High Voltage lifepo4 Battery

High Voltage Battery


An L-i-H-V battery is a type of Lithium battery that allows for a higher than normal voltage. The “HV” stands for “high voltage” and it has a higher energy density than standard LiPo batteries. Ordinary LiPo batteries have a nominal voltage of 3.7V and a fully charged voltage of 4.2V. LiFePO4 batteries have a nominal voltage of 3.2V and a fully charged voltage of 3.65V. Compared to these, LiHV batteries have a nominal voltage of 3.8V or 3.85V and can reach 4.35V or 4.4V on a full charge.

The characteristics of LiHV battery

With the increasing demand for lithium-ion batteries with higher capacities for electrical equipment, there is a growing expectation for increased energy density of lithium-ion batteries.

While high-voltage batteries have higher energy density and higher discharge platform, the safety performance is lower than that of ordinary batteries. At present, lithium cobalt oxide has been widely studied and applied as a high-voltage anode material. The structure is non-N-A-F-E-O-2 type, which is more suitable for lithium-ion insertion and ejection. The production process is simple, and the electrochemical performance is stable.

Based on the limited space and weight of the electrical power supply, the battery energy can be increased by increasing the battery voltage. For instance, increasing the operating voltage from 4.2v to 4.35v can increase the energy density of the battery up to 16%.




三个充满电的电池在4.2V,4.35V和4.4V时的容量差异。 从格雷普夫出发




市场上已经有许多配备了电池管理系统(BMS)的智能电池,可以让我们设置适当的截止电压进行充电,但是还有许多用于FPV 或 RC 车辆的电池 没有BMS,如果没有BMS,则还可以设置充电器的截止电压,以避免过度充电。

Himax - What-Is-The-SEI

The SEI (solid electrolyte interphase) is formed on the surface of the anode from the electrochemical reduction of the electrolyte and plays a crucial role in the long-term cyclability of a lithium-based battery.

Introduction of SEI

During the first charge and discharge of a lithium-ion battery, the electrode material reacts with the electrolyte at the solid-liquid phase interface. After the reaction, a thin film forms on the surface of the electrode material, where Li+ can be embedded and removed freely while electrons cannot. The SEI is about 100-120 nm thick, and it is mainly composed of various inorganic components, such as Lithium Carbonate (Li2CO3), Lithium Fluoride (LiF), Lithium Oxide (Li2O), Lithium Hydroxide (LiOH), as well as some organic components like  Lithium Alkyl Carbonates (ROCO2Li).

Source of SEI

When a lithium-ion battery starts to charge and discharge, the lithium ions are extracted from the active material of the positive electrode. At which point, they enter the electrolyte, penetrate the separator, enter the electrolyte, and finally embed themselves into the layered gap of the negative carbon material.

Electrons then come out of the positive electrode along the outer end loop and enter the negative electrode carbon material. At this point, an oxidation-reduction reaction occurs between the electrons, the solvent in the electrolyte, and the lithium ions. As the thickness of the SEI increases to the point where electrons cannot penetrate it, a passivation layer is formed, which inhibits the continuation of the redox reaction.

SEI’s impact on batteries

The formation of the SEI film has a crucial impact on the performance of electrode materials. On one hand, in the formation of the SEI film, parts of the lithium ions are consumed, which increases the irreversible capacity of batteries and reduces the charge and discharge efficiency of the electrode material.

On the other hand, the SEI is insoluble in organic solvents and can exist in stable conditions in organic electrolyte solutions. Furthermore,  solvent molecules cannot pass through it, thus effectively preventing the co-embedding of the ions and avoiding damage to the electrode material. This greatly improves the cycling performance and service life of the battery.

SEI’s affecting factors

The formation of the SEI is mainly influenced by the following aspects. First, electrolytes (Li salts, solvents, admixtures, etc.), with different compositions will result in different SEI compositions and affect the stability. Next, the formation, that is, the intensity of the first charge and discharges current. High temperature will also reduce the stability of the SEI and affect the battery cycle life. In addition, the thickness of the SEI changes based on the type of negative electrode material.


In-depth research on the SEI with its formation mechanism, structure and stability, and further search for effective ways to improve the performance have been hot topics of research in the electrochemical community.


