Running tests on the WF-139. Interesting results. A must read for WF-139 users.

[Meterman]

I've never before used my WF-139 because of it's reputation at CPF.

To see what's going on with it, I have soldered an external batteryholder to the PCB to have solid access to voltage and current.

Idle voltage without a battery is 4.88xxV, decimal places 3 and 4 very bouncy. (Can you say so?)

The battery was not empty when connected; voltage started jumping between 4.03V and 4.04V. Red LED on, green LED flashing in 1.4s beat. Current was measured by means of a high precision DC current clamp to not influence the circuit. Current jumped between about 0.35A and 0.38A and every 1.4s a dip.

At the scope, using a different current clamp for scoping, the reason was to be seen: the Current to the battery is pulsating with a pause at no current every 1.4s.

The voltage went up and up, so eventually at no longer falling below 4.25V in the rhythm I removed the non-protected battery for reasons of safety.

Thus I could not check for trickle charge.

I'd love to show the graph of the scope, but I don't find a way for attaching it.

Wulf

Edit: Thank you, Mr Happy, seems to work!
PDFs are better, but can't be uploaded this way. I'll see, what I can do.

[/URL][/IMG]

There is current shown, 100mV/A.

 

[Mr Happy]

To attach images to posts, upload them to a free hosting site like ImageShack and then include the image in the post with the image tool on the toolbar (the image tool is the icon that looks like mountains with the sun above them).

 

[Chongker]

Just tested this myself. On my first WF-139 (I have two ), with two RCR123 cells in the charger, I get a charging voltage of 4.30 - 4.35 V, but with only one cell in it, it sometimes jumps up to 4.4V! Is this particularly safe? And if not dangerous, how much is it damaging the poor little cell? Don't want it to eat away too many charging cycles Gonna test it soon with a larger cell soon.

Ohh, and btw, open circuit both my chargers read ~5V. Both were purchased this year (quite a newb here). Seems like the revision Ultrafire did was sometime in the past 1-2 years or so?

 

[OceanView]

Hmmm, very interesting story unfolding in this thread.

I just checked my WF-139 ordered in January 2007. No load is ~11V here, too.

 

[mighty82]

I'm testing my trustfire TR-001 right now. It looks similar to the WF-139 but it's a few dollars cheaper. The open circuit voltage is actually 0.0V. I guess this is a good thing? I'm charging a 14500 battery with a voltmeter attached so I can see if it terminates better than the WF-139. In that case it might be a better alternative Have any one else tried this charger?

 

[lightforce2]

Sweet, looking forward to hearing the results.

Eric

I bridged out the PCB on the Tenergy 18650 (to isolate PCB) & charged - The charge voltage peaked at 4.28v, the cell voltage was 4.20v at termination, the cell then settled to 4.18v. This is the same charging rate that I always see with protected Tenergy's

Interestingly I charged some AW 18650's that came in the post yesterday - Charge voltage peaked at 4.25v, the cell was 4.18 upon termination and then settled to 4.16. In this case it would appear the cells PCB may have terminated the charge otherwise the WF-139 would have taken it a little higher??

There's some very interesting test results showing up with the new vs older WF-139's!!

cheers

 

[jenskh]

My 139 shows a voltage that is constantly fluctuating between 4,95 and 4,75 when no battery. The charget also fluctuates with about 0,2 V while charging. 18650 batteries normally comes ot of the charger with 4,21 V a little while after the charger has turned green. I am also using it for 10440 batteries (I know I shouldn't). They comes out of the charger with 4,1 V.

 

[TigerhawkT3]

My WF-139, bought in December '06, shows about 11.6V OC. My universal NiMH/Li-Ion travel charger from KD shows 9.6V OC. My Nano charger (for AAAs) shows 4.29V OC. None of them have burned down my house yet, but I'd like to keep it that way. I'm guessing that using protected cells (except for sizes like 10440, which don't have a protected version) is the solution, right?

 

[zipplet]

I'd rather use the nano than the WF-139 if I were concerned about safety. Using protected cells works but the way the WF-139 terminates is going to shorten cell life compared to a proper charger such as the pila IBC.

 

[RangerJ]

OK, so we have established that the older WF-139's are no good. But, what about the newer ones. I have a brand new WF-139 with some new AW 18650's. The charger's voltage with no battery is 4.90V. Is this charger going to be OK? Perhaps I need to check the voltage while its charging to see if mine goes over 4.20V. How much over 4.20V can my batteries handle? Maybe I just need to get the Pila charger :thinking:

 

[lightforce2]

The charger's voltage with no battery is 4.90V. Is this charger going to be OK? Perhaps I need to check the voltage while its charging to see if mine goes over 4.20V. How much over 4.20V can my batteries handle? Maybe I just need to get the Pila charger :thinking:

For the battery to charge, current must flow into it. For this to happen the voltage at the charger needs to be higher than the voltage at the battery.
Exactly how much higher should the input voltagebe ? I'm not sure about that, a question that mdocod or silverfox may have the answer for

cheers

 

[zipplet]

It doesn't have to be higher than the max topping off voltage. A simple li-ion charger can supply 4.2V limited continuously with current limiting (a so called CC/CV charge).

