The energy density of batteries can be displayed in two different ways: gravimetric energy density and volumetric energy density.
The gravimetric energy density is the measure of how much energy a battery contains in proportion to its weight. This measurement is typically presented in Watt-hours per kilogram (W-hr / kg). The volumetric energy density, on the other hand, is compared to its volume and is usually expressed in watt-hours per liter (W-hr / L). Generally, we refer to battery energy density as gravimetric ( weight ) energy density, and watt-hour is a measure of electrical energy, equivalent to one hour, one watt of consumption.
In contrast, the power density of a battery is a measure of how fast energy can be delivered, not how much stored energy is available. Energy density is often confused with power density, so it is important to understand the difference between the two.
Calculation formula
The energy density of a battery can be simply calculated using this formula: Nominal Battery Voltage (V) x Rated Battery Capacity (Ah) / Battery Weight (kg) = Specific Energy or Energy Density (Wh / kg).
LiCo and LiFePO4 Batteries’ energy density
Generally speaking, LiCo batteries have an energy density of 150-270 Wh/kg. Their cathode is made up of cobalt oxide and the typical carbon anode with a layered structure that moves lithium-ions from anode to the cathode and back. This battery is popular for its high energy density, and it’s typically used in consumer products such as cell phones and laptops.
LiFe batteries, on the other hand, have an energy density of 100-120 Wh/kg. Although this is lower than LiCo batteries, it is still considered higher in the rechargeable battery category. LiFe batteries use iron phosphate for the cathode and a graphite electrode combined with a metallic backing for the anode. They are ideal for heavy equipment and industrial applications because of their better ability to withstand high and low temperatures.
Conclusion
As far as the single-cell is concerned, the positive and negative materials and production process of the battery will affect the energy density, so it is necessary to develop more reasonable materials and better manufacturing technology to obtain a more efficient battery.
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Californians do not purchase electric vehicles because they are cool, they buy EVs because they live in a warm climate. Conventional lithium-ion batteries cannot be rapidly charged at temperatures below 50 degrees Fahrenheit, but now a team of Penn State engineers has created a battery that can self-heat, allowing rapid charging regardless of the outside chill.
“Electric vehicles are popular on the west coast because the weather is conducive,” said Xiao-Guang Yang, assistant research professor in mechanical engineering, Penn State. “Once you move them to the east coast or Canada, then there is a tremendous issue. We demonstrated that the batteries can be rapidly charged independently of outside temperature.”
When owners can recharge car batteries in 15 minutes at a charging station, electric vehicle refueling becomes nearly equivalent to gasoline refueling in the time it takes. Assuming that charging stations are liberally placed, drivers can lose their “range anxiety” and drive long distances without worries.
Previously, the researchers developed a battery that could self-heat to avoid below-freezing power drain. Now, the same principle is being applied to batteries to allow 15-minute rapid charging at all temperatures, even as low as minus 45 degrees F.
The self-heating battery uses a thin nickel foil with one end attached to the negative terminal and the other extending outside the cell to create a third terminal. A temperature sensor attached to a switch causes electrons to flow through the nickel foil to complete the circuit when the temperature is below room temperature. This rapidly heats up the nickel foil through resistance heating and warms the inside of the battery. Once the battery’s internal temperature is above room temperature, the switch turns opens and the electric current flows into the battery to rapidly charge it. “One unique feature of our cell is that it will do the heating and then switch to charging automatically,” said Chao-Yang Wang, William E.
Diefenderfer Chair of mechanical engineering, professor of chemical engineering and professor of materials science and engineering, and director of the Electrochemical Engine Center. “Also, the stations already out there do not have to be changed. Control off heating and charging is within the battery, not the chargers.”
The researchers report the results of their prototype testing in this week’s edition of the Proceedings of the National Academy of Sciences. They found that their self-heating battery could withstand 4,500 cycles of 15-minute charging at 32 degrees F with only a 20-percent capacity loss. This provides approximately 280,000 miles of driving and a lifetime of 12.5 years, longer than most warranties.
A conventional battery tested under the same conditions lost 20-percent capacity in 50 charging cycles.
