Testet a bit again, the 4th Slot don´t charged so far one cell to full and shows at Grad.Function also to less values.
The 1st slot worked at this try, I wonder whether it depend on the number of used cells or selected current. Mayb I get soon a QC3.0-PSU and test it again.
Update
I ordered a QC3.0-Power supply from Xtar and tried it again.
A Mediarange AA 2100mA was loaded like it should loaded
All other AAA I tried stopped at 50% load or below. Strange, some weeks ago all AAA in bay 1-3 were loaded correctly
This charger seems to be extreme bad for NiMH
Managed to load some 3 AA NiMH successfully, dunno how
But no matter which load current I selected, it was loaded at 500mA
So this charger still get the title worst charger ever (for NiMH)
I also notice this issue with early termination during charging with NiMH batteries (I use both AA and AAA, Eneloop and Ikea Ladda).
I tried contacting Xtar support, and their reply was:
“The main reason, according to our technician, is due to incompatibility. ”
I’m trying to get some more information as to what this means.
Thank you for the info.
Eneloop/Ladda are the reference, if Xtar is overwhelmed with it -> Bad products by Xtar
I bought this charger shortly after release. Keep reading bad stuff about it. Which charger would you guys recommend?
I don’t want to hijack this thread since I think SammysHP’s review should be the focus. I’ve started a new thread here to continue the discussion:
https://budgetlightforum.com/t/-/70506
What IR measurement is considered bad battery?
I think we really need HKJ to come out of semi retirement and review this charger.
I´m not sure if it makes sense. It will be no better charger after the review.
I would be more interested in reviews of newer and upcoming chargers. Vapcell seems to be interested to make chargers with properties ppl want
Today I bought Xtar vc4 plus which is considered to be the retail version of xtar vc4sl with same specifications.
I just placed a Chinese AA Eneloop which is probably in a bad condition, aged and has been over discharged before. Cell is rated 1900 mah and prior to charging it dropped to 0.9V while being used in a wireless mouse which draws very low current so you can consider it totally depleted. Charger measured 60 miliohm and started with 2A. It terminated early at 130 mAh. I pulled it out just after termination and measured voltage, it was 1.45 V and was dropping so fast so it probably reached 1.55V and that’s why it was terminated. When I reinserted it, internal resistance was measured 170 miliohms. So probably charger didn’t terminate early in vain. This time it decreased charge current to 500mA and it’s still charging while I’m writing this message.
So I guess the reason why vc4sl and vc4 plus terminates early is because temporarily internal resistance increases and this also increases total cell voltage. Since charger cares for instantaneous internal resistance but not a moving average of resistance nor an average value, it terminates early.
This can probably be avoided by choosing a lower charge current.
I wish Xtar brought more customization options to its chargers.
I would like to add something more after using the grade function for the first time. I have a very old, many times depleted, over discharged 2700 mah cell. Its internal resistance was measured 760 miliohms. Its capacity was measured 370 mAh. And it stayed at 1V almost from the beginning of discharge so these results were expected. When charging it also terminated fast so I guess charger was able to terminate very old, high resistance cell properly.
But it terminates most cells in good conditions to early, my own experience
Don´t think my VC4SL is faulty, because other ppl have the same poblem. And some other Xtar which tested at HKJ were also unusable for NiMH
And Grade is extremely slow
Grading is slow, it discharges like 250 MA current. That would be much better if it discharged with hight current first and then drop discharge current as voltage approached to 1 V. However there’s already Skyrc mc3000 doing all these and unfortunately it doesn’t have a competitor with lower price. So I cannot criticize at that point. I wish Xtar had a competitor with reasonable price like 50ish USD.
I’ll test the charger with new cells too. And I’ll check if it terminates early. But I still feel like the problem is probably fluctuating cell resistance. My old cells which aren’t charged for 4-5 years have fluctuating voltage during discharge with Xtar. This means their internal rezistance is fluctuating during constant current discharge. I fell like it will stabilize with some charge / discharge cycles.
I’ll inform you if same thing happens with newer cells and if they terminate early. I really wonder what causes this. I don’t feel like it’s a buggy software, it should be more like a component inside. I’ll try to observe it if I can find PC connector if my multimeter. Sadly I don’t have an oscilloscope at home.
By the way what’s your charge rate for nimh while using xtar vc4sl?
Thank you for posting your experiences.
I stopped loading NiMHs with the VC4SL because it´s to annoying if it stops at loading most times half the capacity or less. Maybe it works better with very low charge rate at 250mA, but I never tried it. For AA with 2500mAH, even for my AAA with 1000/1100mAH it´s to slow for me.
The strange thing, some AA were loaded correctly, most AAA not.
I only used the manual charging because I´m not a fan of automatically charging because most/all chargers use the internal resistance as reference. And I had the feeling the VC4SL with manually mode it ignores also my settings. I used 1A but it still loads with 500mA.
With my other chargers I use for AA with capacity of >=2000mAh mostly 1A, for AAA with >=950mAh 500mA. 500mA loading are supported by most chargers
For AA with <2000mAh I use my Opus chargers which also provide 700 or 800mA and with AAA <950mA 300-400mA
IMHO the Vapcell S4 Plus is a good charger/analyzer for NiMH and LiIon. The bay 1 and 4 can discharge with 1A for NiMH, the bay 2 and 4 only with 500mA.
