minimum voltage forlaptop supply

[Simon]

I have a laptop pc, the psu is the pretty much standard 18.5V, but considering that the battery is 10.4 what is the minimum voltage the laptop would accept ? I'd like to possibly run it straight from 12 V or use a boosting circuit to get it up a bit if need be but need it be the full 18.5V ?

[cybergibbons]

They tend to not work very far from the stated spec. They tend to be higher voltage so that you don't need stupidly thick cables and big power connectors - remember it not only needs to power the laptop but charge the battery as well.

My HP laptop gives a warning and drops out around 1V below the power supply. My old Acer laptop gets hotter and hotter and eventually shutsdown.

[saturation]

A simple and good way to find out with your variable PSU.  Attach it and drop the voltage slowly and see where it cut offs.

[Fraser]

Simon,

In my experience modern laptops have power management modules that want to see close to the rated input voltage. I had this issue with old Toshiba laptops. There seemed little reason why they wouldn't work at 12V instead or 15V or 18V but they just wouldn't work. There were several manufacturers of switch mode voltage upconverters to enable businessmen to charge their laptop from a car cigar lighter socket.

I picked up some good quality voltage upconverters (12V to 17.4V) for my Dell laptops on ebay. They were quite reasonably priced at less than £10. It might be worth a search for your voltage requirement. The unit also contain plenty of transient spike suppression to protect itself and the laptop.

[House91320]

My laptop runs at 16vdc and i hit a wall at 14vdc.

[Mechatrommer]

the cheapest method is any 12V batt (high energy though, not the AA sized or smaller) around, no harm i think since its lower than speced. it will either work or not work.

[Simon]

well when I get around to making a variable voltage supply I'l have a go