I believe everyone knows that due to the structure of cells and the specificity of the chemistry, the battery cannot be charged below the freezing temperature. There are still a lot of companies are advertised as “low-temperature rechargeable“, “low temperature -xx℃ charge” words, Grepow’s low-temperature series battery can also charge in the environment of minus 20 degrees, how is it done? What about charging in a low-temperature environment? In this article, I will tell you how to achieve it.

Why can’t I charge the battery in a low-temperature environment?

Materials of lithium-ion batteries, such as separators and electrolytes, are organic materials with a low melting point. If the temperature is too high, some negative chemical reactions will occur inside the battery, which will seriously affect the battery life and even safety performance.

The key materials of the battery under low-temperature conditions: the conductivity of the positive electrode, the negative electrode, the electrolyte, etc. are reduced, resulting in a decrease in electrical conductivity, which will seriously affect the battery life.

Low-temperature protection is when the temperature is too low, the metal lithium in the battery will deposit, no longer react with the substance, resulting in internal short circuit of the battery, which will cause damage to the battery or cause safety hazard of the battery.

2 ways to charge the battery at freezing temperature

Battery charger self-heating charging

This way is rely on a special charger for heating because it can not be charged normally in a low-temperature environment, so the charger heats the battery till the temperature above the freezing point, and then charge the battery.

This method is more safe and effective, but it takes longer time, because the charger can only perform small-rate discharge heating in a low-temperature environment. Therefore, it will take around 1 to 3 hours to heat up before charging.

Advantages: Able to charge even when the battery is empty

Disadvantages: Longer charging wait time; Rely on a special charger

Condition by BMS / PCM

The battery with BMS / PCM can provide two functions, one is a low-temperature alarm, there will be a warning when the battery charge or discharge below the set value, or the protection function, directly disconnect the discharge to prevent damage to the battery caused by low temperature or accident.

The second type is to start the low-temperature self-heating function through BMS/PCM. The specifications are can be customized. For example, a 5000mAh battery with self-heating function BMS will reserve 1000mAh of power in the battery every time it is discharged. Before the battery charging, the BMS will discharge the reserved power to heat the battery until the rechargeable temperature, then the battery will starting charge automatically. These are all based on the settings of the BMS.

Advantages: The waiting time is short, and the reserved power can be customized according to the needs of the ambient temperature.

Disadvantages: The battery’s operating capacity will be reduced because BMS will reserve a portion of the power for low-temperature charging.

 

We know why lithium gets all the credit: the chemistry that makes these batteries so amazing wouldn’t work half without this particular metal.

Considerably other rechargeable battery-powered battery plans are constrained in manners lithium batteries aren’t!

What many people don’t understand, however, is that lithium remarkably makes up a little of the battery itself. Lithium-based batteries speak to one of the quickest expanding parts of the vitality business today. These batteries are long-lasting. Their life span is up to 5-7 years.

Why LifePO4 batteries are expensive because of what features they entail and these features even make better choice for you:

Safety And Stability

LiFePO4 batteries are most famous for their Strong security profile, the consequence of amazingly stable chemistry. Phosphate-based batteries offer unrivaled thermal and chemical dependability, which increases the well-being of lithium-Ion batteries made with other cathode materials.

When exposed to unsafe circumstances, for example, collision or shortcircuiting, they won’t detonate or burst into flames, altogether reducing any opportunity of mischief. However, you’re choosing a lithium battery and envision use in dangerous or sensitive situations. LiFePO4 is likely your best decision.

Environmental Impact

LiFePO4 batteries are non-harmful, non-polluting, and contain no rare earth metals, settling on them a naturally conscious decision. Lead-acid and nickel oxide lithium batteries convey noteworthy natural hazards (particularly lead corrosive, as inside synthetic compounds debase structure over the team and inevitably cause spillage).

Compared with lead-acid and other lithium batteries, lithium iron phosphate batteries offer critical features of interest, including improved release and charge effectiveness, longer life expectancy, and the capacity to deep cycle while looking after execution. LiFePO4 batteries frequently accompany a more significant expense price tag. Still, a much better cost over the life of the product, minimal maintenance, and rare replacement makes them a valuable investment and an intelligent long-term solution.

Space Efficiency

Also worth mentioning is LiFePO4’s space-efficient features. At one-third, the mass of most lead-acid batteries and almost half the importance of the prevalent manganese oxide, LiFePO4, provide an effective method to make use of space and weight. You are creating your product more efficiently overall.

Performance

Performance is a significant fact in figuring out which kind of battery to use in a given application. Long life, slow self-release rates, and less weight make lithium iron batteries an engaging choice. They are relied upon to have a more extended shelf life of realistic usability than lithium-ion. Administration life typically times in at five to ten years or more, and runtime substantially surpasses lead-acid batteries and other lithium formulation. Battery charging time is likewise extensively diminished, another effective presentation perk. However, If you’re searching for a battery to stand the trial of time and charge rapidly, LiFePO4 is the proper answer.

