Richard

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Old 11-23-10, 08:06 AM
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Richard

I am intrested in purchasing a power inverter for my truck to run two heating pads at the same time. Any advice?
 
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Old 11-23-10, 08:30 AM
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You have 2 posts with the same title....why not put a short description of your question from now on? I'm going to change this one to "Truck Inverter" after I know you've seen this.

Now...what kind of "heating pads"? Like you would use at home on a sore back? Surprisingly...most of them are very low wattage. I just checked mine and its only 55 watts. Most any inverter rated for 300W would be plenty..and ones that size are pretty cheap.

Hmmm...thinking now...wonder if the inductive load would be an issue?

I was going to move this to Automotive as well...but maybe leaving it here for now would be better.
 
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Old 11-23-10, 09:01 AM
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Heating pads are a resistive load, not inductive.

Be very careful about using the cigarette lighter for powering the inverter. Fifteen amperes from the cigarette lighter is less than 1.5 amperes (180 watts) at 120 volts. Should be okay for a couple of 120 volt heating pads but not much else.
 
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Old 11-23-10, 09:22 AM
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Oops...I misspoke..thx for clarifying the load Furd.

But...how can a cig lighter inverter like this.. Jensen (JP-30) 300W 2-Outlet Power Inverter : Power Inverters | RadioShack.com provide 300W continuous? Maybe require one of the aux power outlets in a vehicle?
 
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Old 11-23-10, 10:18 AM
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I don't know about that particular item but many inverters have binding posts on the back that require the use of heavy conductors (generally #6 or #4 in the smaller sized inverters) run directly to the battery. The cigarette lighter cable either connects to the binding posts or a separate connector and the instructions specify when each can be used.
 
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Old 11-23-10, 10:25 AM
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Right..I've seen the heavier ones that direct wire. Doesn't make sense to me either....how does 180W somehow ramp up to 300? I even looked at the manual on their website. Any cig lighter outlet...300W continuous out. Very strange.
 
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Old 11-23-10, 10:48 AM
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I don't know what that one has, but I have a 150W inverter for my laptop, and it has an 8A fuse in the cigg lighter plug. I would assume a 300W unit uses a 15A fuse. The problem here lies in the fact that the actual cigarette lighter port is almost always on the same fuse as the interior lights, stereo, and a couple other things. As such you only have a few amps to play with. The 'power ports' are on their own fuse.. I can't use mine in the cigarette lighter, because it pops the fuse.

I'm pretty sure 300W is the largest you can get with a permanent plug. Anything larger has the binding posts (and they will come with a set of battery clamps, not a cigarette plug).
 
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Old 11-23-10, 01:38 PM
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I think they're banking on the fact that most alternators kick out somewhere around 15V. 15V * 20A is 300W so maybe the dedicated power ports in newer cars have a 20A fuse instead of the 10A or 15A on the cig lighter?
 
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