OT: This Swift thing

[Chris Angelico]

On Tue, Jun 17, 2014 at 8:12 AM, Gregory Ewing
<greg.ewing at canterbury.ac.nz> wrote:
>> A few years ago jumbo sized but cheapish CULV laptops suddenly had 10
>> hours plus battery but did anyone notice or care?
>
>
> I think people do care, it's just that going from
> something like 6 hours to 10 hours is not a big
> enough change to warrant much hype. If it were
> 100 hours, without losing too much else, I'm
> pretty sure it *would* be made a marketing point!

Partly that. But also, people want to know how long that will *really*
last. For instance, 10 hours of battery life... doing what? Can I
really hop on a plane for ten hours and write code the whole way
without external power? Or will each minute spent recompiling Python
(with the CPU pegged) cost 2-3 minutes out of those ten hours? What if
I watch videos (on headphones, probably, given how noisy airliners
are!)? That'll surely take more power than the manufacturers estimate.
And what happens six months from now? Will battery life decay to the
point where it's no longer interesting? (Obviously it'll decay some.
But how much?)

These are unanswerable questions. (Unless you count "It depends" as an
answer.) If I have two laptop models I'm looking at, one with a
boasted 10 hour battery and the other with "just" 8 hours, all those
other considerations will be much more important than the two hours of
rated difference. Now, if you had that 100 hour battery, well, then
I'd be interested! Because even after six months of usage, that'll
still be giving several times what a 10-hour battery would be.
Obviously still read the fine print as regards usage patterns, but
even if you get the full hundred hours *only* with the screen on
minimum brightness *and* the absolute lightest usage, it's probably
going to be possible to use that usefully.

That's why purported battery life isn't such an advertisable point.
And it's why the business I worked for recently, where we sold
second-hand laptops, was very clear about our battery testing
methodology - it was approximately equivalent to light usage, keeping
the screen, CPU, and disk all intermittently active. If it lasted two
hours in our test, we expect that it'll last two hours of, say, text
editing. (And yes, the scale is very different. Our idea of a good,
saleable battery was one that lasts one hour; below that was
considered a fault to be discounted for. Two hour batteries were
excellent. Anything more than that was "wow, this in a second-hand
laptop?!?". I doubt we would *ever* see a ten-hour battery.)

ChrisA