How Should I Treat My Notebook Battery?

timothy asks: "I finally have a company laptop (woo-hoo!) but now I'm trying to be a good guy by treating it nicely, with a padded bag, nice accessories, keeping the keyboard free of detritus, whispering gently, etc. But there is one aspect of notebook operation that has bugged me since I first acquired one in 1993 or so ... really and truly, how ought I treat the battery?" Speaking from the opposite spectrum of battery care (my battery is lucky to get any form of pampering, I just slap 'em in and use 'em), are there any special things that you need to do to ensure good long life out of laptop batteries?

"The owner's manual of my (late-model) machine addresses only the first charging of the machine's lithium-ion battery, which must be rather lengthy to my mind. (12 hours.) However, that done, like most people I suspect, I use my laptop frequently on battery but at least as frequently simply as a portable desktop, plugged into both AC and ethernet.

I've heard every permutation of the following, and I'm not sure whether to:

• discharge the battery completely each time before recharging it (not convenient) or it will develop memory effect problems.
• *never* discharge the battery completely, or it will have trouble ever holding a full charge again
• not worry about it -- "modern batteries just don't care." (In that case, why is it so important to charge it for 12 hours before use in the first place, or is that the idea of a sadistic manual writer?)

I would appreciate any better ideas than my usual, which is the last of these -- in truth, I plug in when possible, and nervously watch the battery meter when not, then run for AC..."

I found this...

[Wog]

A simple Google search found this [computerbits.com]. It has an overview of different battery technologies, as well as a few very good tips. Read it in good health.

Compromise

[Syberghost]

Most notebook batteries are going to have a maximum number of "charge cycles" that isn't as large as you might think.

However, within that limitation, you can mostly just plug it in whenever you want, and expect to need to buy a new battery every 18 months or so.

If you're really worried about it, don't charge the battery until it gets below some arbitrary limit, such as 75%.

Memory effect and all that other crap is mostly a thing of the past.

-

Re:Compromise

[Chanc_Gorkon]

Yup! They only time you really have to worry about batteries is if you still have a Ni-Cad battery pack. Other then that, Lithium Ion, Nickel Metal Hydrides or any new tech is always going to not have the memory effect (they learned that mistake with NiCads). Now, if your manufacturer says to fully discharge it, then, well, do it. Other then that, stop worrying.

A good website for battery info

[hansendc]

Check out Cadex [cadex.com]. They make battery chargers and conditioners, but they also have a lot of good charging information. They have a breakdown of which batteries are best for which jobs. It's worth a look.

How to treat the battery

[human bean]

First of all, you must always address the battery as "Your Wattage" or "Your Voltship".

Second, make sure that you battery has the best seat in the house at all times.

When approaching your battery, you should bow, and ask it's blessing upin the computing you are about to perform...

Modern Battery Chargers Are Pretty Smart

[Matt_Bennett]

The battery chargers for most devices today (cell phones, laptops, not the really cheap, bottom of the barrel stuff though) are pretty smart. The real charging circuitry is not in the battery or in the wall-wart- it is usually in the device itself. The wall wart is only a bulk power supply, to this end, let your device decide how to charge it. The thing to watch out for is excessive heat- which is what kills most batteries, especially ni-cads. Once the battery is charged, if the battery is still warm, it is being overcharged- time to disconnect it. Batteries don't like heat.

Lithium-ion batteries are pretty tough, but even with them, the less time spent on the charger the better- since chargers are inefficient, a significant amount of the power just goes to heating up the battery. If you don't really need to charge the battery, don't bother, the heat cycles (and excessive time spent hot) shorten the battery life.

Do these people really know anything?

[Jamie Webb]

Maybe I'm just stange and unusual, but:

• I have a 486 laptop with a Li-ion battery. It's sat plugged into the mains pretty much constantly for the last 4 years. It gets used heavily as a second desktop and the battery gets discharged to below 50% about twice a week. Uptime is still about two hours, which is about as good as it ever was.
• I have NiMH batteries for my MP3 player, which I charged in a supposedly 'smart' NiMH charger. They get discharged below half most days and recharged overnight. In about 5 months, the play-time has gone down from over 8 hours to under 2 hours.
  As a experiment, I put them in a 'really smart' charger capable of recharging standard alkalines and also NiCds. It was made well before NiMH batteries appeared in the shops. The play-time has gone back up to over 6 hours.

Make what you will of that.

Some more info

[crisco]

The websites suggested have some great info so this is a little redundant but I thought I'd post what I know to eliminate a few rechargeable battery myths.

discharge the battery completely each time before recharging it (not convenient) or it will develop memory effect problems.

That is an old myth reserved for NiCad batteries. While a true 'memory effect' is possible, the memory effect most people observed came from overcharging NiCad batteries. By attempting to give a half charged battery a full charge, you overcharge the battery. This makes it act as if it had less capacity than it should have and shortens its life. 'Smart' chargers that monitor the charge current and battery voltage or the battery temperature eliminate this by shutting off the charge current at the proper time. Using these, you don't have to worry about overcharging or producing a memory effect.

*never* discharge the battery completely, or it will have trouble ever holding a full charge again

Again, this held true for the NiCad cells. When people started thinking they had to be dead before they charged them the would discharge the cells into a resistive load until they were completely dead (0V per cell) before recharging them. They quickly discovered that this didn't do good things to the battery life. Many early rechargeable devices did nothing to prevent complete discharge either. Once a NiCad cell goes below 1V, it has a very quick discharge curve (it dies really fast). So in a several volt stack, one cell might die before the rest and effectively receive a reverse current as the rest of the cells discharge. This destroys the delicate balance of the chemical reaction that makes up the battery.

