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Portable AC Power for Engine Block Heater

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docphiliowa's picture
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As the name implies, I live in Iowa. The temp outside this morning is -13F. I am getting an engine block heater installed this week. Of course when I am close to an AC plug, that will be great.

But - I will be having business trips to even colder climates in the next couple months. I may not always have access to AC power.

Has anyone tried using one of the portable AC power packs to supply power to an engine block heater? I don't have the heater with me - so I do not know the specs i.e. how much current it draws.

Would that work?

http://www.amazon.com/400-Watt-Power-Dome-EX/dp/B000WJEPCI/ref=sr_1_54?ie=UTF8&s=automotive&qid=1200754202&sr=1-54

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Re: Portable AC Power for Engine Block Heater

The answer is................maybe. The block heater is a resistive load. That's good. Not knowing what the wattage is presents a problem.

Theoretically, an inverter that has twice the capacity of the device being powered should work with a resistive load. The inverter will continue to power the load to a point where the battery voltagae is deemed marginal to start the engine. This is designed into the inverter and I would not expect all inverters at all price points to have the same specs.

What I just said is: the inverter may very well warm the engine, but don't count on the battery having enough energy left to start the car. There is no such thing as free energy or perpetual motion.

The idea is not far fetched, but bears investigating by experimentation. Even if the experiences of others are considered, remember, all inverters are not created equal.

This is to give you an idea of the possibilities. During power outages where I live, I usually connect a 700 watt inverter to my 300SDL battery and run a fan, table lamp and small TV. I make coffee at the expense of the TV and reconnect the TV when the coffee is done. This has worked very well for several years now.

My car has never failed to start after the inverter shut off due to low battery capacity.

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John Fair 1's picture
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Re: Portable AC Power for Engine Block Heater

You need to find out how many amps or watts the block heater pulls, lets say for example it pulls 5 amps @ 110 volts.

Watts = Amps * Volts
Watts = 5 amps * 110 Volts
Watts = 550 Watts

That little inverter looks too small.

Lets work backwards given a 400 watt inverter.

Amps = 400 Watts / 110 volts
Amps = 3.6 amps

So if you have the 400 watt inverter you can power 3.6 amps @ 110 volts.

Next question is for how long? Once again I am guessing but lets say a 12 volt battery has 400 watts of power for 1 hour.

Amp/hour = (400 Watts / 12 Volts) / hour
Amp/hour = 33.3 amp/hour

I don't now how many amps it takes to start the car but lets say the inverter leaves 10 amp/hours in the battery. That leave 23.3 amps/hour.

Hours = 23.3 amps/hour / 3.6 amps
Hours = 6.5 hours.

So if your block heater pulls 400 watts you should be able to heat the car for 6.5 hours.

Keep in mind I am not a EE just a simple mainframe Systems Programmer. But hopefully you can see that with a little math you can answer your question.

My daily driver is a Ford Taurus and it has a block heater but I haven't a clue how much power it pulls. That said keep in mind that heating with electricity is very expensive so my guess is at least 5 amps if not more.

I live north of you and would be real interested in how much power the block heater pulls. Personally I wouldn't do it because I really want a fully charged battery to start the car when it is below 0.

Regards

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Re: Portable AC Power for Engine Block Heater

Doc,

You will only need to 'plug in' the block heater for an hour and your engine will be plenty warm. You could be really creative and have a second battery added to your car, and some switching circuitry to disconnect 2nd battery from main in order to run the block heater so that you preserve your cranking power. Once you've got the car started, re-connect the 2nd battery to recharge it and keep it charged until needed again.

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Re: Portable AC Power for Engine Block Heater

Doc,

There are a lot of folks out here, me included, who will want to know how this turns out.

Your problem and potential solution are a mix of technologies not often used in automobiles.

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Re: Portable AC Power for Engine Block Heater

What I have done in the past is using heavy duty, outdoor, extension cord(s) between my motel room and my car for about an hour before starting it. Sometimes I start the car every four hours and let it run long enough where it blows warm air. Sometimes I have removed the battery and brought it indoors to keep it warm, sometimes using a plug-in charger to bring it to full power if necessary. A warm battery can produce more power faster. Be sure you disconnect the black terminal first and reconnect it last.

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Re: Portable AC Power for Engine Block Heater

dual setup
triple

It's VERY do able.
oh, and of course, wiring the AC inverter to the battery(s)
750watt inverter

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Re: Portable AC Power for Engine Block Heater

The inverter idea is ingenious but I have my doubts that it will work because it's borrowing from Peter to pay Paul.

Trying to start an engine having a warmed up engine block with a weakened battery in cold weather seems risky. Less risk to start a cold engine with a strong battery, using several shots at the glow plugs, as Don suggests.

If a nearby AC power outlet is not available, why not use a small portable gasoline engine inverter to power the block heater for an hour so as not bother the battery?

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Re: Portable AC Power for Engine Block Heater

Maybe one of ya'll Nothenurs could go to a local trade school and have them try the idea.

A shool district bus system would also be a good place.

Maybe even anyplace that has a fleet of diesels in a cold climate.

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Re: Portable AC Power for Engine Block Heater

I have connected the battery directly to the heater with a fused line.
It makes less heat but saves the battery and helps keep the engine warm after you shut it off.

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Re: Portable AC Power for Engine Block Heater

Adamson;131436 wrote:
I have connected the battery directly to the heater with a fused line.
It makes less heat but saves the battery and helps keep the engine warm after you shut it off.

