laptop power supply

[little col]

i am off on holiday later this year to a dark site but was wondering if it is possible to run my laptop off my power pack i have for the heq5 mount , the power pack is 12 volt but i can step down to 6v/3v and 1.5v

[Photon]

Hi There,
Laptops are different and range from 15/16/18/19/20/22 or 24 volts, so you will need to consult your manual or read the required voltage imprinted on your laptop power supply unit. I recently purchased an Automotive Notebook supply (Jaycar, 6 Amp version) which is settable to any of those voltages mentioned, in my case 19volts. The unit is a step up power converter ie converts 12 volts to the higher voltage. It works really well and cost $48.
Regards IanG

[KG8]

If you have a second battery, which is wise I think if you want to run power-hungry accessories, then you could pick up one of the new generation power inverters from dicksmith that will take 12V to 240V. Then run your standard laptop arrangement off that. I realize there are power losses in this arrangement but they are not "huge" and will be assured of getting the right voltage to your expensive laptop. Up at our astrocamp we regularly run electric blankets off inverters, with timers, to warm our beds for a few hours as we go to sleep. It's all a matter of battery capacity.
A supercheap 70Ah 4*4/marine battery will set you back $120 and an inverter about the same.

[sculptor]

Watch how you use a 240V inverter in a dripping wet paddock at 3 in the morning. Even with a high quality isolation transformer, I'd be rather nervous.

I use two laptops, one to drive the scope and autoguider and work the camera shutter, and one to do real time image analysis. Each uses a 40 AH deep cycle gel battery and one of those JayCar 12V-to-anything converters that Photon mentioned. One of the batteries also works the mount, and the other works the dew heater, but the laptops are the main guzzlers.

The 40 AH battery will drop from 13 volts to 12.5 over about 3 hours. Although its very nonlinear and temperature dependent, at laptop load, a 0.5 volt drop would represent roughly 60% charge still left. Don't like taking them flatter than 50% (about 12 volts) because of (a) margin for error, and (b) sulphation. You can wreck an 18 AH battery pretty quickly by repeatedly flattening it. You can get a lot more out of your battery if you turn the screen brightness to minimum, and actually switch the screen off when you're not looking at it.

[Sentinel]

Originally Posted by little col

i am off on holiday later this year to a dark site but was wondering if it is possible to run my laptop off my power pack i have for the heq5 mount , the power pack is 12 volt but i can step down to 6v/3v and 1.5v

I also recommend a Jaycar adapter. My laptop requires 19V so the adapter converts from 12V to 19V. Has worked well for years. I can even run the laptop of a 7.2 Amp Hr Gel Cell. It cuts out to protect the battery so that you do not run the battery completely flat.

However a word of caution if using the car to run your laptop...cold nights & remote observing sites and laptops running on car battery...do not mix. You may have 12V, but cranking an engine in the cold can be difficult with a fully charged battery.

[KG8]

I must look into these jaycar converters!

[Sentinel]

Try,

http://www.jaycar.com.au/productView.asp?ID=MP3467

Cheers

[AndrewJ]

I also use the Jaycar DC-DC adapter and it works well
One interesting fact
I use a HP lappie, and the std 240V adapter puts out 18.5V
I looked at their DC converters ( very expensive ), but what i found in the process was the lappie will also run off 15V :-)
If you run at 18.5V, the lappie tries to recharge its batteries as well as run.
At 15V, the internal battery charger aparrently cuts out, so you dont waste energy recharging yr batteries from a battery.
Dunno how other lappies work tho

Andrew