Any experts on DC-AC inverters? I need help please.

[Rob]

Hi, My first post in this newsgroup, I have been asking these questions in
various laptop/computer and the Dell computer forums but nobody has been
able to answer.

I need some advice on using an Inverter with my Dell 9100 Laptop. I have
discovered that a modified square wave inverter will damage my laptop power
adapter, so I had it replaced with a pure sine wave inverter, it is this
model,

http://www.powerbright.com/aps300.html - here is another link, but again,
its the same model..

http://www.samlexamerica.com/PDF Downloads/pst30s sine.pdf

I am using it on my 9100, but I have had my 9100 for 3 months and have only
used the inverter heavily for the last 7 days, during these 7 days, the
battery life in the laptop has dropped by about 25%, This is really
troubling me as it was consistent before this. Do you have any idea why this
might be?

I have had the inverter tested and it is outputting a nice sine wave on an
oscilliscope in the store I bought it from..

Also, is it normal for inverters to make cyclic humming sounds when used
with laptops? Mine seems to make a funny buzzing/humming sound every few
seconds, and the dell power supply hums in sync with it. Again, I took it
back to the store and they tested 3 other pure sine wave inverters and they
all made similar buzzing/humming sounds that seemed to cycle on and off, as
if the load was changing every few seconds.

I don't have any prior knowledge on inverters but have researched them a lot
on the internet, however I cannot find anyone or anywhere to answer these
questions, hopefully someone here can help.

Any advice appreciated.

Thank

Rob

 

[Dave M.]

It could be coincidental if the battery's capacity has diminished since you
started using the inverter, but if the inverters output is either low or is
sufficiently distorted, the voltage output of the laptops adapter could be
lower than the full charge voltage needed for the batteries. That cyclic
humming Might be the units output overload protection actuating due to
interaction with the power adapters inductive transformer, clipping the
output pulses (this is not a true sign wave inverter, rather poorly
synthesized). I'm really wondering about the quality of the inverter. You
can't use a cigarette lighter adapter, if it's in a vehicle? Anyway, I'd
look for a better unit with a better (clean) sign wave, if you must have one
of these.

Dave M.

 

[AC/DCdude17]

X-No-Archive: Yes

The typical laptop A/C adapter is more forgiving of poor power than
anything else. It's usually got a range of 100 to 240V A/C because it
has a switching power supply that can modify switching speed and duty
cycle to accmodate for this wide range.

How did you diagnose or who told you modified squarewave damages the
power adapter?

I've used a laptop on a cig lighter plug in 120W inverter and haven't
ever had a problem.

 

[Rob]

Thanks for the response, are there any brands you could recommend that have
a pure clean sine wave??

Thanks again

 

[Rob]

Yes, I had a previous laptop that ran for years on a mod sinewave inverter,
but when I tried the new Dell on it, the power adapter for the new laptop
died within a few minutes.

I should clarify, the power supply for this model has two circuits, one for
powering the laptop and one for charging it, the charging circuit failed
and I could not charge the laptop at all.

So I had the power adapter replaced and bought a pure sine wave adapter and
it works ok now except for the humming/buzzing. Incidentally, I emailed
the manufacturer and they replied with basically the same explanation as
Dave M.

Rob

 

[Rob]

Yes, I received a reply from the techs at the company who made my inverter
and they pretty much said the same thing, they said I needed a higher
capacity inverter (same price - clean swap)

I'll try it later this week when I pick it up. Thanks again for the
response and I have learned a lot this week!