Before I found Xtar battery chargers I had gone through various expensive AA-D size NiMh chargers that were cheaply made and provided poor performance. When I needed to charge my first 18650 battery because I got a fancy flashlight I choose an Xtar battery charger for two reasons. Good product reviews and I simply thought the name was cool. My first Xtar chargers were just able to charged lithium ion batteries. What I use now is Xtar’s VC4 & VC2 plus chargers because they can handle NiMh batteries as well as lithium ion. Xtar offered to send me a charger for free to review so I choose the new VC2s because it is most like the older VC2 plus.
Any USB to micro USB cord can be used to connect the power supply to charger.
The charger decides which charging current is best for each individual battery.
The charger can measure each batteries internal resistance in M ohms, and capacity in
mAh.
The display can also show the charging current given in milliamps.
Best of all the batteries become only slightly warm at most during the charge cycle
because the VC2s lowers the current if it senses the battery or batteries are becoming
warm.
The VC2s takes the battery to its maximum voltage. If it’s a standard 18650 that is 4.2
volts. But then once the battery is fully charged it brings the batteries voltage down to
4.15 volts. I think to help safe guard any device that uses a lithium battery that cannot
handle a full 4.2 volts.
The charging cycle starts with just a milliamp or two and gradually increases the
current to a base current of 500ma, 1 amp, or 2 amps. The charging voltage matches
the batteries initial voltage and increases during the charge cycle.
The batteries I charged were:
A single Xtar 18650 2900mAh 10amp High Discharge Battery.
The battery voltage the night before the test was 2.46 volts. The day of the charge the battery voltage was back up to 3.00 volts.
Internal resistance was measured as 81M ohms.
Battery capacity was measured as 2539 mAh.
Charging current was never greater than 500ma.
Time needed to reach a full charge was 5 hours and 39 minutes.
A single IRC18650-26F protected button top battery.
Battery starting voltage was 3.53 volts.
Internal resistance was measured as 61M ohms.
Max charging current was 1.7 amps.
Capacity was measured as 2704 mAh.
Time needed for battery to reach a full charge was 3 hours and 20 minutes.
A Pair of Samsung 30Q unprotected 18650 flat top batteries. Cells were kept depleted for 48 hours.
Cell #1 starting voltage was 3.52 volts.
Cell #2 starting voltage was 3.53 volts.
Max charging current for each cell was 1 amp.
Internal resistance for cell #1 was measured as 49M ohms.
Internal resistance for cell #2 was measured as 51M ohms.
Capacity measured for cell #1 was 2139 mAh.
Capacity measured for cell #2 was 2062 mAh.
Cell #1 needed 3 hours to reach full charge.
Cell #2 needed 2 hours and 44 minutes to reach a full charge.
A pair of Energizer NiMh 1400mAh AA cells.
Starting voltage for both cells were 1.1 volts.
Starting current for both cells were 200mAh.
Cell #1 max charging current was 1 amp.
Cell #2 max charging current was 500mAh.
Internal resistance for cell #1 was measured as 73M ohms.
Internal resistance for cell #2 was measured as 100M ohms.
Capacity measured for cell #1 as 831mAh.
Capacity measured for cell #2 as 1237 mAh.
Cell #1 needed 1 hour and 44 minutes to reach a full charge.
Cell #2 needed 3 hours and 20 minutes to reach a full charge.
A Pair of new Xtar 800mAh 14500 protected batteries.
I did not check starting voltage for either battery.
The charging current for cell #1 was 397 ma.
The charging current for cell #2 was 331ma.
Internal resistance for cell #1 was measured as 116M ohms.
Internal resistance for cell #2 was measured as 190M ohms.
The time needed for cell #1 to reach a full charge was 48 minutes.
The time needed for cell #2 to reach a full charge was 50 minutes.
What I like about the charger is:
Batteries do not become hot during the charging cycle.
Charger does not need a proprietary power cord.
Charger brings down battery voltage to 4.15 volts.
Charging current is tailored to each battery. No more guesswork on my part.
