115/120v Car and Truck Outlets

[0027647221]

Hi All - I know it's not smart to power a 50w radio in a car's cigarette lighter, but will a 115/120v (i think some are different) safely and effectively power a 50w radio?

 

Thank you!

[W6ORV]

Are you thinking of running a DC power supply off 115vac to power the radio?  

[0027647221]

Thinking of running it somehow off the 115 vac.  Is there a method that will work safely and efficiently?

[SteveShannon]

2 minutes ago, 0027647221 said:

Thinking of running it somehow off the 115 vac.  Is there a method that will work safely and efficiently?

In your vehicle or your house?

In your house just use a 115vac power supply  

In a vehicle using an inverter to get 115vac and then a 115vac power supply to get 13.8vdc is inefficient. Just run it off the battery. Your output will suffer very slightly when the engine is off because your battery probably provides 12.7vdc then. 
 

[0027647221]

Thank you.  It would be in my database.... i may just put the 50watt in the house.

[W6ORV]

12 minutes ago, Sshannon said:

In your vehicle or your house?

In your house just use a 115vac power supply  

In a vehicle using an inverter to get 115vac and then a 115vac power supply to get 13.8vdc is inefficient. Just run it off the battery. Your output will suffer very slightly when the engine is off because your battery probably provides 12.7vdc then. 
 

"50w radio in a car's cigarette lighter"

 

I got the impression it's in a vehicle with either a built in inverter / 115 vac outlet or a portable inverter. 

[0027647221]

Is the DURACOMM LPX-14 POWER SUPPLY, enough to power a 50 watt radio like the Midland MXT575?

[W6ORV]

According to Duracomm literature, its good for 13a 13.8vdc continuous.  Finding power draw in manufactures specs for these GMRS's seems to be impossible, but I googled it and found someone who benched one and got 2.5a / 13.8vdc on high output.  

[0027647221]

Thank you!

[SteveShannon]

13 amps should be fine. 
Midland FAQS say any power supply exceeding 15 amps.
https://midlandusa.com/products/mxt575-micromobile®two-way-radio

That’s almost certainly estimated conservatively, but a radio that puts out 50 watts of RF power must consume more than 50 watts of electrical power.
At 13.8 volts the very minimum the radio can draw while putting out 50 watts must exceed 3.62 amps, so 2.5 amps isn’t right unless the radio was putting out much less RF.



 

[W6ORV]

I did the math too, but these folks aren't using calibrated gear testing stuff going to the moon.  And these radios famously don't put out advertised power.

[KAF6045]

59 minutes ago, WRFH464 said:

I did the math too, but these folks aren't using calibrated gear testing stuff going to the moon.  And these radios famously don't put out advertised power.

Not putting out the full advertised power still doesn't mean that the rigs won't draw 2-2.5 times the direct (watts-out/voltage) for amperage. 50% loss in heat isn't unusual -- at the price most of these rigs cost I wouldn't be surprised if they waste 66-75% as heat. Though at 2.5X I'm still coming in at 9A, call it 10A -- which is the limit for most lighter sockets (though my former Jeep had a standard lighter socket [no lighter] on the left, and a 20A power socket on the right). I don't think the problem is fusing (probably a 15A fuse on the 10A socket) so much as how cheaply made those sockets (and plugs) are -- really high sustained current draws might cause heating in the thin contact surfaces used (ever compare the center contact of a real cigarette light plug to most utility power plugs? And the former is a deliberate heat producing resistor with some insulation).