My Xtar® VC4 is painfully slow when charging utilizing the Blitz-Wolf 2.4 amp supply. The supply is coded as Apple 2.4 amp, so it should be easily capable of providing 2 amps. Instead the VC4 appears to restrict itself to 900mah, which is the standard limit for a USB3.0 port. The 2.1 amp supply you can buy from Xtar works fine, and is coded as Apple 2.1 amp. I guess the Xtar VC4 firmware doesn’t look very hard at the charger coding. At 900ma, the charge rate on each port is about 225ma. There may be a silver lining of sorts. If you want to charge 18340’s or 10440 or 14500 cells, the 225ma is
probably a better choice than the default 500 ma. So if you want low charging rates, just use an USB supply that the VC4 doesn’t recognize.
Perhaps Xtar can enlighten us as to exactly what codes for USB supplies it recognizes as capable of 2+ amps.
The problem is usual voltage, it can be because the usb charger delivers 5 volt or below or it can because the cable/connectors has to high resistance.
If you have a usb meter check your usb chargers, the best one for VC4 is the one with highest voltage (5.2 volt is very good) that can deliver 2A. This does not have much with brand of usb chargers to do, all have random variation in output voltage between different copies of the same usb charger.
I think some users that have this combo also reported the same problem, either here or ver at CPF.
My BlitzWolf can supply 5.22v using a USB meter I got from Banggood, but when I plugged the VC4, the most the amperage reading gives me is around 1.1A with all 4 slots or slots 1 and 4 occupied, which is less than the 2A that the Xtar is capable of.
When I used the BlitzWolf to charge my mini iPad, the charger can go up to 1.7A without any problem
I have contacted Xtar®, and basically all they say is , ‘yes, it doesn’t work’. They are suggesting the supply voltage is too low, however my ZY1266 USB meter shows the voltage between 5.0 and 5.1 at all times, and that is well within the specifications for USB power supply. HKJ’s review of the Blitz Wolf supply showed pretty good voltage regulation out to the design limit of 4.8 amps, so I have my doubts about the answer I have from Xtar in the USA.
My guess is the VC4 reads the id on the Blitz Wolf USB power supply, and if it doesn’t say Apple 2.1 amp, it decides that the supply is isn’t capable of 2 amps and limits the current accordingly. The Blitz Wolf supply appears to be coded as Apple 2.4 amp.
I also had issues with my VC4, playing around with lots of USB power made it work! Also noticed that after hours or charging, very hot power supplies apparently have issues as well.
My apple PSU works best IMHO, also works great in my car (random 12V-5V 2A adapter).
You can do more than doubt as apple coding is done on the data wires and the VC4 doesn’t even connect to those because it uses a barrel connector.
mattheww: Keep in mind that to get fast (1A) charging, you need to put cells only in the two outboard slots. Otherwise the charger limits itself to 0.5A per cell so it will take a very long time to charge a 18650.