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I'm been playing with the Raspberry Pi, which only consumes 4 or 5 watts of power, compiling cgminer on it, etc and combined with this little wireless adapter:

http://www.amazon.com/gp/product/B005CLMJLU/ref=oh_details_o00_s00_i02 (http://www.amazon.com/gp/product/B005CLMJLU/ref=oh_details_o00_s00_i02)

I got to thinking - with the following you could run a totally mobile mining operation out of your truck or car:

1.  Android Phone running a wireless hotspot
2.  Your favorite USB mining device, 12 Volt input connected to a cigarette adapter.
3.  Raspberry Pi running Debian and cgminer
4.  Cigarette adapter - to USB to power the Pi.

You could be driving to Grandma's house over Christmas while mining the entire trip. Or a trucker who lives in his rig could mine.

Bear in mind that a vehicle's "12 volt" electrical system actually can vary from 10 to 15 or so volts.  Powering your thousand-dollar miner by plugging directly into it may not be the wisest choice.

This. Those 12V DC card charges can have some of the worst voltage control, esp if they're really cheap. Example:

http://tabletac.com/images/upload/Image/531370879_o.jpg

Side note: Are you JUST talking about CPU mining on the Rpi? You'd get almost nothing for coins!

No, I'm not talking about CPU mining.

Can a car battery provide 120W constantly? Won't that burn out your alternator?

You don't need rPi. cgminer can run on the phone, and miner can be connected via USB.

Btw. is there a compiled armel binary of cgminer? I found just the source and instructions on how to crosscompile some time ago...

Quite easily.  Your typical alternator can push out 50 amps @ 14v, so 700w.  Certainly, some of that is used for other electrical items (lights being a big user), but a large part of that amperage goes unused.  It needs the extra overhead to be able to recharge batteries drained while the car is off, so using that overhead for other purposes is entirely possible.

Any reliable information on how much a kWh costs in a running car?

I read a little while back that idling a modern car typically uses 0.2 gallons/hour.  So, if you consider that the minimum, then you're looking at at least $0.70/kwh.  It is possible to achieve full draw on an alternator at idle, so I think it is reasonable to assume you could get 700w out of the car at idle.  There would be a nearly negligible increase of load on the engine.  $0.70 / 700w = at least $1.00/kwh.

If you upgraded your alternator to allow for more load, then you might need to also increase the default idle speed to ensure the engine does not stall, which would mean more fuel usage.

EDIT:  Now if you're talking about running it on a car that is moving, I'd say the electricity is virtually free.

I'd say no way it is free. You put a load on the generator, it adds mechanical load to the system, leading to higher consumption of fuel. In case of a hybrid, you could say it's cheap because some of it comes from regenerative braking, but this would require some tweaking of the control systems to ensure optimal capture of energy for this additional load.

I don't think people realize how much a running alternator or other mechanical loads can affect your gas mileage. This is especially true on a smaller car like a sedan. It's still present on a larger car like a truck or something, but will still be present.

I know on my little 2.0L 4 banger, the drop in gas mileage would be more expensive then just paying for the electricity.

Really. The energy has to come from somewhere, and a small ICE along with a cheap alternator are absolutely crappy at turning fuel into electricity. This graphic is actually pretty good since it's 40% conversion of chemical energy to mechanical energy is for a big diesel; for a small gas ICE it is actually very decent.
http://i49.tinypic.com/netj4y.png


Now, you could get almost free power if you tied your mining rig into your ECU. While accelerating you wouldn't actively hash but would just keep valid work queued up. As soon as you tap the brake, start hashing. The increased draw on the alternator would act as a form of really expensive engine braking and would save wear on your brake pads.

Once a rally starts on the market, massive pileups follow on highways... All miners hitting brakes suddenly :D
Seriously, we are onto something here... A hashing unit can be used whenever there is lots power to be dissipated quickly, from vehicular brakes to cut-back protection in high voltage power supplies...

Guys, I never proposed this to save money - I was thinking about the flexibility and the "cool-factor".

Not sure if you earn points with the "cool-factor" by mobile mining.  Interesting yes, cool no.  Now cool factor would be mobile mining that results in greater number of coins produce then can be done standing still.  Everyone here would be all over you and saying cool even though it is not realistic, or is it Mr. flux capacitor.

This idea crossed my mind but in the sense that I could drive and pickup my ASIC rather than it being shipped to me. I could mine on the way home and gain an extra day or so. But then I decided I didnt feel like driving that far.

Step 1. Get on next trip to ISS (international space station)
Step 2. Hook up miners to take advantage of free solar power!
Step 3. Mine while taking advantage of time-dilation.
Step 4. Profit (no question marks needed).

8)

doesn't it cost $10k to lift a pound into space? you're down $10k for the BFL alone

I guarantee you that the power company does a much more efficient job of converting fuel into electricity than your car does. Even a little emergency generator will do better than a car. Power doesn't come for free, and about 85 percent of a vehicle's fuel energy potential is lost from inefficiencies.

In addition, be aware that very high voltage (100+V) transients can occur in car electrical systems from motors turning on and off and such, and if you hook devices up to a car's 12V electrical system that aren't designed for the kind of voltage spikes they will see, expect the magic smoke to come out.

http://www.advantech.com.tw/eservice-applied-computing/newsletters/white%20paper/Power_Challenges_Faced_by_Vehicle_Applications.pdf

So if the "why?" is because you think your car makes free electricity, myth: busted. If the "why?" is because you have no home where you can plug in your miner, you should be rethinking your situation. Otherwise this is as practical as a car-based ice skating rink.

