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?
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.
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.
Certainly yes. 12V is something very universal and almost all people have 12V adapters at home from some old modem or external hard drive, some other peripherals.
Problem with xtar is not allowing fast charge with 5V even if they decided to go with 5V power supply
I could easily plug in a PC power supply 5V output which is 20A or more and everything would still work perfect. But this doesn’t help since charge current is reduced with non qc power supply. So I consider QC support only as marketing gimmick. And they did this only for not supplying just a 12V 2A adapter with charger. They could make it 12V and make the adapter optional, that would be much better.
Understand it for my Skyrc NC1500 because it´s a very compact charger which can be carried in a bag and used with a Powrbank. But the VC4SL is not a handy charger which gets carried normally
I’ve got an old Nitecore SC4 and use that off unregulated 12V (e.g. voltages similar to what you’d get out the cigarette lighter output in a car.) Sadly 21700 batteries (unprotected) barely fit, but finding something that will run off unregulated 12V and fit long cells is proving difficult. Vapcell make a 12V model but it apparently shouldn’t be used on unregulated 12V.
