By and large, lithium batteries bring a wide range of different benefits to the table that are difficult – if not impossible – to replicate in any other way. Also commonly referred to as lithium-metal batteries (due to the fact that they use lithium as an anode), they’re typically capable of offering a very high-charge density (read: longer lifespan) than other alternatives that are on the market today.

For that reason alone, lithium batteries have a wide range of applications in our daily lives, especially for those critical in nature that we tend not to spend too much time thinking about. Specialized types of lithium batteries are used in pacemakers and other implanted medical devices, for example, because they can often last 15 years (or longer) under the right circumstances. They’ve even started to replace traditional alkaline batteries in many everyday devices like clocks, digital cameras, watches, portable data assistants, and more, all thanks to that longer lifespan that minimizes the need to replace the battery over time.

LITHIUM BATTERIES: CYLINDRICAL VERSUS PRISMATIC

Example of cylindrical lithium batteries.

Issues like mechanical vibrations, thermal cycling from charging and discharging, and the mechanical expansion of current conductors are all things that can affect a battery’s lifespan. Therefore, the design of these cylindrical units is intended to help mitigate risk from these and other factors as much as possible.

 

On the inside of a cylindrical battery, a series of cells are combined and operate in parallel to one another. This is done to help increase both the voltage and the overall capacity of the battery pack.

 

For these reasons, cylindrical batteries are usually the kind that are found in the aforementioned medical device systems. Smaller, more specially designed cylindrical cells are also commonly found in portable devices like laptop computers. Notably, Tesla also made headlines recently by selecting cylindrical lithium batteries to power its fleet of popular electric cars.

 

What Are Prismatic Lithium Batteries?

A prismatic lithium battery, on the other hand, features a cell that has been encased in either aluminum or steel, mainly for the purposes of increased stability. This, in turn, creates several key advantages right out of the gate. Because of this unique construction and makeup, prismatic lithium batteries tend to be very thin, very light and offer an effective use of space.

Example of prismatic lithium batteries.

 

Because the rectangular shape of your average prismatic Li battery offers far better layering than other options, they typically give engineers a higher level of flexibility when designing products that will one day feature prismatic batteries as power sources. Because of that, it should come as no surprise that prismatic batteries are typically found in smartphones, tablets, and similar types of electronic devices where mobility is a major priority.

 

Due to these properties, modern day prismatic batteries are also commonly used in larger critical applications like energy storage systems and in electric powertrains.

 

Cylindrical Versus Prismatic Batteries: Breaking Things Down

There’s a reason why cylindrical lithium batteries are the most commonly available (and used) type today. When compared to their prismatic counterparts, they can typically be produced much faster and with a lower cost-per-KWh (kilowatt hour) at the same time. The design itself better supports the types of automation processes that are commonplace in factories and in other manufacturing environments across the country, for example, which only aid in creating a better sense of product consistency and keeping those ultimate costs as low as possible.

 

One of the major reasons why prismatic cells have increased in popularity over the last few years, however, has to do with their large capacity. That, coupled with their naturally prismatic shape, make it very easy to connect four different cells together to help create something like a 12-volt battery pack.

 

The prismatic design does come with its own challenges, however, particularly as they relate to what happens if something goes wrong. If one cell in a prismatic battery goes bad for any reason, for example, the entire battery pack that it is a part of is essentially compromised. Because the cells in a cylindrical battery are combined in a series and in parallel, these are the types of problems that designers and other engineers don’t really have to worry about.

 

Because of the design of cylindrical Li batteries, they also tend to radiate heat (and thus control their own temperature) more easily than their prismatic counterparts. Because of the way that prismatic cells are all placed together, this certainly works to increase the capacity, but it also leaves room for a higher probability of design inconsistency and short circuiting. The larger size of the prismatic cell may also be attractive in certain situations, but it also minimizes the chances that such a battery could be used in a heavily automated environment. That larger cell size also creates perhaps the biggest disadvantage for prismatic batteries: the increased capacity makes it far more difficult for the battery management system to properly regulate heat and prevent the battery itself from overcharging.