Once when my grid power was out for an extended period, I hooked a 1500W sine wave inverter to my car, and ran my fridge, a couple computers, and some other things on it for maybe 7 hours.  It burned through quite a bit of fuel.  Maybe 5 gallons.  That was on a BMW 6 cylinder EFI engine...

Nowhere near as cost effective as grid power.

Well he just asked for cool factor. Doesn't get much cooler than space-travel and time-dilation for increasing number of coins produced imho. Admittedly time to recoup your costs will be high.

The time dialation would actually reduce mining performance https://en.wikipedia.org/wiki/Time_dilation#Time_dilation_and_space_flight (https://en.wikipedia.org/wiki/Time_dilation#Time_dilation_and_space_flight)

Incorrect. You are thinking of a body in relative acceleration to the point of reference. AFAIK the ISS is in stationary orbit WRT the earth. I am referring to Gravitational Time Dilation, http://en.wikipedia.org/wiki/Gravitational_time_dilation .

Cool, TIL.  :)

Nice, but time dilation would work against you.

Sorry but that's just human greed in pure, raw form.

I never claimed it wasnt. In fact i can openly admit that the sole reason I started mining was to turn a profit. yes the idea is cool, but Im not going to drop $5k plus the time/effort setting up and maintaining a GPU/FPGA/ASIC farm just because its "cool". Maybe you have money to burn like that and if so great! Send some my way!

Dude, see like literally 1 post above yours...

That's just 10A. Many modern cars need that for ignition alone, and performance cars may require double that for fuel pump. Racing cars might require 40A just for the fuel pumps!
Even 80's corollas have 55A alternators. Getting a alternator rewired for higher amperage is not even very costly, just make sure the alternator controller is able to work with the increased amperage.
Friend had 110 or 120A alternator on his M3 for the audio setup.
And that's just those cars which aren't especially power hungry ... Let's enter the SPL competition scene: These guys might be consuming 20kW ...

Hell, just last week i sold one amp with 4x30A fuses and rated RMS power of 5000W to 1Ohm (very short peak).

Extending on that, you don't want to run your car at idle for power generation - you want to run it at the peak torque RPM most probably, very often something like 1800RPM-2200RPM. Larger the engine, lower this is.
Also, the typical car here consumes more like 1.5L/hr, so more like 0.35gallons/hour, and at 1800RPM you are probably looking at 0.5-0.6gallons/hour.
Car engines are not designed for low load constant speed - you need to increase the load ie. alternator capacity and utilization dramatically to get the best out of the engine, even at 1800RPM low load you are running perhaps 2% efficiency, while a traditional, older car engine could reach 20%.

for thought experiment, let's think about a modified engine JUST for this purpose.
Turbocharged engine, with mild cams for lower RPM peak output (Where you want to run, or close to it), running lean -> slightly below stoichiometric value (Complete burn, slightly more air into engine than required for complete burn). This kind of engine could reach upto 30% efficiency.
Now we can calculate from energy content and alternator efficiency.

http://en.wikipedia.org/wiki/Gasoline#Energy_content_.28high_and_low_heating_value.29
13kWh/kg or 9.7kWh / liter.
Let's assume we tune this engine for 30kW load, this means we need to burn 100kW worth of electricity, dismissing alternator disefficiencies. After alternator efficiency we get perhaps 27kW of electricity.
That means just more than 10liters per hour.
Please note: I chose 30kW load as load is required for something of that displacement to get to good efficiency rates, even 30kW might be far too low, but let's give it a chance for being tuned for this usage.
At the gas rates like here 95E10 going for about 1.5€ per liter = 15€ per hour and we get under 0.5€/kWh efficiency.
The remaining 70kW could be used to heat your house, or alternative methods used to collect electricity from it. But even at 100% efficiency in all parts it would still cost 0.15€ kWh which is more than double what i'm paying locally right now.

When you are moving it's not free either, but small load disappears in to the existing inefficiencies, 20RPM lower idle RPM don't matter. Even if you are going highway, and trying to get best MPG possible, it will show up there, but it's marginal.


Teal: Big Diesel has higher efficiency than tiny 4 banger. Diesel as a fuel has higher efficiency from chemical to kinetic energy.
Reason tiny 4 bangers gets so high MPG is because they are lightweight and small surface area, not exceptional engine efficiency.
For a gasoline engine 25% is pretty much the norm efficiency rating, depending upon how modern it is.
Many of the tiny 4 bangers getting huge/good MPG (80s-90s Renault Clio, 80s Peugeot 205, Subaru Justy, 80s Nissan Cherry) actually has kind of low efficiency engines in them. They are simply lightweight cars. Subary Justy actually has 3 cylinder engine in it, 1.2l carburated, very peaky output, very low torque at low rpm, even normal driving requires some 3k rpm yet even 4WD on during winter you can achieve better MPG than many big cars. Summer and no 4WD it can achieve 50MPG.

I realize that. That why I said that such an efficiency for a small gas ICE would be very decent.

Can you elaborate on this?  What is different about a "traditional" car engine to cause the large difference in efficiency that you describe, when used to generate electricity?