using laptop charger

NoiseEHC noiseehc at
Thu Dec 12 18:48:21 EST 2013

Thanks for all the answers, I will let you know whether my XO 1.75 will 
be destroyed by the Toshiba adapter... :)

On 11/12/2013 20:29, John Watlington wrote:
> James is correct about 19V probably not working with an XO-1, but with an XO-1.75/4
> you should be fine up to 24V.
> When running with an input voltage higher than 13V, the battery charger on the
> motherboard runs noticeably hotter.     Still within spec at 19V and 45C ambient,
> but you might notice the difference in case temperature near the DC input plug
> if charging an empty battery.
> Cheers,
> wad
> On Dec 11, 2013, at 3:09 PM, James Cameron wrote:
>> G'day Andrew,
>> There is a voltage above which the XO-1 will not charge, which had
>> been often encountered by people using solar panels.  Along would come
>> a cold sunny day, with a greater than normal voltage, and the charging
>> would stop.
>> I don't recall the actual voltage (Richard may remember), but I think
>> it was somewhere near 18V, and it varied slightly between laptops.
>> So it might work, or might not.
>> Instead of using a resistor, you might use two or three large diodes
>> in series, each of which will provide a "forward voltage" 0.6V drop.
>> Pick the diodes based on the maximum current 1.85A (usually double
>> that), and the power that will be released as heat; P = V x I, where V
>> is 0.6, and I is not to exceed 1.85A, so 1.11W minimum "power
>> dissipation".  Place them in a way that does not hold the heat in.
>> p.s. if you find one diode does what you need, then add another in
>> case of variation in the supply or laptop.  You might even add a
>> full-wave bridge rectifier instead of two diodes, that way the input
>> polarity won't matter.
>> On Wed, Dec 11, 2013 at 01:52:54PM +0000, NoiseEHC wrote:
>>> Hi!
>>> I am thinking about using my laptop's charger instead of the OLPC
>>> charger in the future as I move a lot and it's getting really
>>> tiresome to bring both chargers with me. The plan is to create a
>>> converter plug and use only the laptop's but it has different
>>> voltage levels.
>>> laptop: TOSHIBA
>>> part: PA3715U-1ACA
>>> model: PA-1750-24
>>> output: 19V - 3.95A
>>> XO-1.75: DARFON
>>> model: BBOJ-C
>>> output: 13.5V - 1.85A
>>> So can I plug my XO to the TOSHIBA adapter? The page says that
>>> 11-18V needed, while the laptop's is 19V. Shall I use a resistor to
>>> drop the voltage or is it unnecessary? Power usage is not an issue
>>> to me. (BTW I will use the plug from the XO-1's charger, I guess
>>> that it did not change in the meantime.)
>>> Thanks,
>>> Andrew
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>> -- 
>> James Cameron
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