batteries.

What are the classifications of Ni-MH batteries?

We usually see nickel-metal hydride battery packs composed of multiple single batteries connected in series. Compared with lithium-polymer batteries (LiPO), nickel-metal hydride batteries are safer to use. The rated voltage of each individual battery is 1.2V, which means that we see that the rated voltage of the Ni-MH battery pack is a multiple of 1.2V. In particular, we supply 1.2, 2.4, 3.6, 4.8, 6.0, 7.2, and 8.4-volt battery packs. Regardless of the physical size of the battery, the rated voltage of each Ni-MH battery is 1.2V. The physical size of the battery indicates the capacity of the battery. Generally, the larger the battery, the greater the mAh of the batter

Application of Ni-MH battery

As mentioned above, Ni-MH batteries are very suitable for short-term (<30 days) high water consumption. We have seen some consumer use of nickel-metal hydride batteries in digital cameras, communication equipment, personal cosmetics equipment, and laptop batteries.

digital cameras

How to use NiMH batteries?

Ni-MH batteries may have some defects, but what matters is that they discharge themselves. When the battery is not in use, it will slowly deplete its power. If the remaining battery time is long enough, the battery may be permanently damaged. A rough estimate of the depletion of NiMH batteries is that 20% of the battery power will be depleted within the first 24 hours after charging, and 10% will be depleted every 30 days thereafter.

How to charge the Ni-MH battery?

To charge the Ni-MH battery, we need a specific charger, because using an incorrect battery charging method may make the battery unusable. It should be noted that the time to charge the Ni-MH battery is less than 20 hours, because charging for a long time may damage the battery.

NiMH battery charging

How many cycles can NiMH batteries be charged?

Normally, it is expected that the charge/discharge cycle of a standard Ni-MH battery is 2000 times, but different mileage may vary. This is because every battery is different. The use of the battery can also determine the number of cycles that the battery will survive. All in all, the 2000 cycles (or about) of the battery are quite impressive for a rechargeable battery.

What are the precautions when charging Ni-MH batteries?

In order to protect the service life of the battery, you should keep in mind a few precautions: trickle charging is the safest way you can charge the battery. To do this, please make sure to charge at the lowest possible rate, the total charging time is less than 20 hours, and remove the battery at this time. This method basically charges the battery at a speed that does not overcharge the battery but keeps it charged. Do not overcharge the NiMH battery. In short, once the battery is fully charged, it will stop charging. There are several ways to know when the battery is overflowing. The battery chargers on the market are all “smart”, which can help test the small changes in the battery’s voltage/temperature and can indicate the overflowing battery.

How to store Ni-MH batteries?

Initially, nickel-based batteries and storage had widespread problems. Basically, if the battery is not completely drained before charging, over time, this part of the battery capacity will slowly run out. However, the current nickel-metal hydride batteries do not have these problems, but if you do not fully discharge, you can still see the same effect. The newer Ni-MH can be restored by “exercising” the battery (full charge and discharge the battery several times).

Can NiMH batteries replace alkaline batteries?

This is totally possible. If you are using alkaline batteries, you can pick up some Ni-MH batteries to replace them. The voltage drop experienced by alkaline batteries during use offsets the voltage difference (alkaline 1.5v, NiMH 1.2V). Every battery is a little different, and the quality of the battery is also different. Before charging for the first time, be sure to check the battery data sheet/product information.

Want to know more about nickel-metal hydride batteries? you can consult us directly, we will provide you with professional battery solutions.

,

Car Battery Life: When is it Time For a Change?

Himax - Car-Battery-12v

Car batteries are one of the most important components of any vehicle, yet for some reason, they are often overlooked. Your car needs the electrical charge it gets from the battery to start the engine, which is why you should always be aware of the age and status of the battery in your vehicle. It can be a major inconvenience if you go to start your car one day only to find that the old battery has lost its charge. To help you avoid this issue, and to get the most out of your battery during its natural lifespan, take a look at some of the guidelines below that will help you determine when it is time to change your old car battery.

Average Battery Lifespan

To get started, let’s think about how long a brand new car battery will last under typical driving conditions in a city like Vancouver. There are many factors that affect the amount of time your automobile battery will function efficiently. Weather can have a big impact, especially cold temperatures. The power demands you place on a battery will also have an impact on how long the unit will last. In ideal conditions, a battery can last more than five years. Unfortunately, ideal conditions for a battery are not exactly common in a place like Vancouver, which sees a significant amount of precipitation, as well as hot and somewhat cold weather each year. Also, with the increasing number of electronics owned by a typical person, and the corresponding chargers, cables and devices that connect to a car’s electrical system, the average driver asks more of their car battery than ever before. With these factors in mind, you shouldn’t be surprised if your battery doesn’t last longer than three years. There really is no exact amount of years that a car battery is guaranteed to last, so let’s say the average lifespan in a city like Vancouver could be between three and five years.

When to Change?

