Review: XTAR ST2 - 4.1 Fast Battery Charger

Batteries and Chargers Chargers
1
XTAR ST2
4.1A Fast Battery Charger




The XTAR ST2 charger was sent to me directly from XTAR for review.
For specifications on the manufacturer's page: http://www.xtar.cc/product/XTAR-ST2-Charger-117.html




Main features of XTAR ST2:

- Ultra-fast Charging for Two Slots
- Max 2x4.1A, the fastest charger ever
- Protection test of internal battery resistance
- Battery temperature test with overheat protection
- 1A / 2A / 4.1A optional current for each slot
- OV activation restores the over-discharged batteries
- Built with fireproof material to extend the life of the loader and ensure safety.
- LCD information screen
- Type C port, double rapid recharge protocol
- Delicate design, excellent touch sensation
- Manual and automatic, flexible control
- Simple operation, clear display
- Small and portable, stay in one hand
- Input: PD2.0 (15V-3A), QC3.0 (5V-3A / 9V-2A)
- Current: PD2.0: 4.2V-4Ax2 / 2Ax2 / 1Ax2 - QC3.0: 4.2V-4Ax1 / 2Ax2 / 1Ax2
- Apply at 3.6 V / 3.7 V Li-ion / IMR / INR / ICR
- Supported batteries: 18650/20700/21700/22650/26650.




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The XTAR ST2 arrived without packaging and manual. Together with the ST2 charger I received a USB Type -C power supply with European
two-pole connection, a 80 cm long Type-C to Type-C USB cable and a USB-A to Type-C cable of the same length compatible with the charging protocol quick QC3.0.
The sales package will contain:
- XTAR ST2 battery charger
- USB-A to USB-C cable
- USB-C to USB-C cable
- Manual




Let's see some images of the power supply sent to me by XTAR and the cables supplied with the XTAR ST2. Note in particular the USB
Type-C output on the power supply:







The XTAR ST2 charger:



The XTAR ST2 charger is the latest product released by XTAR. The key features of the ST2 are fast charging up to 4.1A x2 and intelligent
temperature control of the batteries being recharged. With the XTAR ST2 we can charge a 18650 2000 mAh battery in just 30 minutes.
Battery temperature monitoring in real time, prevents overheating of the battery, safeguarding its duration and performance.
The well-defined LCD display shows all the information on the battery charge status.
Very nice the design of the XTAR ST2 in this version. Beautiful line where the blue stripes on the sides stand out and the feel is excellent.
The XTAR ST2 is built in fireproof and resistant ABS + PC material.

In the upper part we find beyond the two recharging slots, equipped with a contact for reading the battery temperature, a very defined display
with white writing on a blue background, the two status LEDs and two buttons (CH1 and CH2) that distinguish the two recharge slots available
with the XTAR ST2.









The XTAR ST2 charger is equipped with a USB Type-C input to connect our ST2 to a compatible power supply as well as a Power bank. The
specially designed Type-C input is available to support the PD2.0 and QC 3.0 protocols, compatible with various adapters.
There are also openings that help dispose of the heat produced during operation.






In the lower part we find 5 soft rubber feet that raise the charger giving stability and allowing, through other slits, to dispose of part of the heat produced.
The data of the charger and the serial number are then shown in white.








Il funzionamento:

Operation:

With the XTAR ST2 charger we have the ability to charge 3.6V / 3.7V IMR / INR / ICR Li-ion batteries of the
18650/20700/21700/22650/26650 format and up to 4.2V with 4A, 2A or 1A for slots.
It is also possible to charge 21700 Li-ion batteries protected up to 76mm.

- To activate the "Upload" function:
Connect the device to the power supply and insert the batteries.

Three-stage Charging Makes Batteries healthier
Specially-designed TC-CC-CV charging method safely and efficiently charges your batteries.The charger uses trickle current (TC) to "awake"
and protect batteries when the battery voltage is very low. After the voltage becomes normal, the charger starts constant current (CC) charging,
and the charging speed is guaranteed with a larger current.When the battery is almost fully charged, the charger starts constant voltage (CV)
charging, to make sure the battery is fully charged and less-damaged.

Once powered, the XTAR ST2 checks the display (very clearly legible)..



Charging will start automatically. Press the CH1 or CH2 button to adjust the charging current. The notification LED above the display
changes from green to red to indicate the charge status. On the LCD display we can read the information regarding the voltage of the
batteries, the percentage of charge, the charge current, the internal resistance and the temperature of the batteries.

The XTAR ST2 battery charger intelligently selects the most suitable current by reading the internal battery resistance. It is however possible
to change it and switch to the three currents (1A / 2A / 4.1A) according to different needs.










The charging temperature is monitored through the built-in sensors throughout the recharging cycle. In my tests I never exceeded 50 ° C; in
that case I loaded a Samsung 30Q with 4.1A until the complete recharge of 4.20V.
The built-in high-precision MCU makes the cut-off voltage up to ± 0.05 V and the XTAR ST2 charger at the end of charging (at 4.20V),
automatically interrupts it and the notification LED turns green.