How is the battery saved when the block heater is drawing power from it?

Since the fuse in the line merely limits the current being drawn from the battery, how does the fused line prevent the battery from getting discharged?

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Re: Portable AC Power for Engine Block Heater

The saving is done by eliminating the DC to AC converter.
The battery can be discharged if you let it connected to the heater for extended periods of time. I used it for daily commuting. The fuse is also a safety factor.

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Re: Portable AC Power for Engine Block Heater

I used to plug in my block heater on my 300TD when it got down as low as -15 with great results. I had a Honda gas generator (600w) that was very small and weighed maybe 20 lbs. I locked the generator to the tow loop on the front of the car, started the generator, and plugged in the block heater. I was always able to warm the engine enough to start in 30-45 minutes. I always kept the generator in the back of the car in the winter where it took up very little space.

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Re: Portable AC Power for Engine Block Heater

glisch;133252 wrote:
I used to plug in my block heater on my 300TD when it got down as low as -15 with great results. I had a Honda gas generator (600w) that was very small and weighed maybe 20 lbs. I locked the generator to the tow loop on the front of the car, started the generator, and plugged in the block heater. I was always able to warm the engine enough to start in 30-45 minutes. I always kept the generator in the back of the car in the winter where it took up very little space.

This is a good idea. After reading this, I bought a Chinese-made generator at ACO Hardware for $83. It's 15"x13"x12" and weighs 38 lbs. It's 8 lbs. heavier but $760 cheaper than the smallest Honda I could find. I have a friend who uses a Honda for astrophotography. He needs the cleaner power to run computers. It's very quiet.

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Re: Portable AC Power for Engine Block Heater

glisch;133252 wrote:
I used to plug in my block heater on my 300TD when it got down as low as -15 with great results. I had a Honda gas generator ...

You'd consume less petroleum just leaving the car's motor running.

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Re: Portable AC Power for Engine Block Heater

lkchris;133444 wrote:
You'd consume less petroleum just leaving the car's motor running.

Maybe not. For me, I would use less fuel running my 63cc generator for 1/2 hour than by idling my 2,200cc car engine over the weekend.

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Re: Portable AC Power for Engine Block Heater

Your generator burns fuel at the rate of 1 part fuel to 15 parts air. At all rpms.

Your diesel burns fuel at idle at a rate of around 1 part fuel to 150 parts air.

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Re: Portable AC Power for Engine Block Heater

A couple of thoughts that are different.

You need heat to warm the engine. It does not need to come from electricity. Back when I was a boy, we did not have electricity. I can recall my father warming the oilpan on his truck with a can of fuel oil. He lit it on fire and slid it in under the oilpan for a bit. I'm not sure I would recommend that exactly with your MB but there may be something similar and less dangerous available. Some type of flameless heater like a catalytic tent heater might work.

I would also suspect that if you are going to colder areas, there should be outside plugs that are expressly for plugging your car in. I'm in Winnipeg and there are outside plugs all over the place to plug in cars.

Don't know how well it would work with an old diesel but an auto start system might be possible as well. I have a friend who has it installed on a Tahoe. They go to their cottage in winter and leave the truck on the other side of the lake. There is no electric power there and they leave it for days in very cold weather. It is set up so that when the temperature drops to a certain point the engine will start and run for long enough to warm up and then stop. It will do this regularly for days if necessary.

Randy

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Re: Portable AC Power for Engine Block Heater

Block heater power draw: Using my "Kill A Watt (tm)" and a 20' extension cord, I checked the block heater on my '72 220D and came up with the following numbers: 120.7 v., 59.9 hz, 3.48 amps, and 420 watts.

Kent, how much money are you willing to bet that running my generator for 1/2 hour will use less fuel than idling my car over a weekend? Are we willing to bet titles? If it's worth my while, I would be willing to drive from MI to NM and idle my car in front of your house so we can check fuel usage. Maybe we can do it during the next hot air balloon festival and make it into a party.

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Re: Portable AC Power for Engine Block Heater

Leaving an MB diesel engine to idle for such extended periods should be reserved for a 'worst case' scenario. Unlike the big rig trucks, our indirect injection engines will carbon up, which drastically increases engine wear.

Webasto makes engine heaters that are fueled by either gasoline or diesel fuel, I believe. They are more common in Europe, where electricity is much more expensive than in the U.S. Check out their website for more info...

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Re: Portable AC Power for Engine Block Heater

http://www.webastoshowroom.com/blueheat/blueheat_products_ttc_specs.htm

Fuel usage at 'full' is 0.16 gal/hour, and 'reduced' is 0.08 gal/hour.

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Max Dillon
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'87 300TD, 334k miles (head is off, getting ready to install a different used head...)
'95 E300 Diesel, 348k miles (daily driving duty)
'73 Balboa 20

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Re: Portable AC Power for Engine Block Heater

lkchris;133444 wrote:
You'd consume less petroleum just leaving the car's motor running.

I agree with M. Dillon. I worry more about engine wear than fuel consumption when someone suggests leaving a car idling overnight or longer (in case it's too cold when you want to start the car later). This further supports my argument that it's better to run an $83 generator for 1/2 hour than to keep an expensive MB engine running continously. Nevertheless, I would be willing to risk my $1,000 car to upgrade to a newer model, especially if it's a bet that has a high probability of success.

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