The voltage of HV battery

An L-i-H-V battery is a type of Lithium battery that allows for a higher than normal voltage. The “HV” stands for “high voltage” and it has a higher energy density than standard LiPo batteries. Ordinary LiPo batteries have a nominal voltage of 3.7V and a fully charged voltage of 4.2V. LiFePO4 batteries have a nominal voltage of 3.2V and a fully charged voltage of 3.65V. Compared to these, LiHV batteries have a nominal voltage of 3.8V or 3.85V and can reach 4.35V or 4.4V on a full charge.


The characteristics of HV battery

With the increasing demand for lithium-ion batteries with higher capacities for electrical equipment, there is a growing expectation for the increased energy density of lithium-ion batteries.

While high-voltage batteries have higher energy density and higher discharge platform, the safety performance is lower than that of ordinary batteries. At present, lithium cobalt oxide has been widely studied and applied as a high-voltage anode material. The structure is non-N-A-F-E-O-2 type, which is more suitable for lithium-ion insertion and ejection. The production process is simple, and the electrochemical performance is stable.

Based on the limited space and weight of the electrical power supply, the battery energy can be increased by increasing the battery voltage. For instance, increasing the operating voltage from 4.2v to 4.35v can increase the energy density of the battery up to 16%.

In terms of the discharge rate of high-voltage batteries and ordinary batteries, high-voltage batteries have higher discharge rates and stronger power. Therefore, high-voltage batteries are more suitable for products and equipment that require high-rate discharge.


The following graph reflects the difference in capacity between the three fully charged batteries at 4.2V, 4.35V and 4.4V.

the difference in capacity between three fully-charged batteries at 4.2V, 4.35V, and 4.4V. From Grepow

From these three curves, you can see that LiHV batteries can release more capacity than ordinary LiPo batteries, thus providing your device with longer duration.

Charging tips

It is worth noting that you need to know the maximum charging voltage of the battery in advance to prevent overcharging. This is because the oxygen and electrolytes released during overcharging may cause changes in the structure of the cathode material, resulting in capacity loss or violent chemical reactions that reduce the life and performance of the battery. In severe cases, an explosion or fire may occur.

There are already many smart batteries on the market that are equipped with a Battery Management System (BMS) that allows us to set the proper cut-off voltage for charging, but there are also many batteries for FPV or RC vehicles that do not have a BMS, and if there is no BMS, you can also set the cut-off voltage on the charger to avoid overcharging.

Himax - Camping-Trips

10 Tips For More Eco-Friendly Outdoor Adventures & Camping Trips

Posted March 31, 2021

The percentage of people that enjoy camping three or more times each year has increased 72% since 2014, according to a recent report, particularly in light of the COVID-19 pandemic and associated international travel restrictions. Between the rapid increase in outdoor recreation and the rise of climate change, it’s more important now than ever to ensure the environment is protected during outdoor adventures in line with the U.S. Forest Service’s Tread Lightly principles.

Although our safe, most environmentally benign lithium iron phosphate energy storage systems help to reduce carbon emissions, especially when used in wind and solar power systems, we believe it’s essential to challenge our limits to further mitigate any additional harmful effects on the environment. Through our Limitless Blue initiative, we are committed to giving 1% of our net revenue annually to fund eco-friendly, earth-conscious causes and organizations around the globe. We also stand by, and recommend, the following tips when it comes to adventuring sustainably:

1. Use environmentally friendly transportation

Did you know that cars and trucks account for nearly one-fifth of all U.S emissions, emitting around 24 pounds of carbon dioxide and other global-warming gases for every gallon of gas? This is part of why we recommend taking a look at your mode of transportation to see how you can possibly cut down on your transport emissions before your next camping trip, fishing trip, or other outdoor adventure. Consider choosing a trip location that you can walk or cycle to or else look into public transportation options. If this isn’t possible, then try to carpool to minimize your emissions.

2. Bring DIY, organic snacks and meals instead of single-use food items

When planning snacks and meals for your next outdoor adventure, think carefully about how you can reduce waste. For example, buy in bulk, get creative and try making your own meals to decrease unnecessary packaging waste. You can also use reusable containers or beeswax wraps instead of plastic bags to transport the food. Additionally, try to only purchase organic food, as traditional agriculture uses synthetic fertilizers, pesticides and herbicides that can damage the environment, unlike organic agriculture.

3. Pack eco-friendly sunscreens, insect repellents and ointments

In order to avoid polluting lakes, ponds and rivers, leave water-soluble products at home. Also, if insecticides like permethrin (bug repellent) seep into natural water sources, they can be toxic to aquatic life. Protecting your skin is important, but so is protecting wildlife and natural sites so that they can be enjoyed by generations to come.

