How do I extend the long-term life of my new laptop battery?

October 27, 2005 1:00 PM

How do I extend the life of my new laptop battery? I'm not talking about per-charge capacity, but long-term reusability - maximizing the amount of time before this battery becomes a useless brick like the last one.

This is in particular reference to li-ion and li-po batteries.

Various bits of possibly conflicting information I've collected:

a) You're not supposed to store batteries empty. Batteries left out of the machine will lose charge over time. Batteries left in the machine will lose charge over time.

b) You're not supposed to leave the battery in the machine and run on AC all the time. Doing so will kill the life expectancy.

c) You're not supposed to charge cycle the battery frequently, as the long-term life expectancy is measured in charge cycles.

d) You're not supposed to deep discharge the battery (not sure what this means in terms of reported battery capacity).

e) You're not supposed to use the battery before it has finished charging, once you start charging, but it needn't be fully discharged before charging (unless you want to blow a cycle without fully using it).

So, my question is two-fold:

1) Which of these are true?

2) What's the best strategy for maximizing the long-term life of a laptop battery, assuming you have access to AC power on a regular basis if you need it?

posted by Caviar to technology (18 comments total)

I'm fairly sure that (c) is true, as I have been a lot more careful about charge-cycling (use battery fully, charge fully, and minimize switching from charging/discharging) than I was with my previous battery. This one is still at about 90% of the original capacity after a year. I usually run my laptop with the battery in, on AC power, so if there is a detrimental effect to that, it happens a lot more slowly than power-cycling or improper charging.

My advice is to avoid using the battery for just a few minutes. If you use the battery, drain the battery, then recharge once it gets down below 5-7%. Otherwise, keep it on AC power, with or without the battery inside. This has worked well for me.
posted by jenovus at 1:10 PM on October 27, 2005

No matter what I've done, every laptop battery I've had ends up being unable to keep a charge right around the three year mark. Oh, and if you're buying a new battery for a three year old laptop, it'll cost about a third of what the laptop did.
posted by LukeyBoy at 1:24 PM on October 27, 2005

this is the first google hit for "lithium ion battery care", has an authoritarian tone, and consistent details.
posted by andrew cooke at 1:29 PM on October 27, 2005

In addition to the battery university link, I also refer people to the Wikipedia Lithium ion battery page and Apple's Lithium-ion battery advice.
posted by nthdegx at 1:32 PM on October 27, 2005

That wikipedia page is self-contradictory.

It says "Every (deep) discharge cycle decreases their capacity. The degradation is sloped such that 100 cycles leave the battery with about 75% to 85% of the original." and also "A unique drawback of the Li-ion battery is that its life cycle is dependent upon aging from time of manufacturing (shelf life) regardless if it was charged or not and not on the number of charge/discharge cycles."

They can't both be true. Which is it?
posted by Caviar at 1:51 PM on October 27, 2005

Also, the Apple page contains this ludicrous-sounding claim which I've never heard elsewhere:

"A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could listen to your iPod for a few hours one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, so you may take several days to complete a cycle."

Really? So, if I use 1% of the battery's power and then top it off, and repeat 100 times, I've only done one charge cycle?

I DO NOT believe that.

The Thinkpad information says a charge cycle is when you discharge more to less than 85% capacity and then recharge.
posted by Caviar at 1:55 PM on October 27, 2005

I DO NOT believe that.

Why?
posted by nthdegx at 2:14 PM on October 27, 2005

"Why?"

a) Because a recommendation like that sounds made up, explicitly for the purpose of being a simple rule that someone who doesn't understand what's going on can follow.

b) Because the Thinkpad site directly contradicts it.

c) Because I've never heard that advice anywhere else.

d) Because from what I understand, the battery life will depend on how far it's discharged, and discharging more or less before charging will actually drastically alter the life the battery, rather than being a linear approximation of a "full charge equivalent".
posted by Caviar at 2:33 PM on October 27, 2005

Really? So, if I use 1% of the battery's power and then top it off, and repeat 100 times, I've only done one charge cycle?