Lithium-ion batteries degrade when rapidly charged under 50 degrees F because, rather than the lithium ions smoothly integrating with the carbon anodes, the lithium deposits in spikes on the anode surface. This lithium plating reduces cell capacity, but also can cause electrical spikes and unsafe battery conditions. Currently, long, slow charging is the only way to avoid lithium plating under 50 degrees F.
Batteries heated above the lithium plating threshold, whether by ambient temperature or by internal heating, will not exhibit lithium plating and will not lose capacity.
“This ubiquitous fast-charging method will also allow manufacturers to use smaller batteries that are lighter and also safer in a vehicle,” said Wang.
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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%.
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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.
Graph
The following graph reflects the difference in capacity between the three fully charged batteries at 4.2V, 4.35V and 4.4V.
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.
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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 recentreport, 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.
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.
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.
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With President Joe Biden in the White House, ink drying on a spate of new climate-focused executive orders and an extension of the federal Investment Tax Credit on the books, the immediate future looks relatively rosy for solar.
The U.S. Energy Information Administration anticipates that renewables will be the fastest-growing source of electricity through midcentury. While solar accounted for about 15 percent of renewable electricity generation in the U.S. in 2020, according to EIA, that will increase to nearly 50 percent by 2050. And solar will be the cheapest form of electricity across the United States by 2030, according to a recently released Wood Mackenzie report. The consultancy expects solar costs to decline 15 to 25 percent over the next ten years.
In a recent series for Squared, I cataloged some of the technological innovations that could define the next decade for solar. Here, I’ll dig into the macro trends Wood Mackenzie analysts expect to drive the resource’s next decade.
Costs will continue falling through 2030
In 2011, the Department of Energy launched its SunShot initiative, modeled after the moonshot effort of the mid-twentieth century, to “reduce the costs of solar energy and reestablish U.S. global leadership” in solar. A decade later, the U.S. has accomplished at least one of those goals; three years before DOE had targeted, SunShot successfully lowered utility-scale solar prices to its goal of $1 per watt.
Cost declines have been the most integral tool in allowing large-scale solar to grow. Worldwide, solar system prices fell by more than 80 percent from 2000 to 2010, according to WoodMac’s analysis.
Meanwhile, installations grew.
Although SunShot floundered under President Trump, prices kept falling in the U.S. Overall, prices for the engineering, procurement and construction of large-scale solar systems fell by more than 30 percent during Trump’s presidency, according to WoodMac.
That happened amid uncertain policy; the Biden administration’s support should provide more stability to the industry. WoodMac expects that costs will continue dropping. Solar is already competitive in a swath of the West and much of the Southeast. That trend will make its way into more of the Northeast by 2021 and the Mountain West by 2022. It will come for the frigid northern Midwest by mid-decade.
By 2030, solar will be the lowest-cost source of generation across the entire U.S.
Corporate purchases
Solar power’s downward price trajectory has caught the eye of corporate buyers. That’s a big market for renewables: Commercial and industrial electricity consumption accounted for more than 60 percent of electricity sales in 2019. And large companies have already become some of the most significant buyers of renewable electricity. In Q4 of 2020, these buyers accounted for 20 percent of the contracted pipeline for large-scale solar. In 2019, commercial solar installations grew 10 percent over the previous year, according to tracking from the Solar Energy Industries Association.
Analysts expect continued declines in the levelized cost of solar energy to strengthen that demand, which in turn has significant potential to reshape energy markets. After signing onto a growing slate of contracts tied to renewables projects, many companies are now looking for even more control of their electricity supply. A recent statement spearheaded by the Renewable Energy Buyers Alliance, a group with members including Facebook and General Motors, lays out the energy policies corporations hope to see advanced under the Biden-Harris administration. Their asks include expanding wholesale electricity markets to smooth the trading of electrons across regions. Some companies, such as Google, have already joined regional transmission organizations to gain more leverage in determining how those markets function.
The ability for solar to compete on price alone means that more merchant-centric projects could also be on the horizon, according to WoodMac. Most solar projects in the United States have relied on long-term, contracted revenue streams that last for at least a couple of decades. But as investors have become increasingly comfortable — perhaps too comfortable, some might say — with the structure of solar deals and the returns associated with the projects, shorter contracts have become more common.
