Charging a surface Pro from an external Battery-pack

Thread Starter

ElectronVolt

Joined Jul 5, 2020
3
Hello,

I hope i will find some help here.

what i am trying to do is to charge my surface pro 2017 from a external Li-Ion battery pack instead of the AC charger.
the rated values from the AC charger of my surface are 15V , 2,58A
i am using 12 x ( 18650 cells ) in 3 series and 4 parallel config so the output of the pack is 10,8 - 12.6 V (Max discharge current 5A per cell ; 20A for the pack ).
I am using a 3s BMS for the pack and, a buck-converter (Max current 4A) to boosted the 10,8- 12,6V to constant 15V.
the good news is it works ! the bad news it charges too slow !

when i measured the charging current i found that it is significantly less than the measured charging current when using the AC charger!
some mesurments results :
when charging using the pack -----------> Iboost ~ 0.8 A @15V
when charging using the AC Charger ---> ICharger ~ 2.3 A @15V

and now my actual question is:
i don't understand why the surface drowse different current if the Voltage is the same (ohms low !) !?
how could i possibly solve this problem !?
 

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Thread Starter

ElectronVolt

Joined Jul 5, 2020
3
I wonder if the surface talks to its charger before switching to a high charge rate?
i don't really know how to check that the best way ! but i don't have an oscilloscope (if absolutely necessary i could get access to one).
but i have one of the AC chargers open and i can see the main ic's
i attached a photo that shows the main ic's.

the main ic's datasheets:
1- https://www.ti.com/lit/ds/symlink/tps54226.pdf?ts=1594022706845&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTPS54226

2- http://dalincom.ru/datasheet/OB2269.pdf

i am not sure if a communication could be achieved with one of those ic's !?
 

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Irving

Joined Jan 30, 2016
763
On the face of it, no, there no comms. Intriguing that there are two smps chips though, can you do a pic of the top side please.
 
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