CC = constant current - the battery absorbs energy at a maximum limited current until it hits the top off voltage.
CV = constant voltage - the battery is at the top off voltage (4.2V for normal li-ion), but is still charging (current is dropping)

 

[lightforce2]

It doesn't have to be higher than the max topping off voltage. A simple li-ion charger can supply 4.2V limited continuously with current limiting (a so called CC/CV charge).

If the charger had a maximum output of 4.2 then the charging would be self limiting once the battery voltage was raised to 4.2, in effect the charger & the battery would equalise??

 

[zipplet]

Correct that is what happens however it is good practice (and manufacturers insist) to terminate charging once current drops below a certain level (I'm using 0.1C) otherwise you keep the cell at that voltage for a prolonged time which causes degredation.

 

[harddrive]

I just checked my WF-139 ordered in January 2007. No load is ~11V here, too.

Mine is about that age too and reads about 11.6V.

 

[lctorana]

If the charger had a maximum output of 4.2 then the charging would be self limiting once the battery voltage was raised to 4.2, in effect the charger & the battery would equalise??

Yes. That is right.

However, during the earlier, "CC" stage, it is perfectly acceptable for a much higher source/supply voltage to be used via a current regulator. Then, when the battery reaches a certain voltage (SilverFox, please tell us what that knee voltage should be), the source voltage shoud be rigidly clamped at 4.2V (or 4.19 or whatever) for the "CV" phase.

 

[Mr Happy]

Yes. That is right.

However, during the earlier, "CC" stage, it is perfectly acceptable for a much higher source/supply voltage to be used via a current regulator. Then, when the battery reaches a certain voltage (SilverFox, please tell us what that knee voltage should be), the source voltage shoud be rigidly clamped at 4.2V (or 4.19 or whatever) for the "CV" phase.

Actually, that voltage would be 4.2 V (say).

What happens is that if you applied 4.2 V to a discharged battery, the current would be higher than the maximum permitted. The current regulator in the circuit works by reducing the voltage below 4.2 V and thus reducing the current to the designed limit.

As the cell charges, the cell voltage rises towards 4.2 V, where it stops and should go no higher. Meanwhile the cell continues to charge and the current limiter has less and less work to do. Eventually, the current limiting drops out of circuit and the current slowly falls towards zero.

When the current reaches a preset minimum value the charger should switch off.

Not all real chargers (e.g. the WF-139) may follow exactly that algorithm, but that is theoretically how Li-ion chargers are supposed to work. The voltage should not be allowed higher than 4.2 V because that may cause chemical damage that will reduce the life of the cell, and the current should not be allowed higher than the permitted maximum because that may be too much for the cell to absorb and may also cause damage.

 

[Norm]

My WF-139 is an older one measures 11.8V.
Fortunately I no longer use it, I do all my charging with http://www.hobbycity.com/hobbycity/...me=iCharger_iC6_Digital_Balance_Charger_6cell
and a VoltCraft battery holder https://www.candlepowerforums.com/posts/2471925&postcount=56
Interesting thread, just wondering what people think of the older Wolf-Eyes Charger CH-02 it seems to depend on the battery's protection circuit to terminate the charge, I once put an unprotected 18650 in it and the voltage was way over 4.2V (can't remember exactly how high).
Norm

 

[EssLight]

Just to add my own data to the mix, I have a WF-139 that I bought from Lighthound in August 2007. When charging AW protected 18500s, the protection circuit on the cells would reliably terminate charge at 4.25 V, at which point the charger would then show 4.60 V across the open protection circuit. I got in the habit of monitoring the charge and manually stopping it when the cells were around 4.15-4.20 V. With no battery in the charge bay, the voltage across the charger terminals is 4.90 V.

I feel reasonably confident using my WF-139 to charge protected cells, as long as I keep an eye on it. I'm curious at what voltage my charger would terminate with an unprotected cell, but I don't have sufficent fire protective gear to run that test.

EssLight

 

[mdocod]

The only unprotected cells I own are some Emoli 18650s obtained recently. Since this is a much safer chemistry I wasn't afraid to leave em on the charger and see what would happen, I didn't monitor them to see how high the charge voltage got up to during the charge, but the cells were sitting at 4.18V when the light turned green, not too bad I suppose.

For now I'll continue using this charger and mostly just avoid letting it sit and trickle after it turns green, as that is really the biggest problem with the charger. The CC only charge style that ramps up to ~4.30V during the charge is really not as awful as it sounds, it's not *good* but it in and of itself is very unlikely to cause an explosion or anything, especially on a protected cell that can terminate the charge if it gets way out of hand. As mentioned previously, the Wolf-Eyes system has been using this charging method for a long time, and I have not heard ANY reports on these forums of a wolf-eyes cell exploding.