[PLUG] Failure Mode in 20 volt Power Adapters

[Dale Snell]

On Wed, 27 Jan 2016 18:17:46 -0800, in message
20160127181746.4a63daa8 at Devil-Bonobo, John Jason Jordan wrote:

> On Wed, 27 Jan 2016 17:17:20 -0800
> Dick Steffens <dick at dicksteffens.com> dijo:
> 
> >On 01/27/2016 05:08 PM, wes wrote:
> >> the center pin is a "data" line, the computer uses it to identify
> >> the power adapter powering it. the computer may refuse to do things
> >> like run at full speed, or charge the battery, if it cannot verify
> >> that the power adapter is capable of handling that load.
> >>
> >> I think it's some sort of fire prevention scheme?
> 
> >Interesting. Overload protection sounds logical.
> 
> The power brick for my System76 laptop has four contacts. I have been
> told that the extra contacts are to communicate the charge level of
> the battery to the brick, lest it overcharge the battery. I'm not
> sure I buy that, but then, I'm not terribly clever with electrical
> circuits.


Laptop batteries have small microcircuits in them that detect and
communicate to the laptop the charge state of the battery.  In
doing so, they prevent the laptop from over-charging the
batteries.  The better batteries can also detect if one or more of
the internal cells is going bad.

The extra contacts in the power brick connector are indeed a data
connection, which the laptop uses to tell the brick to reduce the
charge current.  At least, that's what my memory tells me.  It
could be worng.


--Dale

-- 
"Text processing has made it possible to right-justify any idea, even
one which cannot be justified on any other grounds."
		-- J. Finnegan, USC.
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