120v to 12v conversion

[Backwoods Rambler]

Can a device designed to operate on 120v be converted to work on 12v? If so, what's involved??

Since I'm sure it depends on the device, I should let you know I'm looking to use a spare housdhold electric blanket for vehicle use in an effort to save some cash vs buying the $80 bunk heating pad that I really want.

 

[eugene]

If an item is electronic like a radio or tv they usually operate from a low voltage internally so you just need to replace the power supply. Anything that is a simple electrical device is just a coil of wire, be it a motor or a resistive like in a heater, like your heating blanket. To change the operating voltage you change the motor or resistor so you would basically be removing the heating element and replacing it, i.e. replacing the main component and not be cost effective.

 

[Backwoods Rambler]

Got it, thanks.

 

[pete.wilson]

Hey

If you want to run your AC electric blanket; just buy an appropriate sized inverter which takes 12v DC and bumps it to 120v AC. You may want an additional battery in which to run it and leave the trucks battery alone. If you also have an onboard switch you could charge it while you drive, then isolate it only to run the "house" battery and not your "start" batteries; this can be done electronically also, which is better.

Pete Wilson

 

[jcbrandon]

Sounds like that would cost a lot more than the $80 he's trying to save by not buying the 12-volt blanket.

Inverters are not very efficient. An inverter big enough to power an electric blanket will cost about half of the $80. A solid dual-battery system can easily run into several hundred dollars.

 

[Backwoods Rambler]

Even if I do get an inverter and run an AC elecric blanket, won't that still suck up a TON of power from the 2nd battery?

I have a bday coming up so I'll be asking for the 12v elect instead of the other option.

 

[BigJim]

How many watts

does the electric blanket draw? I suspect not very many AC watts.

Inverters are not 100% efficient. I de rate (sp?) my calculations and assume my inverter is only 80% efficient and my battery voltage will slowly drop over time.

Blanket draw 120 AC watts, (guess)
120/12 vdc = 10 DC Amps, assuming 100% power conversion.
Estimate 12 Amp DC draw

Depending on your battery setup and charging system 10 Amps could be considered alot of current. And obviously the blanket will not operate 100% of the time you are asleep.

How much current does the DC blanket draw

 

[jnaut]

Hey

If you want to run your AC electric blanket; just buy an appropriate sized inverter which takes 12v DC and bumps it to 120v AC. You may want an additional battery in which to run it and leave the trucks battery alone. If you also have an onboard switch you could charge it while you drive, then isolate it only to run the "house" battery and not your "start" batteries; this can be done electronically also, which is better.

Pete Wilson

I agree with Mr. Wilson. You don't want to start modifying your standard AC appliances to 'work' with 12v. From an engineering standpoint that's a 'decentarlized' solution- and it requires a case-by-case hardware specific modification.

Figure out what the wattage of your AC device is and then just get an inverter of the appropriate capacity. That way your device remains intact- can operate back on 110/115 ac, without making secondary modifications.

 

[gary in ohio]

Spend the money and buy a 12v electric blanket.

 

[jnaut]

does the electric blanket draw? I suspect not very many AC watts.

Inverters are not 100% efficient. I de rate (sp?) my calculations and assume my inverter is only 80% efficient and my battery voltage will slowly drop over time.

Correct, they're not 100% efficient, but depending on your use, batteries etc., this won't matter most of the time.

Blanket draw 120 AC watts, (guess)

Probably not. I think you mean mean 120 ac VOLTS. The wattage will either be a secondary statistic (probably printed on the controller) or is rated in Amps. To calculate watts from amps, multiply volts * amps. 120 vAC * say, 2 amps would be roughtly 240 watts.

 

[jnaut]

Even if I do get an inverter and run an AC elecric blanket, won't that still suck up a TON of power from the 2nd battery?

I have a bday coming up so I'll be asking for the 12v elect instead of the other option.

If there's a 12v version available, I would strongly suggest getting that because as another poster noted, inverters aren't 100% efficient. There is some loss. An appliance made for 12v will run more efficiently than one made for 120vac on an inverter.

 

[BigJim]

No I meant Watts

Not volts.

I have run an ac blanket in camp off my inverter. I think the nameplate said it was 120 Watt @ 120 VAC. I never measured it as I have plenty of good old wet cell technology with me.

My example was to demonstrate what current draw the guy was up against using a 120 VAC appliance.

Happy high current DC

Correct, they're not 100% efficient, but depending on your use, batteries etc., this won't matter most of the time.



Probably not. I think you mean mean 120 ac VOLTS. The wattage will either be a secondary statistic (probably printed on the controller) or is rated in Amps. To calculate watts from amps, multiply volts * amps. 120 vAC * say, 2 amps would be roughtly 240 watts.

 

[chet]

A typical 120v electric blanket probably draws around 1000W. typical heating type appliance. to get the required W from 12V you would need 1000/12= 85A circuit! I'd say that will drain a battery pretty quick! I did find one 120V electric blanket that said it was low voltage but offered no details.

 

[tdesanto]

What is the purpose of the electric blanket? Since the exact purpose wasn't stated, I'll assume it's for sleeping in the vehicle?

May I suggest a well-made sleeping bag instead? This will serve you far better, as it won't need a single amp to power it, yet it will keep you warm when you need it to.