Testing of Ultrafire WF-138 and WF-139 chargers

[GrAndAG]

Recently I've made some tests of my Ultrafire chargers and just wanted to share some results...

UltraFire WF-138



Test results (Li-Ion 3.6V)

- averaged by 10 sec
- without averaging (click to enlarge)

The charging was started at 260mA current, which decreased slightly and almost constantly during the process to 180mA at the end. The charging voltage was 4.35V at the end of charging. When the charging was finished there was no charging current (0mA, no tickle charging), the battery voltage was 4.26V (after 0.5 sec), after 30 min - 4.20V.
It seems the charger uses CC method only, but the its power supplier is a bit weak to provide proper power.


Test results (LiFePO4 3.0V)

- averaged by 10 sec
- without averaging (click to enlarge)

The charging was made by 320mA current during almost whole process, and only at the last 3 minutes there was a slight decrease to 250mA with rapid increase in voltage (to 4.0V) simultaneously. Battery voltage was 3.80V just after the charging, and decreased to 3.40V after 3 minutes.



UltraFire WF-139


Note: I have the new generation charger, the 5V open circuit.

Test results:

- averaged by 10 sec
- without averaging (click to enlarge)
- zoom on transition phase (click to enlarge)

The specs clam that the charging current is 450mA, but the actual charging was made at 360mA. When 4.15V was reached the current started decrease slightly, which should be supposed to be the CV stage. But the weird things happened here - the charging current dropped to 220mA, continued decreasing during following 70 seconds to 170mA, after that the charging almost stopped. After 10 seconds the charger "woke up" and increased the current back. the rest time it tried to work in CV mode, but without a huge success. The maximum charging voltage was 4.25V (260mA) at the end, after that the charging stopped. When the charging was finished there was no charging current (0mA, no tickle charging), the battery voltage was 4.16V (after 0.5 sec), after 10 min - 4.14V.

Addendum: After an hour I decided to continue charging of that battery by switching off/on the charger. The charging recommenced. The charger easily exceeded the previous stop limit and continued to feed the battery. During the next hour it additional added 250mAh to the battery. Why did it stop the charging earlier before? I have no idea.
But! After that hour, when the charging voltage was 4.35V (@200mA), the interesting thing happened - the voltage started jumping from 4.35V to 4.9V and back! I suppose it was the result of battery protection PCB work. But the charger ignored that event and continued to charge. After 25 minutes I decided to abort the experiment, because it seemed the charger wont stop. The battery voltage showed 4.28V after the experiment and did not decrease after 10 minutes.
The charts:

- "overcharging" (click to enlarge)
- magnified (click to enlarge)


P.S. Sorry for my ugly English.

 

[EngrPaul]

Thank you!

What battery are you charging?

 

[GrAndAG]

WF-138 was tested with:
- DX's BTY CR123A 3.7V 850mAh
and
- DX's Lithium LiFePO4 Battery (350mAh)

WF-139 - with:
- DX's Ultrafire 3.7V 2400mAh LC 18650 Protected Battery

 

[rantanplan]

I monitored the charging voltage of my WF-139 some time ago and the charging voltage reached levels of above 4.30V too ... even though the battery measured only 4.18V after correct charge termination, I don´t use my WF-139 anymore.

The RC guys with their LiPos are saying that even some milliseconds above certain critical voltage levels do harm their batteries ... so for myself I assume that LiIons with cobalt chemistry don´t like such high voltages neither. There are cheaper chargers that do that job better than the Ultrafire crap ...

In the meantime I got a RC charger which can charge everything pretty nice, so my WF-139 is already half in the garbage can ...

 

[SilverFox]

Hello GrAndAG,

It is generally thought that any time spent over 4.20 volts will reduce the cycle life and capacity of a Li-Ion cell. This charger seems to spend a lot of time with the cell over 4.20 volts...

Many cell manufacturers recommend charging at 0.7C. It seems that at this rate the time spent a 4.20 volts is somewhat minimized.

The RC people have tried charging at faster and slower rates and they have settled on 1C. This is a little faster than the 0.7C recommendation, but it seems to work well.

I don't know how much this over voltage effects the cells. Does anyone have any information on cycle life with cells charged on this charger?

Tom

 

[konut]

There are cheaper chargers that do that job better than the Ultrafire crap ...

In the meantime I got a RC charger which can charge everything pretty nice, so my WF-139 is already half in the garbage can ...

And which charger would that be?

 

[jirik_cz]

I have Digital Li-Ion 18650 Battery Charger from DX. It has 4.18V open circuit voltage. Light goes green at 4.15V then trickle charges to 4.18V and stays there. But my friend has this charger too and it overcharges to 4.27V Has anyone experience with solarforce chargers?

 

[cheetokhan]

GrAndAG, what equipment did you use to measure the voltage and current and to generate these graphs?

