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Mac mini Sans Wires - Batteries Inside the Case
An anonymous reader writes "Running Debian (or Linux generally) on a Mac mini is old news. Silas installed rechargable batteries inside the case, delivering a couple of hours of runtime while retaining the small form factor. Although it runs fine without wires, he had to plug in the monitor to be able to show that it was really up."
VNC is the obvious way to talk to the machine without a monitor connected...
If an external battery could be housed in a mac mini form factor external case (stacked under/ontop of the mini) I bet battery life could be equivelent or longer than a power-book (no LCD to run). Could provide some interesting low-cost remote monitoring solutions...
A Call For A New Slashdot Moderation Level!
Exactly how is the LiPo battery charged ?
0 9187
Without a proper charger, combining the energy density of a 80Wh battery with highly reactive Lithium is a recipe for disaster.
http://www.rcgroups.com/forums/showthread.php?t=2
Flourescent (adj): smelling like ground wheat.
Wow, at only 12W for the entire system? It is pretty hard to get a x86 box that low for that
cheap.
-Benjamin Meyer
Do you changes clothes while making the "chee-chee-cha-cha-choh" transformation sound?
Mac Mini Surgery
I had an itch to scratch so here it is...
Earlier this week I read an article on the Debian Weekly News, about a Debian box running on 3 Watts, and it reminded me of a project that I was asked to put on the shelf some time ago. The gist of the article linked to by the DWN was that Alex Perry got to wondering how much power his Linksys switch was sucking down whilst running 24/7, and found that his Manga, an ARM based router box, not only consumed less power but was able to run full blown Debian to boot. His point was "If I am going to pay to have a switch run 24/7, I might as well have the switch be a useful server as well." Following his article the PepLink community promptly got X11 working on the Manga and Alex's website was updated with the screen shots, which I might add are quite amusing.
While I do sympathize with the original thrust of the article, I must say that the Manga's ARM is a rather diminutive processor for a desktop machine these days. So my question is why would you run a Manga as a desktop to get down to the 3 Watt mark when for just a few more Watts you can run a box with a G4 processor? Yes, I am talking about that little machine that all of my geek friends (me included) seem to be drooling over as of late. The Mac Mini!
Several months ago I was in need of finding a small but powerful computer that could be run for a long period of time on batteries and not be a burden to carry. I was looking at several embedded options from places like kontron and mini-box, when I saw an article on the Mac Mini. Looking at the limited specs for the Mac Mini on Apple's website I began to suspect that if I removed the cdrom drive I would be able to fit a "lithium-ion polymer" battery pack inside the vacated space. I say that I suspected this because Apple is lousy about posting specs about internals and stuff that your Grandparents wouldn't normally ask about. So I ran down to the local Apple store with my trusty calipers and had one of their technicians go into the back and measure the dimensions of the cdrom drive for me. The numbers that he gave me made my day, the batteries would fit! Now about power specs. Apple of course did not have the DC power specs online, and nobody I talked to at the Apple store or on the support line could get them for me. In an act of desperation I resorted to sending email to combinations of addresses like steve_at_apple.com sjobs_at_apple.com, steve.jobs_at_apple.com, etc asking for the specs. Funny enough I got a reply (No, not from Steve Jobs) from an Engineer who was quite helpful. It looked like the Mac could do it, so I decided to get one and hack on it. The Mac was dirt cheap compared to the embedded systems so it was a very limited risk approach to proceeding on the project.
I ordered the Mac, a 4GB Hitachi Microdrive, and a laptop-IDE to CF adapter. I also talked to Mike (Dr. Zhang) at SKC PowerTech, Inc, and he was kind enough to send me some batteries for evaluation. The batteries were a new design and were not yet in production, so there was a bit of a lead time on those, but at the end of two days I had the rest of the necessities at hand. First things first, I measured the out of the box power draw of the Mac Mini, which turned out to be only 12 Watts! This was better than the specs I was given. I then proceeded to remove the hard disk and replace it with the Microdrive-CF adapter setup. Then I got me a Debian (Sarge) disk *GRIN*. This was the first time I had touched a Mac, and I was pleased to find that the Debian install on the Mac was smooth and painless. After getting the system up and running, I did some stress testing on it. The testing involved running simultaneous FFT routines (like 30 of them) on 80MB data files. The system was so heavily loaded that it took about 15 minutes to log into the machine from another terminal, and another 15 minutes to get to the bash prompt. During this utter thrashing of the system the highest the power usage spiked to was 20 Watts, but it stayed around 14
you forgot to add "that's slower than an external firewire enclosure"
Try with Mac OS X 10.3 or later. If there are no display devices on-line the window server will create a virtual framebuffer.
In Tiger, Mac OS X 10.4, fast user switching gets a related feature. When a user session is switched off-screen, if a screen watching program such as OSXvnc-server is running, the off-screen session will get a virtual framebuffer so that it can be remote-operated while another user session or a login window is on the hardware console.
Try running OSXvnc.app, for example, and switching users. A remote VNC viewer will be able to connect to the session switched off-screen, so you can continue working from a remote location. When you set this up, make sure you set up a password for access and take the usual security precautions for a remote-controlled system.
Several things:
The author likely measured average consumption sans peaks. In other words, the multimeter he used does not respond to short huge current demands. Depending on the meter, in fact, and the switching regulator inside the mini he may have a very bad reading. This kind of measurement is difficult to take accurately without equipment meant to measure this - one which integrates the current consumption over time, including peaks, for instance.
The cells are rated for 4AH, but there's no guarantee that he charged them to capacity, or that their usable capacity is 4AH.
There are four cells at 3.7V making a 14.8V battery, multiply times 4AH to find that the pack's maximum charge is actually some 59WH.
His initial measurements were made with a power supply of 18V, and he is supply under 15V. It is likely that the mini's switching regulator is less efficient at the lower voltage.
To obtain the maximum energy from a battery you typically must limit consumption. In other words, you can get more energy out of a battery when drawing 100mA than you'll get when drawing 500mA. He is drawing over 1A from these cells (perhaps as much as 2A, with peaks of many Amps), and the efficiency of the battery is lower at this discharge rate. You can see this effect by taking a laptop with two batteries - use them one at a time and they'll last for 2x minutes, where x is the amount of time you would get from one. Use them simultaneously and you should get more than 2x (should, because some manufacturers still consume from only one available battery even when two are available).
There are many other factors affecting this, such as keyboard power consumption (100mA, or 1/2 watt), heat, and other efficiency variations.
-Adam
the older titaniums are definitely louder than the new aluminums. i had a 667 titanium and that thing's fan was on all the time. my 1 Ghz titanium's fan was still pretty active. i have a new 1.67 Al and it's pretty quiet. i have to be doing quite a bit to get the fan running and i've never heard it as loud as my titaniums. the cooler chips seem to be doing the trick.
He includes (basic) instructions on how to make such a system work.