Charging Laptop Computer

[SailDan]

Situation:
Have 1-year-old Dell 5100 laptop computer which we intend to use on the C-34 next summer.  Also planning to replace my old 1994 vintage Heart 2000 Inverter / Xantrex  with a new one this spring (Old "black box" gave up ghost last fall).  

Assumption:
Can use the boat's inverter to charge computer when we lack access to shore-power, e.g. at anchor or sailing.

Quickie Test Results :
Since I can't test it on the boat until I install the new inverter, I decided to do a quick "test" last week by purchasing a small 75W inverter (modified square wave) designed for use in an automobile at Kmart ($17 "el cheapo") .  Plugged the inverter into the Jeep's dash-accessory outlet and then attached the lap-top's AC adapter (transformer).  It seemed to work but the indicator light on the on the lap-top's adapter seemed to cycle (dim-bright-dim-bright-... etc).  Also when the computer was turned on, the LCD screen also cycled (dim-bright- etc).

Question :
Charger / AC adapter that comes with the laptop uses 120 VAC, 60 cycle and outputs 20V, 4.5A.   House current is "true" sine wave.  I understand the standard Heart 2000 output is a "modified" sine wave (square shouldered).  Some electronics don't like this (e.g. digital clocks). Bottom line...Will this work on the computer? (I know Xantrex makes an inverter which outputs a true sine wave but its costs $$$$$!).

Any thoughts / experience?

[Ray & Sandy Erps]

Hello Dan,

Isn't it just nutty that laptops aren't designed to run directly off 12 volts?  We run our laptop off a cheap 400 watt inverter that we bought at Costco.  My brother-in-law runs his laptop off a little 75 watt inverter that is palm sized.  So far-so good.  Neither of us have experience the dimming problem you described however.  Does the dimming only occur when it's on the inverter?  I took a small 13 inch T.V. down to the boat one day to see if that would run on our inverter.  I had heard that the square sine wave can create "noise" in some electronic devices.  It ran the T.V. fine too, for the short time period of the test.  

I see that you mentioned that your transformer's output was 20 volts at 4.5 amps.  That's over 75 watts, so maybe the test inverter just wasn't up to the job and you'll be fine with the bigger inverter.

[Philip Imhof]

I have the same laptop from dell, and we use it out on the boat also. You can't get a 12 volt adapter from dell as they don't sell any for the 5100's. I have a small inverter, but it is not of sufficient wattage to charge it up after a complete discharge. The inverter will click off after a few seconds. A 400 watt inverter should do the trick without a problem.

[Jim Price]

I am not an expert but my experience with my Dell 9100 (which requires a 150W supply and only Dell makes that converter) was that it is very important to not use REDUCED power supplies or you can do damage to the recharging circuits in the laptop battery and kill the battery.  The major power needs are the screens and video devices.  That is why if you have less than wattage the screen will dim, and according to Dell, that ain't good.  Be safe and overkill.  Laptop batteries ain't cheap either and when dead only AC will work and that is hard to find off shore.  

[Ron Hill]

Dan : Think that you might be getting things mixed up.  
Your laptop runs off of  DC all of the time whether you are plugged into 110vAC or have a 12vDC cigarette lighter adapter.  All that the plug in's do is give a DC charge to the laptops DC battery!!

I have an Dell Inspiron 4150 and bought the 12v Air/Auto adapter and use that all of the time.  
I wrote this up somewhere a couple of years ago:  
I had trouble with the 12v adapter which seemed to be cutting in and out while plugged in so I called the LIND Company that made it in Minneapolis and complained.  When I told them I was on a boat, he said "it cuts in and out doesn't it!"  I was surprised to say the least!  He told me I had the wrong 12v adapter which was set for 12-16 volts and when the voltage drops below 12v it cuts on/off.  If I would send that adapter back to them they'd swap it out for a 12v adapter with a range of 10-16 volts.  Did that and I've not had a problem since.  It works GREAT!

If you have an accessory like a 110v printer, that's when the 110vAC sine/modified sine wave is important!!  I have an HP450 and use a Zantrax 125w plug in inverter and the printer operates just fine!!  

[Jim Price]

You know, Ron is right.  I totally forgot about the Air/Auto adapters as I never use the laptop in a car and most planes I fly don't yet have the power receptacles.  The Air/Auto would be the way to go.  May have get one myself of the boat now....

[SailDan]

Thanks for the insights and suggestions.  

You got me to thinking. In retrospect, I suspect my simple "quickie test" with the 75W inverter was faulty -- Laptops adapter output was 20V x 4.5A= 90 Watts! Erps was right... makes sense. I suspect that the 75W inverter was kicking in-and-out giving rise to the dim-bright-dim-bright response.  The use of at least a 400W on the boat per you-all's recommendation will probably work. In the mean time, I may just try a second experiment with a 150W "Kmart special"; if the original results were due to insufficient Watts, it should work.
DH

[SailDan]

Oops,
Apology required ...Wrote my above reply before I had read Ron's response and comments about the Air/Auto 10-16V adapters.  

Ron, I did understand that the Laptop runs off 12V DC all the time and that the Laps-top's adapter just charges the Lap-top's battery. However, thanks for reminding us.

Ron, 2 related follow-up questions :

(1) Air/Auto inverted - Is the Wattage output of the inverter important or is it just the drop in voltage? I assume Watts is also important since the the tag on the 120V adapter that came with my Dell 5100 lists an output of 20V, 4.5A, thus 90W.

(2) HP Inkjet 450ci Mobile printer - I just purchased one of these from CDW (http://www.cdw.com/shop/products/default.aspx?EDC=425596) for use on the boat.  It runs off a "lithium ion battery" as well as 120V adapter.  The adapter charges the battery which is attached to the back of the printer (just like the Laptop). I get the impression from your response that you need a different inverter for your 110V HP450 (not battery operated?).  Does the Zantrax 125W plug-in inverter you purchased for the printer produce a true sine wave?

[Ron Hill]

Dan - On your questions:
1. Air/Auto inverted - Don't know what inverted means??  On my DC adapter it says "Output 20V 3.5A".
2. My HP Deskkjet 450   I thought I'd try it without the HP DC adapter or the printer battery pack first, before I bought those expensive accessories.  I found that the HP450  preformed perfectly when the AC adapter is plugged into the Zantrax inverter.  Looking at the printers AC plug in, I'll guess that it probably operates off of DC.  It's input is very tolerant  100 - 240V ~1.5A  50-60Hz.  The output is 19V --- 3.16A LPS.  I'm sure that my inverter is a MSW, because of the price!  It may even be a 175 rather than a 125 - can't remember.

As far as a true sine or modified sine wave inverter - don't think it makes much difference if the AC items that you plug in operate off of converted DC.  
With the Blue tooth card I don't need a cable connector between the laptop and the printer.  
A few thoughts.  

[SailDan]

Thanks for information Ron.  You answered my question.

[Ray & Sandy Erps]

I think the car/air converters are more expensive than a medium sized inverter and the inverter has the added benefit of running other small appliances, so it serves more than one function.

[Ron Hill]

Ray : You're absolutely right on the small inverter cost and the fact it can run other small AC equipment.  However, the inverter takes power to operate, whereas the DC adapter doesn't.  
It's a trade off - your choice!!  

[Ted Pounds]

Ron,

"The Dc adapter doesn't" require power to operate???  Are we talking free energy here?  This may be the solution the world is looking for.