[ltp] Running with line power and no battery

[Henrique de Moraes Holschuh]

On Fri, 29 Feb 2008, Joerg Bruehe wrote:
> Ok, I get what you mean, even though I lack the knowledge about the  
> details. I guess the strength of the effect depends on the supply  
> network topology, and here in Berlin (Germany) that is quite a dense  
> mesh of which I hope it will reduce them.  I may be wrong.

A strong mesh can, in fact, cause a far worse overshoot if you're unlucky.
There is only one proper way to deal with it, and it is to do a
stage-by-stage power up of the grid, and even that might not save your
stuff, so doing the equivalent of that on your home *after* the grid
stabilized is the best defence, regardless of whatever the power grid
utility is doing.

> Are you (more) concerned about that effect on your power supply, or on  
> the notebook itself ?

I am concerned about every PSU and electrical or electronic ampliance in the
house :-)

> (My main concern would have been the halt with files open, operations in  
> progress etc - loss of data, file system damage, ...)

That's mostly it, yes.  But you could get a fried PSU *and* a fried thinkpad
if the PSU fails bad enough and let the surge through.

> Regarding the power supply, I don't see how the battery in the laptop  
> could help these external electronics when the mains power goes wild.

It doesn't help at all when power goes wild IF the PSU breaks down.  If the
PSU doesn't break down, a battery avoids data loss (as it works like a UPS).

> Regarding the notebook, I assumed a power outage (without battery)  
> causes a shutoff so when the power returns it will be off.

All thinkpads power on the EC, the VR, battery packs and all associated
circuitry when AC comes back.

You really want it unplugged if you want to make sure it is off.  And given
a few bug reports on the latest Lenovo thinkpads, I'd say you have to pull
out the battery packs too until we find out what the heck is causing them
not to power everything off when we tell it to :)

> You live in Brasil ?  According to Wikipedia, your voltage is 120 V  
> then, while we are at 230 V. Accordingly, your currents would be higher  

Wikipedia is on crack.  Almost all of Brazil runs either 127V or 220V, all
at 60Hz.  127V in the older parts of the power grid (which includes the
majority of the cities, unfortunately), and 220V in the newer grids.

And you get 220V from a two-phase 127V outlet, so most heavy loads are 220V
throughout the country (driers, heaters, etc).

> Makes sense.  Until now, I had not opened the breakers, but most of my  
> devices have "old" switches which really break the power, or I have  
> switchable sockets between the wall outlet and the device(s) (especially  
> for my PC and accessories) and would switch these off.

That helps a lot, of course.  It is about the same as opening the breakers
in a normal grid powerup.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh