Mac mini draining battery

Ive been working on installing a mac mini in my car (2000 Volvo S70) for a few months now (Build details here), and now that Ive finally got it finished, Im having problems with it draining my battery.

I hoped that the mac's power consumption during sleep mode would be small enough that this would not be a problem, or that the power supply's (carnetix cnx-p1900) low voltage protection would keep it from draining the battery - but no such luck.

I'm sure that other people on this forum have had this issue and I was just wondering what you recommend.

Ive seen some mention of a second battery - but that seems a little excessive, and I wouldnt even know where to start
The other solution that comes to mind is the newer carnetix supply, the 2140, with the adjustable low battery threshold.

What would you guys suggest?

Thanks

I may sound like an idiot because I'm not too familiar with mac setups, but is there anyway you could hibernate it instead of putting it in sleep? That would eliminate your problem with draining the battery. Doesn't the low voltage protection just kill the power to the computer anyway? Making you do a cold boot... Correct me if I'm wrong

I actually looked into hibernating it. You can enable a feature called "safe sleep" where it will save the state of the machine and shut off.

But I dont know if this would actually be any faster than just shutting the computer down and restarting it, since thats basically what you're doing.

Well with sleep, the computer is staying on and draining your battery, with hibernate the computer shuts off completely, meaning no power consumption. At least thats how it is with windows...

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Originally Posted by TheNeuralBit

I actually looked into hibernating it. You can enable a feature called "safe sleep" where it will save the state of the machine and shut off.

But I dont know if this would actually be any faster than just shutting the computer down and restarting it, since thats basically what you're doing.

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"Safe Sleep" comes up faster than a cold boot. It doesn't work very well with Parallels or VMWare Fusion though. That may have changed with newer version of the software.

Draining the battery in what period of time?

One often overlooked source of battery drain is USB devices. The Mini will supply USB devices with power when sleeping. This increases the drain significantly.

The only real way around this is to use a powered USB hub and make sure that it either does not pull power from the Mini when it is sleeping or alter the cable to cut the power wires from the Mini to the hub. (You can also put tape over them on the connector if you are careful about it)

Do you have something like a USB device that could be a cause of power drain? My experience with a sleeping Mini is that I could easily sleep it over a weekend without draining my car battery.

Adding another battery is simple enough. Use a battery isolator to charge it. Search for 'tank circuit' for more info.

It would take about three days for it to drain my battery.

The only USB device I have connected is the touchscreen monitor, which gets its power from the P1900's 12V output, so I dont think its drawing anything through the mac mini.


I measured the sleeping current of the entire system to be 150mA, does that seem reasonable?

How old is your car battery? A drain in 2 days off of 150 mA sounds a little quick, but if your battery is older then it's possible.

The battery is only about a year old I think.
It actually took a few cycles of driving it for about 20 minutes then parking it for a few days before it finally died. Maybe I just wasnt driving enough?