# Powering Laptop With Inverter



## Turnstrike (Jan 1, 2019)

Good Afternoon Folks,

New member posting for the first time, be gentle, I've been told you're a friendly bunch 8)

Here's the problem: I'm going to have an inverter fitted to a HGV in order to power a laptop when I'm at work but I can't establish what size inverter I need. I have a rough idea of the conversions but I could use a more experienced opinion on the requirements of the laptop in question.

I've attached a photograph of the power supply label, and if I've worked this out right, 100-240V at 3.2A means the laptop needs to be able to draw at least 768W of power to run. I hope to be _massively_ wrong here.

Alternatively the output at 19.5v at 11.8a suggests 230w. Meaning that I could, in theory, run this laptop on a 400w inverter without too many problems.

Any thoughts folks? It's confusing the life out of me.

Thanks so much for any help.

- Jamie

--

Edit: Removed the remark about running this on a 230w car charger since apparently they don't exist!


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## MrGenius (Jan 1, 2019)

1. Input is one thing. Output is another. What you'd need to be concerned with is the input, as far as not exceeding the specifications of the inverter. Which you're way off on. Let's assume you have a 12VDC to 120VAC inverter. And you want to be able to draw at least 3.2A with it. The wattage required would then be 384W.
2. I don't recommend running a laptop with an inverter. You'll risk damaging the battery if you do. Don't ask me how I know. 
3. A 'cigarette lighter' is 12V(presuming the vehicle it's in has a standard 12VDC electrical system, which almost all do).


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## R-T-B (Jan 1, 2019)

MrGenius said:


> I don't recommend running a laptop with an inverter. You'll risk damaging the battery if you do. Don't ask me how I know.



This be true if you drain it too far.  You'll want an inverter with a low voltage shutoff.

Also keep in mind a "cigarette outlet" will only deliver around 300W in modern vehicles.  Fused output.  Again, experience here.


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## silentbogo (Jan 1, 2019)

I wouldn't do it for that MSI laptop. Better get an extra battery or something more reliable as a power source.
When it comes to laptops, using an inverter in a car is a bad idea. Not only you are losing lots of efficiency by adding an extra stage to power conversion, but you also endanger laptop's power circuitry by running it off an unstable power source (unless you invest into a very good pure sine wave inverter), or burning up the lighter socket.
For a normal modern laptop (e.g. 45-60W) you'll be better off using a boost converter or a good universal car charger for laptops.


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## Turnstrike (Jan 1, 2019)

Brilliant replies here folks, thanks so much for the guidance. 

I should have added a few other details: the inverter is the main choice in this situation because I work away from home in the vehicle for sometimes two weeks at a time, so a spare battery although a wonderful idea would only give me another hour or so. The owner of the HGV isn't too bothered about the engine running to recharge the battery, a lot of our vehicles run microwaves and TVs from the batteries but I suspected the laptop would have a different power requirement than those! Thankfully the vehicle has a display showing how much power is remaining in the battery 8)

The battery on the vehicle is 24v (2x12v in series) so it'll likely be hardwired directly to the battery supply instead of through a socket, I realised this was a problem when I tried to shop around for a 19.5v /11.8a car charger and completely failed...

The main concern is the decision between a 400w and an 800w inverter. From the replies above it looks as though a 400w will likely do the job for an hour or two on an evening when I'm parked up, or during the day when I'm making deliveries. I assumed the laptop pulled 760w - apparently that was completely wrong. This is why I'm a HGV driver haha!

Thanks so far folks!


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## flmatter (Jan 1, 2019)

This or this   or similar. You would want something like pure sine or true sine wave. if you are only running a laptop 500 watt should be enough. I always go a step up in case you want a printer at point so hence the 800watt linked. You can google pure sine wave inverter for your area for more choices. Definitely connect it to the main vehicle batteries and put the fuse as close to the battery as you can. I do this a lot at work for our vans.  I use THESE ones mainly but if you go under support it has diagrams on how to wire it in. Xantrex outlet


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## newtekie1 (Jan 1, 2019)

Turnstrike said:


> The main concern is the decision between a 400w and an 800w inverter. From the replies above it looks as though a 400w will likely do the job for an hour or two on an evening when I'm parked up, or during the day when I'm making deliveries. I assumed the laptop pulled 760w - apparently that was completely wrong. This is why I'm a HGV driver haha!



