Any experiences with power inverters?

mkoprulu · Post by **mkoprulu** » Mon Apr 18, 2005 11:38 am

This one is an odd question really... Has any of you tried to stick a power inverter to the ciggie lighter socket to plug in any electrical device (tv, laptop, etc) that works with mains?

I bought a cheapo inverter from Hong kong, and i tried my laptop with it... The moment you stick it in, there's a horrible ticking sound coming somewhere from the inside of the dash (maybe from the fuses in the engine comp.) and it's not charging/powering the laptop.

I think it is the inverter being faulty, because i tried the power box which i keep for emergencies (the one that charges off the mains and is used to charge the battery if you run it empty). The power box has two cigarette lighter sockets to enable it to supply electricity, and i tried to use the inverter with it, and the lights on the power box (which is capable to charge the car battery!!) have gone out. It was ok when i plugged the inverter out, but went off again when i plugged it back in.

I'm planning to get an inverter from argos and test with it, then return if it works to make sure it's not the car's or my power box's fault...

Any ideas?

What would be the danger of that ticking sound that i heard? If i burn any fuses, can i find replacements? They are the old type fuses from BC 1000 or so...

mkoprulu · Post by **mkoprulu** » Mon Apr 18, 2005 12:02 pm

oopps, just found my own answers from maplin's site.

here is a copy/paste from faqs

"Q: I am looking to run a Toshiba Portege 4010 from the car. The charger indicates it requires a 100-240v 1.2Amp input, with a 15volt 3Amp output. Does this mean I could use the 150W inverter (Jamie: 15/07/2004 )
A: No, as you work out the wattage by the following - Voltage X Amps = Watts - the input of the adaptor is 240v X 1.2A = 288Watts

An inverter is typically 80% efficient, this means that 20% of the 12v power is wasted in the conversion loss. So If you want to calculate the battery power used you just divide the 240v mains power requirements by 0.8 . If you were to consume 150w on the mains side this would equate to 187.5 watts on the 12v side (remember 80% efficiency). This would mean that there would be a little over 15 amps @ 12 volts as you have suggested."

therefore:

My laptop charger requires: 110-240 @ 1.5amp

which makes 240*1.5 = 360watt requirement

add the inverter loss: 360/0.8 = 450w needed!

so my 250w is totally out of question...

time for some more cheap inverter hunting then

Tahrey1043 · Post by **Tahrey1043** » Mon Apr 18, 2005 5:48 pm

besides the ciggy sockets on old cars were made for that purpose alone, and no intention of having power-draining equipment plugged in - it's quite likely it just can't take the strain, as the design wattage is probably a lot closer to 25 than 250...

personally i never dared plug anything more potent than a 6v adaptor for a mobile phone or MD player in

GroovyCarrot · Post by **GroovyCarrot** » Mon Apr 18, 2005 6:17 pm

My lighter socket is no longer capable of even powering a lighter. Tried to light a cigarrette for a friend the other day, the most I could get the thing was luke warm.. years of neglect and a decidedly dodgy (and part burnt out

) behind dash wiring loom seem to have finished it off.

mkoprulu · Post by **mkoprulu** » Mon Apr 18, 2005 8:03 pm

I won a proper inverter today rated 600w and it can be plugged directly to the battery using croc clips, so i'm hoping that it will work this time.

Groovy, did you try holding the lighter in with your finger even after it bounces back thinking it's heated up? I used to do the same on my dad's car which worked. Just make sure you don't hold it more than like 20 seconds or so, or you might start melting the car

Tahrey1043 · Post by **Tahrey1043** » Mon Apr 18, 2005 8:32 pm

well like i say, only 25 watts

thats why it takes such a tiny bit of resistance wire so long to get up to about 475 farenheit...

a 600watt inverter that clips right on the battery! What in the world are you going to run off of that? a microwave? there's little else other than a lighting / AV rig that would draw so much..... (having an outdoors party? right on...)
make sure you have the engine on and revved up a little past idle, and the alternator is working right!

Young_Un · Post by **Young_Un** » Mon Apr 18, 2005 9:08 pm

Power = Current x Voltage

So, depending on your alternator rating you might get away with it:

60A alternator power = 60 x 12 = 720W

55A alternator power = 55 x 12 = 660W (getting dodgy if you've got lights on, will still work - but you'll start to drain the battery)

45A alternator power = 45 x 12 = 540W (will probably work, but definately drain the battery)

This assumes 100% efficiency of the inverter though... But, having said that - you reckoned on 360W from the laptop and around 450W taking losses into account - so you should be okay as long as the laptop is the only device plugged in to the inverter.

GroovyCarrot · Post by **GroovyCarrot** » Mon Apr 18, 2005 10:27 pm

mkoprulu wrote:Groovy, did you try holding the lighter in with your finger even after it bounces back thinking it's heated up? I used to do the same on my dad's car which worked. Just make sure you don't hold it more than like 20 seconds or so, or you might start melting the car

Yep, my lighter's clips don't hold it in anyway so I was sitting there holding it in for ages. There's obviously some current getting through as I got it warm enough to light the cigarrette in the end, but certainly it's not behaving like it should

Dashboard rewiring time! What fun

mkoprulu · Post by **mkoprulu** » Tue Apr 19, 2005 9:40 am

Tahrey1043 wrote:well like i say, only 25 watts

thats why it takes such a tiny bit of resistance wire so long to get up to about 475 farenheit...

a 600watt inverter that clips right on the battery! What in the world are you going to run off of that? a microwave? there's little else other than a lighting / AV rig that would draw so much..... (having an outdoors party? right on...)
make sure you have the engine on and revved up a little past idle, and the alternator is working right!

no mate, just my laptop

As far as the calculations go, i need that sort of power apparently... I hope it works this time, because i'll be going on a holiday to lake district and it will be my first time there, so i don't want to get lost (gonna use a gps mouse with it)

GroovyCarrot · Post by **GroovyCarrot** » Tue Apr 19, 2005 11:57 am

Ever tried a road map?

