Power inverter.. Please help

fplowman

Need an inverter. Is a pure sinwave inverter neccessary to run a laptop wihtout any strange electronic anomolies? Can Dave or someone here with experience on this please help me decide on my purchase?

The cost difference in a sinewave and non sinewave is tremendous
 
Just saw a 200 watt inverter at Costco for $25. It had two A/C outlets, and an LED readout that indicates how many watts you are drawing and the car battery voltage.

I'm not sure about needing a pure sine wave. I have used relatively cheap inverters before without a problem.
 
I have used several different types and have had no proplems with any of them. get at least a 300 watt with a cooling fan built in. I am currently usein a coleman 400 watt unit I got at big lots for about $40 :D
 
Laptops use switching power supplies. These things actually like square wave input. The more jagged, the better.

The "modified sine wave"
[Broken External Image]:http://members.cox.net/geonerd/images/sine.jpg
produced by most inverters is slightly less favorable, but still perfectly safe/effective.

The only way you'll hurt your laptop is if the inverter's output voltage sinks too low. (This will happen if the 12v supply sags. To compensate for the reduced V, the laptop's P/S will draw more and more current, eventually triggering a meltdown.) Get an inverter that automaticaly shuts off off when battery V drops to a threshold level.

FWIW, I've run several laptops off an extra battery and cheapo 120VAC inverter for hours at a time (an astonomy sky atlas program) w/o issues.

-Greg
 
If the power from the AC side started dipping down, wouldn't the laptops internal battery start taking over and pickup where needed? I have noticed that happen when were were running LOTS of stuff off the inverter, that it just switched to battery when needed.
 
Yea, that would be a good design aspect. I hadn't even thought of that. :| My old (P-90 ) Compaq won't even touch the batteries (other than to charge them) when on any form of external power. :?

Modern units like yours should be a bit brighter. Once the laptop's supply folds to a certain point, the batteries kick in. If the system is well designed, this will occur before the P/S fries itself trying to choke down the 70 (or whatever) VAC that is coming from the inverter.

-GRC
 
not to hijack the tread too bad but where is a good place to buy new laptop batteries? mine wont last 30 minutes unplugged after being plugged in for a long time. i think part of the problem is this is my primary computer and i left the battery in with the power cord attached. i know batteris like to be run down and recharged and this one definatley wasnt treated like that. It's a Dell inspiron 2600. Sure i can go to dell, just wondring if anywhere else is cheaper. (not ebay, wouldnt want to get a batt thats actually worse then the one I have now)
 
Originally posted by Blake Michaleski
not to hijack the tread too bad but where is a good place to buy new laptop batteries? mine wont last 30 minutes unplugged after being plugged in for a long time. i think part of the problem is this is my primary computer and i left the battery in with the power cord attached. i know batteris like to be run down and recharged and this one definatley wasnt treated like that. It's a Dell inspiron 2600. Sure i can go to dell, just wondring if anywhere else is cheaper. (not ebay, wouldnt want to get a batt thats actually worse then the one I have now)

I know you said you didn't want Ebay, but I wanted to tell you about these guys:

http://stores.ebay.com/Battery-Inc

I have bought several different kinds of batteries and so far so good. I got one of those all day camcorder batteries from them for my Sony that looks and functions IDENTICAL to the factory battery (I am betting made in the same place) for 1/3 the cost.
 
i dont mind ebay if they are brand new. thanks for the heads up.

We're leaving SJT shortly for MOB. Sorry I didnt have a chance to catch up with you and Graham.
 
With similar concerns in mind, I threw the output from my regular laptop supply onto an oscilloscope to see what kind of crap might be on there; in my case it was pretty clean, even when attempts were made to introduce noise from the vehicle (lights on/off, AC, revving engine etc.). I was using a 400W inverter for the test.

Having said that, in the end I ended up buying a universal laptop supply from APC that plugs right into the 12v source.... a bit less cumbersome than the inverter/power supply combo.
 
Bought my 300 watt with cooling fan and 2 outlets for $30 at STAPLES... WHo would have thought Staples.....I was on a Chase and needed one asap,,,, Staples had plenty..and there are plenty of Staples
 
yeah ok .. read your postafter purchasing a 150 watter sima from microcenter at 34.95 :(
 
I upgraded my inverter this year from a 300W to 750W with cooling fan, $70 at Home Depot. I found a main bus wire under the dash (fuse protected under the hood) and wired directly to that with 8 gauge wire. I use a surge-protected power strip to plug the laptop into, no problems.

Direct-wiring the inverter to the battery or a main power feed will greatly help performance. My new vehicle's stock wiring (cigarette outlets) was causing major undervoltage problems when running the laptop through both the 300w and 750w inverters. Now the inverter will run everything with no undervoltage alarms, even when the engine is off.
 
Back
Top