I DO NOT believe that.

Why not? It sounds like the issue with LiIon batteries is that they are made of a chemical compound that depleats depending upon how many electrons pass through it. A single "charge cycle" is the amount of electrons that the battery can release (yeah, I know electrons go the other way, forget that for now) before requiring a charge. So if you take that amount of electricity and multiply it by the mean expected cycles, you should get the total lifetime of the battery. It seems that the battery matrix ALSO degrades over time, regardless of whether you run electrons through it or not. I would guess that the two decay rates are different, it probably decales more quickly when in use than when not in use.

At any rate, 3 years seems about right to me.
posted by b1tr0t at 2:36 PM on October 27, 2005

But, you know - there's so much misinformation out there, and it's all contradictory. So, it's difficult to know what to believe.

It makes me wonder if, in fact, lithium-ion batteries are derived from technology we got from aliens, or if there's anyone on Earth who definitively understands how they work.
posted by Caviar at 2:36 PM on October 27, 2005

Oh, and if you're buying a new battery for a three year old laptop, it'll cost about a third of what the laptop did.

My laptop battery hass (the things about 4 years old, battery lasts about 2/5ths what it could when I got it) started to die - your comment promted me to check eBay.

Brand new (ie., manufacturer's packaging) batteries for ~$30. I' think I'm going to go grab one.

I guess it depends on how popular/widespread your particular laptop is.
posted by PurplePorpoise at 2:49 PM on October 27, 2005

b1tr0t said:
Why not? It sounds like the issue with LiIon batteries is that they are made of a chemical compound that depleats depending upon how many electrons pass through it.

I don't think that's accurate.

Say you're using 20% of the capacity of the battery in a sitting. Take these two scenarios --

Scenario A: You start at 100%, discharge to 80%, and charge back to 100%.

Scenario B: You start at 80%, discharge to 60%, and charge back to 80%.

These should both use the same amount of electricity (if the battery is delivering continuous voltage throughout the discharge cycle), but as I understand it, they're not the same in terms of battery lifespan.
posted by Caviar at 3:04 PM on October 27, 2005

You guys are totally derailing.

Of the question parts:

a is completely true and is the reason for e.

c is true-ish, I'll give you a better way to say it.

Plug into AC power whenever possible.

The rest of them as far as I can tell are false or apply to a different battery type.
posted by onalark at 3:34 PM on October 27, 2005

Batteries are a consumable. There are different types of batteries, so find out which type, then research that type. Except for AA style household batteries, they are very toxic, and it's very important to recycle them.
posted by theora55 at 7:09 PM on October 27, 2005

There are different types of batteries, so find out which type, then research that type.

That would be why I included "This is in particular reference to li-ion and li-po batteries." in the question.
posted by Caviar at 7:58 PM on October 27, 2005

So, I seem to possibly have a conclusive answer.

Your battery will lose charge over time, resulting in somewhere between a 2 and 3 year lifespan from time degradation, and over that time, the maximum per-charge capacity will slowly decrease. If you manage to charge cycle the battery more than around 800 times in that time, the life will be even shorter. The cooler you keep it (without actively putting it in the refrigerator), the longer it will last, but still probably not longer than 3 years. Leaving it plugged in and topped off most of the time is probably good, but not all the time, as it will get hot.

Does that sound right?
posted by Caviar at 4:22 PM on October 28, 2005

Sounds good to me, though but not all the time, as it will get hot is simply not true. Your laptop is going to get hot as a function of usage, the only reason this would be connected to being plugged in is if your laptop has a power management function for reduced power consumption (i.e. slower processor clock) to extend battery life.
posted by onalark at 8:27 PM on October 29, 2005

I'd assume there's heat given off in the gradual discharging and recharging of a plugged in battery. Maybe that's inconsequential compared to the heat generated during use.

But I think the tip remains the same - turn the laptop off when you're not using it. Presumably, standby is also better than on from that perspective.
posted by Caviar at 3:32 PM on October 30, 2005