Laptop Battery Maintenance and Optimization Laws: How To Get More From Lithium Ion Batteries

So let me get this straight, you're telling me someone is now saying their iPod nano exploded? Okay, so the heat in my MacBook Pro can get pretty bad so I can see how a little chemical reaction going the wrong way, a drop of the old nano [that's what they say] could set the heat on meltdown. But man, are we really basing our systems around little nuclear fuel cells that are nearing critical runaway on any given hot day?

To recap from an earlier post on battery maintenance:

  1. Short battery life in a laptop is mainly caused by heat rather than charge / discharge patterns.
  2. Consider taking out the battery if you are going to be on fixed power for an extended period of time. (your battery will receive and generate no heat, thereby saving some wear and tear on the molecules that make up the powering magic of the lithium ion.
  3. Avoid frequent full discharges because this puts additional strain on the battery.

laptop battery monitoring, battery capacityRecently in a ZDNet article the Apple Corps guys chronicled a story of taking in a MacBook when the Lithium Ion battery failed to hold a charge. What he saw was that the Apple Genius ran his battery through a software evaluation and determined that his battery "could" be replaced under warranty. The shocker was learning that there was a standard under which his battery would not have been replaced. And there were no published instructions from Apple on this standard. Not is his MacBook materials, not online, no where.

Here is what this Apple Genius says about their best-practices for battery life. [And if you don't abide by these rules you might see your "paid-for" AppleCare warranty wind up useless if your battery tanks.] Remember these tips are NOT ON APPLE'S SITE. And why not Apple?

The chemistry inside a rechargeable battery works best when it’s used — translation: charged and discharged — and that if it’s always plugged into AC power (and fully topped off) most of the battery isn’t being used and will gradually decay. The genius helping me claimed to have 700+ charge cycles on his three-year-old battery and said that it still gets three plus hours of run time as as result.

So to complete this outline let's go over some of the newly revealed information.

  1. The molecules inside your lithium ion battery want to be excited by being charged and discharged. But not too much. The recommendation is every 30 charges of so to let the battery run down to "low battery" status. There is no need to "fully discharge" the battery. In fact, discharging the battery too far puts it at risk for what is called Deep Sleep, from which the battery may not recover.
  2. Frequent use off-plug is a good idea. The little cycling is enough to keep most of your battery happy. But try and get to the "low battery" status at least once a month.
  3. Taking the battery out [only if you have a removable battery – doh!] while you are on plug is a good idea because the battery does not stay hot with the residual processing of the notebook. But taking the battery out is a pain, so…
  4. Keep the exhaust vents unobstructed. And adding a little tilt between the laptop and the desk may also help keep things cooler and the hotter air moving up and out of the machine.
  5. Beware that those cool leatherette covers can add to the heat of your machine. [I definitely notice about a 5 – 10 degree difference when I take my bright red cover off, but I like that it keeps my thighs from getting scorched by the aluminum frame of my MacBook Pro.]
  6. Keep your laptop out of the sun and out of hot cars. The ambient temperature can also affect the heat of the battery. If you have a desk fan you could even aim it to push air across the back of your laptop vents when you don't need it yourself.

The part that really gets me is the heat of the overall machine. I don't like the wrist-warming feature of my MacBook Pro. Perhaps on a really cold day it would be nice, but it feels too hot most of the time. [I wonder if it's good for preventing carpal tunnel syndrome. I remember in the early days of the Powerbook I had one with 1/4 inch neoprene pads on the wrist rests. I'd like to have a couple of those now. They might look goofy, but when I'm writing a lot, the only way to get off the heating pads is to use an external keyboard.]

@jmacofearth
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You will see from the chart below, it’s all about heat.

battery maintenance is about heat

When are Laptop Battery Specs Going to Get Real?

Picture 3[My battery thoughts were prompted by some discussions and posts by Patrick Moorhead from AMD. He has done a good job of questioning battery life stats. I think there are a few battery life posts I need to write soon to continue this dialogue, or is it a soliloquy?]

Okay here’s a great metaphor for the “battery life” issue.