Honestly though, the lake district is one of those places that it actually pays to get lost and end up on some winding little back road into the middle of nowhere, it's a lovely area, explore it

mkoprulu · Post by **mkoprulu** » Tue Apr 19, 2005 1:46 pm

a road map??? are you kidding mate? I don't want to spend money on a road map, they are just too expensive

First aim is to get to our destination though, because i don't think we can afford losing the track after 6+ hours of travel with our hyperactive dog in the little polo

We'll have plenty of time to get lost with intention later on.

Tahrey1043 · Post by **Tahrey1043** » Tue Apr 19, 2005 7:54 pm

hold on, they've got their maths cocked up. that theoretical inverter is supplying more power to the laptop plugged into it than it's draining from the car's electrical supply! it's a perpetual motion device!

and........ ... HOW much power rating, for a laptop? That's about as much power as my old 486 desktop used to use! That really can't be right - there's no way even the most advanced laptop battery could power the machine for more than a couple of minutes at that load.

E.g. typical 3600mAh, 15v lithium ion thingamajig... that's 54 watts constant drain for one hour, then it's dead. 27w average if you have a typical big-laptop 2 hour lifespan.

until you came up with those figures, i was considering getting a small inverter just to run a laptop from (mind you i'm thinking of my pentium-75, 10 inch screen ultralight jobbie..). ouch. maybe not then.

and dont some polos have 36A alternators?

(whats the total drain of all the lights and a midrange stereo turned on together, again? say you have fogs and driving lights too... 7x60.... ah, ok, thats 420 before we even start, and assuming you havent held the flasher control on to light both the dips and main beams.. 36A (432w) might be a bit optimistic in that case.. perhaps for the base, 45w main beam, no fogs/driving lamps, crap/no stereo models)

remember that they wont be at their peak output until around 3000rpm - but, at the same time, that they put out 14.4V not 12.0V

er, anyway.

1. GPS mouse?
2. Phillips Large-Scale Drivers' Road Map of Britain. Life saver, that thing. I just badly need to update mine, now, as it only has the m6 toll as a dashed blue line... and the anglesey part of the A55 as a yellow one.
3. wales is equally good for random laneage. before you know it...... snowdon! or a big valley with a huge lake in it. and its getting dark, and you dont know how to get home.

amstrange1 · Post by **amstrange1** » Tue Apr 19, 2005 8:37 pm

Right, just looked at the power rating on my Dell laptop's charger - it suggests a constant power drain of 70W when the laptop is relying totally on it for its power. It also says up to 1.5A peak @ 240v, which means an instantaneous power of 360W - but that's not the mean power drawn - the fact that we're dealing with AC, as well as the 1.5A being a peak current makes the 70W mean power consumption what we're interested in.

If we're talking Mk2 Polos, alternators are 45A; 55A and 65A. Voltage regulators on the alternator mean dependant on engine revs you might see up to 14.4v - but under load this drops to a value approaching 12-13v depending upon a multitude of different factors. Using 12v as our voltage (after all this is the voltage the alternators current ratings are given at), a 45A alternator can deliver up to 540W.

Let's say you have full beam on - 2 x 55W = 110W, a combination of taillights, and brakelights = 84W (assuming 21W bulbs) gives us 340W to play with, knock off a couple of hundred watts for other bits and pieces and you've still got 140W left to power a laptop. The invertor could only be 50% efficient and still power the laptop fine.

Just my 2p.

Tahrey1043 · Post by **Tahrey1043** » Tue Apr 19, 2005 8:50 pm

right, that's it, you're doing my physics homework for me tonight. oi, get the hell back in here! there's cold beers in the fridge for the asking and as many pringles as you can chow, plus a cabinet literally bursting with videos for after yer done. plus you can order up the fantasy channel on telewest cable using our pin if you like.

it's LRC circuits and is doing my bonce in

mkoprulu · Post by **mkoprulu** » Wed Apr 20, 2005 9:51 am

Tahrey1043 wrote:

er, anyway.

1. GPS mouse?
2. Phillips Large-Scale Drivers' Road Map of Britain. Life saver, that thing. I just badly need to update mine, now, as it only has the m6 toll as a dashed blue line... and the anglesey part of the A55 as a yellow one.
3. wales is equally good for random laneage. before you know it...... snowdon! or a big valley with a huge lake in it. and its getting dark, and you dont know how to get home.

You're confusing my already weak electrical skills... I have no idea about the alternator/battery/lights power drainage thingy. What i thought was when you plug an inverter into the lighter socket/battery, it drains only what the typical lighter would drain right? Anyway, the whole purpose of the inverter is to convert the 12v dc electricity from the battery to 240v ac so that the house plugs can be replicated in the car right?

1- GPS mouse is the cheap solution to the homemade gps system. Just a matchbox sized gps receiver unit with usb cable really. Search on ebay for it.

2- I use autoroute 2005 at the mo. But i'm thinking of trying mappoint as well because autoroute doesn't give any voice or graphical directions. I found a nice program for mappoint which is called AGPS for Mappoint, an add-on that gives you voice directions...

3- my next heading could be wales then!