# Converting 12V DC Current (From a vehicle) to 120V A/C



## Rick (May 10, 2002)

I have a couple of questions....

Background: I have a block heater on my Diesel Pick-up that measured 590 Watt power usage on a Kill A Watt. It didn't seem to surge at all, but let's figure a 1000 watt inverter is needed.

My first question is, would I loose many watts by using a 2500 watt inverter for such a lower need?

My second question is, could I expect the charging system in a 1.5 Honda Civic engine to generate the power that a 600W, 1000W or 2500W inverter would need? 

Thanks,

Rick


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## wy_white_wolf (Oct 14, 2004)

Rick said:


> I have a couple of questions....
> 
> Background: I have a block heater on my Diesel Pick-up that measured 590 Watt power usage on a Kill A Watt. It didn't seem to surge at all, but let's figure a 1000 watt inverter is needed.
> 
> My first question is, would I loose many watts by using a 2500 watt inverter for such a lower need?


It really matters on the manufacture of the inverters but most I've looked at wouldn't be but 10 to 20 watts apart



Rick said:


> My second question is, could I expect the charging system in a 1.5 Honda Civic engine to generate the power that a 600W, 1000W or 2500W inverter would need?


I would say no to all of them. 600w would be (600/12) 50 amps at 12volt. I don't think that little alt. is that big and it would also have to supply amps for the vehicle to run. I think propably about a 75 amp alt would be min to draw the 600w from.

Thinking outside the box - 

How about rigging up some quick disconnect heater hoses to use engine coolant from the civic to warm up the truck? We had setup like that to warm-up a D-8 cat from our pickup. It would only take about 15 min to move the temp gauge on the cat when it was -20 F out.


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## Rick (May 10, 2002)

wy_white_wolf said:


> ......................
> 
> Thinking outside the box - How about rigging up some quick disconnect heater hoses to use engine coolant from the civic to warm up the truck? We had setup like that to warm-up a D-8 cat from our pickup. It would only take about 15 min to move the temp gauge on the cat when it was -20 F out.


I like that kind of thinking. I would need to freshen up the antifreeze in the poor, old car.


Thanks,

Rick


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## JAK (Oct 15, 2005)

As far as I know a block heater is a simple resistance device, so you could feed it a lower voltage, even 12v DC. You will get less heat, but you will also draw a lot less amps off you battery.

590 watts / 115 volts = 5.13 amps
115 volts / 5.13 amps = 22.4 ohms

Running on one 12volt battery for 8 hours:
12.0 volts / 22.4 ohms ~ 0.5 amps
8 hours x 0.5 amps = 4.0 amp-hours
12.0 volts x 0.5 amps = 6.0 watts
6.0 watts x 3.413 = 20.5 BTU/hour

Running on two 12volt battery in series for 8 hours:
24.0 volts / 22.4 ohms ~ 1.0 amps
8 hours x 1.0 amps = 8.0 amp-hours from each battery
24.0 volts x 1.0 amps = 24.0 watts
24.0 watts x 3.413 = 82 BTU/hour

It might only warm up the oil a few degrees, but it at least it won't run the batteries down. The batteries also run alot more efficiently at a low current draw and you eliminate the cost and inefficiency of the inverter. I would guess steady state would be reached in one hour so it might be better to put it on a timer. Of course there are other options for heating than using the battery. That radiator coolant idea sounded good. A pan of boiling water or a small candle under the engine might be safe enough in a jam. Or you could just start the darn thing cold. 5W-30 helps.


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## John Hill (May 12, 2002)

Hmmmm! I wonder how effective it would be to blow Honda Civic hot exhaust gases through the front of the truck's radiator?


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## barn-apart (Feb 10, 2005)

Rick,
I believe most power inverters run off the battery, so if your car has a full charged battery any size inverter should function for your purpose . A larger watt will generaly draw more idle amps.I use mine for other purposes , refrigerator, battery chargers for cordless tools, 110v lights, ect. Often using it without the vehicle running. Handiest things those inverters.
Rick


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## RobD (Mar 2, 2006)

Rick,
I don't know if this would help but I live in a cold climate too so I'll suggest what I do. I don't use block heaters I use sythetic oil and teflon filters. Between the two I can turn my car over at 20 below (F) with no problems. I did this for someone who worked all day and had no way to heat her block after eight or nine hours. Guess what? More often then not she drove away when a lot of other people didn't!

I use the teflon filter from Fram with sythetic oil from Castrol. You can use Slick 50 but try to get the emulsion suspended in sythetic oil not regular oil. 

The plus is your mileage will go up too!

