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Surface 3 Charging

GreyFox7

Super Moderator
Staff member
This thread is all about charging.

To charge or not to charge.

I did a preliminary test using a battery pack with two charging ports. One port provides 1 amp while the other port provides 2.1 amp. The supplied Surface 3 Charger provides 2.5 amps as labeled.

Note this was done over a short period of time, more extensive testing is required.

With the internal battery starting at 63% and my battery pack starting at 95 % I connected the cable to the 1A port. during a period of varying usage the Surface indicated it was at times charging and other times not charging although allways indicated it was connected. Throughout the time the internal battery remained at 63% while the battery pack dropped to 75%. Once I pressed the Surface power button the rate of drain on the battery pack seemed to stop or at least slow significantly. Note this was done over a short period of time. After a few minutes I pressed the Surface Power button again and recorded 65% charge on the internal battery.

Then I switched the cable to the 2.1 A port. We are now at 66% charge on internal and 72% on external battery.
I kicked off a benchmark test to generate load and we immediately switched to not charging and internal battery level dropped to 64% over the duration of the test. This was a little unexpected and it seems the 2.1 A port generally refused to charge as the external battery level never dropped.

Perhaps something flakey there, switched cables, now seeing power level drop on ext batt so rerunning the test again. Internal batt at 63%. This time again we see status switching from charging to not charging and ext batt level dropping down to 63% while int level increased to 64%. Another run of the test and initially we are NOT charging... after some futzing around it's charging and holding the internal battery at 63%.

Clearly something strange or maybe its the magical 63%. need to spend more time on this.
This is also a new battery pack, could be a problem with it. I was using this because it has it's own power meter so it was convenient in that respect.

Update1:
Connected to the charger the Surface 3 only draws 1.3 A and its only getting 1.1 amp from the battery packs (I tried two of them) but they ramp down after about 5 minutes and then shutoff for a while so they appear to not be continuous duty cycle devices, at least the MS charger keeps charging at the 1.3A rate. This was observed while the Surface 3 was on but idle.
 
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TPadden

Member
My Anker 12000mAh external never shut down and took the S3 from 70% to 100% in about an hour, most of the time the S3 was sleeping with 5-10 minutes use, using about 40% of the battery by it's led gauge ...... unscientific but exactly what I was looking for.
 
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GreyFox7

Super Moderator
Staff member
My Anker 12000mAh external never shut down and took the S3 from 70% to 100% in about an hour, most of the time the S3 was sleeping with 5-10 minutes use, using about 30% of the battery by it's led gauge ...... unscientific but exactly what I was looking for.
Which model Anker battery pack?
I used a Limefuel lp200x and a rugged power bank model they both behaved the same.
As did a Samsung 2.0A USB charger for a Galaxy Note 10.1.
 
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GreyFox7

Super Moderator
Staff member
Very good, I was thinking about getting that one to see if it charged faster because of the 4A capacity.
Can you install BatteryBar and indicate what the mw charging rate is?

Looks like I may be returning these other battery packs although I did send a support question to Limefuel to see if the LP200x is supposed to operate on continuous duty cycle or not.
 
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GreyFox7

Super Moderator
Staff member
On the charger I just went from 72% to 100% in about 1.5 hours although it wasn't completely idle during that time with a charge rate of around 6,600 mw. It looks like it burns around 2,000 +/- mw sitting on the Desktop doing nothing.

I'm not sure how Batterybar is reporting these numbers. I'm assuming it means we are drawing a total of 8600+ mw from the charger while idle and charging. i.e. the number reported as charge rate + the idle discharge rate.
That might explain the total capacity usage i.e if we used 6500 mw under load + 6500 mw charging we would be at 13,000 mw or 13w (2.6A) which is the capacity of the charger. That's over the capacity of the 2.1A battery pack port however, that's not how it really works, the battery pack should only deliver what it can and any overage would come from the internal battery.

I just observed a peak of 8900 mw discharge rate when running the benchmark on battery. It would seem to imply the Limefuel Battery Pack is either not limiting to 2.1 A or not capable of continuously delivering that rate as the peak 8900 mw is only 1.78A which should not have been a problem.
 

netuser

Member
Is it possible to get a charger that charges even faster than the OEM charger or is the stock charger the maximum the Surface 3 can use?
 
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GreyFox7

Super Moderator
Staff member
Is it possible to get a charger that charges even faster than the OEM charger or is the stock charger the maximum the Surface 3 can use?
That was one of the things I had set out to determine. It appears from TPadden's post above that the Surface 3 wont draw more as the Anker Battery pack is capable of supplying up to 4A per port (20,000 mw).

It remains to be seen if the intelligent power charging circuitry can be tweaked via FW update to allow for faster charging or if that limit is a function of the micro USB connector current carrying capacity (which after a quick search appears to be the case). One recent review I read mentioned that offhandedly and stated USB-C for that reason was the right connector.
 
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