“There’s definitely a lot of buzz in the market about the prospects of having merchant-based projects. But in the truest sense of the word, I don’t think there is a single [merchant solar] project yet,” said Ravi Manghani, WoodMac’s head of solar research. “Developers would need to come up with the right sort of hedging tools, whether these are physical tools like potentially storage, or financial tools, like hedges or insurance products. Those will have to become more commonplace as these projects start to be truly merchant.”
The role of storage and transmission
Cost declines have helped solar gain momentum. But overall, solar provided only about 2 percent of U.S. electricity in 2019. And if the resource is to grow significantly enough to meet clean energy mandates and climate goals set out by states and countries, it needs more support.
Energy storage is already being added to more utility-scale projects, and more projects are being designed to allow for its later addition, to help extend the hours in which solar projects can deliver electricity. Developers and asset owners such as Capital Dynamics have said storage is a consideration, if not the default, for every project.
“In the long run, as solar washes over the United States, storage follows along behind,” John Breckenridge, Capital Dynamics’ head of clean energy infrastructure, told Greentech Media this fall.
While storage will help balance uneven solar production, transmission is needed to carry it from where it’s most cost-effectively generated to where it’s most in demand.
Lack of transmission capacity has major potential to constrain solar growth, stymieing decarbonization efforts like those set out by the Biden-Harris administration. Already, experts and wonks are asking the new administration to confront that challenge. Clean energy groups supported by numerous past members of the Federal Energy Regulatory Commission highlighted that need in a report released this week.
“There is no climate plan that is serious if it does not anticipate a significant regional transmission upgrade,” said Pat Wood III, who served as FERC chair from 2001 to 2005, in an event spotlighting the report.
The administration appears to be paying attention to these issues already. An order President Biden signed this week urges the acceleration of federal permitting for transmission. And in a Wednesday Senate hearing on her nomination to head the Department of Energy, former Michigan Governor Jennifer Granholm named building out transmission to transport clean electricity as a “high priority” if she is confirmed.
“I’m very eager to work with FERC to get transmission lines established ASAP,” Granholm said Wednesday. “I feel like this is a conversation that’s been had for years, about having the right transmission lines in place to take power…(clean power especially) from places that are generating to the power and load centers.”
Aside from storage and transmission, which will make solar easier to use in more places and at more times of day, solar itself is becoming more efficient.
Bifacial solar, which allows for the absorption of sunlight on both sides of a panel, is perhaps the most significant solar technology improvement in recent years, or at least the one to become most mainstream. It’s already the default choice for numerous developers in the U.S.
The Section 201 exclusion that bifacial solar enjoyed for a time aided that development, though the exclusion was ultimately reversed by the Trump administration (solar groups are challenging the verdict).
Despite the policy confusion surrounding tariffs, analysts at Wood Mackenzie name bifacial among just a few technological innovations that are likely to boost solar production and help cut costs in the coming years. (Others are larger panels and wafer sizes, as I cover here, as well as improvements in solar trackers). Commercial bifacial solar modules offer production gains of 7 to 8 percent while costing not much more than single-sided panels. Analysts expect “the next decade will be marked by steady technological improvement along the entire solar value chain.”
“Every little improvement in generation or production means the capacity factor continues to go up, and that has direct implications in terms of the levelized cost,” said WoodMac’s Manghani.
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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
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.
Conclusion
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.
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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.
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We have introduced voltage difference in battery packs and used it as an important criterion for measuring the quality of batteries. At this time, we’ll review how to prevent voltage difference.
Match the cells
The best method in preventing cell voltage difference is to match the cells before the battery pack is assembled and to select the cells with the closest consistency for assembly. To put it simply, you match the batteries with the most similar specifications according to the configuration of the battery pack. There are many ways you can match the cells, but the most important elements to consider are the capacity, internal resistance, and voltage difference.
Ensure the quality
In Grepow, in addition to the conventional matching standards, we match the content of the battery cell’s production batches, material batches and other standards to ensure that the quality of the battery packs we produce is the best. If the matching standard is stricter, then the probability of the battery cell voltage difference will be smaller. On the contrary, if the battery cell matching standard is less strict or if there is no matching at all, the probability of the cell voltage difference will be greater, and this will result in premature battery failure.