Gypsy 20

4. Use rechargeable batteries and products powered by the sun

Instead of relying on noisy, polluting diesel generators or batteries which cannot be recharged, look into using rechargeable, safe batteries that are powered by solar energy. Whether this means switching out the system that powers your van, overland vehicle, RV, or campervan, or something as simple as choosing to use a solar-powered lantern or phone charger, endless options are available for reducing waste and pollution on your next trip.

5. Bring used equipment or rent or repair old equipment

Before you buy a new piece of gear, try repairing old gear, renting gear, or buying used gear. The longer you can keep using a product, the less negative impact new products have on our environment. This will also likely save you money when preparing for your next adventure.

6. Take reusable bottles or water storage tanks

Although it can be convenient to fall into the habit of buying disposable plastic water bottles, with a bit of planning, you will never have to do that again. Bladders and reusable bottles are not only eco-friendly but also very easy to hike with. Water tanks or water storage bags are also great for front-country use.

7. Stick to designated trails and camping spots and avoid sensitive areas

Even though it can seem liberating and adventurous to occasionally wander off beaten paths, it can cause massive erosion, destroy delicate vegetation, and impede future vegetation growth. As best you can, try to avoid damaging surrounding foliage and always aim to set up camp at durable sites that have already been traversed by previous campers.

jarrod tocci

8. Wash 200 feet away from streams and lakes and scatter greywater

The U.S. Forest Service’s Tread Lightly program recommends washing 200 feet away from streams and lakes and scattering greywater so it filters through the soil. Be aware that most detergents, toothpaste, and soap can easily harm fish and can be extremely toxic to aquatic life. If possible, try to only buy eco-friendly and biodegradable soap and toothpaste to mitigate your impact on the environment.

9. Practice fire safety while also reducing firewood use

Beyond increasingly common wildfire risks in light of climate change, campfires are also a source of air pollution. Burning wood releases a surprisingly large number of compounds, including nitrogen oxides, particulate matter, carbon monoxide, benzene, and many other potentially toxic volatile organic compounds. Aim to keep your fire smaller, limited in duration, and protected from the wind so as to minimize the amount of firewood needed and air pollution emitted.

10. Leave no trace and separate out trash, compost and recycling

It’s always important to remember to pack it in and pack it out and aim to leave a campsite better than you found it. Challenge your limits and do your part by making sure to also separate out trash from compost from recycling and using biodegradable bags where possible.



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.

Himax - New-Battery-Technologies

Your phone is about to go dead—again—and you can’t find a place to plug it in. Your laptop is getting hot…is the battery about to catch on fire? How far from home should you drive your electric vehicle? As scenarios like these become increasingly common, it’s clear that we need batteries that store more, last longer, and are safer to use. Fortunately, new battery technologies are coming our way.

Let’s take a look at a few:


1.     NanoBolt lithium tungsten batteries


Working on battery anode materials, researchers at N1 Technologies, Inc. added tungsten and carbon multi-layered nanotubes that bond to the copper anode substrate and build up a web-like nano structure. That forms a huge surface for more ions to attach to during recharge and discharge cycles. That makes recharging the NanoBolt lithium tungsten battery faster, and it also stores more energy.


Nanotubes are ready to be cut to size for use in any Lithium Battery design.

Source: http://nanoboltbattery.com/



2.      Zinc-manganese oxide batteries


How does a battery actually work? Investigating conventional assumptions, a team-based at DOE’s Pacific Northwest National Laboratory found an unexpected chemical conversion reaction in a zinc-manganese oxide battery. If that process can be controlled, it can increase energy density in conventional batteries without increasing cost. That makes the zinc-manganese oxide battery a possible alternative to lithium-ion and lead-acid batteries, especially for large-scale energy storage to support the nation’s electricity grid.

Source: www.pnnl.gov

3.     Organosilicon electrolyte batteries


A problem with lithium batteries is the danger of the electrolyte catching fire or exploding. Searching for something safer than the carbonate-based solvent system in Li-ion batteries, University of Wisconson-Madison chemistry professors Robert Hamers and Robert West developed organosilicon (OS) based liquid solvents. The resulting electrolytes can be engineered at the molecular level for industrial, military, and consumer Li-ion battery markets.


