Laptop Batteries


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Laptop Batteries: Myths debunked ...

There is a myth that if you take your battery out of the notebook while you have it plugged into AC with the adapter for long periods of time it will last longer. Sorry not true, I will explain further down the page.

There is another myth that if you take the notebook battery out when plugged into AC for long periods of time and then put it back in once a month for a recharge it will last longer. Sorry not true either.

Laptop Batteries - Leaving a dead or defective battery in your computer may result in a fire!The truth is that once Laptop Batteries are charged they will began to degrade, that is to say that after the initial charge the battery will never charge to it's full potential again. Most manufactures will tell you this if you read their product information. When you buy a battery and the manufacture says it will last x hours the manufacture is giving you a ball park figure. The battery at first will last longer by fifteen to thirty minutes, then the time slowly drop down until you decide to buy a new one.

I have a IBM T30 that I use on a everyday basis, the battery when brand new would last almost 2 hours. I know it lasted that long because I took it on a overseas flight to the UK when the battery was brand new and played some games on it until the battery died.

To understand why your battery will degrade after the initial charge you have to understand how the battery is made and how it is charged.

The battery that you take out of the notebook is really a pack of smaller batteries in a plastic case. Depending on the manufacture there can be anywhere from six to twelve or more batteries in the pack. Each battery is a 1.5 volt Li-Ion or Ni Cad battery. The better type of battery is Li-Ion. If you look at the battery pack it will say something to the effect that the pack will supply x volts at y AH (Ampere Hours). If you want to know how many batteries are in the pack divide the x number by 1.5 and you will get the total.

With computers you can also use the smaller condensed "Check list" to accomplish a single repair task.The charger is built into the notebook, it is part of the power supply. The charger will do what is called a trickle charge, it does not apply a lot of voltage and amperage to the battery, just a small amount. In a laptop batteries pack there is a small board that controls how fast the battery is charged and discharged, this makes the battery last longer.

The Laptop Batteries myths:

When you discharge a Li-Ion or Ni Cad battery you do not completely discharge the battery. So think of your battery as a glass of milk, you drink part of the milk, you can see a ring where the glass was full down to where you stopped drinking, a milk ring, after you are done with the glass of milk depending on how many times you sipped out of the glass you will see some milk rings.

Now let's use this analogy and say instead of sipping the milk it is the length and number of times you have powered up you laptop and then recharged the battery. If you do not let the battery discharge completely - to the low battery warning beep - when you plug it into to AC the battery will start charging at that point. The first milk ring. This phenomenon is called battery memory, each time you use the notebook on battery and then plug it in to AC power it builds up memory until the length of time the battery will last gets shorter and shorter.

The next myth is if you keep the battery out of the computer and recharge it once a month.

This will cause the battery to build memory faster. The battery will have a charge already. If you do not discharge the battery to it's lowest potential before you recharge it the memory build up will start where the battery was discharged to. In other words the battery will over time discharge by it self. If you charge your battery then take it out the notebook for a month and don't complete the discharge the memory build up will start where the battery has a charge at.

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If you have a notebook and know you are going to use it on AC for most of its life ( like my T30, it is my primary business computer) then discharging the battery as far as it will go then removing it before plugging the laptop in to AC will extend the life of the battery. You will just have to remember to charge the battery before you head out with the notebook,

We just have to live with the fact that a notebook battery will only last for a certain length of time then buy a new one and try to not let the new one build up memory.

One last word of caution, one of my friends pointed out to me that his battery would not hold a charge and it is still in the notebook.

This is not a good idea because it could over heat and short out, if it did not cause a fire it surly will damage the computer and the power supply.

Another thing to consider about notebooks being used as a desktop for long periods of time is that once the battery reaches it's full charge then the power supply has to do a trickle charge while it is installed.

My recommendation: discharge the battery to its lowest point then remove it and store it until you are going to use the notebook on battery only then charge it. Now this is not a very good plan for those 'power out' emergencies which no one can predict but it will save the battery and the power it takes to keep it charged.

Newer Li-Ion laptop batteries have a built in charge and discharge circuit that limits the amount of charge or discharge the battery can do. That is the circuit will not allow the battery to be over charged or charged too fast nor will it allow the battery to be discharged to rapidly. (That is not to say you can not short the positive to negative terminals and discharge the battery, you can and that is dangerous!). By limiting the amount of current (amps) that the battery is getting while charging or discharging the battery will last longer. The heat build up during these two cycles is lower, this makes for longer battery life. The circuit also eliminates the build up of "memory" where the last discharge and charge cycle ended thus even an older battery will get a better charge and the discharge time will be longer.

This is not to say that the laptop battery after a few years constant use will not need to be replace, it will but two or three years of use is better than one year of use.

The recommendation from laptop manufactures is if you use the laptop with AC power for extended period you should remove the battery from the laptop with a full charge, then periodically put the battery back in the laptop and charge it fully (the recommended period will vary, once a month is the average).

Long term storage of the laptop (I have one laptop that I use "occasionally") you should also remove the battery and store it separately (in an anti static container) and charge it periodically also.

Laptop Batteries Life expectancy chart:

The image, table, or PDF was removed because it will not display on your device. Check back on a PC....

Battery Life expectancy chart

A new battery will recharge to 100%, as the battery ages the charge capacity decreases. This chart is from my experience with laptop batteries and is not a scientific study. Using the guide above you can beat the average a little bit but in the end after a year or so of continuous use you may need a new battery.

If you want to extend your notebook battery's usage consider putting a SSD in place of the mechanical hard drive. I replaced the battery in my older T-30 notebook recently. I also did an experiment to test the idea that using a SSD would extend the time a Li-Ion battery would last. That is using a brand new battery fully charged with a mechanical hard drive vs a SSD.

With the proper knowledge and care your battery will last longer.The new battery with a mechanical hard drive lasted one hour and twenty-two minutes. To insure I was getting a quality test I repeated the test three times and that was the average after each recharge of the battery.

With the SSD installed I am getting a constant 2 hours and seven minutes of life from the new battery. I have been testing this everyday for the last two weeks, once a day, giving the battery a full over night charge. I am very pleased.

Another benefit of using the SSD in your notebook is the reduction of heat under the drive bay. The old hard drive would get very hot, almost to the point that if I had to use the notebook on my lap I had to put something between the notebook and my leg it was that uncomfortable.

Never Short The Battery TERMINALS!
The battery will discharge so fast it could explode, it will catch on fire!

If you would like to test your laptop batteries here is a procedure I have written to assist you - stress tests.

(You could buy a battery tester, they are quite expensive. But why buy something you all ready have? Your Laptop is the best tester for your battery! Just sayin'...)


A complete chapter for laptops - Self Computer Repair Unleashed 2nd Edition E-Book.

Disposing of old battery Recycle your old battery

IBM/Lenovo ThinkPad's Support this is the start page, you will need the product number or model number.

Compaq/HP Support  this is the start page, you will need the product number or model number.

Dell Support this is the start page, choose your notebook to continue.

You will also find items like carrying cases, docking stations, and laptop batteries on eBay In the right hand column enter your search term.

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