In addition to the matching of cells before assembly, the use of a BMS balancing circuit is another great way to prevent voltage differences. At present, most BMSs on the market have charging balancing circuits. The function of the balancing circuit is to equalize the voltage of each cell during the battery charging process and to keep the voltage of the cell as consistent as possible. If you are using a BMS to prevent voltage difference, ensure that the one you are using or selecting has the balancing feature.
Others
There are other possibilities that may also cause a voltage difference, such as cell damages and high-temperature storage.
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Note: Most of the information in this article comes from the Solar Living Sourcebook.
Sunlight doesn’t just power your solar panels – it heats your batteries. With fewer hours of sunlight per day, winter is the time of year when it’s most important to make sure the energy storage component of an off-grid solar system or grid-tie solar system with battery backup is working efficiently. Unfortunately for those of us in the northern U.S. and Canada, winter can bring extreme cold, creating the worst environmental conditions for those deep-cycle batteries.
But just because deep cycle solar batteries have a harder time in cold temperatures doesn’t mean you need to suffer through the winter with them. Learning a few simple tricks to keep solar batteries warm in winter will substantially improve their performance during the part of the year in which you rely on them most.
Note: Lithium-ion and sealed lead acid batteries (AGM and gel cell) fare much better in cold weather than traditional flooded lead acid batteries do, and are now so safe that they can – and should – be installed indoors. If you’ve got these batteries and they’re installed indoors, you should have nothing to worry about when it comes to cold weather!
Why Are Cold Temperatures Bad for Solar Batteries?
First let’s clarify that cold temperatures are actually good for batteries when it comes to holding a charge; a battery placed in a refrigerator will self-discharge more slowly than the same battery in a warmer setting (and in fact, some people keep their household AA and 9V batteries in the fridge). Where cold becomes a detriment to batteries is in situations where charging and discharging is frequent and the cycles are deep – like in a renewable energy system. This is because cold slows down the chemical reactions that take place inside a battery as it supplies electrical current. Colder temperatures reduce current, which in turn lowers energy storage capacity.
The cold weather problem is compounded with deep cycle batteries used for solar storage because cold weather usually coincides with storms or the shorter days of winter. In both cases, PV production is lower due to the reduced number of sun hours, and the loads in the house are often higher due to active heating.
How Cold is “Cold” When it Comes to Solar Batteries?
Most batteries are rated at 77°F (25°C), meaning their technical specs are based on how the battery’s cells perform at 77 degrees. As a rule of thumb, batteries lose about 10% of their rated capacity for every 15-20 degrees below 80°F as measured in the cells.
How Can You Keep Your Solar Batteries Warm?
The best way to keep deep cycle solar batteries warm is simply to give them shelter and insulation. Let’s look at how to best do this, depending on what kind of deep cycle batteries you have.
How to Keep Lithium-Ion Solar Batteries Warm in Winter
Lithium-ion solar batteries can be safely installed inside your house, meaning the “shelter” and “insulation” boxes are already checked and no additional action needs to be taken. However, if they are installed someplace where there’s a risk of freezing, special care must be taken because – while they can safely discharge in temperatures as low 0°F (-18°C) – lithium-ion batteries should never be charged in sub-freezing temperatures (below 32°F or 0°C).
Nearly all lithium-ion solar batteries on the market today include at least a basic built-in battery management system (BMS) that can activate an external heating source when ambient temperatures approach freezing, ensuring the battery’s environment stays warm enough for safe charging. A few more advanced lithium batteries even have internal heaters that are managed by their BMS.
How to Keep Flooded Lead Acid Solar Batteries Warm in Winter
Even though flooded – or “wet cell” – lead acid batteries can charge at lower temperatures than lithium-ion batteries (as low as -4°F or -20°C), they typically require the most attention in winter because they cannot be installed inside your house where temperatures are nicely regulated. (When in use these batteries release hydrogen gas – which is explosive at even a modest 4% concentration.)
Instead, flooded lead acid batteries should be kept inside a battery box or enclosure with 2″ holes near the top and bottom for ventilation. If the enclosure is inside an insulated garage or shed, they most likely won’t need any extra help staying warm. But if the enclosure itself is not in an insulated area, it should be “reinforced” with insulation and thermal mass to stabilize temperature swings. Because the batteries generate a bit of heat when they are charging, the insulation will keep that heat inside the enclosure, keeping the batteries warmer.