Source: http://silatronix.com



4.     Gold nanowire gel electrolyte batteries


Also seeking a better electrolyte for lithium-ion batteries, researchers at the University of California, Irvine experimented with gels, which are not as combustible as liquids. They tried coating gold nanowires with manganese dioxide, then covering them with electrolyte gel. While nanowires are usually too delicate to use in batteries, these had become resilient. When the researchers charged the resulting electrode, they discovered that it went through 200,000 cycles without losing its ability to hold a charge. That compares to 6,000 cycles in a conventional battery.



5.     TankTwo String Cell™ batteries


A barrier to the use of electric vehicles (EVs) is the slow recharging process. Seeking a way to turn hours into minutes, TankTwo looked at modularizing a battery. Their String Cell™ battery contains a collection of small independent self-organizing cells. Each string cell consists of plastic enclosure, covered with a conductive material that allows it to quickly and easily form contacts with others. An internal processing unit controls the connections in the electrochemical cell. To facilitate quick charging of an EV, the little balls contained in the battery are sucked out and swapped for recharged cells at the service station. At the station, the cells can be recharged at off-peak hours.


Source: http://www.tanktwo.com


For now, we may have to put up with phones going cold, laptops getting hot, and EVs not ranging far from home. Solutions seem to be on the horizon, however, so a better battery-powered future is within sight.



When I started this hobby the thing that shocked me the most was how short flight times were.

5 minutes??? Sometimes more. Sometimes less.

To make matters worse, most people drive to a park or a field where they don’t have access to electricity to recharge their batteries.

Yes, you can buy a couple dozen batteries so you can get a couple hours of flying in. But what many people do is they make portable charging stations so they can stay out in the field.

Car Batteries

A lot of DC input lipo chargers will work at 12 V. For example, the SKYRC iMAX B6AC V2 has an input voltage range of 11 V to 18 V.

This means you can use a lead acid car battery to power you lipo charger.

And because a lot of us drive our cars to get to where we want to fly, this has become a popular solution for charging in the field.

There are a couple options here.

  • You can literally use your car battery.
  • You can buy a separate car battery that you only use for charging lipos.

Option 1 is cheap. The only thing you have to worry about is killing your battery. By charging your lipos with your car battery you are, of course, discharging your car battery. Discharge it too much and your car might not start.

Option 2 involves buying another car battery, which can cost a lot. They are also heavy to move around. And if you are going to be regularly discharging it you are going to need a battery charger to charge it back up.

There’s one more problem with using a car battery for this.

Car batteries were meant to start your car’s engine. This means it needs a whole lot of current for a short period of time. Starting your car only discharges about 3% of your battery. This is the opposite of what you need when charging lipos … a little bit of current for a long time.

More on this in the next section.

Deep Cycle / Marine Batteries

As I mentioned above, car batteries aren’t designed to be discharged all the way and then charged back up.

Because of this a better solution would be to use a deep cycle batteries. Deep cycle batteries are designed with thicker lead plates that allow it to be fully discharged and fully charged for many cycles. This is ideal for field charging lipo batteries.

These are sometimes called marine batteries because they are used for things like trolling motors.

High Capacity Lipo Batteries

Deep-cycle lead acid batteries aren’t the only type of batteries that are made to repeatedly go through a charge-discharge cycle. Lipo batteries like we use on quadcopters are designed to do that, too.

This means they would be perfect for charging in the field.

The 2 things you need to keep in mind if you go this route would be 1) input voltage and 2) capacity. If you need a refresher on what those terms mean, check out my lipo battery guide here.

For input voltage, I would recommend using a 4s lipo for most DC chargers. The nominal voltage of a 4s battery is 14.8 V and this puts you right in the middle of the voltage input range for most chargers.

For lipo capacity, I would recommend the biggest you can afford. The higher the capacity, the more times you are going to be able to use it to charge in the field. This battery is 16,000 mAh.

The great thing about this solution is that you don’t have to buy an extra charger like you do with a lead acid battery. You can use the same charger that you would use for your quad batteries.

(One caveat with this … Some of these bigger batteries use XT90 connectors while smaller capacity batteries usually use a smaller connector, like an XT60. Again.)

Portable Generator

portable generator for lipos
Why use a battery when you can make the electricity yourself?

There are a number of advantages to using a generator.

  • You don’t need to worry about capacity. Most generators will be able to provide more than enough energy to parallel charge multiple lipos.
  • Most generators have both an standard AC output and a 12 V DC output.  This means you have more options for what charger you can use.
  • You don’t have to worry about charging up yet another battery.  All you have to do is fill it up with gas.
  • Generators can be used for all sorts of other things: in emergencies if your electricity goes out, if you go camping and want to be able to do things like make coffee in the morning, etc.