Lithium Iron Phosphate (LiFePO4, LFP) is a rechargeable battery ideal for high power applications. They are the immediate substitution for lead-acid batteries. If you’re interested in buying or custom LiFePO4 batteries, then you have come to the right place. Continue reading to find who makes and where to buy or custom LiFePO4 batteries. Email us: sales@himaxelectronics.com

Lithium iron phosphate battery is one of the safest batteries we using, and its durability and safety are definitely superior to other lithium ion batteries. So, can we overcharge lithium iron phosphate batteries? What range of voltage can be allowed it be overcharged? Under normal circumstances, the answer is NO!

What are lithium iron phosphate batteries?

The lithium iron phosphate battery is a lithium-ion battery that uses lithium iron phosphate as its positive electrode material. It is also called a LiFePO4 battery for short.

What is overcharging?

Overcharging a battery means that the battery charger is charging the battery too far past its fully-charged voltage. For example, the full-charge voltage of a monolithic lithium iron phosphate cell is 3.65V. When the charge exceeds 3.65V, it is overcharged.

What will happen when a lithium-ion polymer (LiPo)  battery is overcharged?

Overcharging a battery cell will cause permanent damage to the cell. In terms of testing for safety, we internally test the different overcharge levels of the battery cells. The following are our test standards:

LiPo battery cell: No fire when the charging voltage reaches 4.8V (one of the necessary conditions)

LiFePO4 battery cell: Charging voltage reaches 10V and does not catch fire (one of the necessary conditions)

Charging with a damaged or non-corresponding charger may also cause overcharging. When the voltage is too high, a large amount of lithium ions overflow from the positive electrode, and lithium ions that cannot be absorbed by the negative electrodes can form dendrites on the surface of the battery, which can cause a short circuit inside the battery. The short-circuit current will generate a lot of heat, and the rapid temperature increase may cause the electrolyte as an organic solvent to burn (organic solvents are extremely flammable). In severe cases, it will cause a decomposition reaction of the positive electrode or the reaction of the negative electrode and the electrolyte. This can generate a large amount of gas; this can result in an explosion especially since the cells are enclosed.

If a battery doesn’t have the Battery Management System (BMS), continuously charging the battery will raise the voltage. In this situation, the lithium ions remaining in the cathode are removed and more lithium ions are inserted into the anode than under standard charging conditions.

It has been observed through ARC studies that the thermal stability of a cell is highly dependent on its state of charge. An overcharged Li-ion cell was found to have much lower thermal stability with an onset runaway temperature as low as 40ºC

Source: Science Direct

Since LiFePo4 is safer, can we over-charge it?

Our suggestion is to never over-charge/discharge a cell!

The most common causes for premature failure of LiFePO4 cells are overcharging and over-discharging. Even a single occurrence can cause permanent damage to the cell, and such misuse voids warranties. A Battery Management System (BMS) is required to ensure it is not possible for any cell in your pack to go outside its nominal operating voltage range.

What is a BMS?

The Battery Management System is a piece of hardware with an electronic system on board that manages a rechargeable battery (cell or pack) and is the link between the battery and it’s user. It can more intelligently manage and maintain each cell, improve battery utilization, prevent battery overcharge and discharge, prolong battery life, and monitor battery status.

If you need a customizable BMS to prevent overcharging or other potential issues, please contact us to get more information.

What is the deep cycle battery?

A deep-cycle battery is a battery that is designed to be able to store a large quantity of energy while having the ability to discharge from 100% down to 0% without hurting the battery.

A deep-cycle battery also ensures that a steady amount of power is being delivered to applications over a long period of time without interruption or failure. It is constructed with thicker plates and a denser active material ratio. Due to these features, a deep-cycle battery achieves greater cycling capacities.

 

What is DOD (Depth of Discharge)?

The Depth of Discharge (DOD) of a battery represents the percentage of the battery that has been discharged relative to the overall capacity of the battery. For example, if a battery has a nominal capacity of 100kWh and discharges 30kW, the Depth of Discharge comes out to be 30%.

Its DOD is (30x 1) / 100 = 30%.

The more often a battery is charged and discharged, the shorter the battery life will become. It is generally not recommended to completely discharge a battery as it will greatly reduce the battery life. Many battery manufacturers specify the recommended maximum DOD in order to maximize the battery performance.

 

If a manufacturer of a 10 kWh battery recommends a maximum DOD of 80%, the battery should not use more than 8 kWh without charging. The DOD is an important factor to consider because a higher DOD means that more of the energy in a battery can be used. The DOD of many modern lithium-ion batteries is 100%.