Modern devices shut off well before the cells reach a complete discharge point so this is another non-concern.

"modern batteries just don't care." (In that case, why is it so important to charge it for 12 hours before use in the first place, or is that the idea of a sadistic manual writer?)

The chemicals that make up the battery are shipped in a 'non active' state to extend the shelf life of the battery. That first charge cycle (of first few charge cycles) take longer because the checmicals have to 'form', they have to completely react against the charge current before they can discharge anywhere near full capacity. Often this takes a few charge-discharge cycles and takes longer than the working charge time.

Nickel Metal Hydride and Lithium Ion batteries are not subject to these kinds of overcharging or 'memory effect' problems. They are usually accompanied by a smart charging system due to their own peculiar charging requirements. For example, I've heard from various people that Lithium Ion batteries will Explode if overcharged. So they have to have a 'smart' charger, nowdays often built into the battery. I've also heard, but haven't confirmed from a reliable source, that these battery technologies do better maintaining a charge at most times - You should charge them whenever you get a chance instead of waiting until they are dead.

One last thing. Batteries like the same temperatures that you do. If you have to store them, do so inside. You'll also get the best capacity by using them at room temperatures. And charge them every month or so, they will have a much longer shelf life charged than if left to sit.

Give it HELL

[WowMan]

I've used the following technique to revitalize my laptop batteries. This also works for NMiH batteries too!

1) Discharge completely.
2) Shock the battery with a large DC voltage.
3) Recharge!

Use 2x or 4x the battery's rated voltage. Only apply pulses - continuous application will destroy the battery! I've used a car battery charger and "touched" the battery's contacts several times (12-24) with the charger leads. (Your battery says: "Short Pulses Please!")

Re:Modern Battery Chargers Are Pretty Smart

[crisco]

a significant amount of the power just goes to heating up the battery.

This is somewhat misleading, batteries generate heat as part of the chemical reaction that charges them. The battery should not get too hot (if that is the case the charger or the battery is bad) but they will heat up as an unavoidable consequence of being charged.

Some chargers are very effecient, using the same switching technology that your computer power supply uses. Even if the charger itself generates heat, it should be separate from the battery to avoid heating the battery. Some chargers rely on the battery rise in temperature to determine when to shut off.

If you're using a well engineered product, you should trust the charger, especially if it is designed to charge the battery in four hours or less or is using Lithium Ion technology. These are significantly different and better than the old NiCad technology that we are all familiar with and you have to be willing to throw out the old rules you learned when you had that radio controlled car back in the day.

Re:Modern Battery Chargers Are Pretty Smart

[Matt_Bennett]

Some chargers rely on the battery rise in temperature to determine when to shut off.

Very true- but the primary failure I've seen in battery packs (after the individual cells) is the temperature sensor (usu. on Ni-Cd packs). If the temp sensor goes bad, the charger never goes off, and you can destroy a good battery. Thankfully, good Li-ion battery chargers don't rely on temperature to determine charge.

Very true that heat is part of the charging process, excessive heat is the problem. Any more heat than is necessary is a bad thing.

Hints about Ni-Cd batteries

[Baloo Ursidae]

I often hear people saying that its best to drain Ni-Cd's completely before recharging or they'll develop problem areas. To me, this indicates that they have the wrong charger. They're using a charger meant for Nickel Metal Hydride or other cheaper charger.

Ni-Cds require digital chargers to charge properly. With one, you really don't have to think about draining them, just slap them in there overnight and you're good to go.

I have been using the same Ni-Cd laptop battery with very little change in lifespan since 1994 because I use the right charger.

Often times the manufacturer will give you a shitty charger that doesn't charge Ni-Cds properly. Its best to go get a third-party charger, from my experiance.

This also applies to other kinds of rechargable Ni-Cd batteries.

Battery Calibration

[spencste]

Most notebooks have have a battery learning or battery calibration utility which can recalibrate the internal gas gauge. But some notebooks actually have built in calibration ciruitry which will automatically calibrate the capacity of the installed battery. Fully discharging these notebooks results in a re-calibration of the gas gauge. Some notebooks have a utility built into the BIOS setup utility which will discharge the battery and then recharge it, e.g. Gateway Solo 5100, 9300. Others have a similar DOS utility which does the same thing. e.g. Gateway Solo 2500. Not too sure about other notebooks, most OEMs will point in the right direction.

Finite battery life. Less then you think.

[sanemind]

The number of effective charge/discharge cycles of a battery are often less then you think... But then again, if you start to worry about it too much, and only use the battery when 'absolutely neccessary', your probably wasting more resources then just buying a new bat when the one you have dies.
Li ion : mean avg og 500-700 cycles NiMH: mean avg of 400-500 cycles NiCD: mean avg og 300-500 cycles


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man sig

Store batteries in the freezer?

[suky]

I always heard that you should keep batteries in your freezer if you are going to store them long-term? Is this just a myth, or does freezing the batteries actually do something with the chemicals inside them

Re:Hints about Ni-Cd batteries

[Detritus]

I used to work in a electronics maintenance shop that did a lot of work with Ni-Cad batteries. Part of the standard periodic maintenance was the complete discharge of the battery. This was done by discharging the battery to a low level, then the battery was disassembled and the individual cells were discharged down to zero volts. The battery was then reassembled and given a full charge. This isn't practical with most consumer grade batteries. They should never be completely discharged, as this could ruin some of the cells from reverse voltage.