There are some disadvantages, of course. They will be noisier than the other options (although not as noisy as you would expect) and they will be more costly. But other than that, they are a good option.

Find a field with electricity

The last option is maybe the best option if it is available. Find a place to fly that has electricity available. Some RC clubs may have fields that have electricity available.  Or try to find a park that has publicly available outlets.


I’m sure there are other options that people have come up with for charging your lipos in the field.  It’s a pretty common problem.  Let me know in the comments if you’ve tried anything else.

Himax - Puffed-Lipo-Battery
puffed lipo

Anybody who uses lipos will eventually encounter a puffy or swollen battery.

And the first question that inevitably comes up is “What should I do?”

This post is all about what causes that swelling and what to do when it happens to one of your lipos.

Are Swollen Lipo Batteries Dangerous?

Yes. Next question.

Seriously, there are so many examples of puffed batteries that start on fire that this shouldn’t even be a question.

That doesn’t mean that every battery that is puffed is going to explode as soon as you use it but it does mean that a high enough percentage of them are going to be dangerous that it isn’t worth the risk.

What Causes Lipo Batteries to Puff Up?

puffed lipo batteryGas generation in lithium ion batteries is a normal thing. Even if you don’t abuse your battery, the normal everyday use of your battery will generate gas through a process called electrolyte decomposition.

The electrolyte decomposition occurs even faster if you overdischarge a battery or overheat a battery.

What is electrolyte decompostion?

Simply put, a battery is made of three things: the anode, the cathode and the electrolyte. The cathode and the anode are the positive and negative terminals on your battery.

The electrolyte is a chemical inside the battery that allows charged ions to flow from the anode to the cathode during discharge (and the other way during charging).

Electrolyte decomposition is what happens when that electrolyte chemically breaks down. So in a lipo battery, as the electrolyte breaks down you end up with lithium and oxygen. This forms lithium oxide on the anode and cathode (depending whether you are charging or discharging).

But what you also end up with is excess oxygen that doesn’t adhere to the anode or cathode. This excess oxygen is part of what causes a battery swell. And oxygen likes to burn. See here for more details. He also goes over some other reasons a battery might swell.

Other gases that can be found in the battery during the normal chemical reactions of a battery are carbon dioxide (CO2) and carbon monoxide (CO). For a technical overview of this, see this paper.

How to Fix a Swollen Battery


Just Don’t.

Dispose of it properly (see below) and buy a new one.

It’s not worth injuring yourself or burning your house down to save a few bucks.

How to Dispose of Puffed Lipo Batteries

The proper way to dispose of a swollen lipo battery is the same as what you would do when you throw out any old battery. You need to discharge it completely first.

The two main methods that people use to discharge a battery completely is to hook it up to a light bulb or to put it in a bucket of saltwater.  There are debates about which method is better but I will avoid that debate here for now.

If you decide to hook it up to a light bulb, I would recommend these 12 V, 20 Watt halogen bulbs. They are easy to solder to so you attach lead wires and connector pretty easily. This makes it easy to just plug in your battery to let it discharge. You can hook multiple in parallel to get the discharge rate you want. If you have any questions about this, let me know in the comments.

After you’ve completely discharged the battery, I recommend finding your nearest battery recycling drop-off point and bringing it there. Make sure you call ahead and ask if they accept damaged batteries.

Tips to Avoid a Swollen Battery

  • Proper charging – Make sure you charge your battery properly using a quality battery charger.  For safety, make sure you put your batteries in a lipo bag while charging.  If you don’t have a lipo bag, I highly recommend you buy one.  For around $10, you can insure that if something does go wrong at will at least be contained.
  • Don’t over-discharge – Make sure you stop using your battery before the voltage gets to the minimum cut-off voltage.
  • Heat kills batteries – Don’t use batteries or charge batteries when they are warm. After you’re done using them, give them a little time to cool off before you charge them. And after you are done charging them, give them a little time before you use them.
  • Proper storage – Do not store your batteries in a hot location. (For example, don’t keep them in the trunk of your car during in the summer.) Store lipo’s at the proper storage voltage. The article I linked to above showed that swelling increased significantly after only 4 hours of storage when batteries were at a state of charge above 80%.


