What is the impact of charging a laptop for a long time?

It will not damage your battery.

It will shorten its life though, but there is nothing practical you can do about it.

Lithium Ion batteries age in two ways, one is through what is termed “Calendar Life” and the other is Cycle life.  Here is what you need to understand about both:

Calendar life  – the time spent at a given state of charge (SOC) and a given temperature causes a loss of capacity and increase in internal resistance that is proportional to the square root of the time.  Higher SOC imparts greater degradation.  Higher temperature imparts greater degradation.  Keeping your computer plugged in all the time with the battery ensures that the battery stays hot and charged as much as is possible.  If nothing else, turn down the performance of the laptop when you don’t need it to overperform so that it runs cooler.

Cycle life – while you might think that it makes sense to fully discharge the batteries, rather than put lots of little cycles into it, the opposite is true.  Lots of little cycles do virtually nothing to the cells.  100% discharges are the bane of their existance.

So, the reality is, you could optimize battery life by keeping the battery about 50% charged, letting it discharge a bit and then recharging it, and if chargers allowed for it, floating them at a SOC that was not 100%.  However, it is much much easier to just get on with life and use your laptop and not worry too much about this.  Assume your battery costs you $1 a day.  Put that much away for its replacement.  When it is fine on the day you buy your next computer, you have now paid for that new computer, or a good size chunk of it.

Will charging a mobile phone using a laptop decrease the laptop’s battery life?

A laptop battery typically has a capacity of 4000 to 10,000 maH and voltages ranging from 10 to 14 volts.

A cell phone like the iPhone 6 has a 1800mAh 3.7V battery.

First you are right, if the laptop is on charger than charging the cellphone by USB port does not cycle current from the laptop battery. The current comes from the laptop charger and only slows down the rate at which the laptop will recharge.

Second case, if the cell phone is charge from your laptop running on battery. Then the charge will come from the laptop battery and potentially reduce is life by using up charge cycles.

But the  iPhone 6 absorbes 6.7 WH for a full charge (3.7V x 1810 maH)
The laptop lets assume is a 10.2V 6000 maH system and therefore has energy of about 60 WH.

So charging a fully depleted iPhone from the laptop battery will take about 1/10th of the laptop charge.  or 1/10th of a discharge cycle. probably the laptop is rated for 1000 full discharge cycles? So a small part of its life is given up. I’d do it when travelling for convenience or emergency but not every night when at home.

Is it good to keep laptop batteries charged upto 100%?

It’s perfectly alright, you can work no problem

Well, modern batteries are intelligent enough to know whether they are fully charged or not, once they are completely charged the laptop automatically stops charging and starts working with direct D.C supply from the adapter.

I always connect my laptop to charger when i was in home and places where i have facility to connect.

This makes my battery give backup like the new one even after two years.

by the way, it will not increase the temparature. It even cools the laptop, because during charging battery heats up, it makes laptop hotter. If you connect it with charger, laptop works with D.C supply from adapter directly without the involvement of battery. so no heat will be generated from battery.

Lithium battery such as Li-Ion and Li-Pol has no memory effect.

Li-Ion has cycle life between 400 and 1200 cycles (most of them 800-1000), Li-Pol about 500-800 cycles. But it mean full cycle. If you discharge battery by 1% and then charge it to 100% it does not mean full cycle. Only 1% of full cycle.

Lithium battery must not by priming (or formatting). They do not need it. Formatting lithium battery just short their life.
Deep discharge is harmful.

In regard to Lithium battery has no memory effect I recommend charge laptop battery anywhere and anytime you can. Battery can powering standard notebook for about 2-5 hours (ultramobile notebooks can last more than 10 hours). It is very short time so everytime you have oportunity, charge!

But if you use laptop only in home, look for settings and try find function for extend battery life. Many modern notebooks have such function (in various names). It charge battery to maximum 80%.

If your laptop does not leave even your desk, charge battery to 50%, unplug battery from notebook and store it in 15°C. Twice per year check it. If voltage drop under 3 volts per cell, charge it again to 50%.

How do I keep my laptop’s battery in good health?

You’ve probably heard some people say you should drain your battery completely before charging it, or that you should keep it between 40% and 80% all the time to make it last longer.

Most of these rules are outdated, applying to older nickel-based batteries. Luckily, most or all of your gadgets these days run on Lithium Ion batteries, which are easy to take care of.

They last longer when you perform shallow discharges, keep them cool, and don’t leave them plugged in while they’re running at 100%. Honestly, though, batteries have a finite life no matter what, and your efforts will only go so far—so don’t stress about it.

Focus your efforts on getting better battery life out of your phone or laptop on a given charge instead—and knowing how to replace the battery when it starts dying.