 

A battery’s “cycle life,” the number of charge/discharge cycles in its life, depends on how much battery capacity is typically use. Rather than completely draining a battery to its maximum DOD, a user will be able to attain more cycles in their battery regularly discharging it with a lower percentage of charge.

 

For example, a battery may have 15,000 cycles at a DoD of 10%, but only have 3,000 cycles at a DoD of 80%.

What applications need deep-cycle batteries?

• Floor Machines
• Electric vehicles
• Materials handling
• Renewable energy
• Aerial work platforms
• Commercial transit
• RV and Marine
• HME Mobility Telecom UPS
• Security Electronics

All of these applications require high energy retention, deep-cycle discharge, a large number of cycle lives, and a stable discharge performance.

Why choose LiFePO4 deep cycle batteries?

Another way to think of the DOD is the extent to which discharge begins to stop during use. 100% DOD refers to discharge at full capacity.

 

The life of a lead-acid battery is greatly affected by the DOD. A lead-acid battery is likely to fail quickly on a user as it normally only allows 50 to 80% DOD.

 

In contrast, A LiFePO4 (Lithium Iron Phosphate) battery, which is newer technology, has a deep-cycle discharge, so it can reach 2000 cycles with 100% DOD. Lithium batteries can also be discharged at a specific C-rating. With a working temperature of 25° C and a discharge rate of 0.5C, a LiFePO4 battery can reach 4000 to 6000 cycles.

 

Compared to lead-acid batteries, the advantages of deep-cycle lifepo4 batteries are the following:

• Eco-friendly
• Good high-temperature resistance
• Good safety characteristics
• No memory effect
• Higher-capacity compare with same size lead-acid battery
• Longer cycle life than other lithium-ion batteries
• Ideal drop-in replacement for lead-acid batteries
• Lower total cost of average use

 

Lithium batteries, or Lithium-ion Polymer (LiPo) batteries, are batteries that use Lithium as a negative electrode material and use a non-aqueous electrolyte solution. In 1912, Lithium metal batteries were first proposed and studied by Gilbert N. Lewis. In the 1970s, M.S. Whittingham proposed and started researching Lithium-ion batteries. However, due to the complications of using the unstable Lithium metal, the batteries were not popular at the time.

 

It is now with further development that Lithium-ion Polymer batteries have fast become a preferred power source for many applications and industries.  It is for this reason that we will explore the charging cycles of lithium-ion polymer batteries in-depth in this article.

 

What is a charging cycle?

Some consumers may have that the charge and discharge life of lithium-ion polymer batteries is “500 times.” But what is “500 times?” It refers to the number of charge and discharge cycles of the battery.

 

Let us look at an example: Let us say there is a lithium battery that uses only half of its charge in one day and is then charged fully.  On the next day, it again only uses half of its power.  Although the battery has been charged twice, this does not count as one charge cycle but two.

 

A charging cycle is when a battery goes from being fully charged to empty and then from empty to fully charged; this is not one single charge. Just based on the previous example, it’s clear that it can usually take several charges to complete a cycle.

 

Every time a charging cycle is completed, the battery capacity decreases a bit. However, the reduced capacity is very small. High-quality batteries will still retain 80% of their original capacity after many cycles of charging. Many lithium battery products will still be used after two or three years. Of course, after the end of the lithium battery life, it still needs to be replaced.

 

Ultimately, a 500-cycle life means that a manufacturer has achieved about 625 recharge times at a constant discharge depth (such as 80%) and reached 500 charging cycles.  In other words, if we ignore other factors that could reduce the Lithium-ion battery capacity and we take 80% of 625, we receive 500.

 

However, due to various factors in life, especially considering how the depth of discharge (DOD) during charging is not constant, “500 charging cycles” can only be used as a reference to battery life.

 

Overall, it is better to think of the life of the lithium battery as related to the number of times the charging cycle is completed and not as directly related to the number of charges.

Deep and shallow charging

Here is another way to think of the cycle lives of lithium-ion polymer batteries: the life of a Lithium battery is generally 300 to 500 charging cycles. Assume that the capacity provided by a full discharge is Q. If the capacity reduction after each charging cycle is not considered, lithium batteries can provide or supplement 300Q-500Q power in total during its life. From this we know that if you use 1/2 each time, you can charge 600-1000 times; if you use 1/3 each time, you can charge 900-1500 times. By analogy, if you charge randomly, the number of times is uncertain. In short, no matter how a Lithium battery is charged, it is constant to add a total of 300Q to 500Q of power. Therefore, we can also understand this: the life of a Lithium battery is related to the total charge of the battery and has nothing to do with the number of charges. The effects of deep charging and shallow charging on lithium battery life are similar.

