Transformers... 12v to 230v to 19v... Or 12v directly to 19v...

[DNS1]

Hi chaps,

I'm in the midst of kitting out my motorhome (converted Renault Master).

Going to have a 1000w inverter in there to feed a couple of 230v outlets.

Trying to work out how much more efficient it will be to get a charger for my laptop which will convert directly from the 12v vehicle supply, to the 19v laptop supply, rather than using the inverter and normal power pack.

What's everyone reckon? Enough of a difference to warrant buying a 12v laptop supply, or not bother?

 

[DNS1]

Just realised that there is now a dedicated Auto Electrics forum... Sorry admin, feel free to move this thread!

 

[Lucien Nunes]

Depending on various factors, saving of 20-30% of its consumption. The conversion efficiency of each of the components is around 80-90% under normal load but the inverter will be very lightly loaded when the laptop is fully charged and at minimum consumption, so its efficiency at that load point will be lower. A well-designed DC charger can also theoretically have lower losses than the AC one due to its simpler power handling path.

I often have to design mains-powered units into the mains/battery powered systems that I build and it is always a dilemma - whether to include an inverter and transfer relay or to adapt each unit to run on DC and feed the DC bus from a central PSU when on AC. Because of the importance of saving power on DC this is usually the way we go, converting the power twice from mains (when efficiency is not so important) but only once when on DC (when it has a direct bearing on battery life).