To sum up: As lipo’s age and if they are misused, gases start to form in the battery and cause it to swell. Once you have a puffy lipo, the safe thing to do is to discharge it completely and then recycle it.

If you want to learn more about lipo’s, check out my in-depth lipo battery guide. There I go into a lot of detail about all aspects of lipo’s.

Himax - Bluetooth Headsets Battery

Compared with ordinary earphones, the battery life and battery life of Bluetooth headsets are relatively short when you keeping connect with Bluetooth. In addition, the Bluetooth headsets currently on the market have made the size smaller and handy to adapt the needs of market users for portability and appearance. Therefore, we have to extend the battery life, and its the most significant part for Bluetooth headsets.

Excluding the impact of battery quality and environmental factors, in order to extend the battery life of our Bluetooth headsets, I think there are only three things we can do:

  1. Reduce the power consumption of the headset;
  2. Make a bigger battery (bigger size);
  3. Break through the energy density of the lithium battery.

Reducing the power consumption of the headset

Devices connected with Bluetooth capabilities will generally consume extra power. Even when the device is not in use, power will still be drained to a certain degree.

In 2020, SIG (Bluetooth Special Interest Group) attempted to increase the potential for lowered power consumption when it officially released its Bluetooth 5.2 of the audio technology standard, LE Audio (LE Power Consumption).

LE Audio not only improved the audio quality of headsets but also added low-power consumption features. It optimized the power consumption of Bluetooth devices and maximized the battery life and lifespan of lithium batteries in Bluetooth devices.

Those interested in this technology can find more here. This video introduces the basics of power consumption in Bluetooth and LE battery life.

Making a bigger battery

Longer battery life is always ideal, and the logical next step would be to make a bigger battery to do so. However, Bluetooth headsets are already designed to be as portable and small in size as possible, and they are generally made with rectangular batteries. There really isn’t the space to produce a bigger battery without sacrificing size for the overall product itself.

What if we change to a Round battery?

So then, what other options can we consider?  We can consider changing the shape of the battery first.

Combined with a PCB, a rectangular battery doesn’t occupy the full space of Bluetooth headsets.  In the below images, you can see how only about ⅔ of the device is inhabited, which wastes potential space.

 JBL T450BT Bluetooth Headsets (Disassembly)
JBL T450BT Bluetooth Headsets (Disassembly) – from YouTube
 JBL e55bt Bluetooth Headsets (Disassembly)
JBL e55bt Bluetooth Headsets (Disassembly) – from YouTube

If we leave the confines of a standard rectangular battery, we move onto considering special-shaped batteries.  These batteries can be customized into a plethora of different shapes according to the needs of a product.

Of shaped batteries, the round battery is the most frequently requested shape, and this shape in particular can maximize the use of the battery while filling up the internal space of Bluetooth headsets.

To customize round batteries, the radios (R), height (H), and thickness (T) of the battery must be provided.

Line drawing of the Round Shaped battery
Line drawing of the Round Shaped battery

Let us “pretending” to replace its original battery with a Round battery. Is this a perfect match?

Lithium Round battery replace JBL e55bt rectangle battery

Energy density of lithium batteries

Lithium batteries have one of the highest energy densities of any battery technology today (100-265 Wh/kg or 250-670 Wh/L). In addition, Li-ion cells can deliver up to 3.6V, which is 3 times more than that of technologies like Ni-Cd or Ni-MH.

So what does this mean?  Energy density represents how much energy can be released by different batteries under the same weight or volume.  If we want to achieve longer battery life, we need to break through the energy density threshold of lithium batteries.

Increase the upper limit of battery voltage

Generally, the nominal voltage of a lithium-ion battery is 3.7V (and 3.2V for lithium iron phosphate batteries), and the fully-charged voltage is 4.2V (and 3.65V for lithium iron phosphate battery).

The discharge cut-off voltage of a lithium-ion battery is 2.75V to 3.0V. Therefore, the higher the upper voltage limit, the higher the capacity and energy.  This creates a high-voltage lithium-ion battery (read more here).

High-voltage batteries have high energy density and high discharge platforms. They can also deliver more capacity under the same conditions of use, so their battery life is longer while delivering more power. Under normal circumstances, the lifetime of Grepow’s high-voltage batteries will increase by 15-25%.