RobD


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## Rick (May 10, 2002)

Thanks Rob. Is that diesel or gas fuel- just curious. 
I shouldn't drop below 0 degrees F, so that should more than account for the diesel engine. 



RobD said:


> Rick,
> I don't know if this would help but I live in a cold climate too so I'll suggest what I do. I don't use block heaters I use sythetic oil and teflon filters. Between the two I can turn my car over at 20 below (F) with no problems. I did this for someone who worked all day and had no way to heat her block after eight or nine hours. Guess what? More often then not she drove away when a lot of other people didn't!
> 
> I use the teflon filter from Fram with sythetic oil from Castrol. You can use Slick 50 but try to get the emulsion suspended in sythetic oil not regular oil.
> ...


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## RobD (Mar 2, 2006)

The cars I run are on gas but I don't see a problem with diesel. In fact I would think diesels would 'like' sythetics.

One more thing once you have run enough teflon into your engine you don't need to use a teflon filter any longer and you can just run synthetic. That should happen after the first teflon filter or Slick 50 oil change. If you run the slick 50 with regular oil in it then do it in the summer and run regular oil in your vehicle. When it comes to an oil change then you can go with the synthetic oil and a standard filter.

I alternate teflon and extended life filters. Once I run synthetic in my car I only change the oil once a year. I change the filter at the end of its advised mileage by the manufacturer. I've had a couple of 250k mileage engines with no problems (gas). Diesel should last longer but you might have to change the oil even though it's synthetic. Talk to someone who really knows diesels on this. It's not my area of expertise.

Rob

ps. 0-F is no problem. I've seen 20 below for a couple of weeks.


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## Rick (May 10, 2002)

wy_white_wolf said:


> .....
> 
> I would say no to all of them. 600w would be (600/12) 50 amps at 12volt. I don't think that little alt. is that big and it would also have to supply amps for the vehicle to run. I think propably about a 75 amp alt would be min to draw the 600w from........





barn-apart said:


> Rick,
> I believe most power inverters run off the battery, so if your car has a full charged battery any size inverter should function for your purpose . A larger watt will generaly draw more idle amps.I use mine for other purposes , refrigerator, battery chargers for cordless tools, 110v lights, ect. Often using it without the vehicle running. Handiest things those inverters.
> Rick


My gut tells me that WWW is right, but my heart cries out for an cheap, easy solution. 

barn-apart....how many amps is that refrig?? It must be more than 6 amps!


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## Rick (May 10, 2002)

RobD said:


> ...........
> 
> Rob
> 
> ps. 0-F is no problem. I've seen 20 below for a couple of weeks.


Sorry about that- you must have wonderful Summers!

We just experienced our first 18 degree F night- with a propane heater in the motor home (28 degrees inside) to warm things up in the morning!

Rick


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## barn-apart (Feb 10, 2005)

Rick said:


> My gut tells me that WWW is right, but my heart cries out for an cheap, easy solution.
> 
> barn-apart....how many amps is that refrig?? It must be more than 6 amps!


Fridge is 3 cu. ft. draws 3.5 amps We run it during the summer for cold drinks and to keep lunch in.As well as charging the 18v cordless batteries (couple a day) during work without the truck running, and still start the truck after work. I use a 750 watt contiuous. The battery is a standard 12v that was in the truck when I bought it a year or so ago.
Rick


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## wy_white_wolf (Oct 14, 2004)

barn-apart said:


> Fridge is 3 cu. ft. draws 3.5 amps We run it during the summer for cold drinks and to keep lunch in.As well as charging the 18v cordless batteries (couple a day) during work without the truck running, and still start the truck after work. I use a 750 watt contiuous. The battery is a standard 12v that was in the truck when I bought it a year or so ago.
> Rick


A frig. is a lot different type of load. It only has to run for 5 or 10 min. every hour to stay cold, were as a block heater pulls a continous load. Same with charging the batteries. Load turns off once the batteries are charged.

Rick
The easy solution here would be to use like a 1000w generater to run the block heater. Propably cheaper on gas to than the honda.


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## RobD (Mar 2, 2006)

Rick said:


> Sorry about that- you must have wonderful Summers!
> 
> We just experienced our first 18 degree F night- with a propane heater in the motor home (28 degrees inside) to warm things up in the morning!
> 
> Rick


Trade offs. 
No ticks, chiggers,copperheads or neighbors. No windmill or solar panel restrictions, a 12 foot deep stocked trout pond and a stream.


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## Rick (May 10, 2002)

wy_white_wolf said:


> ........Rick
> The easy solution here would be to use like a 1000w generater to run the block heater. Propably cheaper on gas to than the honda.


Yeah- I know; It's right around the bend. I have resisted getting one- we'll start to use it and rely on it


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