 

[GrAndAG]

I used Medusa Power Analyzer Pro.

 

[mdocod]

GrAndAg,

You're english is great IMO! Don't worry about that! The Tests are Awesome!

I am really glad to see these tests and I can not tell you how much I appreciate it. I am always looking for more good information about chargers and batteries.

So we know that these chargers are not following the recommended charging algorithm as per manufactures recommendations for li-ion cells. Very few actually do. Oh well....

I've found myself using my old DSD more and more lately after I did a crude test of my 139 and found it pushing cells over 4.30V during charging. The DSD will bring cells up around ~4.25V at the highest during the charge, and always terminates without trickle and cells always settle quickly after termination to less than 4.20V.

 

[rantanplan]

And which charger would that be?

The "Digital Li-Ion 18650 Battery Charger" (sku.6105) from Dealextreme is working fine. It is using the CC/CV method and charges the batteries close to 4.2V. no serious overcharging ... and that for less than $9 shipped .

I´m using now a GT Power A6-10 (=chinese copy of e-station BC-6 from Bantam, $80 w/o shipping from HK). The A6-10 can charge 1-6 cells (LiIon/LiPo) with up to 10A and NiMH, NiCD and PB of course too. There are lots of similar chinese charger (iMAX, Mystery,...) ... they are much cheaper than original ones, therefore the quality you get is a "lottery" too. I had luck with my charger so far, others didn´t with this "cheap way". I chose this one because of the PC interface ... if you don´t need that, the "Tenergy Microcontrolled ...." charger (1-4 cells), available at all-battery.com, should be a nice one too.

My A6-10 tends to undervolting by 20mV, so a single LiIon comes out with 4.18V max ... fine for me-

But I would still use my cheap charger from DX for my 18650s, but I fried one channel during testing. I remembered that I´d done some tests with my chargers a couple of month back, I even found the graphs :

... my WF-139 did over 4.4 volts, now I remember.

Ultrafire WF-139

bigger one

Digital Li-Ion 18650 Battery Charger

bigger one

In both tests I used two discharged Trustfire 2.500mAh. Voltages of both channels were monitored by a Labjack U12 DAQ device. The measurement wasn´t the most precise one which you can see at some spikes due to movement I guess, but it should good enough. The behaviour of the WF-139 was interesting. Every couple of seconds it stops charging and the battery drops to resting voltage. You only have to look at the lowest values of a small period of time and get the real battery voltage. You can see clearly see too that the WF-139 use only a CC charge ... that´s why the voltage gets so high.

 

[12Johnny]

Thanks for the superb test!

 

[moldyoldy]

The "Digital Li-Ion 18650 Battery Charger" (sku.6105) from Dealextreme is working fine. It is using the CC/CV method and charges the batteries close to 4.2V. no serious overcharging ... and that for less than $9 shipped .

I´m using now a GT Power A6-10 (=chinese copy of e-station BC-6 from Bantam, $80 w/o shipping from HK). The A6-10 can charge 1-6 cells (LiIon/LiPo) with up to 10A and NiMH, NiCD and PB of course too. There are lots of similar chinese charger (iMAX, Mystery,...) ... they are much cheaper than original ones, therefore the quality you get is a "lottery" too. I had luck with my charger so far, others didn´t with this "cheap way". I chose this one because of the PC interface ... if you don´t need that, the "Tenergy Microcontrolled ...." charger (1-4 cells), available at all-battery.com, should be a nice one too.

My A6-10 tends to undervolting by 20mV, so a single LiIon comes out with 4.18V max ... fine for me-

But I would still use my cheap charger from DX for my 18650s, but I fried one channel during testing. I remembered that I´d done some tests with my chargers a couple of month back, I even found the graphs :

... my WF-139 did over 4.4 volts, now I remember.

Ultrafire WF-139

bigger one

Digital Li-Ion 18650 Battery Charger

bigger one

In both tests I used two discharged Trustfire 2.500mAh. Voltages of both channels were monitored by a Labjack U12 DAQ device. The measurement wasn´t the most precise one which you can see at some spikes due to movement I guess, but it should good enough. The behaviour of the WF-139 was interesting. Every couple of seconds it stops charging and the battery drops to resting voltage. You only have to look at the lowest values of a small period of time and get the real battery voltage. You can see clearly see too that the WF-139 use only a CC charge ... that´s why the voltage gets so high.

With an oscilloscope this was a good test. A DMM simply cannot react fast enough to register the resting voltage which evidently is the basis for cutoff of charging.

FWIW, My observations also support the theory that the WF-139 uses a CC charge. the best example of that is to observe the voltages when charging an 18650 cell and when charging an RCR123 cell, both AW branded. The 18650 cell overshoots the intended 4.2v cutoff by very little because of the much lower internal resistance. Charging the RCR123 cell results in voltage much higher than 4.2v because of the comparatively much higher internal resistance.

