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Why Is a Laptop's Battery Dearer Than a Lawnmower's?
Barence writes "PC Pro's contributing editor Paul Ockendon has bought a new lawnmower powered by lithium-ion batteries — part of a recent flood of such lithium-ion-powered garden and workshop tools which are taking over from NiCd and NiMH thanks to lighter weight, longer life and lack of the pernicious 'memory effect.' This is pretty much the same battery technology used in laptops, mobile phones and MP3 players, so volume manufacture is already established. Yet laptop manufacturers charge more per Watt-hour than lawnmower makers. This blog investigates whether such a seemingly ludicrous situation can be justified."
This was mentioned in the article, but not as size, but weight. The power to weight ratio is more important. Density of the individual battery cells, and continuous use vs. burst usage also come into play.
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The guy from Sony answered it: size, weight, and output differences. Would someone actually critique that instead of talking about markets, price settings, and conspiracy theories?
I believe the reason is actually another.
Laptop batteries sold separately are generally sold after the laptop was purchased, or at least after the decision was made to purchase that particular laptop. People don't generally spend the time to price out more than 2 laptops including all options before picking which one they want, they usually look at the base unit price. Therefore the laptop manufacturer has a monopoly (or close to a monopoly, at least, for some things you can get third-party components) on the sale of laptop options like batteries. A monopoly means being able to charge what the item is worth to the buyer, instead of only being able to charge a little more than the productions costs like in a market with perfect competition. The only challenge is to avoid scaring the cheapskate buyers away that you only make a small profit on without lowering the price for everyone, but differential pricing is solving that "problem".
Options and spare parts are generally examples of market failures.
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The Phillips head was developed for use in automated manufacture - it's designed so that the machine driving it will tend to slip the slots rather than over-torque the screw.
And for that purpose it works really well.
What it wasn't designed for is screwing by hand, where any other design works better.
"I do not agree with what you say, but I will defend to the death your right to say it"
Laptop batteries all use a standard cell which is slightly larger than AA. What you need are unprotected 18650 Li-Ion cells. You can find made in China cells for $3/ea from places like DealExtreme.
Just keep in mind you assume all the risk yourself when you rebuild Li-Ion packs. The cells aren't intended to be sold to end users because they must be certified together with the electronics that protect from overcharging and discharging. That said, there isn't nearly as much specialization in cell selection as some posters imply. 18650 cells may be rated for different capacities, but they're all compatible with any other 18650 charger. Just don't mix new and old or different capacities.