Inverter power needed for Laptop (charger) in car

Either there is something obvious here I can't see or I have one of the worst cases of dry joints in recorded history

I am trying to use a laptop in a car. I have an inverter rated at 50w. It worked for a few months and then peremptorily stopped with a sudden rattle from within and no light going on to show that it is ready. When I opened it up I found a whole power transistor rattling around inside with all three joints seemingly not connected and the glue from the rear of the transistor seemingly having come off. Curiously the ends of the connectors don't actually look as if they were ever connected?? (The holes on them from the motherboard do look as if at least something was once connected to them as they are filled with slightly disturbed-looking solder)

Is this just a lousy joint on some cheap chinese-looking inverter which worked while the pin ends merely touched the mainboard slightly or does the power charger need SUBSTANTIALLY more than a puny 50 watts to work: The charger reports that it needs an input of from 100 to 250 volts at 1.5 amps to give an output of 18.5 volts at 2.7 amps. Can someone do the maths for me and let me know what power inverter this charger will need please?

I am suspicious of the puny nature of the inverter because although I can't see a laptop using all that much power, I have also got a huge heavy duty Coleman PMP400 inverter with fins all over the place and a heavy duty sounding onboard fan rated at 400 watts (peak surge 800 watts at 3.5 amps) and after about ten minutes of use, IT starts to overload on this laptop charger (meaning the red warning light comes on and the inverter starts giving symptoms of blowing): The red light won't now go off: I am wondering if I have blown this inverter as well? (Curiously it didnt last as long as the 50 watt one).

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What happens when you solder the transistor back in?

If you look at the numbers, you might conclude that your adapter takes

150W in to put out 50W. That's seriously overloading your 50W inverter.

The good news is that the numbers written on the brick are more likely to satisfy some regulatory requirement rather than express what's actually happening in your case.

The bad news is that while charging, your laptop probably does use all all 2.7A = 50 watts. There is at least some loss in the adapter, so you're still seriously overloading the 50W inverter. Not surprised the transistor melted out.

Switching power supplies do put a serious stress on square wave, or modified sinewave inverters...but a 400W unit should work ok? I had no problems with a 30W laptop on a 140W inverter.

Check the 12V input under full load. If you have losses reducing the input voltage, the current will go up to compensate.

I once had a problem with a car installation. Turns out that I'd hooked the inverter to the wire that was intended to dim the radio dial light. Had serious problems if the dash lights were dimmed ;-) mike

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mike

You have other choices besides an inverter. A DC to DC converter that takes in 12 volts and puts out 15 volts with a plug soldered onto it that fits the back of your computer would work a lot more efficiently than an inverter into a power supply. Also, you can run a laptop directly off a car battery. Just make a cable with a cigarette lighter plug on one end and a plug for you computer on the other end. That's how I run my computer in the car. Your laptop's battery won't recharge from a 12 volt supply, but you won't be using the laptop's battery anyway. Why not keep it simple -- no inverter or anything, just a cable with a plug on each end. What's more, your computer might even charge plugged directly into the cigarette lighter if you are driving the car, because your car's voltage will be between 14 and 15 volts when you are driving. I don't use my computer when the car is running because I want to protect it from the hash on the car's power circuits. But I would have it plugged in to the cigarette lighter with the car running so it would charge, as long as the computer is actually turned off. I'm to lazy to put a filter on the cable I made, or I could use the computer with the car running.

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kellrobinson

NO,NO,NO,NO,NO,NO,NO,NO,NO,NO!!!!!!!! DO NOT DO EITHER OF THESE THINGS.

Using a car adapter NOT DESIGNED for your EXACT model computer is very risky. You can probably get away with it if you take out the battery. If you leave the battery in, you risk serious damage to your battery and maybe yourself when it explodes. Does this happen EVERY time? Of course not. HOW LUCKY DO YOU FEEL?

PLUGGING ANYTHING NOT SPECIFICALLY DESIGNED TO PLUG INTO A CAR DIRECTLY INTO A CAR ELECTRICAL SYSTEM IS A SUICIDE MISSION FOR YOUR LAPTOP. THE BATTERY ISSUES DESCRIBED IN THE PREVOUS PARAGRAPH ALSO APPLY. Go read this before you contemplate a direct computer connection:

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THEN QUIT CONTEMPLATING IT.

Yes, you'll find idiots who claim they never had a problem. Again, how lucky do you feel stuffing 300V high energy pulses into your laptop???

Get an inverter that works. mike

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mike

I figured that if the computer's power supply says it needs 100 to 250 volts, it must mean something which doesnt equate to "use any old 12 volt supply, if possible bumped up to 15 volts"

So the position is that the 50 w one was simply too weak and the 400 watt one probably had something wrong with it? I also have a 1200 watt Coleman one which I am now reluctant to use (principally because it is so darn huge) but if this is the rationale, I should just go ahead and try.

I just thought that those big Coleman units dont go wrong all that often but there again I have come across warehouses full of dead inverters. Maybe Coleman just arent too much more reliable than all the others?

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There's no way it's *that* inneficient, even a linear power supply would have far lower losses. More likely it draws about 65W, but the power factor is probably quite low, so it pulls a lot more amps than the wattage would suggest which may well have killed the little inverter.

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James Sweet

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Bennett Price

No, the charger is fine, it is more likely that the power consumptoin killed the little inverter and there is something wrong with the bigger 400 watt one: I should call Coleman and ask them if those inverters were unreliable?

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killed

unreliable?

LOL what do you expect them to say? "Yeah our products suck, sorry!"

Even if they know they're unreliable they won't say anything, Coleman doesn't actually make the inverters anyway, they buy them from some company in China and slap their logo on them. They're cheaply made just like all the other cheap inverters on the market.

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James Sweet

Good point, I didnt know that: I thought that the weight, complex APPARENTLY high quality circuitry, not low price (for high power items) and all those fins meant something. Is that why no one seems to bid on them on ebay?

I wonder if this means that like Sony, they will instantaneously replace any non-repairable unit or will they just deny responsibility for what they know to be poorly made products?

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I have a friend who is using one of those Coleman 400-watt inverters with a couple of AGM batteries for lighting and small electrics at a remote home site. She has been using it over two years, and during that time the fan has failed and it has been filled full of gypsum dust, but it still works fine. It's mounted in the back of a car and runs 24/7 as we found that the idle current was less than 150mA, so it is more of a headache to deal with turning it off and on than to just leave it running. It has been absolutely troublefree.

-Keith

Reply to
Keith Jewell

It really depends, the cheap stuff can be just fine, but it's hit or miss, the quality control is not always there. You don't have a lot of choice though, virtually all inverters are pretty much the same inside.

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James Sweet

The QC goes straight down the toilet once they start outsourcing to CHina: The chinese will apparently just cut any corner they can and use any inferior component they want to if they think it will reduce costs. That is why as high quality a company as Sony realises that now they have outsourced they need to replace everything as soon as any complaint comes in because the product is so lousily made that they need to do this to preserve their reputation.

Other companies take the opposite view: 'We have provided you with a ludicrously cheap unit. Don't be surprised or blame us if it fails (hopefully) not-too-quickly'

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