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Power Inverters

G

Guest

Jan 1, 1970
0
We're looking for a power inverter to recharge our Compaq notebook
in the car. Is it better to buy one with a larger rating (400W) rather than
a smaller one? Black & Decker has a 100W model ($13) and it gets
decent reviews:

http://tinyurl.com/5fstl9

But the notebook uses ~90W, so we'll be very close to this inverter's
capacity. The alternative is something larger, e.g.

http://tinyurl.com/6nfbrp

This one's 400W, but we're wondering if the extra cost is worth it.

Thanks for any advice/opinions/info.
 
F

f825_677

Jan 1, 1970
0
We're looking for a power inverter to recharge our Compaq notebook
in the car. Is it better to buy one with a larger rating (400W) rather than
a smaller one? Black & Decker has a 100W model ($13) and it gets
decent reviews:

http://tinyurl.com/5fstl9

But the notebook uses ~90W, so we'll be very close to this inverter's
capacity. The alternative is something larger, e.g.

http://tinyurl.com/6nfbrp

This one's 400W, but we're wondering if the extra cost is worth it.

Thanks for any advice/opinions/info.
As a thought - what is the DC requirements of the Laptop ? - it might
not be necessary to go up to mains voltage and then back down.

If it is - what other use might you want from the inverter ?

The 90W the notebook needs, is this its DC loading on its own charger or
the chargers loading on the mains ?
 
G

Guest

Jan 1, 1970
0
f825_677 said:
As a thought - what is the DC requirements of the Laptop ? - it might
not be necessary to go up to mains voltage and then back down.

The notebook's AC adapter has these specs:

Input: 100-240V
Output: 18.5V 3.5A

Which, now that I've actually looked, is ~65W not 90W.
If it is - what other use might you want from the inverter ?
None.

The 90W the notebook needs, is this its DC loading on its own charger or
the chargers loading on the mains ?

65W is the DC loading on its own charger.
 
We're looking for a power inverter to recharge our Compaq notebook
in the car. Is it better to buy one with a larger rating (400W) rather than
a smaller one? Black & Decker has a 100W model ($13) and it gets
decent reviews:

http://tinyurl.com/5fstl9

But the notebook uses ~90W, so we'll be very close to this inverter's
capacity. The alternative is something larger, e.g.

http://tinyurl.com/6nfbrp

This one's 400W, but we're wondering if the extra cost is worth it.

Thanks for any advice/opinions/info.

The most efficient option is to get a DC-DC converterthat changes 12
volts from the car to the 19 volts the laptop needs.

These are available for under $60US.

John
 

neon

Oct 21, 2006
1,325
Joined
Oct 21, 2006
Messages
1,325
90w is very close to the rating of the unit and it should be ok. However there are unknows to consider like temperature rise with prolong usage. doing work at 75 degrees is not the same as 120 degrees and car do get that high with windows closed just sitting there my advise is 200w or 400wmore then that is just waist.
 
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Sjouke Burry

Jan 1, 1970
0
Dave said:
Makes you wonder just how all the various computers in the modern car
survive...
Fat wires directly to the battery has always served me
well in a number of instrumented cars.
Only one accident with a blown regulator in a generator,
suddenly about 100 volt instead of 12 volt.
That was over a period of 40 years.
The battery works like a rather big capacitor. :)
 
C

Clint Sharp

Jan 1, 1970
0
Claude said:
Cheap inverters put out a modified sign wave that looks more like a
stepped pyramid than a sing wave. Not good for electronics and
transformers.
Cheap UPS devices designed to run servers and PCs only put out a
modified sine wave, they seem to cope fine.

About the only symptom I've ever seen from using devices on inverters
in my cars is that they generate a little more noise than they normally
would when under load. Other than that, nothing. All of my laptops have
been run in the car on inverters but I'd have to agree with another
poster, the most efficient way to do this is with a DC to DC converter.
 
I

IanM

Jan 1, 1970
0
Clint said:
Cheap UPS devices designed to run servers and PCs only put out a
modified sine wave, they seem to cope fine.

About the only symptom I've ever seen from using devices on inverters
in my cars is that they generate a little more noise than they normally
would when under load. Other than that, nothing. All of my laptops have
been run in the car on inverters but I'd have to agree with another
poster, the most efficient way to do this is with a DC to DC converter.

If the equipment the inverter is running contains a typical switched
mode power supply with a bridge rectifier or voltage doubler input
circuit, it is almost certainly under less stress running from a
so-called modified sine source than it is from the power line. The peak
voltage is designed to be the same, but as the waveform is basically
flat topped, the peak input current is reduced and the input diodes and
resevoir caps will run a little cooler!
 