Later this month I am going to charge some of the batteries once more using the VC2s and compare charging time, capacity, and internal resistance. New batteries I can understand having a lower capacity for the first charge because they are partially charged already. I think I altered the the capacity and internal resistance measurements by pressing the function button to often as the charge began for all the other batteries. My bad. Also I tried to post the images I have of the display for each battery charge but could not get then to post correctly. Hence they are in order but will be in post 2.
My one big complaint about the charger is: It is near impossible to remove any 18650 battery because there is not enough room to do so gracefully. You need a small flat head screwdriver to lift the battery out. However inserting batteries into the VC2s is a breeze and any battery small than 18650 are easy to remove.
The stopwatch times are from my cell phone. All other images are from the display of the VC2s charger. For each battery I have tried to give an assortment of images during each charge. So people can get a feel of how the charger works. I used a 2.1 amp Xtar power supply when charging the Xtar 2900mAh battery and the ICR-18650-26F battery. All the rest I used a 6 bay USB power supply made by Xtar. Those are the power supplies I have and use.
As a power bank it states that it will drain the battery in the left slot first but uses both slots. How does that work... does is drain the left battery to a certain voltage and then switch over to the battery in the right slot?
Thanks for posting that. I would assume then that it may possibly drain the battery in the first slot to a safe level before switching over...hopefully.
You are welcome. The above graphic lists the types of batteries the charger can handle. I will check with Mr. Hu from Xtar and double check about LiFePO4 charging capability for you next week. The termination voltage is 4.2 volts and can not be changed. That is when the machine cuts off charging current and voltage.
When my pair of Samsung 30q’s are empty I ’ll use the VC2s with some generic 2 amp USB power supply and see how fast they charge. Then I can say if the charger is fast or not.
I think if you are nearby when the battery(ies) are finished and take them out as soon as the light turns green you got yourself some fully charged 4.2 volt batteries. Voltage only comes down if you let them stay in the machine.
That makes sense but it would be interesting to check with a multimeter to see if the voltage readings are accurate , I’ve just recently got the gyrfalcon all88 & it reads 4.2 but it’s actually 4.17 , my opus 3100 used to be like that until I unsoldered the J1 bridge & now it charges to a true 4.2v.
I think a lot of chargers are designed to over read the voltage for safety reasons.
Just an hour ago I finished charging my new pair of unprotected 14500 Vapcells. I took them out while the VC2s still said 4.2 volts. My $20.00 Ideal 61-310 multimeter read #1 cell as 4.13 volts and #2 cell as 4.17 volts just minutes ago. So basically who knows what’s going on.
I just charged three Fenix 14500’s on the all 88 , the charger said 4.2v but one cell was actually 4.13 & the other two were 4.15.
I think most chargers are doing the same thing but hardly anyone is double checking with a meter to see what the voltage actually is.
I have an xtar vc4 which is quite good ,cells are actually 4.2 when pulled off the charger.
Based on my experience with a TC1, I’m leery of the voltmeters and some of the automatic controls of the newer XTAR chargers.
While the end result is on target at 4.2v, verified by a meter, a discrepancy between the displayed voltage and measured voltage always exists when they are put in for charging, so I question whether the internal meter is accurate. The last time, a 30Q at 3.5v read 3.8v when first installed in the meter.
Additionally, of late, the charger was displaying odd behavior, with everything, including the indicator light fluctuating between being engaged in the charging process and being empty, of finished. Cleaning all the contacts mostly mitigated that, but it’s still sensitive to movement, which can result in momentary loss of contact. These are the same flat-topped 30Qs that had no issues earlier in the charger’s life. Worse, it now refuses to charge them at greater than 1A, on cells that are relatively new.
The VC2S looks great on paper, but if it has the potential to act in any way similar, then IMO a lot of the utility is lost and it might be better to look elsewhere.
On the flip side, my ANT MC1+ promises nothing except that it will indicate the general progress and let me know when it’s fully charged. It too, is on target, so the fundamental process is sound, so perhaps it’s better to keep things simple.
Regardless, the next charger I choose will allow manual control of charging current.
