Power Inverter and use of laptop in car?

[Sarah]

Hi,

I am looking to buy a power inverter so I can use my laptop (M35) in the
car. The power rating on the laptop's charger is; AC 100-220 1.5A and DC 12V
4A. There is a compact and nice inverter that I want to buy, it is rated at
70W. Would it be sufficient to run my laptop? I don't know much about power
so I am hoping that someone can help out. Thanks.

 

[RHinNC]

That is plenty.

 

[micky]

Thank you very much! Can I bother you again and ask how did you figure this
out? Just for future reference. Thanks again.

 

[V Green]

Thank you very much! Can I bother you again and ask how did you figure this
out? Just for future reference. Thanks again.

Watts = Voltage * Current

12V * 4A = 48W (assuming 100% efficiency
of the AC-DC adaptor)

you SHOULD have a 22W "buffer"

But *some* el-cheapo inverters will NOT run
the advertised output power...there's no guarantee
that even though your connected load is below the
70W rated output that the inverter will start & run.
I have, unfortunately, experienced this a few times and
now always buy larger than I should need.

Just make sure the place you buy it from has a return
policy that alows you to return it if it won't work for
you.

 

[Sleepless in Seattle]

You may have problems with voltage drop across the wiring from the cigarette
lighter. Direct connection to battery is best.

 

[micky]

Thanks V! I kinda remember that formula from the old days but was not sure
if I needed to use it with the AC or the DC ratings on the charger! Now I
know! Thanks.

 

[johnf]

What a lot of rubbish - don't confuse him.
A cigarette lighter plug and flying leads are normally designed to supply
another alternative appliance apart from lighting cigarettes & the kit
cables are heavy duty.
Most are labelled with the maximum current / wattage rating. If it's well
above 4A or 55watts - no problem.

 

[Sleepless in Seattle]

This is contrary to my experience with numerous inverters both cheaper
modified sine wave and the more expensive pure sine wave devices. The
cabling supplied with cigarette lighter attachments has been inadequate to
supply the required current.

 

[micky]

Watts = Voltage * Current

12V * 4A = 48W (assuming 100% efficiency
of the AC-DC adaptor)

you SHOULD have a 22W "buffer"

Ok, I am confused now!! I posted the same question on Japan.comp.Toshiba and
I got the following;

"VA=Watts. So your 110 volts times your 1.5 amps equals 165 Watts. I'd
recommend an inverter of about 350 watts. Gives you power to spare and
won't run so hot as a 175 watt unit might even if it did work."

I really don't get my Laptop busted! I just got it and I am just starting to
fall in love with it. The money is not an issue, I'd go out and buy a 500W
inverter, but I want to get a small one so it is easy to use and move
around!!

Thanks again to all and hope to get to the bottom of this.

 

[micky]

What a lot of rubbish - don't confuse him.

HER..otherwise thanks!

 

[johnf]

Try again
VA is an AC power measurement
Watts is DC

 

[johnf]

Oops, sorry, don't have a camera on my PC

 

[Sarah]

Thanks Johnf. I am going to pick one up tomorrow an try it. I am just
confused because the laptop charger has 2 ratings on it, the AC and DC as I
mentioned. I am not sure which one to use to do the calculation. Here, you
guys are using the DC 12X4 but at the other newsgroup the guy is using the
AC 110X1.5!!!

I'll try one tomorrow and I hope that it won't damage my Laptop! Thanks
again.

 

[Sarah]

That's ok. It is my fault, I am using my account (Sarah) on my PC and my
husband's (Micky) in the same thread!!

 

[Ron Sommer]

Why do you want to buy an inverter?
The laptop charger is converting AC to DC.
The inverter would convert DC to AC.
The car is 12V DC.
Buy a cable and forget the charger and inverter.
Here is an example:
http://www.lindelectronics.com/cgi-...D!/cables/CBLIP-00229/dbx_gen_detail_product/

 

[johnf]

Sorry, I completely disagree.
The car provides roughly 12VDC when turned off.
When driving, the alternator pushes the battary up to at least 14.2V.
Without going into analysing the voltage input specification limits of the
PC to see what regulatory system system is built into it & what the MAXIMUM
SAFE limits are, I don't think using a lead DIRECTLY suppying the battery
voltage a very wise idea, as that can run up to 17% overload!
Stick with the inverter.

 

[R. McCarty]

I have a Car DC-AC converter. It's convenient, but the jumble of
cables can be pain. However, it is nice to be able to simply use the
normal AC/DC converter unit that comes with most things, especially
on long trips. My son took it and our portable Media player on a
trip out west. He and his friends got to listen to their favorite music
and never had to change/or charge a battery.
The unit also has another car lighter jack, so they plugged their cell
phone into it as well.

 

[johnf]

One is talking about the input voltage from the mains point (designed to be
plugged into a 110v~ powerpoint only, but slightly difficult to plug into a
cigarette socket; therefore completely irelevent).

The other is actually talking about the inverter's output voltage & current
supplied into the PC, (12/4) which is the important part as far as you're
concerned., ie., you need 12VDC out of the inverter with at least 4A
continuous capability. If it's 12V out, but a higher 'A' rating, that's no
problem, as the PC will only use as many amps as it needs at the time.

--

johnf

Thanks Johnf. I am going to pick one up tomorrow an try it. I am just
confused because the laptop charger has 2 ratings on it, the AC and DC
as I mentioned. I am not sure which one to use to do the calculation.
Here, you guys are using the DC 12X4 (fine, that's what you want)

but at the other newsgroup the guy is using the AC 110X1.5!!! -
(irrelevent!)

 

[David]

Try again
VA is an AC power measurement
Watts is DC

Arrgh... So much wrong information. VA is absolute RMS volts times absolute RMS amps. Watts is the of the real part of VA. This distinction is important for loads that have a non unity power factor which includes most computer power supplies. RMS = root mean square. For DC, VA equals Watts. For AC, not always true.

Regarding an inverter for the car. Get something over 100 VA and you should be fine. The larger units do not connect to the cig lighter outlet since it is usually fused at 20 amps.

David

 

[Ron Sommer]

Sarah stated that she had a M35.
Toshiba Satellite M35 is the only M35 that a search returned.
A battery for the M35 is 10.8 volts.
M35 chargers are listed as 15 volts.
Universal chargers can be adjusted to 15 - 24 Volts.

I am curious as to what laptop Sarah has and if the output is actually 12V
DC.