Xtar VP4 Plus Dragon - Good for 21700?

berfles

Newly Enlightened
Joined
Jun 18, 2007
Messages
153
I just got my first 21700 and it barely fits in my Nitecore D4, so I want a new charger. Was looking at the Xtar VP4 Plus Dragon, what is everyone's thoughts about it?
 

AbnInfantry

Newly Enlightened
Joined
May 17, 2009
Messages
95
Location
USA
21700 cells fit fine in my Xtar VP4 Plus Dragon. My only disappointment is it doesn't have a setting to charge at 4.35 volts current as the Xtar VP2 and some other less expensive chargers will.
 

berfles

Newly Enlightened
Joined
Jun 18, 2007
Messages
153
Is there one that's more recommended then? I have a bunch of 18650s that I still charge so I'd like to get one charger for all my cells.
 

XTAR Light

Enlightened
Vendor
Joined
Apr 26, 2010
Messages
710
Location
China
In that case, you can try a XTAR VC8, it can charge 8pcs 21700 or 18650 batteries at one time. And it is also a budget battery analyzer.
 

berfles

Newly Enlightened
Joined
Jun 18, 2007
Messages
153
Well, I got the VC8 but I don't think I understand what it's doing.

1. I checked my batteries with a multimeter and get a totally different rating than what shows on the screen while it's showing. Says it's fully charged on the charger, but I take it out and it's only 4.15v.
2. The 21700 I have in here actually has gone down from 4.12v to 4.08v since I put it in there.
3. What charging rate should I be seeing with multiple cells in there? The most I've seen with one cell is 900mA even with it set to 2000.
 

LED Monkey

Enlightened
Joined
Apr 25, 2016
Messages
281
Location
Massachusetts
As far as the battery voltage is showing it may show "full" which in most cases will be 4.2v or close to that +/- a small amount. As soon as you remove the batteries from the charger the voltage can sag down some and it can vary depending on the age and health (resistance) of the battery. You said your 21700 cell dropped from 4.12 down to 4.08 and that is the battery not the charger causing that. So when you pull the batteries off the charger they can show a lower voltage reading with a multimeter.
As far as the charge rate is concerned if you're not using a wall USB adapter that can supply enough power to the charger it's not going to be able to give the full charge rate that the charger is set to and it's possible the charge rate may drop some as it's closer to being fully charged too. I don't have this charger but these are some of the variables that may come into play here. I think the VC8 may also adjust the charge rate according to the measured internal resistance of the batteries so that may drop the rate too.
 
Last edited:

LED Monkey

Enlightened
Joined
Apr 25, 2016
Messages
281
Location
Massachusetts
Of course XTAR has replied to this thread so they can explain anything about the VC8 or if I'm not correct about your charger.
Straight from the horse's mouth.:knight:
 

berfles

Newly Enlightened
Joined
Jun 18, 2007
Messages
153
Thanks for the info, that's kind of what I was thinking. As far as what I use to plug it into the wall, I was surprised to see that none of my quick charging Samsung adapters would even power the charger, yet my laptop does. What in the world kind of power does this thing need?

EDIT: Wound up finding some info in older posts, I'll post links tomorrow in case anyone else needs them.
 
Last edited:

XTAR Light

Enlightened
Vendor
Joined
Apr 26, 2010
Messages
710
Location
China
@LED Monkey is right.

Actually there is a very small deviation in the cut-off voltage of all chargers. The cut-off voltage of VC8 is 4.2V±0.05V. As the battery also has an internal resistance of about 100 milliohms, so the battery voltage after charging is generally about 4.15V. And after a long-time use, the internal resistance is large, so the battery voltage will be low.

For the charging rate, the current coming from the input port is actually evenly distributed to each slot after put batteries in. The constant current of VC8 is 3A*1, 2A*2, 1A*4, 0.5A*8. When the battery is about to be fully charged, the VC8 will automatically reduce the distributed current to ensure the safety of the later charging and fully charge the battery as much as possible.

In addition, if the battery resistance is too large, the VC8 system will initiate protection measures to automatically reduce the charging current.

As for the charging adapter, I tried a Samsung adapter and a usb charging cable, both can power VC8.
View attachment 11670
View attachment 11671

Please change different charging cable to test whether the original cable has any problem.

If it is still not solved, maybe you can post your adapter spec or the process pics to see if there is any other problems.
 

berfles

Newly Enlightened
Joined
Jun 18, 2007
Messages
153
Your attachments didn't work, could you post them again?

Odd about the Samsung adapter, I tired one from my S7 Edge and one from my current Note 9 and neither would even turn the charger on. Maybe it is the cable it came with, I'll try my Note 9 cable as well.


EDIT: Definitely not the cable. This S7 Edge adapter literally powers the charger on for about a second, and then the displays go black again. It's like it doesn't even make it through the initial boot up/scan. The black Note 9 adapter doesn't even turn the displays on at all.


nrDKHLr.jpg




IuPYtnl.jpg






Also, I still don't understand why I've been charging this 18650 for 30 minutes and it has gone from 4.09v to 4.11v, back to 4.9v. How could it possibly lose charge while charging? And why would it sit there and not increase for 20 minutes and then shoot up from 4.09 to 4.11 in a matter of minutes, then back to 4.09?

Also, when doing the Grade function, I have let this battery discharge for well over an hour now and it's only gone from 4.2v to 4.04v. I really don't understand this thing and why it takes so long to do anything. Then when I unplug it and try again, it goes from 4.04v all the way up 4.16v in a matter of seconds.
Also
 
Last edited:

XTAR Light

Enlightened
Vendor
Joined
Apr 26, 2010
Messages
710
Location
China
I tried with a very old Samsung adapter. The text on this adapter has been worn away, so I don't know its specifications.
1.jpg
And I learned that now most Samsung adapters have their own fast charging procotol, i.e. its adaptive fast charging marked on the adapter. Samsung's own products of different models are generally not universal. So your Samsung adapters maybe not fit, that's why the VC8 charger's screen display light and then went black quickly.

For the issue you mentioned voltage went 4.09V-4.11V-4.09V, that's mostly because your adapter has insufficient power and cannot input enough current, so that the charger will activate the protection function.

I also tried another way:
2.jpg
use a USB cable to connect VC8 to a laptop. It could work.

For the discharging in Grade function, the discharge current is only 300mah, so it needs a long time to finish its work. When you unplug and then plug, the charger will automatically go to charging function. The screen display shows the real-time current and voltage. And the real-time voltage calculation formula is: real-time voltage = real voltage + resistance * current.
 

Latest posts

Top