Note that some battery charger designs do not like to have the power cycled in the middle of charging - that messes up their programming. First the mains power, then insert the battery. If you want to restart charging, always remove the battery, then reinsert some seconds later.

I wonder about the presumed cell damage under conditions of a constant current charge cycle raising the cell voltage above the desired 4.2v when in fact the cell chemistry is still below a nominal fully charged state. Is the cell damage incurred by overcharging the chemistry beyond a full charge? Or does is the cell damage incurred at any time when the cell is above 4.2volts regardless of the status of the cell chemistry?? When does the proposed cell damage occur?

 

[moldyoldy]

<snip>
P.S. Sorry for my ugly English.

u vas otlichnij anglijskij yasik. Pyatyorka! :wave:

 

[DHart]

139 user listening closely...

 

[mdocod]

With an oscilloscope this was a good test. A DMM simply cannot react fast enough to register the resting voltage which evidently is the basis for cutoff of charging.

FWIW, My observations also support the theory that the WF-139 uses a CC charge. the best example of that is to observe the voltages when charging an 18650 cell and when charging an RCR123 cell, both AW branded. The 18650 cell overshoots the intended 4.2v cutoff by very little because of the much lower internal resistance. Charging the RCR123 cell results in voltage much higher than 4.2v because of the comparatively much higher internal resistance.

Note that some battery charger designs do not like to have the power cycled in the middle of charging - that messes up their programming. First the mains power, then insert the battery. If you want to restart charging, always remove the battery, then reinsert some seconds later.

I wonder about the presumed cell damage under conditions of a constant current charge cycle raising the cell voltage above the desired 4.2v when in fact the cell chemistry is still below a nominal fully charged state. Is the cell damage incurred by overcharging the chemistry beyond a full charge? Or does is the cell damage incurred at any time when the cell is above 4.2volts regardless of the status of the cell chemistry?? When does the proposed cell damage occur?

:twothumbs

I really like the way you explained the "CC" only charge methods and proofing that based on the different effects on different cells sizes (I've come to the same conclusions but I really appreciate your method of explaining it as we need more ways to make this make sense to the masses!)...

As for when and how much cell "wear-and-tear" occurs during CC-only charging... this is something I have wondered quite a bit myself. After a great deal of pondering on this one, I have come to the conclusion that cell manufactures would have noted a CC-only charge method in their "specs" if it were equally viable as the CC/CV and could generate equally good cell health and life. Problem is, I haven't seen a single spec sheet even mentioning this charging routine, which leads me to believe that it is probably not the best thing for the cells.

Imagine filling a tank or bottle with a fluid. when you force fluid in a stream into the container, a "bubbly" surface of the fluid develops. If you want to fill the container to the top without spilling anything, you have to slow down the fill rate towards the end so the bubbles can settle. I think of filling a Li-Ion cell very much like this, if you want to "fill it up" properly, without any wasted cycle life, (spilled fill material), you have to slow down the charge rate at the end of the charge.

 

[moldyoldy]

Hmm, here is a rather hard-nosed view of Li-Ion chargers from an engineering design standpoint:

A product is designed to a set of requirements. That product is later released for sale with identified specifications. Any use outside of those identified specifications not recommended. Any deficiencies in design as derived from usage reports is then incorporated into a revised set of requirements. The design cycle begins anew.

It needs to be noted that the sales and specification information posted on the average reseller's website is up to the reseller as to how accurately the information reflects the original specifications for the product. Even more pointedly, a nominal perusal of the specifications from the manufacturers website (or as close as I am able to find) for some sample Li-Ion battery chargers indicates an inconsistency between the identified specifications and the information posted on reseller's websites or the reported casual use of Li-Ion chargers by flashaholics.

Using the charger specifications for the WF-139 charger as an example: Battery to be charged: "18650, 17670, 18500, 14500, 17650, 17500". Battery type identified is "Li-Ion". That is all. The WF-139 charger specifications do not identify an RCR123a or an IMR 16340 cell. Just because the charger output is for 3.7v @ 450ma and cuts off at 4.20v does NOT mean that the charger is automatically applicable to any Li-Ion cell of the 3.7v output type. The WF-139 is commonly sold with spacers to charge lower capacity cells such as the IMR16340 or RCR123 cell in a charger slot intended for a maximum of the 18650 size. This usage practice is NOT per specification of the charger.

In the case of the WF-139 Li-Ion charger, a high capacity cell such as an 18650, which was identified in the charger specifications, evidently does stay w/in acceptable charging tolerances. A low capacity cell such as the RCR123a, which was NOT identified in the charger specifications, often demonstrates an overvoltage while under charge (exceeding 4.2x volts). Since the constant current charging method briefly stops charging to measure the cell voltage, a digital voltmeter is not an acceptable measurement device for the cell while the cell is being actively charged. Caveat: The number of test samples is relatively low - 5 of the RCR123a and 4 of the 18650 types.