S

Sjouke Burry

Jan 1, 1970
0
Dave said:
To get 100 volts you'd need not only a faulty regulator but a faulty or
disconnected battery. Turning the average alternator hard on only usually
results in the high teens volts wise. Although I've no idea what happens
with some of these modern ultra high powered water cooled types. ;-)
At those heavy overloads the battery will form a gas layer
between electrolyte and electrode.
That gas layer will act as high resistance(for a short time),
long enough to explode the caps in a number of convertors.
After servicing about 12 supplies and an assorted 10 opamps,
we were back in bizness.
The generator survived.
The battery as well.
The regulator needed two transistors and a new zener diode.
But spikes as mentioned? Never a problem.
 
J

jakdedert

Jan 1, 1970
0
Clint said:
Cheap UPS devices designed to run servers and PCs only put out a
modified sine wave, they seem to cope fine.

About the only symptom I've ever seen from using devices on inverters
in my cars is that they generate a little more noise than they normally
would when under load. Other than that, nothing. All of my laptops have
been run in the car on inverters but I'd have to agree with another
poster, the most efficient way to do this is with a DC to DC converter.

Certainly more efficient; but I change laptops too often to buy a
dedicated 12v supply every time. The 110 inverter works for me; but I
'have' seen universal models. My Dell laptop is sensitive to power
supplies, though. The cheap Targus unit that came with it will run the
computer, but won't charge the battery (one of the reasons I got it so
cheap).

jak
 
C

Clint Sharp

Jan 1, 1970
0
jakdedert said:
Certainly more efficient; but I change laptops too often to buy a
dedicated 12v supply every time.
There are universal 12v adapters just as there are universal AC
adapters.
The 110 inverter works for me; but I 'have' seen universal models. My
Dell laptop is sensitive to power supplies, though.
Some of the Dell laptops can positively identify a genuine Dell PSU and
won't charge if it isn't genuine. Dell put a silicon serial number IC
inside the PSU which the laptop can read.
The cheap Targus unit that came with it will run the computer, but
won't charge the battery (one of the reasons I got it so cheap).
It's fairly simple to add the serial number if you can find a defunct
PSU (although a major reason for Dell adapters being faulty is that the
serial number chip dies!) but genuine AC adaptors are pretty cheap on
eBay.
 
C

Clint Sharp

Jan 1, 1970
0
Michael A. said:
The DC to DC converter is nothing more than the inverter & switching
power supply in the same case. The incoming DC is chopped, stepped up,
and regulated to the required voltage.
It's just a boost converter, there's no separate 'step up' stage
followed by a regulator. Can be done with a single IC but most of the
ones I've seen have been based on the MC34063 controlling a high current
MOSFET switch driving a toroid.
 
G

Guest

Jan 1, 1970
0
Michael A. Terrell said:
The DC to DC converter is nothing more than the inverter & switching
power supply in the same case. The incoming DC is chopped, stepped up,
and regulated to the required voltage.

Thanks all for the info and advice.

Any recs for a specific make/model# would be greatly appreciated.
 
J

jakdedert

Jan 1, 1970
0
Clint said:
There are universal 12v adapters just as there are universal AC adapters.

Some of the Dell laptops can positively identify a genuine Dell PSU and
won't charge if it isn't genuine. Dell put a silicon serial number IC
inside the PSU which the laptop can read.

It's fairly simple to add the serial number if you can find a defunct
PSU (although a major reason for Dell adapters being faulty is that the
serial number chip dies!) but genuine AC adaptors are pretty cheap on eBay.
The reason this was such a great deal was that I already 'had' a genuine
supply for it. I once had a surplus of Dell bricks, but I've gone
through a few, since. I could use another 90 watt supply for my D400
docking bay. If you boot it with the original 70 watt unit, the laptop
knows. You get a message in POST that tells you it knows...and it won't
boot the docking bay.

jak
 
D

David Lesher

Jan 1, 1970
0
Clint Sharp said:
Some of the Dell laptops can positively identify a genuine Dell PSU and
won't charge if it isn't genuine. Dell put a silicon serial number IC
inside the PSU which the laptop can read.

I thought Dell had stopped this BS [along with nonsense such as
non-standard desktop power supply pinout], but in any case it's a reason
to avoid Dell....

It's fairly simple to add the serial number if you can find a defunct
PSU (although a major reason for Dell adapters being faulty is that the
serial number chip dies!) but genuine AC adaptors are pretty cheap on
eBay.

How do you do this?
 
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