18650 Li-Ion Chargers Round-up (6+ slots): Xtar vs Foxconn vs Trustfire – [En]

        I have reviewed 3 of the 4 high slot count chargers available currently on the market. All chargers have been intensively used on the long term, so the conclusions should be quite relevant. Here they are:

        Xtar WP6 6-slot
+ Does not use clamps
+ Comes with spacers
– Can overheat batteries
– Dual channel
– Charge status reset
– Does not charge NiCd
– No over-disharge recovery
Maximum simultaneous 26650 cells: 4/6
Overall Rating: 47/100

        The Xtar WP6-II is the first charger with more than 2 slots I used. The case design is pretty good. LEDs are red when charging and turn green when cells are fully charged. The charger does not use retractable clamps, which makes putting in cell and removing them pretty easy. For other than 18650 Li-Ion cells (10440, 14500, 14650, 15270, 16340), it uses spacers which are very well designed (can be stacked). I truly prefer such a system compared to clamp-based one. Clamps can even damage you when using them (seriously, some are very hard to open and when you remove a battery you must be quite careful not to injure yourself). The power adapter for this charger is external, goes directly into the outlet.

Unfortunately, this charger has some bad things in it’s design. Even if there are 6 slots, they work in pairs, that means when you use all 6 slots, you will get half the current per cell you would get if using up to 3 non-consecutive slots (1,3,5 or 2,4,6). Also, that means you will have to charge cells of very similar total and current capacity in consecutive slots (1,2 ; 3,4 ;5,6). Doing something like putting a cell with 4.0V (almost charged) in slot 1 and a 3.3V (completely discharged) in slot 2 would not be good at all.

Another big issue is excessive overheat of cells. There is no protection, and if you use cells that are partially not good (that do not charge at full capacity), the charger will persist in trying to charge them to full and cause excessive overheat, up to setting them on fire. So don’t let it on over-night if your cells are in bad shape.

A little bug I encountered with this charger is that sometimes if you remove one or 2 cells, some of the others’s LEDs will turn green even if the cells are not charged and you will have to re-insert them (kind of a forced refresh). Then LEDs turn back to red and cells keep charging. This bug does not happen when inserting new cells, only when removing some of the charged ones.

The biggest problem I actually had with this charger it was that at a point it just started dying. It started to reset after a few minutes (cell status was re-read, just like re-plugging it in). Then more often and then it didn’t work at all. Upon investigation I have determined that one component on the main-board was overheating. It was a small (1mm) resistor of 47 Ohms. I did some further testing and everything else looked fine. So (rocket surgery time), I took a good old Soviet-era 4 cm length by 1cm in diameter 47 Ohm resisor (the dark green one, electronics fans will know), I replaced the inferior one, making sure that part is the last thing that will even burn out in that circuit. Worked fine ever since and I’m glad it wasn’t a complex I.C. damage because I would not had a replacement for that. Regarding battery spacing, you can charge 6 18650s with thicker casing, but no 26650 can fit in.

Given all the above, I rate the Xtar 47/100.

        Foxconn Universal Intelligent Charger 8-slot

+ 8 Slots
– Battery contacts
+ Charge level LEDs
– Charge level inaccuracy
– Can overheat batteries
+ Battery Space
+ Independent channels
+ Can charge NiCd
+ Over-discharge recovery
Maximum simultaneous 26650 cells: 7/8
Overall Rating: 83/100

        The Foxconn Universal Intelligent Charger 8-slot I ordered on-line from UK, since it was not available in my country at the time I wanted to acquire one.
Having 8 truly independent slots was gold for me, since I sometimes charge batches of dozens or more cells. What I liked about it is that it has charge level indicators. There are 3 nice orange LEDs that indicate load level. They could use a redesign, though. Unfortunately, they are not calibrated properly and most of the time the load level will be at 2.5/3 (2.5 meaning 2 LEDs on and 3rd blinking). If you put in an over-discharged cell, the 1st LED will blink, but as soon as the voltage reaches the one of discharged cell, the indication will be 2.5 again, even if the cell is completely empty. I found a trick here: reinserting the cell after a few minutes will make the charger reevaluate the indication and it will start showing 1.5/3, which is way better compared to showing 2.5 for hours. Now those indications could really use some tweaking. Instead of showing 0.5/3, 1.5/3 2.5/3 and 3/3 (fully charged indication) they should also have 1/3 and 2/3 indications (1 LED on and 2 LED on with none blinking).
As a general recommendation, when you add cells that are near empty or over-discharged, re-insert them after about 1 or 2 minutes and you’ll have a more accurate (well, actually less inaccurate – to be grammatically correct) charge level indication.

Since I’m talking about LEDs, I’d like to mention that the charger also has a general power indicator blue LED. This one is pretty powerful and can light your room at night, so you may be bothered by this if you want to sleep with the charger in the same room. But, that LED light can also help if you want to change batteries at night. You won’t see cell colors in their true color but you won’t have to turn the light on just to change cells. Since it can be an advantage and a disadvantage in the same time, I don’t take this LED in the overall rating consideration. If you can’t sleep due to its bright light, put a coin on it and it’s ‘fixed’. The power adapter is brick-style (like notebooks have). Cell overheating is lower compared to the Xtar.

Battery spacing is quite enough to accommodate 18650s with larger casing. You can fit in 26650s if you skip the near-by slots. Another advantage of this charger is that it can also charge NiCd, but I do not use it for thins since I consider NiCd obsolete. What I did not like about this charger is that the battery contacts are a little weird. At the (+) pole, there’s a pin on the lower side and one a little higher, but in the case of recycled 18650s both pins can land on the case instead of the (+) center area of the cell, while the metal center of the cell is not in contact with the charger pins . Nothing a little moving around can’t usually fix.

Considering all this, I rate the Foxconn 83/100.

        Trustfire TR-12 6-slot

– Sometimes needs retries
+ Internal power adapter
+ Independent channels
+ Can charge NiCd
– Can overheat batteries
– No over-discharge recovery
Maximum simultaneous 26650 cells: 3/6
Overall Rating: 72/100

        I got this from a local dealer, since needed one more charger because I was in the process of repairing the Xtar. I find it good overall, all 6 cells are independent and charge quite well. There is no space for anything extra, though. If the casing of your 18650 cells is custom and a little thicker, you will have some trouble fitting in the cells. LED indications are standard, green for ‘charged’, red for ‘charging in progress state’.

A convenient thing for this charger is that the power adapter is internal, built-in the charger casing, which is pretty comfortable since you only have the power cord externally. This is though problematic if you need to change the adapter, but for the average user the comfort is a plus. The charger can also charge NiCds, but as I said I’m not personally interested in this. It’s a plus though, so it counts. Unfortunately the charger cannot recover over-discharged cells. Would of been nice if it could.

I found bug in this one too: sometimes cells are just not detected on the 1st try. Although you insert them, the LED does not turn RED and charging does not start. Does not happen too often and when it does it’s mostly for nearly charged cells. It’s fixable by re-connecting the cell (may take 2-3 retries). This charger can also overheat cells in bad shape, but not as fast as the Xtar.

Taking all capabilities into account, I rate the Trustfire 72/100.

        In conclusion, my pick out of the 3 today would be the Foxconn, mostly due to the possibility of over-discharge recovery.


I did not had the opportunity to review the Klarus C8 (no avaialbility near-by at this point), which could of been a worthy contendent to the other 3, but if I do in the near future, I will add it to this round-up.

I did not take pricing into consideration. Prices were too variable to make some relevant averages. That, combined with various special offers, made me think it’s better to ignore this aspect.

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