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Powering Mac Mini off PSC Powermax Ultra?


Glacierjay

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Jay,

PSC is just down the street from me, and I know Ron lurks here from time to time, but here's what I know from very lengthy talks with him about powering from his gear...

Each output on the Powermax Ultra has its own polyfuse, which will trip if overloaded.  They can handle about 4 amps at 12v DC, if I am not mistaken.  Not sure what the power requirement of the MacMini is, but I would guess it is more than that.  You can have the outputs modified to handle a bigger draw, or you can simply plug an inverter into an open connector on your block battery.  If the inverter is drawing less than the continuous charge of the Powermax Ultra, then your system is staying ahead of your AC power requirements.

I would suggest calling Ron at PSC.  He is a genius, and I'm sure he'd be glad to talk to you about what you are trying to do.

Robert Sharman

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The Mini power supply is spec'ed like this:

Input:  100-240 VAC

Output: 18.5 VDC @ 85 watts

The "spec" mathematics say that it's a 4+ amp draw, but in my experience, the Mini draws significantly less, 1.5A or less.  I once borrowed an amp-meter from the electric dept. while the significant components of my cart (mixer, audio interface, computer, computer monitor) were all running on the 12V battery, and the draw coming off the hot lead of the battery was somewhere between 1.5A and 2A.  The mini was running off the Carnetix P1900.

I've found other sources (see link below) that have indicated that the real world draw of the Mini doesn't get over about 40W, which corresponds to about a 2A draw @ 18VDC.

In other words, I don't think the Mini will exceed the Powermax's 4A limit.

So why not dial up one of your Powermax Ultra outputs to 18.5 VDC, slice up a Mini power cord, and feed the Mini directly from the Powermax?

FYI, you'll have to sort out the mysterious grey iSense cable in the cable that feeds the Mini.  The Carnetix manual says this:

"The Mac must sense the presence of the appropriate power supply through the iSense wire on the

P1900 output. Connect the WHITE iSense wire from the P1900 to the small GREY wire on the Mac

mini DC power cable. "

And another site has some very good info, as well as a solution for wiring up the iSense:

http://www.blisstonia.com/eolson/notes/kensingtonmacmini.php

Currently, my whole cart is in a state of power transition for the moment, as I've added a gaggle of AC-only components, inverter, etc., the whole nine yards.  On the last feature, I ran the Mini via inverter, but I'm leaning toward re-implementing the Carnetix supply for 12V use, because I think a DC conversion will ultimately be more efficient than 12V to inverter, followed by AC-DC conversion thru the power supply to the Mini.

Let us know what you decide.

Brian

PS - I went thru this a couple years ago:

http://soundfacility.com/location-sound/mini-power-the-dc-hurdle/37

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Anybody ever figure out if there's a way to power a MacBook directly from DC (without an inverter)? As far as I know, nobody yet has a "MagSafe" adapter that will plug into DC, even with a voltage Juicer.

--Marc

Hi, Marc

Some options here: http://www.mikegyver.com/index.html

Expensive, but available.

Best regards,

Jim

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  • 2 weeks later...

I'm a little late with my answer about the Powermax/Mini powering situation, but the Carnetix works pretty well and seems to be pretty efficient. The box also provides a 5 volt output that could prove handy for powering a small drive enclosure, an option I'm about to explore. There is also an cable to connect the Carnetix directly to a Mini, about $30, that could be adapted to pretty much anything that puts out 18 volts. I think it saved me about an hour or so with a voltmeter and a soldering iron.

I'm running the Mini via the 12 V. output of an older Powermax and it seems to work just fine.

The big drawback is that the Carnetix unit comes with no paper documentation, so you do have to download and then print the applicable pages. The documentation is organized around the most popular car PC's so you'll have to look for the pages that are applicable to the Mini.

Best regards,

Jim

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I don't know if the powermax has some failsafe mechanisms... but it's worth noting that the Carnetix (P1900 anyway) has a chip controller that will  auto-shutdown below 10.6V.

From the P1900 manual (p 9)

"The SSC also contains a battery monitor which will shut the P1900 down in the event the battery

voltage drops below approximately 10.6 volts. This will help prevent deep discharge and damage to

your battery. "

Just an FYI to keep you on top of your voltage drain.

Brian

PS - I used the additional 12V and 5V outputs to power an external HD enclosure with good success for a few years.  Last job I did, I used Lacie drives powered by the FW bus, which alleviated the powering responsibility from the cart.  I liked that.

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"The SSC also contains a battery monitor which will shut the P1900 down in the event the battery

voltage drops below approximately 10.6 volts. This will help prevent deep discharge and damage to

your battery. "

Hi, Brian,

Exactly why I'm using the P1900. It's regulated to below the cutoff voltage for most everything else I'm powering off the Powermax. I have the older Powermax, that only provides 6, 12 and 18 volts with essentially no regulation. You've got a lot more experience with this than I do and I'd be interested to hear about any tips you have, particularly regarding power.

I'm mostly on commercials for this rig, so there is AC almost everywhere, but the P1900/Mini seems to add less than I expected to the cart's total power requirement.

Best regards,

Jim

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