Hello,
Since I start again racing 1/8 buggy last year I'm using a B6mini charger. Fine unit, no problems, but charging rate for 4s packs never tops to the claimed 6 Amperes. That would be useful on the track to quick cycle among packs and increase the driving time.
I power the B6 with a SkyRC power supply, rated 60W-15V-4A and I get 3.2A max charge power.
I already decided to buy a more capable charger and to convert a desktop pc power supply to drive it.
In the meantime, I found an old xbox power brick rated 200W-12V-16A. I quickly modded it and I tested with the B6. With great surprise, the recorded max rate was only 2.3A. Kind of bummer, considering such powerful power supply.
I don't really have deep knowledge on electric stuff, so I ask if someone can explain me what's going on.
Thank you!

Although the charger is rated 6A it is also rated 60watt, so there are 2 maximums!

4s Lipo needs a charging voltage of 16.8 volt, with a maximum of 60 watt a maximum of 3.5A is possible.

Only when charging 2S batteries (8.4v) makes a charging current of 6A possible.

If you do not know how power, current and voltage are related:

power = current x voltage

Thank you for answering! So it is a limit of the charger, no matter its power supply?
Do you have any idea on why the xbox power supply, despite its greater rating, can only reach 2.3 when charging 4s?

Battery almost full? Then the current will be lower

Nope... battery was at storage charge.
I did notice that the input voltage is around 14.5V with the cheap 60W power supply and slightly less than 12V with the xbox one. May this be the reason?