 

As previously stated, the thin form factor of a prismatic battery leads to increased flexibility for product designers – this does, however, create a few disadvantages of its own. It is that very same design that ultimately makes prismatic batteries somewhat difficult and expensive to properly design and manufacturer, which are costs that are almost certainly passed along to consumers. That flexibility has also created a limited number of “standardized” cell sizes, which only adds to difficulty in that regard. This also contributes to a higher than average KWh price as well.

 

It’s important to note, however, that the topic of costs is also one that comes with a few important caveats. Experts agree that because prismatic cells can often be larger than their cylindrical counterparts and will thus cost more initially, they offer more opportunity for cost reduction in the long-term. Based on that, you may want to think about the cost factor in the following way: is it more important to save money now by going cylindrical, or can you depend on your ability to innovate and potentially save a larger amount of money over time? The answer to that question, of course, is one that only you can answer based on whatever it is you’re trying to do.

 

Maybe the biggest advantage of cylindrical batteries in most situations is that they are very safe. If the internal pressure of a cylindrical lithium battery grows too high, most of the cells are designed to rupture – thus mitigating safety risks from situations like a fire or an explosion.

 

In The End

None of this is to say that cylindrical lithium batteries are inherently “better” than their prismatic counterparts, or vice versa. As is often the case with these types of situations, there is no “one-size-fits-all” approach to battery selection. Much of your decision will ultimately come down to the eventual application and the amount of risks and potential disadvantages that you’re willing to accept as a result. There will be some situations where a prismatic battery absolutely makes the most sense. There will be situations where cylindrical batteries seem like the logical choice.

 

More often than not, choosing the right type of lithium battery to meet your needs will come down to three factors:

 

The amount of money you’re willing to pay, the effectiveness of the battery you’re trying to unlock, and the safety considerations given the application.

If space isn’t necessarily at a premium and you need to find a cost-effective way to guarantee both performance and longevity, cylindrical batteries offer what you need.

If cost isn’t a factor and you need as much power as possible in an already small space, prismatic is likely the direction you’ll want to head in.

Only by trying to learn as much about these options as possible will you be able to make the best decision given your needs in the moment. Ultimately, your ability to do that successfully is all that matters.

Written by Anton Beck
Posted on August 16, 2019 at 9:03 AM

 Within the context of a discussion about batteries, defining the term “state of charge” is simple. It’s a term that essentially refers to how “full” your battery is, at least in terms of its remaining energy. Compared to how much energy a battery can store at 100%, your current state of charge shows you how much is remaining, thus allowing you to predict when a recharge may be in order.

The larger implications of that term, however, are far less straightforward.

If you truly want to get the most out of your battery and make sure that it lasts as long as possible, there are a few key things about concepts like charge/discharge cycles, End of Life and more that you’ll definitely want to know more about.

Learn How To Expedite Your Battery Pack Design & Development

Charge And Discharge Cycles: Breaking Things Down

At its core, a “charge/discharge cycle” is exactly what it sounds like – a situation where the energy in a battery is discharged before subsequently being charged back up again.

It’s important to note that rarely does this ever mean taking a battery from 100% capacity to 0% and back again. Instead, most manufacturers use an 80% DoD (depth of discharge) formula for a battery’s overall rating. This means that roughly 80% of the available energy in a battery is delivered, while about 20% remains in reserve. Using this technique is an efficient way to increase a battery’s overall service life, prolonging its lifespan significantly in many applications.

 

The expected charge and discharge cycles for a battery depend less on the battery chemistry and more on the overall capacity of the battery itself. The only real difference has to do with when a full charge must be applied. For lead acid batteries, for example, a full charge should be applied every few weeks (or at least every few months) because a constant low charge will ultimately cause sulfation and damage the unit. With nickel-based batteries, a partial charge is totally acceptable. With lithium-ion batteries, a partial charge is actually better than a full charge because of the implications it brings with it for the long-term health of the battery.

End Of Life

The end of life for a battery is exactly that – the moment where the battery reaches the end of its usefulness and/or lifespan and can no longer operate at anywhere close to the peak capacity that you once enjoyed.

Generally speaking, end of life for a battery will be determined in one of three different ways depending on the product’s manufacturer.