Note:
The battery charger is equipped with a "Dual Protection" protection system to guarantee safe charging and maximize battery life. The "Dual
Protection" system consists specifically of protection against internal resistance and thermal protection.
1. Protection against internal resistance: the charger immediately detects the internal resistance of the battery. If the internal resistance is too
high to allow recharging with 4.1 A, the device will automatically switch to a current of 2 A. Users can still change the charging current to 4.1 A
by pressing the button (CH1 or CH2) . However, this change could damage the battery life.
2. Thermal protection: the charger monitors the battery temperature throughout the charge. If the battery temperature is too high, the device
will automatically reduce the charging current to protect the battery.
Note: when the temperature is above 60 ° C, the charger automatically stops charging; when the temperature decreases, users must remove
and re-insert the battery to continue charging.

With the integrated intelligent detection system, when the polarity of the battery is reversed or the charging channel is short-circuited, the
charger does not start charging, so as to ensure the safety of batteries, chargers and users.

- Turn on / off the backlit screen:
The display goes dark one minute after the end of use. Press and hold the CH1 or CH2 button for 1.5 seconds to dim the screen and
reactivate each function.

- To activate the "0V Activation" function:
Insert the completely discharged batteries; recharging will begin after 10 minutes.

- Legend of the color of the LED indicators:
Green: standby / charge complete / contact defective / polarity reversed
Red: charging / activation in progress
No light: power supply disconnected


I did some charge tests with different batteries and with different currents:

18650 Samsung 30Q 3000 mAh - Speed 4.1A - Start 2.90V - End 4.20V - Time 56 min.
18650 XTAR 3500 mAh - Speed 1A - Start 2.98V - End 4.20V - Time 3.40 hours.
21700 Samsung 50E 5000 mAh - Speed 2A - Start 3.07V - End 4.20V - Time 2.20 hours.
26650 Efest 5000 mAh - Speed 2A - Start 3.31V - End 4.20V - Time 2.10 hours.

We see the XTAR ST2 charger with some batteries inserted inside it:










Conclusions:

I really enjoyed the XTAR ST2 charger. It is a complete and fast product, capable of recharging a battery up to 4.1A for both slots using compatible
power supplies. Excellent materials and the possibility to load even the long 21700 protected. Important is the monitoring of the battery temperature,
the OV activation to restore the over-discharged batteries and the possibility to manually choose 3 charging speeds.
Really an excellent product recommended for purchase.

2

What voltage does it switch over from the fast charge? How long does it take to get there on your 30Q for example? I see it took 56min to fully charge it, but I guess the real benefit of this charger should be how fast it can get you back to basically full and going again.

Thanks for the review!

3

Thank you for the review, interesting charger. I never had a Xtar device before but two cells is what I could go for.

4

I have not measured the voltage does it switch over from the fast charge, but I think that, looking at the test I did with the 30Q, the declared values on the charge speed are correct.

5

Thank you for reading it.

6

What adaptor would you recommend, that could be bought on BG/GB/FT?

7

Isn’t 4,1A charging each cell rather bad for cycle life, especially for high capacity cells?

8

I’m wondering that too. I’m wondering if since they are temp monitored that it may not be so bad. My other thought is, even if it is bad, how bad is it? Will I only lose 5% of my charge cycles? That may be worth it for some to be able to charge this fast.

9

What voltage does the charger terminate at, measured with an accurate multimeter?

10

It’s a little over 1( or 2C) for most of 18650s, of course the cycle life will be reduced,but not too dramatic, not all people care about that, mostly it’s the people who doesn’t store 18650s at home

11

A compatible PD2.0 (Power Delivery) or QC3.0 (Qualcomm’s Quick Charge 3.0) adapter.
QC3.0 is quite common and you find it without difficulty.

12

For me, recharging to 4.1A is to be used only if necessary.

13

My multimeter finally scored me 4.19V.

14

/\ . 4.19V…. nice. :+1:

Very good review… thank you!! :beer:

15

Not bad at all,very close to perfect :+1:

16

Great charger, but that’s a bit disappointing. For example why not 3A if the cell allows that. This way only very good cells benefit from the 4.1A. 2A charge isn’t very special.

BTW great review, it gave me a lot of info.

Do such cells fit easily in the charger? I’ve seen chargers that are 21700 compatible, but the fit is so tight a crowbar is needed to get them in their slot :slight_smile:

Last question. In my car I use a 2A 1 slot Basen charger. 26650 cells fit and charger but due to their size contact is bad. A bad road can be enough to shift the battery a tiny bit and charging stops.
So my question is: does this charger has that problem?

17

I’m one of those some…. but I admit putting more spare cells in my car might be the smarter option. But even then, life can be chaotic and a quick charge can be needed.

Don’t forget about 26650 cells (5200mAh). For those cells 4.1 amps is more suitable.

Another thing is that the charger picks a safe current. That means that the charger doesn’t blindly pump 4.1A into every cell. Yeah, the user can override that. Can XTAR be blamed for that?

18

That’s correct, but still a small warning about car chargers.

The max input of the charger is 3A @15v.

This charger is QC3/QC4 but only outputs 2A @12v. (24 watt)

So:
XTAR can handle 45 watt
Car charger maxes out at 24 watt

2 cells charging at 4.1 amps (possibly) require 34 Watt.

So… while QC3 this charger isn’t powerful enough for the XTAR.
I have charger of this brand to charge my OnePlus with Dash charge in my car. It works great until outdoor temps reach the upper 80’s then it suddenly charges much slower. Overheating I guess.
So while roma58 is 100% right QC3 chargers are easily to be found, it’s not so that all allow you to reach the full potential with the XTAR.
Just my two cents.

19

Perhaps you can tell if its USB C could also work for output (i.e. power bank mode)?

20

No, it doesn’t have that function.