how much cheaper would laptop battery be if we only wanted 30 mins of power, not 4 hours?

let’s imagine the idyllic world where there are plentiful electrical outlets in airplanes, trains, cafes and various other public accommodations where people are likely to use laptops. In this case, IMHO, a battery that holds enough charge for 30 minutes (enough time to go to the bathroom in Starbucks and come back or to carry laptop from point A to point B in the office where it would get plugged in again) would have been quite sufficient.

Well, so how much of a saving would that be on batteries? If nowadays a replacement battery seems to cost on the order of $70-80 (well, then again, surprisingly enough here is one for $35 ), how much would a 30 minutes battery cost?

One thing to note (and this doesn’t really address your question) is that this scheme wouldn’t work very well with current battery technologies. Using laptops tethered to the mains is, in general, a recipe for very short battery life.

You probably wouldn’t save much. A lot of the costs of a modern laptop battery are in the custom size and shape of it. Some of the costs are also due the fact that the manufacturer can charge whatever they think they can get away with since it’s a custom battery that only they make. If they wanted you to buy any old battery, they’d design it to be powered by a bunch of AA cells.

Lithium ion batteries are used not only because of their good charge density, but also because of their light weight. There are plenty of cheaper battery technologies out there, but those other batteries aren’t as light. Most of the other battery technologies last a lot longer as well. Lithium ion batteries, in addition to being expensive, lose capacity over time no matter how well you treat them. They lose capacity even faster when they run hot, as they often do in laptops. If you were willing to sacrifice weight, you could easily have a much cheaper battery that didn’t have to be replaced after a few years.


if brand-name companies (Dell comes to mind) selling the batteries are profiteering (as is indeed suggested by the $35 example I linked to above), why don’t we see the market flooded with low cost external batteries for the budget conscious consumer with a big backpack? I mean, there are external batteries on the market, obviously, but they don’t look cheap and people complain about their poor quality.

So why don’t we see Schumpeterian creatively destructive “sell your overpriced battery on ebay and use our wonderful, cheap external battery with 2 year warranty” type of marketing campaigns?

My thoughts exactly. Within a few months I think that the 30 minute life would be down to 1 or 2 minutes.
Think about the fact that most people end up getting a new phone not because they are having problems with the actual phone, but because it’s time for a new battery. Usually, when they find themselves having to charge it in the middle of the day.

Why is this? Is the machine running off of battery power while being simultaneously recharged from the wall? Does that essentially count as a charge cycle which hurts the life of the battery?

the problem of battery wearying out from being connected to electrical outlet sounds like gross design flaw, not a fundamental limitation. Why doesn’t anybody sell batteries that turn off electrical connection once they are fully charged, so that this problem would go away?

As you’ve noticed, batteries in general don’t cost much anyway. Saving 50% on $50 isn’t a lot.

I believe it subjects the battery to a large number of small charge cycles (as the battery drops below full, then charges back up again - and that although these cycles may not individually be so damaging as a deep cycle, there are a lot more of them.

Why do you say this? It is a standard office setup to have your laptop in a docking station so while you are at your desk. This allows the laptop to run off of mains power and you get bigger monitor keyboard and mouse. But you can pull the laptop out of the docking station if you need to go elsewhere. I have been doing this for years and never had a battery degrade to the point I needed a new one.

My experience has been substantially the opposite of yours. I work in IT support and I see no end of cases where laptops are used mostly tethered - and when the time comes to use them on battery power, they have very little capacity - forcing the laptop user to take the power brick with them. This often happens as soon as six months after unpacking.

The HP dv6000 laptop I have does come with a battery that lasts only 30 minutes. Sure… you can eke out 75-90 minutes if you dim the screen and do nothing more taxing than typing in WordPad, but for real use? At absolute peak demand (like playing games) you can drain the battery in less than 25 minutes. NetFlix watch instantly will drain it before 45 minutes, which is about the same life you get doing general web browsing at sites like this. Before I replaced an old battery, it got bad enough to start shutting the computer down after just 10-15 minutes of use.

HP makes a higher capacity battery, but it doesn’t actually fit into the laptop (it sticks out on the bottom). Since I don’t like ruining the form factor, I keep the power cord around and use the battery like the OP describes.

As for price… the low-capacity one is still a $50 battery. There’s minimal savings to be had by going smaller.

Even in the ideal world with abundant power outlets, I’m not sure 30 minutes would really be enough. When I give presentations on my laptop, I need it to run for an hour at a time, and although there’s a power outlet available in the presentation room, it’s much more convenient to not need to use it: That’s one less thing that I have to hook up in preparing for my talk.

Frankly, this whole thread is absurd.
Nobody is going to buy a laptop that advertises 30min battery life, unless the manufacturer essentially gives it away. It would be like advertising NEW! IMPROVED! 2 GALLON GAS TANK! GO 50 MILES BETWEEN FILLUPS! Just so the car would cost $19,950 instead of $19,999.

My HP dv6000’s battery lasted almost 2 hours when new, but after several years deteriorated to 20 minutes. I just bought a $25 new replacement battery with a 3-year warranty off eBay. My battery meter says it’s good for 2 1/2 hours.

Which is still a design flaw. Once the charger detects that the battery is charged, it should completely stop using it as long as there is other power available. I was flabbergasted when I first discovered this was not done on even the most expensive devices. If I can fix the problem by manually removing the battery, they can fix it by using an automatic switch.

Should batteries be removed in a laptop that is mainly being run on mains power then? Or is there some downside to doing that?

I just bought the first laptop I have had for a long time, so I am a bit of a laptop noob. I intend to use it plugged in, as a desktop replacement, for at least 90% of the time, but I would like to have the possibility of occasionally using it under battery power to remain available.

According to this site, the main culprit is heat in combination with fully charged batteries - the laptop is usually quite hot when run off mains, since it is not (usually) set up to save power. Since the battery (naturally) is situated close to the power circuitry, the battery in turn gets heated, and suffer more capacity loss. The solution to this would, if I read the article correctly, indeed be to remove the battery from the laptop when running from mains - and this, naturally, would have to be done manually :slight_smile:

If you want to maximize your battery’s longevity yes, you should. But, depending on the brand you are using and the relative low cost of replacing batteries, it hardly does seem worthwhile does it? (I for one am much to lazy to unplug the battery whenever running off mains…)

Well, I actually expect it to be running of the battery pretty rarely. However, I am a little concerned that the battery will lose its charge if I leave it unplugged for long periods, and it might then be inconvenient to have to charge whenever I do need to use it. Will it, in fact, lose its charge?