I ended up having the same immature termination with Nimh like you. Empty 2300 mAh FDK made Japan energizer extreme cells terminated at 300-400 mAh charge. I’m almost sure that the problem is related with implementation of Quick Charge. This charger seems to be terminating both by voltage or negative delta V, whichever arises first. If you charge a Nimh with 2A and then reduce charging current to 500mA when the cell is at 1.5V, it terminates. Probably because the cell voltage drops when you reduce charging current.
Quick charge only uses 9V. When you plug in the charger to a QC adapter, it starts with 5V. Even if you place only one battery, it negotiates voltage to 9V and never increases again. If you remove the cell, it drops down to 5V again. So it’s more likely a QC2 standard since it doesn’t use small voltage increments.
I feel like there’s a little voltage change when negotiating with the charger. And this triggers negative delta V termination. Negative delta V termination can even trigger when the cell is at 1.45 V. In fact this is a good thing when charging very old cells with high resistance since cell voltage never increases enough to trigger voltage termination.
When you’re feeding the charger with a usual 5V power supply there’s no premature termination and everything works perfect. Unfortunately the charing current is reduced.
I used a low quality 5V 2.4 adapter and the charger decreased charging current even more to 500mA with only one cell loaded. Because voltage dropped to 4.9 V under load after initializing charge current. Insufficient voltage was also evident since screen brightness was flickering between charge and battery voltage measurement periods. When I used 15W 5V adapter of my old Motorola moto Z everything was fine. This charger probably ramps up voltage with higher current drawn from it to compensate for cable voltage loss. No screen flickering, no voltage drop after initializing charge. This way charging current is 2A for one cell, 1A for 2 cells and 500mA for 4 cells. I checked termination with even 500mA while 2300 mAh cells were loaded and termination seemed good to me. It terminated at 1.5V without reaching 1.55V and with negative delta V.
So charger is fine but slow of you decide using it with just 5V adapter without QC. When you load 4 cells when using QC adapter, 3 of them terminates premature and last one terminates as it has to do. This is also a sign of bad QC implementation.
If we can somehow trick the charger using QC adapter but without furthermore negotiation with adapter, it will probably work fine. There are QC trigger adapters, they let you chose voltage of adapter and the adapter keeps working at the voltage you chose. But probably it won’t work since adapter only negotiates with qc trigger, not with xtar charger . I tried feeding 7V from an adjustable power supply but it still charged slow since it didn’t recognize the power supply as qc adapter. I didn’t want to increase voltage because I’m afraid that it will be fed to the circuit directly and qc circuit inside the charger will be bypassed when using no qc adapter.
It was really silly to make such a charger for Xtar. Charger always uses 9V no matter how many batteries you load and which current you select.
They could just use a 9V charger or better use a 12V universal charger which probably exists in all homes since almost all old modems, routers used it and everyone probably have one of them at home. This QC implementation was really unnecessary and I can only consider it as marketing gimmick.
Somehow the quick charge circuit inside the xtar has to be tricked and charged should think its always connected to a qc adapter. And 9V or 12V adapter should be fed to the xtar and it’ll work perfectly.
Thank you for the detailed explanation 
OK, we have in some cases similar behaviors, in some not.
I had also the case the ay 1-3 charged correctly, the 4th stopped much to early.
I used a power supply (no QC) with 2A from my LG-Smartphone and have the early termination with it.
With another power supply from a Samsung-Smartphone (no QC) the Display stays dark.
I have a Xtar power supply with QC and it also failed with the termination.
I have other power supplys without QC but I´m not sure if I wasting my time again with the VC4SL 
It looks like Xtar fails with basic requirements.
According to HKJ the VC8, VC2S and MC4S have also problems with NiMH.
The Dragon is good (HKJ Review), but a charger with this price should offer a discharge function and different charge currents for every bay.
The Dragon have a power supply included, could that really help to work better than with other Xtar chargers which are deliver no supply?
I don’t think that included power supply matters. If the charger works fine, it should work with any power adapter. Dark screen is because of low voltage power supply. Voltage drops a lot when it starts charging. Power adapters which ramp up current to compensate for cable voltage loss are much better. So you’re guaranteed to get promised voltage in your circuit no matter how much current is drawn. Many xiaomi chargers have that property. Some other chargers HKJ reviewed also had it.
I’m surprised that your xtar terminated early with no QC adapter too. I’ll inform if I’ll have same problem.
By the way grade function showed real capacity. I tried with a 1900 mAh Chinese Panasonic cell and it showed 1945 mAh. It discharged to like 0.8-0.9 V. And it already showed 1900 mAh when the cell was 1V. I also measured it with multimeter too. I tried to trick the charger applying 1.6 V at battery terminals if I could start discharging without charging cell but I couldn’t succeed.
My understanding is that USB have standards, so the different devices should work together.
The problem with a dark screen I don´t had. Atm I don´t know the requirements for the VC4SL.
It´s strange (strange is common by this charger) that my 2A LG PSU works a bit with the charger and with my 3A Samsung the screen stays dark with or without cells.
And I still don´t know whether the problems are only happen with NiMH
There are so many differing USB fast charging standards it’s not surprising a USB battery charger could have “issues” with some chargers.
There the various revisions of QC (Quick Charge), plus PD (Power Delivery) and some manufacturers (I believe Samsung is one) have their own standard. They all use differing voltages and currents to achieve the fast charging.
Here’s an article that goes through them How Does Fast Charging Work? Every Standard Compared | Digital Trends
It’s why I’d much prefer a charger that has a 12VDC input.