There are a few telltale signs that indicate your battery is nearing the end of its lifespan. For the most part, if you check your car battery every six months or so, you should avoid any unwanted surprises or startup issues. If during your check you notice a bad smell coming from the battery that reminds you of rotten eggs, you should start looking for a replacement right away. You should also keep an eye on the regular electrical components of your vehicle such as interior lighting and headlights. If these lights flicker for any reason while you’re driving, idling or starting your car, that is also a good sign your car battery is near the end of its lifespan. You should also make more frequent checks if your car battery is more than three years old, especially if, as discussed above, you live in an area that sees high temperatures in the summer and significantly low temperatures in the winter. One final indicator that your battery needs to be changed is the battery light on your vehicle’s dashboard. When this light starts to appear on a regular basis, regardless of how old your battery happens to be, you should take a look and consider a replacement as soon as possible.

 

For more helpful tips about car batteries, or if you have any inquiries about other battery Himax, be sure to visit the experts at Polar Battery today!

Email: sales6@himaxelectronics.com

 

,

Wide Temperature-Range Ni-MH Battery

1800mah-Nimh

NI-MH 2200mah AA

Temperature has one of the greatest impacts on the charge and discharge performance of batteries. The electrode/electrolyte interface is considered the heart of the battery, and the electrochemical reactions at this interface are closely related to the ambient temperature. If the temperature drops, the reaction rate of the electrode also drops.

When NiMH batteries are charged and discharged, multiple factors must be considered: the surrounding environment of the batteries but especially battery performance and service life under extreme temperatures.

We will explore what occurs to NiMH batteries, particularly wide temperature-range NiMH batteries, when under low and high temperatures.

Wide temperature-range NiMH batteries

Wide temperature-range NiMH batteries, as their name implies, are a type of NiMH batteries with a wide working-temperature range and excellent performance at -40°C to 80°C. In other words, these batteries can operate efficiently at both low and high temperatures, and their temperature limitations are greatly reduced.

Under low temperatures

The discharge efficiency of ordinary nickel-hydrogen batteries are significantly reduced at low temperatures. At -20°C, the lye reaches its freezing point and the battery charging speed greatly diminishes. Charging at low temperatures (below 0°C) increases the internal pressure of the battery and possibly causes the safety valve to open.

In order to charge effectively, the ambient temperature range must be controlled between 5℃ to 30℃. Generally, charging efficiency increases with the rise of temperature. However, when the temperature rises above 45℃, the performance of the battery degrades, and the cycle life of the battery greatly shortens.

Under low temperatures, the viscosity of electrolyte becomes higher, the proton transfer rate inside the electrode becomes slower, and the ohmic internal resistance also increases, which leads to larger polarization of the battery during discharge. Some batteries cannot discharge at low temperatures due to large polarization.

Under high temperatures

Under high temperature, the viscosity of the electrolyte decreases, and the hydrophilic ability of various materials increases. Liquid absorption also increases, which leads to the expansion of the electrode sheet, and liquid starts to leak from poor electrical receptivity.

The following is the electrochemical principle of charging and discharging Ni-MH batteries with KOH as the electrolyte (7moL/LKOH+15g/LLiOH).

Charge

Positive Pole: Ni(OH)2+OH-→NiOOH+H2O+e-

Negative Pole: M+H2O+e-→MH+OH-

Total Response: M+Ni(OH)2→MH+NiOOH

Discharge

Positive Pole: NiOOH+H2O+e-→Ni(OH)2+OH-

Negative Pole: MH+OH-→M+H2O+e-

Total Response: MH+NiOOH→M+Ni(OH)2

In the above formula, M is the hydrogen storage alloy and MH is the hydrogen storage alloy with adsorbed hydrogen atoms. The most commonly used hydrogen storage alloy is LaNi5.

Characteristics of a wide temperature-range Ni-MH battery

The following are a couple of the characteristics of a Grepow’s wide temperature-range Ni-MH battery:

The charging and discharging efficiency of 0.2C at -40℃ can reach 80%

The charging and discharging efficiency of 0.2C at 80℃ can reach 85%

Ni-MH battery technology has been tried, tested and proven for commercial and industrial applications especially in automotive batteries and outdoor power supplies in high and cold temperatures. Its safety and reliability are unparalleled in the market.

Grepow Inc. offers a variety of Ni-MH batteries with a wide temperature range. These batteries provide new electrode-development technologies that can achieve a long life, and they have good usability and stability with compatible sizes.

, ,

High C-rate Ni-MH Batteries

NI-MH-Battery

NI-MH-Battery-Pack

A nickel metal hydride (Ni-MH) battery is similar to a nickel cadmium (NiCd) battery, but it has higher capacity, less memory effect, and lower environmental pollution (or more simply, it doesn’t have the toxic cadmium) than the NiCd battery. Its recycling efficiency is better than that of lithium-ion batteries, and it is known as the most environmentally friendly battery.

The discharge performance of NiMH batteries can also meet the needs of most electronic products, and it is particularly suitable for products that require stable voltage over long discharge times.

High C-rate

Typically, high C-rate Ni-MH batteries can be charged at 1C and be fully charged in just over an hour. When discharged with a current of 5C, the median voltage of the battery can reach more than 1.24V and still discharge over 90% of its capacity.