Carry a Battery Backup

Increasingly, though, the former is just not an option. Laptops with a removable battery, nowadays, tend to be fleet-oriented business machines, and in these cases, the simplest option is a second battery. (Indeed, this can be a good reason to opt for one of these machines even if you’re not a typical business buyer.) Spares can be ordered directly from the manufacturer (we don’t recommend buying third-party batteries), often for less than $100. Simply swap the old battery for the new one once in a while when charging, and bring along the charged-up spare whenever you expect to be away from a power outlet for an extended period.

Another, similar option is to buy an external power pack. While it is also technically a battery, these external power sources plug in to your laptop the same way your charger does. They generally cost between $100 and $200, but come with adapters for use with many different laptop models. They can be used on more than one system, and even for other devices, such as your phone or tablet.

These strategies will help you make the most of the battery you have. If you’re in the market for a new laptop, however, and battery runtime is one of your key concerns, check out our roundup of the laptops we’ve tested with the best battery life.

Simplify Your Workflow: Closing Apps, and Using Airplane Mode

On the other hand, if you’re writing a novel or playing a local video file and don’t need to be distracted by notifications, it’s fine to enable Battery Saver. It’s a good habit to adjust your laptop use in more battery-conserving ways, such as by sticking to one app at a time and closing everything else when you’re not using it. It’s a bit like turning off the lights when a room is vacant. If you’re going back and forth between the kitchen and the pantry all the time, or between Firefox and Word, by all means keep both sets of lights and apps on and open. But if you’re just cooking or watching a YouTube video, you’ll be best served by turning off and closing everything else.

In addition to aiming to single-task, consider enabling Airplane mode in Windows, or turning off Wi-Fi and Bluetooth in macOS if you know you’ll be editing a document with no need for web access. In addition to eliminating distractions, Airplane mode eliminates a significant source of battery drain: not only the wireless radios themselves, but also the background apps and processes that constantly use them, such as updaters and push notifications.

Use Battery Settings on macOS

Apple’s MacBook, MacBook Air, and MacBook Pro laptops don’t have a battery slider, although many of the same settings described above are present in the Energy Saver preferences.

To open it, click on the Spotlight magnifying-glass icon in the upper right corner of the screen, search for Energy Saver, and then click on the Battery tab. If you want to approximate the Windows Better Battery or Battery Saver modes, make sure that the options “Put hard disks to sleep when possible” and “Slightly dim the display while on battery power” are checked, and the option “Enable Power Nap while on battery power” is unchecked. (With Power Nap enabled and your MacBook asleep, the machine will wake up now and then to check for updates. Disabling it keeps your MacBook fully asleep when it is asleep—until you choose wake it up.) On recent MacBook Pro laptops, the display brightness adjusts to 75 percent when you unplug the computer from power if you have “Slightly dim the display while on battery power” enabled.

So, if you want the best battery life, should you use Battery Saver all the time? Not exactly. Because Battery Saver mode disables some useful features, you might want to use it only when your battery is below 20 percent and a power outlet isn’t near. Likewise, turning off Power Nap can mean it will take longer to catch up on notifications you’ve missed while you’re away from your MacBook. That’s why most users should use the Better Battery setting and enable Power Nap most of the time.

Use the Windows Battery Performance Slider

The first stop on our battery-life betterment tour is the Windows battery performance slider, a recent addition to Windows 10. It aims to group all of the settings that affect battery life into a few easy-to-understand categories. The company that made your PC determines exactly which settings the battery slider controls. But in general, keep these guidelines in mind:

  • The Best Performance mode is for people willing to trade off battery runtime to gain performance and responsiveness. In this mode, Windows won’t stop apps running in the background from consuming a lot of power.
  • The Better Performance setting limits resources for background apps, but it otherwise prioritizes power over efficiency.
  • Better Battery mode delivers longer battery life than the default settings on previous versions of Windows. (It’s actually labeled “Recommended” on many PCs.)
  • Battery Saver mode, a slider choice that will appear only when your PC is unplugged, reduces the display brightness by 30 percent, prevents Windows update downloads, stops the Mail app from syncing, and suspends most background apps.

Perfect Battery Life Estimates Are Impossible

Battery life is always hard to estimate. Even while you’re using a laptop, Windows might go from saying you have five hours left to only two hours depending on what you’re doing. That’s because performing more demanding activities on your laptop increases power consumption. A laptop won’t use much power while it’s just playing hardware-accelerated video on low brightness but increase the brightness level, and it’ll draw more power. If you start a demanding task that requires CPU power, it will draw even more power. That’s the real problem. Laptop battery life varies dramatically depending on what you’re doing. Manufacturers have decided to take the most unrealistic number they can find, but there’s no single battery life estimate that would work for everyone. However, a battery life test that simulates normal web browsing would be much more accurate and useful for most people.