Cycle life. This refers to the total number of times that a battery can be charged and discharged, as outlined above. Manufacturers will typically include the recommended cycle life on the product’s packaging or in other documentation available at the time of purchase.

Warrantied life. This will usually be outlined in a specific number of years, like any other product that you may have. A battery with a 10-year life under warranty is typically expected to reach true end of life by roughly that time.

Total energy throughput. This is the total amount of energy that will pass through the battery over the course of its lifespan and this will usually be measured in megawatt-hours.

Occasionally, manufacturers will reference end of life using a measurement called expected operational life. If this is present, it will usually be somewhat longer than the “warrantied life” measurement. At that point, your battery will no longer be covered under any type of manufacturer’s warranty, but it will still continue to function until about the time that the listed number of years have passed.

It’s important to note, however, that end of life does not mean that your battery will suddenly become useless after a certain amount of time has passed. Far from it. It simply describes the total amount of time that you can expect your battery to operate at peak performance.

For the sake of example, consider the battery in your smartphone, tablet, or other type of mobile device. When you charge your phone for the first time after buying it, 100% may get you approximately 10 hours of use before you must charge the battery back up again. Over time, that number will slowly decrease. You may notice that you only get nine hours out of 100% capacity, or eight-and-a-half, even though your general use and operational conditions haven’t changed.

Once that battery reaches true end of life, that number is going to start to rapidly drop. This is because 100% no longer represents the same amount of stored energy that it once did. You’ll still be able to use your battery, but there will come a day where it won’t be able to hold a charge at all, at which point it will likely have to be totally replaced.

Best Practices For Prolonging The Life Of Your Battery

Consumers can absolutely manage their batteries differently to obtain more life cycles from a battery. They just need to remember to follow a few key best practices over time.

For starters, you should always keep your battery at a moderate temperature whenever possible. Instances of extreme heat or extreme cold can cause the battery to expand or contract, both of which will cause long-term issues and could ultimately lead to problems like corrosion.

Along the same lines, always store your batteries in a cool place whenever you’re not using them. If you’re going to be storing a battery for an indefinite period, don’t allow its charge to deplete to zero. Instead, store your battery with a charge of about 50% for the best long-term results.

For certain types of batteries like lithium-ion, you should also avoid deep cycling; don’t let your battery drain down to 0% before you charge it back up again. Experts at Battery University agree that lithium-ion batteries tend to last the longest when they are operating between 30% and 80% charge as often as possible.

Finally, you should also do whatever you can to avoid abusing your battery over time. Batteries will always experience additional stress via harsh discharges and rapid charges. If you’re going to be using a battery with a particular application, make sure that the battery is optimized for the power and energy requirements you’re working with. If necessary, increase the size of your battery to combat this type of unnecessary stress.

When a lithium-ion battery in particular reaches its natural end of life, you should also make sure that you dispose of it properly. You can’t just throw them in the garbage. They are technically considered to be hazardous waste in this state. Instead, contact your local landfill to find a battery recycling drop-off location in your area.

 

There’s lots of press about how to conserve battery power, but not much about how to take care of your batteries. Here are a few things you can do to increase battery longevity.

In today’s mobile world, battery life is precious. If you don’t believe me, go to an airport and watch the road warriors. It can get downright nasty when two spot the only available outlet at the same time.

It doesn’t take long to learn what helps preserve the current charge on the battery. What’s not well known is how to care for the battery itself. That’s just as important. Doing so allows the battery to operate efficiently. Here are a few ways to keep your lithium-ion batteries healthy.

1: Keep your batteries at room temperature
That means between 20 and 25 degrees C. The worst thing that can happen to a lithium-ion battery is to have a full charge and be subjected to elevated temperatures. So don’t leave or charge your mobile device’s battery in your car if it’s hot out. Heat is by far the largest factor when it comes to reducing lithium-ion battery life.

2: Think about getting a high-capacity lithium-ion battery, rather than carrying a spare
Batteries deteriorate over time, whether they’re being used or not. So a spare battery won’t last much longer than the one in use. It’s important to remember the aging characteristic when purchasing batteries. Make sure to ask for ones with the most recent manufacturing date.

