Inverters

[maddie]

I've fitted a 300W inverter onboard MADDIE to power a laptop, but it seems to take a high amperage from the battery. I'm not clever enough to work out the sums, so can anyone tell me what the current drain might be? The boat batteries are 12 volt, and the Compaq takes 220 volts AC from the inverter, though it's own inverter (?) to give the laptop a DC input of 18 volts. Any help gratefuly received.



<hr width=100% size=1>Fabian

 

[charles_reed]

Between 26 and 31 amps, probably 45 on start-up.

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[tr7v8]

Your numbers seem a bit high to me, they'd be OK if he's taking the full 300watts.
I'd reckon the Compaq takes 3.5A at 18V =63Watts Reckon 80% conversion efficiency for PSU and inverter gives a nadge under a 100Watts so around 8-9amps. Agree start up current will be probably a huge increase in that say 2-3 times. I've heard of people struggling to get these to work on 150Watt inverters.

<hr width=100% size=1>Jim

Draco 2500

 

[andyball]

We have a 150W inverter powering a Dell laptop, no trouble at all. dell psu is marked 80-120W if I remember rightly.

It runs off a 10Amp breaker in the switchbox which has never tripped yet.

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[maddie]

Thanks to all for the info. That would explain why a 10 amp fuse keeps blowing. it's a high price to pay for a laptop, which I want to run for my chart software. Do any of you have experience of the Targus DC to DC converter? It claims to take only 3.5 amps, which is a little better on the battery.


<hr width=100% size=1>Fabian

 

[mike_pk_waters]

Use the Targus DC to DC almost every day on my Compaq in the car, absolutly great. Its the best bet in my opinion.

<hr width=100% size=1>Its small but its paid for

 

[tr7v8]

Its probably the start up current is the issue a good site is
<A target="_blank" HREF=http://www.mobilityelectronics.com>http://www.mobilityelectronics.com</A> not used them and no connection.



<hr width=100% size=1>Jim

Draco 2500

 

[bedouin]

Inverters tend to be about 90% efficient, DC-DC converters are probably slightly more efficient, but either way the current drain on the battery will be the roughly the same.

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[snowleopard]

you jest!!!

my 300 watt inverter draws 3amps when powering my laptop. the laptop is rated at 2.5amps at 18 volts. the inverter is pretty inefficient, it still draws close to 3 amps with no load.

incidentally the 220vac-18vdc converter supplied with the laptop is not an inverter, it's just a transformer/rectifier. you only need the inverter when going from dc to ac.

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[maddie]

Re: you jest!!!

Snowleopard,
I presume you use the transformer/rectifier (se, I'm learning all the time!) in the line to run your laptop? 3 amps is not too bad.
Maddie

<hr width=100% size=1>Fabian

 

[snowleopard]

Re: you jest!!!

correct, the connection sequence is:

battery

12v / 3a

inverter

220v / 0.15a

laptop's power pack

18v / 2a

laptop

important note: when not using/charging the laptop, cut off the power to the inverter as it will still be drawing close to 3a and also pushing out 220v which has been known to kill yachties with wet hands!

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[tr7v8]

Re: you jest!!!

Err, Snowleopard not wishing to be picky here but that means we've put 36W in and we are getting 36W out which equals 100% efficiency.......I suspect not!



<hr width=100% size=1>Jim

Draco 2500

 

[qsiv]

In recent times Dell have increased their power supplies to 90W - the earlier ones were (if I remember correctly) 70W. You can however run new laptops on old PSU's - but they run on the 'battery' profile rather than the 'AC' profile.

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[charles_reed]

I jest not

volts x amps = watts

Therefore 300/12 = 25amps

Of course if you decide to draw only a small proportion of the load your pull will be less.

My 150 watt inverter driving the laptop was (until I changed it) tripping the 10 amp trip on the socket.

Input on the charger is 1.5 @ 100-240, output 3.5 @ 20 volts.

If you connect up with fully discharged batteries in your laptop you'll see a different picture to the one you paint.

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[saturn]

my invertor pulls 0.3 amp off load and 3.5 amps when running my laptop(gateway 2000).

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