Laptop Battery life

50Twuncle

stupideejay wrote: »

Hello,
I've got a Samsung Laptop running an i3 processor etc. The Laptop is only 3 months old. The battery charge is set for 80% to preserve the life of the battery. Great idea but I'm only getting about 1-1 1/2 hours usage. When the battery gets to about 50% the time drops dramatically and then needs to be recharged. I use it mainly for surfing. Does anybody else have the same problem. It was bought from Currys.
Thanks for reading

I assume that it was factory set to charge at a maximum of 80% charge to "preserve battery life" ?
This cannot help - since Lithium batteries are designed to be fully charged and then totally flattened - this increases battery life
I remember about 17 years ago - my first laptop was powered by a NiCad battery - you had to follow the instructions to the letter with these - or lose the full charging ability within a month or less !!
My current laptop (HP) - still holds its charge for a good 4 hours and it is now 4 years old..

booler

21Twinkle wrote: »

This cannot help - since Lithium batteries are designed to be fully charged and then totally flattened - this increases battery life

Can you show us a source for this info?

gjchester

21Twinkle wrote: »

This cannot help - since Lithium batteries are designed to be fully charged and then totally flattened - this increases battery life.

Sorry no. The only thing good about fully flattening and then recharging a Lithium battery is it may re-calibrate a laptops battery life gauge.

Lithium batteries are very good at giving a constant voltage over there output, they tend to give out 3.8V until they are exhausted then the voltage falls rapidly, unlike NiCad or NiMH which the voltage decline in use.

However as I said if you do fully discharge them and drop them too far (usually 2.6V or less ) then you can get chemical changes in the battery and its at best not going to hold much charge, or at worst can become dangerous.

Lithium battery's have a lot of urban myths around them, and charging is not fully understood by a lot of people, however there's some understanding starting to appear.

Take two batteries, charge them both and use one till the device cuts off, (i.e. it thinks the batter is flat) and the other recharge at 50% used. The one fully discharged will need replacing after far less charging cycles than the one discharged 50%. Simply put the less discharged before charging the longer the battery will last.

That does over simplify it. Lithium batteries are more temperature sensitive than NiCad or NiMH, keeping them over 30'C reduces the amount of cycles they can do, as well as the ability to hold charge. Leaving a Lithium battery in a car on a hot day can damage it, and lets face it most laptops get warmer than that, and are often placed on beds/laps and so on where the air cannot circulate well and the heat builds up. Leaving a Lithium battery discharged for a any length of time can damage it too, as can rapid charging or discharging, although most laptops are built to not allow that to happen.

gjchester

booler wrote: »

From Wikipedia ..
If overheated or overcharged, Li-ion batteries may suffer thermal runaway and cell rupture. In extreme cases this can lead to combustion. Deep discharge may short-circuit the cell, in which case recharging would be unsafe.

Biggest issue is usually damage and cell rupture. Remember at School when you dropped lithium or sodium in water? It shoots around and fizzes. The fizzing is the Lithium or sodium reacting with the water forming a hydroxide and in the process releasing a hydrogen atom.

If a battery is damaged and the cell punctures it allows water that's in the air in and in the process generates hydrogen and a little heat. That heat causes the reaction to proceed in the next atom and so on building up hydrogen, which is easily ignited and so increasing the temperature further.

What may seem minor to most people is the reason being reported as to why Boeing has a lot of it's Dreamliners currently grounded.

Peter999_2

I bought an Asus UL30A for my parents when they go abroad so they could use it on the plane going to the US etc.

The battery life started off at 11 hours in 2009 and still lasts for well over 9 hours and they do use it everyday. It really does last an amazing length of time and the laptop itself was only £349 - great buy.

They have never done anything special with the battery, just plugged it in constantly at home and then used it on battery when on holiday and just charge it every few days. I'm always a bit suspicious with all these recommendations of how to extend the life of the battery. At work I've had identical laptops to over people and my battery has always been the same as colleagues who attempt things to keep the battery life good whereas I've just used the laptop and never really thought about the battery.