3: Allow partial discharges and avoid full ones (usually).
Unlike NiCad batteries, lithium-ion batteries do not have a charge memory. That means deep-discharge cycles are not required. In fact, it’s better for the battery to use partial-discharge cycles.

There is one exception. Battery experts suggest that after 30 charges, you should allow lithium-ion batteries to almost completely discharge. Continuous partial discharges create a condition called digital memory, decreasing the accuracy of the device’s power gauge. So let the battery discharge to the cut-off point and then recharge. The power gauge will be recalibrated.

4: Avoid completely discharging lithium-ion batteries
If a lithium-ion battery is discharged below 2.5 volts per cell, a safety circuit built into the battery opens and the battery appears to be dead. The original charger will be of no use. Only battery analyzers with the boost function have a chance of recharging the battery.

Also, for safety reasons, do not recharge deeply discharged lithium-ion batteries if they have been stored in that condition for several months.

5: For extended storage, discharge a lithium-ion battery to about 40 percent and store it in a cool place
I’ve always had an extra battery for my notebook, but it would never last as long as the original battery. I know now that it’s because I was storing the battery fully charged. That means oxidation of lithium-ion is at its highest rate. Storing lithium-ion batteries at 40 percent discharge and in the refrigerator (not freezer) is recommended

Final thoughts
Lithium-ion batteries are a huge improvement over previous types of batteries. Getting 500 charge/discharge cycles from a lithium-ion battery is not unheard of. Just follow the above guidelines.

Himax-home-page-design-news-3

Lithium Ion vs. Lithium Polymer Batteries – Which Is Better?

Lithium-ion or lithium-polymer? The (what seems like) endless debate on batteries in modern consumer electronics. Today, we’re going to talk about the differences between these battery types. While we may not be able to settle the score once and for all on which is better. we hope to give you the information you need to make the best possible choice!

What’s the Difference?
A lithium-ion battery is a rechargeable battery format that first grew in popularity thanks to their adoption by major electronics companies in the early 1990s. They are essentially a group of very rigid electricity generating compartments, which consists of three pieces: a positive electrode; a negative electrode; and an electrolyte, or liquid chemical compound between them. Most lithium-ion batteries, unlike more traditional ones, also include an electronic controller, which regulates power and discharge flows so your battery doesn’t overheat or explode.

The most significant difference between lithium-ion and lithium-polymer batteries is the chemical electrolyte between their positive and negative electrodes. In Li-Po batteries it isn’t a liquid. Instead, Li-Po technology uses one of three forms: a dry solid, which was largely phased out during the prototype years of lithium polymer batteries; a porous chemical compound; or, a gel-like electrolyte. The most popular among these is the last one, which is the type of battery you’ll find in newer laptop computers and electric cars. The catch is that plenty of companies are not actually selling you a true Li-Po battery, instead it’s a lithium-ion polymer battery, or a Li-ion in a more flexible casing.

Is One Better than the Other?
Both lithium-ion and lithium-polymer batteries have their pros and cons. Typically, the advantages of a lithium-ion is their high power density, lack of what’s called the memory effect (when batteries become harder to charge over time), and their significantly lower cost than lithium-polymer. In the words of Wired, “Lithium-ion batteries are incredibly efficient. They stuff freakish amounts of energy in a tiny package.” But, as anyone might have seen with the recent saga of a certain cellphone brand being banned from flights, lithium-ion batteries are inherently unstable, suffer from aging, and are potentially dangerous. If the barrier that separates the positive and negative electrode is ever breached, the chemical reaction can cause combustion (fire). As Li-ion batteries have become more popular in consumer electronics, businesses have tried to lower costs by cutting corners. While quality batteries are perfectly safe, you should always be careful when buying no-name brands.

Lithium-polymer batteries, on the other hand, are generally robust and flexible, especially when it comes to the size and shape of their build. They are also lightweight, have an extremely low profile, and have a lower chance of suffering from leaking electrolyte. But lithium-polymer batteries aren’t perfect either: they are significantly more costly to manufacture, and they do not they have the same energy density (amount of power that can be stored) nor lifespan as a lithium-ion.