Comparison of 4.2V and LiHv 4.35V, 4.4V, 4.45V Grepow lithium battery
Comparison of 4.2V and LiHv 4.35V, 4.4V, 4.45V lithium battery
Himax - Battery-Bms


The power output depends on the battery, and the battery management system (BMS) is the core of it. It is a system for monitoring and managing the battery. It controls the charge and discharge of the battery by collecting and calculating parameters such as voltage, current, temperature, and SOC. The process, the management system that realizes the protection of the battery and improves the overall performance of the battery is an important link between the battery and the battery application equipment.

BMS mainly includes three parts: hardware, bottom layer software, and application layer software.

The hardware of the battery management system (BMS)

1. Architecture

The topology of Battery Management System(BMS) hardware is divided into two types: centralized and distributed.

(1) The centralized type

The centralized type is to concentrate all the electrical components into a large board, the sampling chip channel utilization is the highest and the daisy chain communication can be adopted between the sampling chip and the main chip, the circuit design is relatively simple, the product cost is greatly reduced, but All the collection wiring harnesses will be connected to the mainboard, which poses a greater challenge to the security of the BMS, and there may also be problems in the stability of the daisy chain communication. It is more suitable for occasions where the battery pack capacity is relatively small and the module and battery pack types are relatively fixed.

(2) The Distributed type

Distributed includes a mainboard and a slave board. It is possible that a battery module is equipped with a slave board. The disadvantage of this design is that if the number of battery modules is less than 12, the sampling channel will be wasted (generally there are 12 sampling chips. Channel), or 2-3 slave boards to collect all battery modules. This structure has multiple sampling chips in one slave board. The advantages are high channel utilization, cost-saving, flexibility in system configuration, and adaptation to different capacities. Modules and battery packs of different specifications and types.

2. Function

The hardware design and specific selection should be combined with the functional requirements of the vehicle and battery system. The general functions mainly include collection functions (such as voltage, current, and temperature collection), charging port detection (CC and CC2), and charging wake-up (CP and A+) ), relay control and status diagnosis, insulation detection, high voltage interlock, collision detection, CAN communication and data storage requirements.

(1) Main controller

Process the information reported from the controller and the high-voltage controller, and at the same time judge and control the battery operating status according to the reported information, realize the BMS-related control strategy, and make the corresponding fault diagnosis and processing.

(2) High voltage controller

Collect and report the total voltage and current information of the battery in real-time, and realize timely integration through its hardware circuit, and provide accurate data for the calculation of the state of charge (SOC) and the state of health (SOH) for the motherboard. Charge detection and insulation detection function.

(3) Slave controller

Real-time collection and reporting of battery cell voltage and temperature information, feedback of the SOH and SOC of each string of cells, and a passive equalization function, effectively ensuring the consistency of cells during power use.

(4) Sampling control harness

Provide hardware support for battery information collection and information interaction between controllers, and at the same time add redundant insurance function to each voltage sampling line, effectively avoid battery short circuit caused by wiring harness or management system.

3. Communication method

There are two ways to transfer information between the sampling chip and the main chip: CAN communication and daisy chain communication. CAN communication is the most stable. However, due to the high cost of power chips and isolation circuits, daisy chain communication is actually SPI communication. The cost is very low, and the stability is relatively poor. However, as the pressure on cost control is increasing, many manufacturers are shifting to the daisy chain mode. Generally, two or more daisy chains are used to enhance communication stability.

4. Structure

BMS(Battery Management System) hardware includes power supply IC, CPU, sampling IC, high-drive IC, other IC components, isolation transformer, RTC, EEPROM, CAN module, etc. The CPU is the core component, and the functions of different models are different, and the configuration of the AUTOSAR architecture is also different. Sampling IC manufacturers mainly include Linear Technology, Maxim, Texas Instruments, etc., including collecting cell voltage, module temperature, and peripheral configuration equalization circuits.

Bottom layer software

According to the AUTOSAR architecture, it is divided into many general functional modules, which reduces the dependence on hardware, and can realize the configuration of different hardware, while the application layer software changes little. The application layer and the bottom layer need to determine the RTE interface, and consider the flexibility of DEM (fault diagnosis event management), DCM (fault diagnosis communication management), FIM (function information management), and CAN communication reserved interfaces, which are configured by the application layer.

Application layer software of the BMS

The software architecture mainly includes high and low voltage management, charging management, state estimation, balance control, and fault management, etc.