Silverfox and many others have already amply warned the CPF community of inherent difficulties with lower capacity cells charged in a higher capacity charger, even the PILA charger! On the other hand, you "get what you pay for". A cheap charger with loose tolerances, even if designed for the RCR123a Li-Ion cell, can be just as "bad" as the WF-139 which was not designed for the RCR123a Li-Ion cell.

However, from a practical usage standpoint, I have been unable to determine a usage life difference between chargers that over-voltage the cells vs chargers that never allow a charging voltage to exceed 4.2 volts. So far in my limited experience, the variability between cell brands is more the determining factor of lifetime than the charging method as used by the Nano, WF-139, WF-138, Pila, SoShine, including the use of spacers in charger slots for cells of the 14500 size or above. My lack of experience with only maybe a 100 Li-Ion cells of various brands will automatically defer to the experts such as Silverfox, et.al.

Back to the design engineering aspect of CC vs CC/CV vs whatever charging method for Li-Ion cells. I am so far unable to find design information for a Li-Ion cell which addresses my own question regarding over-voltage applied to the cell terminals vs charge state in the cell.

I was able to find ample information on many ICs designed for single and multiple cell charging of Li-Ion cells/batteries as well as reputable information sources such as the "batteryuniversity.com" website. English or German language websites for IC specification information were accessed. These websites were all quite consistent in identifying a common charging method for Li-Ion cells, namely the CC/CV method. The primary control is focused on the cell terminal voltage (3.7v types). An initial condition with a lowered cell voltage results in a low-rate current controlled charge. Once the cell voltage reaches an acceptable voltage level, a full-rate current controlled charge is initiated. However some ICs simply release the full constant current rate into the cell until the cell voltage reaches the target voltage. When the cell voltage at the terminals rises to 4.1 or 4.2 volts, the charge method is transitions to a constant voltage charge method. With a constant voltage applied, the charge current is free to ramp down. Once a certain low-current level is achieved, charging is stopped. No trickle-charging.

CC vs CC/CV chargers? CC is cheaper to implement than a CC/CV which requires two control methods.

Another design comment. The open terminal voltage on low-cost chargers is only an indication of the design methods used in the charger. It has no real relevance on the charge delivered to the cell. Any electronic control circuitry requires some "overhead" of voltage with which to regulate the voltage to a lower level. Lowest cost power supply design will not regulate or poorly regulate the output voltage with no load. ditto for chargers. Once the charging is stopped, the voltage rises to the uncontrolled level. The change in design of the WF-139 from 11.x volts open circuit to 5.x volts open circuit is just that - a change in design. Evidently that change was to accomodate the revised design requirement to NOT trickle-charge a Li-Ion cell.

Having said all this, I recommend that this thread be converted into the other much longer thread running on the WF-139 charger and this thread be closed. No point in having 2 threads to track!

Sorry for the length of post!

 

[foxtrot29]

Odd, it seems the wf-139 is inconsistent from user to user.

Mine seems to terminate at 4.15, consistently (RCR123), then the cells seem to drop to about 4.14.... This is sufficient for me, however I'd like if it took them to at least 4.18. I can get them up that high by taking them out and putting them back.

 

[moldyoldy]

Odd, it seems the wf-139 is inconsistent from user to user.

Mine seems to terminate at 4.15, consistently (RCR123), then the cells seem to drop to about 4.14.... This is sufficient for me, however I'd like if it took them to at least 4.18. I can get them up that high by taking them out and putting them back.

Understood that your sample may be "ok". However if you review the graphs w/o averaging presented in post #1 and click on them to obtain the larger image, depending on the cell type under test, the peak voltage may well be above a desired limit. A digital voltmeter will only see the averaging, not the peak voltages. Most of us do not have an oscilloscope or equivalent recording device to record the highs and lows of the pulsed voltage across the terminals of a cell under charge. That is why it is so difficult to compare answers for different chargers.

 

[foxtrot29]

Understood that your sample may be "ok". However if you review the graphs w/o averaging presented in post #1 and click on them to obtain the larger image, depending on the cell type under test, the peak voltage may well be above a desired limit. A digital voltmeter will only see the averaging, not the peak voltages. Most of us do not have an oscilloscope or equivalent recording device to record the highs and lows of the pulsed voltage across the terminals of a cell under charge. That is why it is so difficult to compare answers for different chargers.

It's too complicated, most people won't even check the voltage out of the meter. I can't be expected to do much more! lol

I'll just hope this is good, continue with my inferior testing, use my ZTS, and be happy. If I get shortened life out of my cells, so be it -- I'll buy more!