I have a 2006 Toyota Prius and the fuel indicator has an eight bar indicator for gas level. I also reset my trip meter after I fill up. And here’s where I think Toyota has missed the mark. I can go upwards of 120 miles and the gas meter still shows FULL, all 8 bars are still lit.

The car actually gets around 340-370 to a ten gallon tank. I average 38 mpg combined, even when I’m driving pretty aggressively. So, at the top of the gauge the measure is useless. But as the car moves closer to that magic 340-350 range the lights practically go out at in pairs. And if you see that last LED marker flash and the “add fuel” message on the dash, DO NOT PASS ANOTHER STATION. Get gas immediately.

So the fuel gauge is useless in the Prius. I know I get near 350 miles per tank with a gallon or so to spare. And the only indicator that causes me to take action is the flashing light, and if I have let the fuel get THAT LOW then it IS an idiot light.

My laptop battery has similar issues.

When unplugged, my laptop does its best to calculate time remaining to standby. And the accuracy of the minutes to black is less important than the final “please plug in your laptop to avoid standby” message. Or the equivalent of the flashing “add fuel” message.

So in the real world my laptop with a 2.4 Intel Core Duo 2 gets approximately three to three-and-a-half hours on a full, overnight, charge. But the real measure, the real indicator I look for is that final “add fuel” warning.

Now, I am waiting with anticipation for a new laptop with an "enhanced" Li battery. Advertised and marketed at eight hours battery life, I am not so concerned or worried about “exactly” how long the battery will last, but more about how much additional warning I will have between when the battery says, “add fuel” and when the machine powers down in the middle of my Spore victory dance.

In terms of reporting battery performance, doesn’t some of the problem originate with the battery itself? Does an ATI battery and a Sony battery and a who-knows-what-brand battery all perform the same?

And what I learned recently in doing some “battery” research is, that HEAT is a bigger issue for Li batteries than anything else. So even in standby, if your Li battery and laptop are in a hot car with the windows rolled up, the battery will drain much faster than if it were on a shaded table in a coffee shop.

FACT: Short battery life in a laptop is mainly cause by heat rather than charge / discharge patterns. [1]

I would like to see battery ratings gain more reputable metrics and here are some things I'd like to see:

  • I want the battery to last a long time (anything beyond 3 or so hours is pretty good, but I don’t travel a lot.);
  • I want the battery to not die prematurely (1 – 1.5 years seems like a reasonable amount of time before a replacement battery is necessary.);

But, more important to me than any spec (3DMark06 or MMO7) is this:

  • I’d really really, really like the battery to be GREEN. Less lead, less bad stuff, less waste.

Then we should really think about how to cool the battery better, so my palms aren’t on fire atop my 140 degree, and my thighs aren’t blistering red. If we can keep it cool, while under duress (like when running 3DMark06 benchmark), guess what? The battery performs better and lasts longer.

Now, back to cars for a second, I understand that the Prius outside the US has been offered with an EV override button that forces the car to use more electric power than it does in “normal” mode. It was taken off the US models by pressure from somewhere. (Not hard to imagine where that lobbying pressure came from.)

So with my laptop I would often hit the “TURBO” switch to keep the machine running at top performance even if that meant having to keep it plugged in. But I would like an “ECO” mode as well.

The upcoming 2010 Prius comes with three modes including “EV.”

By all means, let’s keep getting better and honest about our metrics. But let’s not obsess about a 91 3DMark06 vs a 95 3DMark06. Quite frankly, even if you tried to explain it to me, I don’t know what that 4 point 3DMark06-spread means in terms of actual battery time.

So when manufacturer says the new laptop will get 8-hours runtime (or is it 12?) I don’t really know what that means. Will my Prius really get 42 city 48 hwy? I don’t care. But when that “add fuel” message pops up on my laptop or my Prius, then I will sit up and take immediate action.

Ref: #1. The Battery University for all you ever wanted to know about battery stats.

That's it, Power On!

@jmacofearth
permalink: http://bit.ly/batterylife

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