Laptop power

I installed a 12v to 19v converter & wired up the plug to fit the laptop but I get the message "The Smart AC Adapter power output is too low for this computer".

I did the same thing on my last boat, it was an older lappy though, and it worked fine.

I then bought, off ebay, a cig lighter adapter specifically for my HP lappy & I still get the same message.

There is a centre pin in the plug, apart from the +ve & -ve, that senses the power requirements of the laptop & this won't let it charge.

Does anyone know how to make this work so I can run my 19V lappy from my 12V system??????

It's going to suck the power out of your battery no matter how you try to get around it, I cannot see how you can charge up a 19 volt battery with a 12 volt battery, as the 12 volt battery only has the 12 volts, you may have to get a second 12 volt battery, but then electricity is a funny thing so it's possible (even likely) that I'm wrong.

what wattage is your official power supply?

apparently you can make a standard 2 conductor power supply work by tying the 19V to the 'Smart Pin' with the appropriate resistors to give the correct voltage (which tells the laptop how much power is available from the supply). as you have found, if the 'Smart Pin' isn't sensing anything (or the wrong voltage) then the laptop won't be happy. have a look here (with the usual disclaimer about not messing with electrical stuff if you don't know what you are doing):

www.techspot.com/community/topics/smart-pin-voltage-to-capacity-correlation-for-laptop-power-supplies.178875/

Thanks for that ^^^ - this is exactly what I need

I think the wattage of the "official" power supply is 90W (I'll check when I get on the boat) & the 12v > 19V adapter is 152W 8A.

I'm definitely no "techy type" but I'll have a look in Jaycar & do some more researching & give it a go. I'll try putting a resistor (200k?) between +19V & the Smart pin to get the required Voltage. I'll measure what it is on the "official" power supply (13.5v?)

I don't really care if the laptop charges I just want it to run off the house batteries.



You're right HG - the best part of seabreeze is swapping ideas and knowledge.

Update.

I finally got around to doing this.

First I used my multi meter to read the voltage of the centre "smart" pin with the 240v charger running - was just over 18v. (Different brands have different voltage)

So, using the equation below, I bought the appropriate resistors (55c for a pack of 8) to get from 19V (Vin) to just over 18v (Vout) on the centre "smart" pin & wired them in as per the circuit diagram below. I am using a 12 > 19V converter from eBay to get the required 19v to the +ve side of the plug.

Worked like a charm!! I can now run my Laptop permanently with very little draw - would probably be a bit less if I removed the laptop battery but I'll leave it in case I want to take it out into the cockpit.

Thanks heaps fishmonkey for your post - I'd just about given up!!

How good is the "brains trust" here!!!!!!!!!!!!!!!!!