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I bought a Duralast 130W inverter and it says 260 peak watts and it plugs into the 12V cigarette lighter. I want to charge my HP laptop with it. Is it bad for the car?

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No.

Your 12V socket is designed to deliver 12V, at a current described in your car manual. Most of my 12V sockets in the car can deliver up to 5A apparently (haven't tested this though, but I run a 200W invertor when I go car-camping. It is handy for everything)

The worst that can happen is if your invertor tries to draw more than the 12V socket is fused for - in which case the fuse for it will blow.

And as @Paulster pointed out in comment, you could drain your battery without realising it if you use the inverter with the engine off.

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  • The only other caveat is draining your battery. Be aware of what your battery can handle. I have a 1000w inverter which I've run in several different vehicles without issue to the system or to the battery. They truly are a great little piece of merchandise to have around. – Pᴀᴜʟsᴛᴇʀ2 Nov 1 '15 at 20:10
  • Don't depend solely on the fuse. Make sure you're not overloading the circuit: make sure the total wattage of your devices is less than than your socket and inverter are rated for. – Mathieu K. Feb 28 '17 at 23:10
  • For instance, in my Civic, the "Accessory Power Socket" has a 15-amp fuse, which means up to 12.7V x 15A ≅ 190 watts nominal. So in my vehicle, unless I was adding my own heavier-duty circuit for the inverter (and maybe a beefier alternator), I shouldn't load my inverter above (i) maybe 175 watts or (ii) a little less than its rated wattage, whichever is lower. – Mathieu K. Feb 28 '17 at 23:26
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Nope. 130 watts at 12 Volts will draw 10-11 Amps of current. My ciggy lighter (Auto power socket) was rated for 10A of draw and has a 10 Amp slowblow fuse in it.

Depending on the load you might have problems if you run something inductive like a motor, rather than a capacitive load like a laptop. Items like blenders, circular saws, and so on are not good for an inverter.

Electric kettles and toasters are also a bad idea, mostly because of the load they pull (1000-3500 watts)

As long as your wiring and fuse are 10A or higher and the devices are appropriate, you'll be fine. If the fuse goes, the socket will be dead. If your wiring is substandard then it could melt and short the car's battery, but this could happen with any big load. Don't just replace the fuse with a higher-rated one if it does blow.

Others point out the risk of a flat battery, but also be aware that over-discharging a Lead Acid battery can make it sad. A 12V car battery should never be discharged below 10.5V, so set your car motor idling if you're using the inverter for a long time, or use batteries that are already old and cranky. 12V 7AH alarm batteries cost around $30 each and can work well.

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    One important sentence: "Don't just replace the fuse with a higher-rated one if it does blow." – sweber Nov 2 '15 at 10:22
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    Indeed. One should use folded foil metal or a paperclip. – Hennes Nov 2 '15 at 13:42
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    Just in case someone has not drank his or her coffee: HELL NO! DO not really do that! (/exclaiming marks) (/bold) (/blinkblinkblink) – Hennes Nov 2 '15 at 13:44
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    Can confirm that paperclips work great! I use them to replace fuses in my house too! – Robert Stiffler Nov 2 '15 at 22:05
  • I installed a 20A ciggy lighter in the rear of my landrover, mostly for running a beefy compressor. I used decent grade wiring all the way back to the battery, and fused it at both ends of the wire. Do it right and it won't be a problem. – Criggie Nov 2 '15 at 22:09
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Nobody has mentioned the load of a charging laptop. My laptop has a 19V 2.1A power supply meaning the maximum power in the worst case is approximately 40 watts. At 12 volts, this means about 3.3 amperes of current draw. However, your inverter might not be 100% efficient, so this amperage draw might be somewhat larger but probably not above 4 amperes.

According to Wikipedia, a cigarette lighter draws around 10 amperes of current. Thus, you probably have no problem operating an inverter in the cigarette lighter receptable in your car. Just make sure not to use it when the engine is off or else you may have a flat battery and may require a jump start. At max 4 amperes of current, you should have the ability to charge the laptop battery for more than 10 hours, because conventional car starter batteries are above 40 ampere hours. However, an old battery might have a much lower capacity, so I would not take risks.

Just to make it sure, you can take a look at the fuse box in your car. See what the fuse rating is for the cigarette ligher fuse. I believe the fuse is either 10A or 15A.

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    Suggestion for paragraph two: don't use a car battery for anything other than starting the car. Car batteries are fairly expensive, and your car may not have a low-voltage cut-off circuit protecting the battery from over-discharge. Further, to my understanding, starter batteries work best if they're only minimally discharged (the starting sequence uses 3%) and then charged up again right away, which the alternator does when you run the car. – Mathieu K. Feb 8 '17 at 7:52
  • @MathieuK. Otherwise correct, but I wouldn't say flooded car batteries are expensive (AGM batteries are expensive but then again AGM is more durable). The laptop battery may cost more than the car battery! Also, destroying a car battery by over-discharging won't happen when the mistake is done only once. I once accidentally left the lights on overnight, and after a jump start the battery worked fine for many years. One discharge? Fine. Ten discharges? Not good, the capacity will suffer much, if we're talking about flooded non-deep-cycle starter batteries. – juhist Feb 8 '17 at 11:25

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