1. High and low voltage management

Generally, when the power is on normally, the VCU will wake up the BMS through the hardwire or 12V of the CAN signal. After the BMS completes the self-check and enters the standby mode, the VCU sends the high-voltage command, and the BMS controls the closed relay to complete the high-voltage. When the power is off, the VCU sends a high-voltage command and then disconnects and wakes up 12V. It can be awakened by CP or A+ signal when the gun is plugged in in the power-off state.

2. Charging management

(1) Slow charge

Slow charging uses an AC charging station (or 220V power supply) to convert AC to DC to charge the battery through an on-board charger. The charging station specifications are generally 16A, 32A, and 64A, and it can also be charged through a household power supply. The BMS can be awakened by CC or CP signal, but it should be ensured that it can sleep normally after charging. The AC charging process is relatively simple, and it can be developed in accordance with the detailed regulations of the national standard.

(2) Fast charge

Fast charging is to charge the battery with DC output from the DC charging pile, which can achieve 1C or even higher rate charging. Generally, 80% of the power can be charged in 45 minutes. Wake up by the auxiliary power A+ signal of the charging pile, the fast charging process in the national standard is more complicated, and there are two versions of 2011 and 2015 at the same time, and the different understanding of the technical details of the charging pile manufacturer’s unclear technical details of the national standard process also causes the vehicle charging adaptability A great challenge, so fast charging adaptability is a key indicator to measure the performance of BMS products.

3. Estimation function

(1) the State Of Power

SOP (State Of Power) mainly obtains the available charge and discharge power of the current battery through the temperature and SOC lookup table. The VCU determines how the current vehicle is used according to the transmitted power value. It is necessary to consider both the ability to release the battery and the protection of the battery performance, such as a partial power limit before reaching the cut-off voltage. Of course, this will have a certain impact on the driving experience of the whole vehicle.

(2) state of health

SOH (state of health) mainly characterizes the current state of health of the battery, which is a value between 0-100%. It is generally believed that the battery can no longer be used after it is lower than 80%. It can be expressed by the change of battery capacity or internal resistance. When using the capacity, the actual capacity of the current battery is estimated through the battery operating process data, and the ratio of the rated capacity to the rated capacity is the SOH. Accurate SOH will improve the estimation accuracy of other modules when the battery decays.

(3) the State Of Charge

SOC (State Of Charge) belongs to the BMS core control algorithm, which characterizes the current remaining capacity state, mainly through the ampere-hour integration method and EKF (Extended Kalman Filter) algorithm, combined with correction strategies (such as open-circuit voltage correction, full charge correction, charging End correction, capacity correction under different temperatures and SOH, etc.). The ampere-hour integration method is relatively reliable under the condition of ensuring the accuracy of current acquisition, but the robustness is not strong. Because of the error accumulation, it must be combined with a correction strategy. The EKF has strong robustness, but the algorithm is more complex and difficult to implement. Domestic mainstream manufacturers generally can achieve accuracy within 6% at room temperature, and it is difficult to estimate high and low temperatures and battery attenuation.

(4) the State Of Energy

SOE (State Of Energy) algorithm manufacturers do not develop much now or use a simpler algorithm, look up the table to get the ratio of the remaining energy to the maximum available energy in the current state. This function is mainly used to estimate the remaining cruising range.

4. Fault diagnosis

According to the different performance of the battery, it is divided into different fault levels, and in the case of different fault levels, the BMS and VCU will take different treatment measures, warning, limiting power, or directly cutting off the high voltage. Failures include data collection and rationality failures, electrical failures (sensors and actuators), communication failures, and battery status failures.

5. Balance control

The equalization function is to eliminate the inconsistency of the battery cells generated during battery use. According to the shortboard effect of the barrel, the cells with the worst performance during charging and discharging first reach the cut-off condition, and the other cells have some capabilities. It is not released, causing battery waste.

Equalization includes active equalization and passive equalization. Active equalization is the transfer of energy from more monomers to fewer monomers, which will not cause energy loss, but the structure is complex, the cost is high, and the requirements for electrical components are relatively high. Relatively passive The balance structure is simple and the cost is much lower, but the energy will be dissipated and wasted in the form of heat. Generally, the maximum balance current is about 100mA. Now many manufacturers can achieve better balance effects using passive balance.

The BMS(Battery Management System) control method, as the central control idea of ​​the battery, directly affects the service life of the battery, the safe operation of the electric vehicle, and the performance of the entire vehicle. It has a significant impact on battery life and determines the future of new energy vehicles. A good battery management system will greatly promote the development of new energy vehicles.