Ni-MH batteries are efficient in their fast charging and high current-discharge performance, which makes them especially suitable for the high current discharge of electrical appliances, such as power tools, large toys (car toys, remote control aircraft) and so on.

Charging efficiency

The charging efficiency is the ratio of the capacity of a battery discharged under certain discharge conditions up to a certain cut-off voltage to the capacity of the battery input, which can be calculated according to the following formula:

Ni-MH battery's charging efficiency formula | Grepow
the battery’s charging efficiency formula

Because the input energy is partially consumed in the side reaction to produce oxygen, the charging efficiency is affected by the charging rate and the environmental temperature. The charging current must be within a certain range when charging: if the current is too small or too large, the charging efficiency will be low.

High charge rate

A Ni-MH cell has many similar characteristics to its NiCd counterpart, and it also follows a similar discharge curve to that of the NiCd. However, the Ni-MH battery is intolerant of overcharging, which can result in reduced capacity.

In order to ensure the best battery life, 1C charging is the recommended charging rate. After fast charging, it is recommended to use 0.03-0.05C trickle charging to compensate for self-discharge and maintain battery capacity.

High discharge rate

Himax’s Ni-MH batteries can offer up to 2 times the C-rate of similarly sized, standard NiCd batteries. Due to their higher discharge rate and energy density characteristics, users can use Himax’s Ni-MH batteries in more powerful devices and applications.

The following picture is the discharge curve of :

NiMH UP43SC2000 Performance Measurement Data Plots | Grepow
UP43SC2000-15C Performance Measurement Data Plots

Here are some specifications of Himax Ni-MH battery:

specifications of Grepow NiMH battery

There are three different series for Himax’s Ni-MH batteries that correspond to thor different discharge rates:

LP series, which stands for low power, means that the medium discharge rate is within a 5C rating. HP series stands for high power, and it has a discharge rating of 10C. Finally, the UP series, standing for ultra high power, has a discharge rate of 15C or more.

The above information comes from Himax, the manufacturer of Ni-MH, LiPO, and LiFe batteries. For more information, please further explore our blog or contact us at sales@himaxelectronics.com.

, ,

The Difference Between Lipo And NiMH Battery

LiPO-US-NI-MH

LiPO-US-NI-MH

The biggest difference between NiMH and LiPo batteries is the chemical properties that enable the charging of the batteries. NiMH (Nickel-metal hybrid) uses nickel-based technology and LiPo (Lithium Polymer) batteries use a lithium-ion technology.

What the battery types have in common is that they both store a certain amount of energy depending on their capacity. Batteries can be manufactured with different voltages and capacities by installing battery cells in series or parallel inside the battery pack. One should be careful not to drop the batteries or damage the cases of the battery cells because it can cause a short circuit. Both battery types must be disposed of properly as hazardous waste.

The Batteries Differ in Their Properties and Uses.

NiMH batteries are easier to use. They must be fully discharged before charging and must be charged full before storing (Unless Manufacturer tells otherwise. Exampl. Traxxas). NiMH battery chargers are also very simple.

LiPo batteries don’t have to be fully discharged and they must be stored with a 50-70 % charge level. The charging must be done with a charger with balance charging. It is good to charge and store LiPo batteries in a LiPo safe bag.

Properties and remarks on NiMH batteries:

NI-MH-Battery

 

  • Easy and worry-free charging and storing “Safe choice for beginners”
  • Cheaper to manufacture
  • A common battery type in home appliances and devices
  • Rated voltage of cells 1.2V
  • Must be fully discharged before charging
  • Storing fully charged (Unless Manufacturer tells otherwise. Exampl. Traxxas)
  • Batteries are built with standard sized cells with metal cases
  • “Memory effect”: Batteries must always be fully discharged in order to keep full capacity available

Properties and remarks on LiPo batteries:

LiPO-Battery

  • Easy to use with the right devices
  • Manufacturing process is more complicated
  • Becoming a common battery type in home appliances and devices
  • Rated voltage of cells 3.0 V when discharging
  • A charger with balance charging must always be used for charging
  • Storing with 50-70 % charge level (Voltage per cell 3.85V-3.9V)
  • A LiPo safe bag must be used when charging and storing
  • Lighter than NiMH
  • Can be built in different sizes
  • “Memory effect”: almost non-existent, batteries don’t have to be fully discharged before recharging

The advantages of lithium batteries compared to NiMH batteries are undeniable.

The weight/power ratio in LiPo batteries is significantly better. LiPo batteries are noticeably lighter and they can store the same amount or more energy relative to their capacity than NiMH batteries. The power output of LiPo batteries is greater in quality and quantity. The power output of LiPo batteries is steady throughout the discharge, whereas the power output of NiMH batteries starts to decrease soon after charging because of higher discharge rate of the battery type.

Therefore with a LiPo battery with the same capacity as a NiMH battery a longer drive time and better performance can be achieved.

Copyright ©2024 Shenzhen Himax Electronics Co.,Ltd. | All Rights Reserved