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Topic: 12V socket oddity (Read 481 times) previous topic - next topic
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Re: 12V socket oddity
Reply #25 –
(It’s a 300 watt inverter, if I remember the formula, divide the watts by 120V, that’s just 2.5 amps.
The TV only needs a maximum of 95 watts, well under the 300 watts.)


I am coming up with the follow formula P (watts) =V (volts) x I (amps)
According to my Laze daze owners manual the TV outlet is rated at max 8 DC amps.  12volts x 8amps = 96 watts.  So 96 watts is the max this outlet will handle.  Also give margin of error so assume less watts then 96.

If the TV draws a max of 95 watts plus you need to add in how many watts the inverter draws that will put you over the 96 watts.

You might try a lower wattage inverter.

Please correct me if I am wrong.

JohnF
2003 TK
Re: 12V socket oddity
Reply #26 –
"divide the watts by 120V, that’s just 2.5 amps."

Yes, but that's 2.5 amps at 120 V. In 12 volt terms, it's 300 watts divided by 12 V, or 25 amps--way more than any 12V outlet can handle. (That's why when Lazy Daze installed an inverter, they hardwired it with AWG 6 wire, and put it close to the batteries.)

The correct way to look at this, as JohnF said, is to take the TV's 95 watt power requirement and divide by 12 volts, yielding 8 amps. Add in the inverter's conversion loss--probably about 10%--and you're closer to 9 amps, which is beyond the outlet's 8 amp capacity.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
 
Re: 12V socket oddity
Reply #27 –
Quote from: RonB  - 
Hi Dave and Andy.  I'd start at the fuse board, but I think there may be a bad connection somewhere along the way to that socket, and most likely at that socket. The whole plate should be easy to unscrew so the back can be inspected.
     I'm suspicious about the inverter. They have a huge surge current, and large capacitors to stabilize the 12 volts as it is 'switched' up to 110vAC. At 300 Watt inverter can draw more than 23 amps, but since the TV's nominal  load is 45 Watts, It may draw much more than that just for an instant, enough to have the small inverter shut off.  My true Sine Wave inverter doesn't allow any grounding, and the neutral output can not be referenced to ground.  That particular 12v socket does run 12v dc up the RF cable to power the pre amp in the Sensar head, so the shield is grounded, and the TV/inverter might not like that setup.  My little 75 watt inverter has no problem with my 19" TV, so I'd have to see this problem live.
     So Dave, you have a 3kw inverter as part of the LIF upgrade, yes?  You should be able to run the TV off of that. Or get a cheap extension cord (no ground wire) to run the 300 W inverter 110v to the TV wherever it is.  RonB

  As an aside: my 2KW inverter runs about 15 watts idle wasted for small loads, cooling fans not on. That inefficiency gets worse with more power being used)

Don’t forget the ground lead. Resistance there is the same as in the power lead. My bet is you can’t find it, I couldn’t. Paralleling the 12 volt conductor didn’t help. For some reason it didn’t seem related to load current. There was always a 1.5volt drop with or without load.

I wanted the inverter receptacles near the TV which is why I ran 6 gauge welding cable, positive and negative direct to the battery.

I would like to hear where the voltage drop is if you find it.
Harry 2006RB