Simply get a sheet or two of rigid foam insulation from your local hardware store:
Do a quick internet search for the proper R-value of insulation you should buy based on where you’ll be using it
Insulation rated for use below grade use is best because it is moisture resistant
Wires and cables pass through wall at bottom of battery box to prevent hydrogen from entering the house (hydrogen rises).
When installing insulation in your battery enclosure:
Cut the sheet to size with a circular saw, or score it with a utility knife and snap it over an edge for a clean cut
Leave an inch or two between the batteries and the insulation (and a little space between the batteries themselves) to allow air to circulate and keep temperatures as uniform as possible across all the batteries
Don’t cover your ventilation holes
Don’t permanently adhere the insulation to the enclosure – you’ll want to remove it when the weather warms up so the batteries don’t overheat in the summer
How to Keep AGM/Sealed Lead Acid Solar Batteries Warm in Winter
Like lithium-ion batteries, sealed lead acid batteries (AGM and gel cell) are safe enough to be installed indoors, giving you a huge leg up on temperature regulation. Also working in your favor is the fact that sealed battery cells freeze at lower temperatures than flooded/wet cells do. It’s best to check the manufacturer’s specs for your specific batteries regarding minimum charging and discharging temperatures. If your batteries are going to be exposed to temperatures lower than the minimums listed by the manufacturers, the same techniques suggested for lithium-ion and flooded lead acid batteries can be used to keep your sealed-cell batteries warm enough for safe use (insulated enclosure and a BMS/heater).
Tools and Tech to Help Keep Solar Batteries Healthy in Winter
MPPT Charge Control Technology
A charge controller with maximum power point tracking (MPPT) technology is probably already part of your battery-based solar system, but those short winter days are when you’ll be happiest to have it. MPPT solar charge controllers squeeze 15-30% more power out of a PV array on average than non-MPPT controllers by converting excess PV voltage into amperage. MPPT controllers perform best with cold PV modules and hungry batteries (sounds like winter conditions!), and can adjust the battery voltage based on battery temperature to help the cells reach 100% state of charge.
Battery Temperature Sensor
A battery temperature sensor can provide an early warning if battery temperatures drop below recommended levels. Some charge controllers will stop charging at certain low temperatures.
Battery Management Systems (BMS)
A battery management system includes functions beyond just temperature sensing, typically including features like voltage and depth of discharge at both the cell and battery bank level. This level of insight can help you identify problem areas in your battery bank, some of which may be cold-related.
A BMS is an absolute necessity for lithium-ion solar batteries (to prevent overcharging and thermal runaway), but most Li-ion batteries on the market today already have a BMS built in.
Battery Desulphators
These deep cycle battery maintenance tools simply connect to the battery terminals and then work automatically to remove lead sulphate buildup on the plates. Lead sulphate will otherwise build up on the plates over time, reducing a lead acid battery’s capacity and ultimately shortening its life. When you’re already contending with cold weather reducing battery capacity during the winter, you don’t need sulphate buildup compounding the problem.
Keep the Water Topped Off
It is important year-round to not let your flooded lead acid batteries go dry. In winter it’s especially critical to make sure there is plenty of water in them. A battery with low water levels is more likely to freeze.
Likewise, keep them charged up. The acid in the water prevents freezing, so a battery with a low charge is more likely to freeze than a charged one.
Adding More Battery Storage
Sometimes all the tricks in the book just aren’t enough to keep an older lead acid battery bank powerful enough to get you through the winter comfortably. Over time, batteries age and their capacity falls, and we add more electric loads to our homes. Sometimes the best way to combat the problem of cold weather limiting your batteries’ performance is to simply add capacity with a couple of new deep cycle lead acid batteries.
Winter or Not, Don’t Forget to Perform Regular Maintenance on Your Lead Acid Deep Cycle Batteries
For lithium-ion and sealed cell lead acid batteries (AGM and gel cell), a simple annual maintenance routine of cleaning the tops of the batteries with baking soda and water (then rinsing with water), and then cleaning/tightening the terminals is sufficient.
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