Overview
The XTAR MC2 is a compact, two-slot USB charger for cylindrical lithium-ion cells, covering everything from small 10440s up to 26650s and protected 21700 cells. It charges both slots at a full 1A simultaneously — no current-splitting penalty for using both bays at once — and uses a 3-stage charging process (trickle, constant current, constant voltage) to bring cells to a full, stable charge without overcharging them.
It's built for people who want a genuinely portable charger that doesn't force a trade-off between size and charge speed: small enough to carry in a bag, fast enough for regular use.
Full Specs
| Parameter |
Value |
| Model |
MC2 |
| Input |
Type-C, 5V⎓2A |
| Charging Current |
1A per slot (both slots simultaneously — 1A x1 or 1A x2, not shared) |
| Charging Method |
3-stage: trickle charge → constant current → constant voltage |
| End-of-Charge Voltage |
4.2V ±0.05V |
| End-of-Charge Current |
<130mA cutoff |
| Operating Temperature |
0°C to 40°C |
| Dimensions |
L103mm x W53mm x H30mm |
| Weight |
54g |
| Compatible Chemistry |
3.6V/3.7V lithium-ion (Li-ion/IMR/INR/ICR) |
| Compatible Cell Sizes |
10440, 14500, 14650, 16340, 17335, 17500, 17670, 18350, 18490, 18500, 18650, 18700, 20700, 21700, 22650, 25500, 26650 |
| Protected Cell Support |
Yes — supports protected 21700 cells |
| Special Feature |
"0V" activation technology for recovering some over-discharged cells |
| Status Indicators |
Green = standby or fully charged; Red = actively charging; Off/unlit = reverse polarity or abnormal insertion |
| Safety Protections |
Reverse polarity protection, short-circuit protection, automatic charge cutoff |
How the Charging Process Actually Works
The MC2 doesn't just dump current into a cell and stop — it moves through three distinct stages:
-
Trickle charge — a small preliminary current tops off and, where applicable, helps activate a deeply discharged cell before ramping up.
-
Constant current — the charger increases and holds a steady current while the cell's voltage climbs; this is where most of the capacity gets restored, and it's the fastest-charging phase.
-
Constant voltage — as the cell approaches full charge, the charger holds voltage steady and gradually reduces current, topping off the last portion of capacity without pushing the cell past a safe voltage.
This is standard, sound practice for lithium-ion charging — it's what protects cell longevity better than a charger that just charges at a flat current until it hits a voltage cutoff and stops abruptly.
What Makes This Charger Worth Considering
-
Real 1A per slot, no splitting — plenty of basic dual-slot chargers cut each slot's current in half when both bays are occupied. The MC2 doesn't do that: each slot gets a full 1A regardless of whether the other is in use, so a typical 18650 charges in a few hours rather than most of a day.
-
0V activation — most basic chargers simply refuse to recognize a cell that's been discharged too far below its normal cutoff voltage. The MC2's activation function can attempt a slow, controlled recovery charge on some of these cells rather than treating them as dead on arrival. It won't save every over-discharged cell — some genuinely are beyond recovery — but it gives borderline cells a real chance.
-
Broad size compatibility — from small 10440s (common in flashlights and ) up through 26650s, plus protected 21700 cells, this one charger covers most of the cylindrical lithium-ion formats you're likely to own.
-
Simple status reporting — the LED colors are unambiguous: green means it's either standing by or done, red means it's actively working, and no light at all is the charger telling you something's inserted wrong before it does anything else.
What to Keep in Mind
-
This charges bare cells only in the sense that it doesn't manage discharge-side protection. The MC2 handles charging safely (voltage/current cutoffs, reverse polarity, short circuit), but if you're using unprotected cells in a device, that device still needs its own low-voltage cutoff — the charger's protections don't extend to how the cell is used afterward.
-
Operating temperature matters. Charging outside the 0-40°C range isn't something this charger is rated to handle safely — keep it somewhere reasonable, not in direct sun or a hot car.
-
Two different cell sizes at once is fine. Because the slots operate independently with automatic detection, you can charge, say, one 18650 and one 21700 side by side without an issue.
Frequently Asked Questions
Q: How long does it take to fully charge a typical 18650?
A: At a full 1A, a 2,500-3,000mAh 18650 typically reaches full charge in roughly 3-4 hours, accounting for the tapering constant-voltage stage near the end. Larger cells (21700, 26650) will take proportionally longer given their higher capacity.
Q:Does charging two cells at once slow either one down?
A: No. Each slot delivers its own full 1A independently — you're not splitting a shared current budget between the two bays.
Q: Can this charge protected cells?
A: Yes, it supports protected 21700 cells. For other protected cell sizes, check the cell's own spec sheet — protection circuits vary and some add length that may not fit every charger's slot depth.
Q: What does it mean if a slot's LED doesn't light up at all?
A: That typically indicates a reverse-polarity insertion or another abnormal condition the charger has detected. Remove the cell, check its orientation, and reinsert.
Q: Is the "0V activation" feature safe to rely on regularly?
A: It's meant as a recovery option for occasional over-discharge situations, not a substitute for storing and using cells properly in the first place. A cell that repeatedly needs 0V activation is showing signs of wear or misuse and is worth watching more closely — or replacing.
