# Holy Crap - why to get a DC-DC for laptop

• 07-27-2005, 01:45 AM
KyleYankan
Holy Crap - why to get a DC-DC for laptop
Jumping Jehusafads Batman! Look what a little math can do for you.

I have a Dell Inspiron 1150, I use daily. Well, My charger always gets VERY hot, so i decided to check out the power labels on it. 65w Charger.
Input: 120v, 1.5a
Output: 19.5v 3.34a

OK, cool... but what does it all mean?

120*1.5 = 180 watts
19.5*3.34 = 65.13

HOLY CRAP ON A STICK! I was losing 115 watts to heat! WOW! Thats alot. Almost all of the Opus 120!

OK, so here's a situation.

65.13/180 = 36.2% effieciency.
Multiply with a 90% efficient inverter: 32% effiencey.

Holy Crap! 32% efficient. On my "65 watt" charger that means it's really sucking up:

65/.32 = 203 watts! HOLY CRAP!
That's like 138 watts of wasted heat! Do you want that heat building up in your car o na hot summer day? Might even cause a fire!

So, that's why you should go with a DC-DC adapter. Much more efficient. :-)

Good day.