18W from battery for server!

[DamonHD]

Having rotten cloudy dark rainy weather here, giving me a practice run for winter, I guess.

With my default very conservative LVD settings I haven't had any off-grid time for the laptop/server for the last couple of days.

So I went and checked that all my panels seemed to be connected properly, etc.  (And managed to blow the fuse in my multimeter by accident so I know that I was getting more than 500mA short-circuit current...  Good job I just happen to have 10x 500mA 20mm fuses hanging around from years ago!)  Yes, all the wiring seemed to be good but the ~80W of panels seem barely able to provide any charge current for the batteries in these conditions.

So, I've bypassed the LVD and I'm measuring power into the DC-DC converter (a Vanson 70W car laptop power adaptor) that steps up from my 12V system/battery voltage to the 20V required by the laptop.  Into that I'm seeing a total power draw of a little over 18W to 19W, once the laptop's internal battery is fully charged, well within my target consumption!

(The laptop's measurement of its power consumption from its internal battery for the same workload is maybe 17W to 18W, so <1W wasted in my external power supply, auto switchover, etc.)

So, I expect to be able to power this kit off 400W+ of panel (plus MPPT) even in winter conditions in London.  Domestic negotiations continue on panel siting, eg displacement of garden plants, and I may have to concede some internal redecoration as part of my bit to save the planet!  B^>

Anyway, ignoring the winter conditions, I'm really pleased to be meeting my power targets.

Rgds

Damon

[AbyssUnderground]

18w is really good! My RE Laptop was down to 1A last night running idle with word open which was great but then its specs are quite low.

[DamonHD]

18W (and thus 1.5A) at 12V note, not at the 20V the laptop wants!

And I'm running a whole bunch of Internet-facing servers, not really 'idle'!

But if you got to 1A@12V you were doing very very well.

I think power consumption has been more-or-less fixed by the fact that laptop batteries have been the limiting factor forever.  So you just get more work done for your average Amp these days if you are careful.

Windows is still better than Linux at power-saving, partly because M$ (allegedly deliberately) made the ACPI power specs vague and obscure.  Surely not!

But Linux has made great strides very recently, not least because Intel has decided to work hard to support Linux, and so in a very recent interview Linus Torvalds ("Mr Linux" himself!) said that he recommends people to get Intel-based gear, at least for the graphics and WiFi, because it is so well supported.

And tools like PowerTOP (http://www.linxpowertop.org/) by Intel staffers really help.

Anyway, I've come in more than 5% under my pie-in-the-sky power budget from 12V, so I'll just have to be simultaneously smug AND be jealous of you!  B^>

Rgds

Damon

[DamonHD]

Sorry, typo: http://www.linuxpowertop.org/

[AbyssUnderground]

Well remember how low the specs on this laptop are, 166MHz, 32MB RAM, No wifi or ether net (requires separate PCMCIA card for both of them). The screen is only 14" as well. I'll do some more tests when I get chance on the current it pulls in various modes (like I did a few weeks ago with my main laptop, sent you an e-mail about them).

[AbyssUnderground]

Hi Damon,

Test results as promised:

Volts in test: 12.9v average

Off: 0.06A (0.77w)

POST: 2.20A (28.38w)

Booting: 2.00A (25.8w)

Idle Desktop: 1.13A (14.57w)

Backlight Full: 1.20A (15.48w)

Backlight Min: 1.02A (13.14w)

Backlight Off: 0.69A (but increases to 0.73A after 30 ish seconds) (8.9-9.4w)

Backlight and Screen Off: 0.73A (9.41w)

Hard Disk Off: 0.68A (8.77w)

Intensive task: 2.00A (25.8w)

[DamonHD]

OK, very interesting!  Thanks.

As I say, I think that laptops have always been engineered with whatever was available up to a certain power consumption and thus battery life.

I'm running my system with the lid down and thus the backlight off (ie as a server).  I can push mine all the way up to about 60W or 70W (I think!) with a really heavy task, ie both CPUs flat out at maximum speed, the disc churning, etc, but I'm trying to avoid getting anywhere near that!  (Backlight max power seems to be about 5W on mine machine, BTW, so again quite similar.)

I think you're very close to me or a bit better (because your machine "idle" is more idle).  But in any case very good.

So I reckon that I need >400W of panel and >400Ah of battery to stay off-grid all year round at the same sort of power as you, ie <20W.  What do you think?

Next time around I shall be aiming for 10W by starting with an ultraportable... B^>

Rgds

Damon

[AbyssUnderground]

The lower the better as always :-)

I bet with linux I could push my usage down a lot too but with so little cpu, ram and hard disk its hardly worth it. Its just a bit of fun for me :-)

[DamonHD]

I'd say you'd have to work hard to do much better (or even as well) under Linux right now.  There's still a significant number of power-saving improvements in the pipeline, but I don't see them (such as "cpuidle", "round_jiffies()" and "deferred timers") getting in (or at least used in) the next kernel revision (2.6.23) or even in the next release of (say) the Ubuntu flavour of Linux ("Gutsy Gibbon").  So I'm just going to sit tight and be patient and wait another 6 months...

If it ain't broke, don't fix it!

Rgds

Damon