 

In fact, shallow discharge and shallow charges are more beneficial to lithium batteries. It is only necessary to deep charge when the power module of the product is calibrated for lithium batteries. Therefore, lithium-ion-powered products do not have to be constrained by the process: they can be charged at any time without worrying about affecting the battery life.

 

Effects of temperature on battery life

If a Lithium-ion Polymer battery is used in an environment higher than the specified operating temperature (above 35℃), the battery’s power will continue to decrease.  In other words, the battery’s power supply time will not be as long as usual. If a device is charged at such temperatures, the damage to the battery will be greater. Even if the battery is stored in a hot temperature environment, it will inevitably cause damage to the battery. Therefore, it is a good idea to extend the life of lithium-ion polymer batteries by using it under normal operating temperatures as often as possible.

If you use Lithium batteries in a low-temperature environment (below 4℃), the battery life will also be reduced. Some older Lithium batteries of mobile phones cannot even be charged under low temperatures.  However, unlike in high temperatures, once the temperatures rise, the molecules in a battery will heat up and immediately return to the previous charge.

Having explored battery performance under these extreme temperatures, the question now becomes if there are any batteries that can be used in environments with low or high temperatures.

Currently, GREPOW’s batteries can be used at temperature ranges of -50 ℃ to 50 ℃ or 20 ℃ to 80 ℃. Our low-temperature Lithium batteries’ discharging current of 0.2C at -50℃ is over 60% efficiency, over 80% efficiency at -40℃, and around 80% efficiency at -30℃.

We can further custom-make batteries depending on your specifications.

Charge-discharge cycle

To get the most out of lithium-ion batteries, you need to use it often so that the electrons in the Lithium batteries are always in a flowing state. If you do not use lithium batteries often, please remember to complete a charging cycle every month and do a power calibration, i.e. deep discharge and deep charge, once.

 

After the nominal number of charge and discharge cycles is used up, a battery’s ability to store power will drop to a certain level, but the battery can continue to be used.

 

Lithium batteries have no limit on the number of times they can be recharged. Regular manufacturers can charge and discharge batteries at least 500 times, and the capacity is maintained at more than 80% of the initial capacity. If charged and discharged once a day, batteries can be used for two years. Usually, batteries in mobile phones are charged 1000 times or more, which causes the batteries to be severely non-durable.

 

Below is a proper method of maintaining your mobile device’s battery:

 

When you charge your phone, fully charge it each time.

Do not fully discharge the battery. The battery needs to be charged when the power is less than 10%.

Charge with the original charger; do not use a third-party charger.

Do not use your mobile phone while it is being charged.

Don’t overcharge: stop charging after the battery is full.

According to the experimental results, the life of a lithium battery continuously declines with an increase in the number of charges.

Lithium battery cycle specified by the national standard

In order to measure how long the rechargeable battery can be used, the definition of the number of cycles is specified. Actual users use a wide variety of tests because tests with different conditions are not comparable, and the comparison must define the definition of cycle life.

 

Lithium battery cycle life test conditions and requirements specified by the national standard are as follows:

Charge at 1C under the environment temperature of 20 ° C ± 5 ° C. When the battery terminal voltage reaches the charging limit voltage of 4.2V, change to constant voltage charging until the charging current is less than or equal to 1 / 20C, stop charging, leave it for 0.5h to 1h, and then discharge it at 1C to the termination voltage of 2.75V.

 

After the discharge is completed, leave it for 0.5h to 1h, and then perform the next charge and discharge cycle two consecutive times. Less than 36min, the end of life is considered, and the number of cycles must be greater than 300 times.

Having gone over the national standard, we should explain the following:

1. The standard specifies that the cycle life test is performed in a deep charge and deep release mode.

 

2. The cycle life of the lithium battery is specified. According to this model, the capacity is still more than 60% after ≥300 cycles.

 

However, the number of cycles obtained by different cycling systems is quite different. For example, the other conditions above are unchanged, and only the constant voltage of 4.2V is changed to a constant voltage of 4.1V for the cycle life of the same type of battery. In this way, the battery is no longer under a deep charge, and the cycle of life can be increased by nearly 60%. Then if the cut-off voltage is increased to 3.9V for testing, the number of cycles should be increased several times.

 

With regard to this statement that the charge and discharge cycle is one less life, we should pay attention to the definition of the charging cycle of a lithium battery: a charging cycle refers to the full charge of the lithium battery from empty to full, and then from empty to full the process of. And this is not the same as charging once.

 

In addition, when we talk about the number of cycles, we cannot ignore the conditions of the cycle. It is meaningless to talk about the number of cycles aside from the rules because the number of cycles is just a way to measure battery life.

 

If you want to learn more about batteries or our custom-made batteries, please contact us at sales@himaxelectronics.com and visit our website: https://himaxelectronics.com/