You have a 230w laptop power supply, so a 400w inverter should work just fine. Make sure the inverter is a good one, ideally pure sine wave, and that it has overheat and overcurrent protection. That way if, for some reason the laptop pulls too much from the inverter, the inverter will shut down before any damage is done.


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## trog100 (Jan 2, 2019)

i use a small cheap 200 watt inverter to run a laptop charger it does run from a specially wired 20 amp 12 volt socket though not the normal one.. 

i use the same system to charge quite large quad copter batteries or anything that needs a mains charger.. the weak spot is a normal socket causes a voltage drop and the inverter will shut down.. 

pulling 200 watts from a 12 volt system is quite a lot.. i dont need to run the engine whilst running the laptop but i do have decent batteries.. 

trog


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## taz420nj (Jan 2, 2019)

Ok let's just clear something up since it hasn't been mentioned yet, and it's important since you're in the UK..  The nameplate power draw on the input of a worldwide power supply is the MAXIMUM that it will be pulling at the lowest rated voltage.  So the 3.2A number is at 100 volts (mains voltage in Japan).  At 230V, the draw is only about 1A. The higher the voltage, the lower the amp draw for any given load.

Now When sizing an inverter for a laptop, all that matters is the charger's OUTPUT wattage (in your case 230W), because that will be the same regardless of the input voltage. So accounting for inverter inefficiency (usually about 70-75% on the cheaper ones) , and good practice of having about 20% more power than you intend to use (to avoid stressing the inverter, which could cause low output voltage and therefore higher current draw with a SMPS), a 500W inverter is what you'd be shooting for.

If the machine weren't so beefy, I'd say skip the inverter (which is stepping up voltage and changing to DC, then stepping back down and converting back to DC) and just get a DC-DC adapter.  However they don't seem to make any that will output more than about 150W and you'll burn them up.  So unfortunately you're stuck going the inverter route.  Nothing wrong with using a modified sine wave unit with a laptop. I've been doing it for over 10 years and never burned out a power brick.  MSW inverters only really cause problems for AC motors.

Since you have 24V available, you COULD use a regulated 24-19V buck transformer (they make them up to 50A output), but that takes away any buffer you have between the electrical systems and if the voltage drops or the regulator fails it could fry the computer.  I wouldn't recommend it.  The power brick will generally produce a stable DC output  with input voltage down to about 60V (although it will get REALLY hot) and up to 260V.


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## R-T-B (Jan 2, 2019)

taz420nj said:


> Nothing wrong with using a modified sine wave unit with a laptop. I've been doing it for over 10 years and never burned out a power brick.



Agree.  The laptop internals are all DC anyways.  The worst that will happen is the place the modified AC goes (in this case, the power brick) may get hot and have slightly higher stress.


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## MrGenius (Jan 2, 2019)

taz420nj said:


> So the 3.2A number is at 100 volts (mains voltage in Japan).  At 230V, the draw is only about 1A.
> 
> When sizing an inverter for a laptop, all that matters is the charger's OUTPUT wattage (in your case 230W), because that will be the same regardless of the input voltage.


Ok then. 320W with 100VAC. Or 230W with 230VAC.

1. Sounds like the old "240V is better/cheaper/uses less watts than 120V" BS argument.

2. And, magically, the inverter will never use more than 230W. Even if you run it on 100VAC. Which you just said draws 3.2A...right? But it's somehow not using 320W?

Really? You sure about that?

That's rhetorical BTW. I'm not the least bit interested in your BS reply.


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## JeffP_in_AU (Jan 2, 2019)

Hello Turnstrike,

I recommend you just buy a car laptop adaptor on eBay. These take the 12v from the cigarette lighter and produce a DC voltage suitable for the laptop.

They vary according to the laptop used. For example I use Lenovo laptops which need about 19v and have a different sort of plug. Your laptop will likely be quite different. Just search on eBay for "xxx laptop car" (where xxx is your brand) and that should home you in.

Prices are typically around the $20 mark. Some of the adaptors have a USB socket so you can charge your phone too.

I run a Lenovo laptop just about every day this way. A typical laptop takes between about 10 watts to 50 watts.

I recommend you do NOT try to produce 110v/220v AC and then use your laptop power adaptor. I am an electrical engineer and I used to do this but no longer. The eBay adaptors are a MUCH! easier solution.


