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BATTERY END OF LIFE VS. STATE OF CHARGE

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.

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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.

 

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Five tips for extending lithium-ion battery life

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.

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Which battery is better polymer or lithium?

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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.