August 12, 2004

12:34 PM

Is there anything I can do to make my laptop battery last longer? I've had two HP laptops, and within months the batteries in both of them stopped holding a full charge. Presently, the icon indicates a fully charged battery, but when I unplug the laptop the battery dies within 30 minutes. Is this an HP specific problem? Is there a "better" kind of battery I can buy?
posted by Harvey Birdman to (10 comments total)

Many laptops are easily confused about the battery level. They don't measure it in a normal manner and won't drain the battery properly. Basically, eventually, the laptop thinks the battery is dead at full charge because the sensor is confused (I can't put it any better than that, sorry, I'm not a laptop expert).

The fix is often to keep trying to drain the battery (usually, the symptom will let the laptop turn on for a few minutes and the battery sensor will turn the laptop off). Keep turnining the machine on until it won't turn on at all any more.

At that point the sensor knows how low the battery can actually go and still have enough juice to turn on the machine. Charge it fully and enjoy.

(I've done this sucessfully with two different laptops now, both Compaqs -- however, since most laptops are NOT manufactured by the company whose name appears on them [Example: Old Macs were made by ACER {UGH}], your laptop might be the same as mine).
posted by shepd at 12:41 PM on August 12, 2004

I'm not specifically familiar with laptop batteries, but most batteries for cellphones, etc., work better if you run the charge fully down before recharging them, unless you have a lithium battery (I think it's lithium anyway). If you run the battery fully dead and recharge it fully the battery life is usually longer. Of course, it's also possible that these batteries suck--as I said, I'm not familiar with them.
posted by The God Complex at 12:43 PM on August 12, 2004

Generally, it's not so much a matter of running the battery down before charging. Modern batteries don't have memory effects like the NiCd batteries did in the bad old days. These battery lifespan problems stem from two different sources, both related to charging behavior:

Overcharging: Lots of people spend more time connected to AC power than on battery, and quite a lot of the charging circuits in laptops and batteries are just too dumb to prevent overcharging from happening if they are connected to a power source for days or weeks at a time. I once had a laptop, with a brand new battery, connected to a power supply for a year. When I finally went to use battery power, the thing could hold about 2 minutes of charge because it had been overcharging so long. That particular model of laptop was especially notorious for a broken charger design, but the problem isn't really rare at all.

If you're mostly using line power, yank the batteries once they've completely charged. Put them back in when you want to roam.

Limited charge cycles: Modern batteries have somewhere over 1000 "charge cycles" in them before they start to go south. Each time you apply charge power to the battery you're using up some of its capacity. If you're constantly plugging and unplugging the laptop over the course of the day -- and I did this before I understood how hard it was on the batteries -- you're eating through charge cycles. I blew through a really nice high-capacity battery, about triple what shipped with the laptop it was in, by doing this. At first I had a run time close to 8 hours. After three months, I was struggling to get an hour out of it.

This is what leads to the common wisdom of "running the battery down." Really what you need to do is minimize the number of times the battery is charged, which (depending on your usage patterns and habits) often amounts to the same thing.
posted by majick at 1:24 PM on August 12, 2004

For whatever the reason, you just need to take people's advice, and get religious about not constantly re-charging the battery when it's only part depleted. It's kind of annoying, but if you set the Windows "low power" alarm for about 10%, and then consistently let the battery run down to that whenever you go onto battery power, you'll find that the batteries last much, much longer. I've got a battery that's two years old in my laptop right now, and it's got a charge capacity now that's as long or longer than it was out of the box. (I don't know if it can technically get _longer_, but it's still really good.)

Regarding majick's point on the charge cycles, I've heard the same thing, but it's basically kind of moot. Yes, lithium batteries don't technically have the same memory effect that NiCad did (I believe that was due something like internal oxidation or buildup), but the net effect is the same. For whatever reasons, rechargeable batteries all run better, longer, when you're not constantly partially discharging and re-charging them. When you're careful about letting them run out, your batteries end up holding much more of a charge.
posted by LairBob at 2:32 PM on August 12, 2004

This is an interesting study in "profit by ignorance": it's certainly not in the battery manufacturers' or retailers' interest for customers to know how to maximize battery life.
posted by ParisParamus at 3:08 PM on August 12, 2004

most batteries for cellphones, etc., work better if you run the charge fully down before recharging them

The "memory effect" applies to NiCad or Nickel Cadmium battieries primarily. Sometimes it's applicable to NiMH or Nickle Metal Halide batteries, and almost never to Lithium Ion batteries.

Most consumer electronics, especially laptops, ship with NiMH or Lithium batteries nowadays. It's unlikely this is the problem. However, battery quality is a variable thing, and you can usually find higher-capacity batteries for your laptop if you shop aftermarket. As with many things, the manufacturer will stiff you anywhere they can, to save a buck or two. They rarely include the highest-rated batteries available when they ship the laptop, especially the big, evil, bankrupt, cookie-cutter manufacturers like HP.
posted by scarabic at 4:08 PM on August 12, 2004

"...but the net effect is the same."

Trust me, NiCd "memory" was far, far worse than the kind of problems people have today with NiMH and Li ion batteries. A couple of short charge/discharge cycles and a NiCd cell can be rendered useless.

You really aren't hurting anything by putting your laptop on to charge at 20 or 30% charge remaining, and if that suits your schedule, go right ahead. The extra meticulousness of draining the battery to discharge or near-discharge is probably not worth the hassle.

Just try to avoid "topping off" the battery if there's enough of a charge in there to get by, then remove the battery or unplug from the charger only after it has had a chance to trickle charge at 100%, and your battery will last 2 or 3 years easily.
posted by majick at 4:22 PM on August 12, 2004

I know the question was about an HP, but in case they are similar, here's Apple's page for ibook/powerbook batteries (which are lithium-based):

http://www.apple.com/batteries/notebooks.html

They say "For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally.", whatever that means. They also recommend periodically running the battery all the way down, so even if there is no memory effect per se for lithium batteries, there might be something similar.
posted by advil at 8:48 PM on August 12, 2004

Apple recommends periodically running the battery all the way to exhaustion because of the way that Apple laptops (or specifically the laptop's PMU) calibrate their time remaining calculations. It doesn't, actually, run the battery all the way down -- just to the point where the laptop wants to stay in suspend mode. Not all other batteries and laptops benefit from doing this, but for those of you with Apple hardware, doing this every couple of months is the only way to get realistic, uninflated numbers from the "time remaining" counter.
posted by majick at 8:56 AM on August 13, 2004

Not related to laptops however be aware Lead Acid batteries do not like to be deep discharged. A few deep discharges of your car battery will physically damage the battery.
posted by Mitheral at 1:35 PM on August 13, 2004