[OLPC library] OLPC charging polarity

[John Watlington]

Mikus,
    Thanks for catching this.

On Sep 7, 2008, at 6:00 AM, Mikus Grinbergs wrote:

> In a 5 Sept message to Greg Smith that was copied to the Library  
> list, John Watlington said:
>
>> We explicitly support powering the laptop directly off a car battery.
>> We do not, however, recommend that you connect the XO directly
>> to a car's electrical system.
>> If you get the wires (polarity) swapped, it will damage the laptop
>> (blow a fuse soldered to the motherboard.)

I apologize about the last statement.   It was true before some final  
changes
I made before going into production, and is still true on the Multi  
battery charger,
but no longer applies to a production (C1 or later) XO.

> If John's statement is true, the laptop.org wiki needs to be  
> changed ASAP.  The Hardware_specification page in the wiki says  
> (under External Connectors):
>>> DC power: 6mm (1.65mm center pin) connector; 11 to 18 V input  
>>> usable,
>>> –32 to +40V input tolerated;
> I interpret that statement (and I suspect so will others) to mean  
> that either negative or positive polarity is acceptable.

The key there is "tolerated".   The laptop will not operate from  
negative polarity,
but no damage to the unit will result until those voltages are exceeded.

Thanks,
wad