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## taz420nj (Jan 2, 2019)

JeffP_in_AU said:


> Hello Turnstrike,
> 
> I recommend you just buy a car laptop adaptor on eBay. These take the 12v from the cigarette lighter and produce a DC voltage suitable for the laptop.
> 
> ...



He's got an MSi gaming rig.  It's got a 230W charger.  They don't make DC-DC laptop chargers that big.


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## JeffP_in_AU (Jan 2, 2019)

> He's got an MSi gaming rig.  It's got a 230W charger.  They don't make DC-DC laptop chargers that big.[/QUOTE]

Oh I hadn't noticed it was some sort of gaming thing. I just read him saying "laptop".

In this event (consuming 230-odd watts), I'd suggest not even thinking of running it in a car. A 100% efficient inverter would consume 20amps (20x12=240) to run it. Worse than leaving your headlights on. You would have to keep the engine running or you'd flatten the battery in an hour or two.

Find a wall outlet / power point.

J.


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## taz420nj (Jan 2, 2019)

JeffP_in_AU said:


> > He's got an MSi gaming rig.  It's got a 230W charger.  They don't make DC-DC laptop chargers that big.
> 
> Oh I hadn't noticed it was some sort of gaming thing. I just read him saying "laptop".
> 
> ...


It IS a laptop.  Just a really beefy one lol!  He's a trucker and this will be installed in a HGV (a Semi in Europe).  I don't know if it's common there, but here truckers leave their engines idling (for heat and air conditioning) during rest/sleep breaks, so I don't foresee consumption being an issue.  Most sleeper cabs here have large hardwired inverters that can also run TVs, mini-fridges, and microwaves.


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## Jakazz1979 (Sep 19, 2019)

I have an Asus ROG Strix gaming laptop. Asus has a DC-DC power brick I bought from them for $80. So all those that keep saying you can’t get one, do better research. If you don’t want to use an investor and would rather have a 12V charger to use in your rig, contact your laptop manufacturer. They should have one available specifically for your laptop. Just be prepared to pay good money for it. DO NOT get a cheap one. Get one DIRECTLY from the manufacturer of your specific laptop.


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## NelchaelSS (Oct 7, 2019)

Jakazz1979 said:


> I have an Asus ROG Strix gaming laptop. Asus has a DC-DC power brick I bought from them for $80. So all those that keep saying you can’t get one, do better research. If you don’t want to use an investor and would rather have a 12V charger to use in your rig, contact your laptop manufacturer. They should have one available specifically for your laptop. Just be prepared to pay good money for it. DO NOT get a cheap one. Get one DIRECTLY from the manufacturer of your specific laptop.




Can you please tell me the model number of the adapter? I tried contacting Asus support in my country, but they have ZERO information about this...

80$ is not that much, that's how much you spend on a decent power inverter + you won't waste energy by converting it 1000 times.


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## shovenose (Oct 7, 2019)

I have a thinkpad t430 mounted in my car and use a cheap peak brand 400w inverter... Definitely not pure sine wave. The Lenovo charger does make a slight buzzing noise but other than that, no issue. I don't believe a pure sine wave inverter is necessary.


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## flmatter (Oct 7, 2019)

@NelchaelSS Asus Charger    although if you current power brick is more than 90w you have to go with something like this or this. The 500 is a bit overkill but the 300 will be fine.


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## NelchaelSS (Oct 8, 2019)

flmatter said:


> @NelchaelSS Asus Charger    although if you current power brick is more than 90w you have to go with something like this or this. The 500 is a bit overkill but the 300 will be fine.



Yeah... that's why I was asking him...The most powerful car charger I could find was 120w, which is not enough for a laptop that has a 230w power brick, and eats ~150 while maxed out in Witcher 3. The most I made it use is 200w while running synthetic benchmarks on cpu+gpu, but it quickly thermal? throttled, and went back to normal. The truck's outlet is rated at 24v 15a (360w) so it's more than enough.

A 180-200w car charger would be enough, but they are rarer than unicorns (or inexistent)... unless I will find something in the next months, I guess I'll be using a 300w inverter.

Sadly, connecting 2 adapters in parallel to boost the Amps won't work, unless you modify the circuitry, and I'm not that good at that to risk a 1500$ laptop.


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## trog100 (Oct 8, 2019)

a 300 watt inverter powers by asus gaming laptop okay with its 240 watt power brick.. i have one wired into my caravan/RV trailer..

trog


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