Wf-137 problem?

I've recieved the ultrafire wf-137 18650 charger recently from dx, along with 2 trustfire protected 18650's. Anyway, i've had the first one in the charger, and while it hasn't overheated at all, it has now been charging for a good 7 hours and the light is still red flashing green.

I cant see or hear any fault with the charger, and it appears to be working just as well as my other two ultrafire models which i havent had any problems with. (wf-138, one for cr123's and the other for 14500 and 10440's)

I don't have any previous experience charging 18650's but i would have thought that with them supposedly coming partially charged from the factory they would be done in under 7 hours? :thinking:

So, does anyone have any advice on what the problem might be, or am i just being impatient?

Thanks for any help.

hmm.. I think i may have just fixed a problem, the one thing that was missing from the charger was that sort of electrical ticking noise you normally get when charging. Anyway, now i whacked it on the table and tried it again it sounds like it's finally working as it should be :laughing:

Ill be keeping a close eye on it now though, just in case my expert attentions did more harm than good..

Actually, there may still be a problem. I don't charge lithium cells overnight for obvious reasons so i've only just noticed that the charger only seems to accept one of my 18650 batteries.. :thumbsdow

It appears to charge one of them without issue, but with the other the light still goes red and flashes green as if charging, but the pulsing sound is gone, and i can just hear a quiet whine as before i 'fixed' the charger.. :sigh:

RedForest UK said:

Actually, there may still be a problem. I don't charge lithium cells overnight for obvious reasons so i've only just noticed that the charger only seems to accept one of my 18650 batteries.. :thumbsdow

It appears to charge one of them without issue, but with the other the light still goes red and flashes green as if charging, but the pulsing sound is gone, and i can just hear a quiet whine as before i 'fixed' the charger.. :sigh:

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Have you checked the chargers open circuit voltage on both channels, or the actual cell voltage when charging ? ... Can you measure the actual charging current passing through each cell ?

I don't hear any ticking or whining noise from my chargers ... There is occasionally the odd whining noise from my Wife though !
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No, sorry, i've only just got into using lithium batteries and haven't got any sort of multimeter yet, so i can't measure the voltage or the current.

The charger is the ultrafire wf-137, and only has one charging channel, i have tried swapping the cells over and listening to see what the charger is doing.
I know it isnt very scientific, but with all three of my other chargers there is a whine on solidly when it is on standby or trickle charge and when charging that whine is interrupted by a sort of electrical ticking sound, which i can only assume is either a pulse of energy as it charges, or a brief stop in the charging as it measures the cell voltage..

On this charger once i put the cell in straight away the pulse was quite regular, (every second or so) and as the battery charged it slowed down over time until now it only pulses about every 5-7 seconds. With the other cell though the pulsing sound seems entirely absent, (or at most every 20-30 seconds) like when my other chargers have completed charging the cell and cut off.

I'm actually now starting to think that the charger is working fine and that the faulty part is the red/green indicator light which is failing to tell me when the charge is complete.. :shrug:

I have decided to take out the first cell that had charged for about 7 or 8 hours and test it in one of my lights, and compare the runtime to what others have reported. If it matches then i will assume that it is simply the indicator light that was broken and that the charger is charging as it should be. If that is the case i will probably simply moniter whether the cell is charged or not by the frequency of the 'pulses' i can hear coming from the charger.

RedForest UK said:

No, sorry, i've only just got into using lithium batteries and haven't got any sort of multimeter yet, so i can't measure the voltage or the current.

The charger is the ultrafire wf-137, and only has one charging channel, i have tried swapping the cells over and listening to see what the charger is doing.
I know it isnt very scientific, but with all three of my other chargers there is a whine on solidly when it is on standby or trickle charge and when charging that whine is interrupted by a sort of electrical ticking sound, which i can only assume is either a pulse of energy as it charges, or a brief stop in the charging as it measures the cell voltage..

On this charger once i put the cell in straight away the pulse was quite regular, (every second or so) and as the battery charged it slowed down over time until now it only pulses about every 5-7 seconds. With the other cell though the pulsing sound seems entirely absent, (or at most every 20-30 seconds) like when my other chargers have completed charging the cell and cut off.

I'm actually now starting to think that the charger is working fine and that the faulty part is the red/green indicator light which is failing to tell me when the charge is complete.. :shrug:

I have decided to take out the first cell that had charged for about 7 or 8 hours and test it in one of my lights, and compare the runtime to what others have reported. If it matches then i will assume that it is simply the indicator light that was broken and that the charger is charging as it should be. If that is the case i will probably simply moniter whether the cell is charged or not by the frequency of the 'pulses' i can hear coming from the charger.

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My first Li-Ion charger was a WF-137 and it only charged for a minute or two then the LED went green ... I couldn't get it to charge for any more than two minutes, so had to have a full refund ... I still have the faulty one here, as the Hong Kong seller didn't want it back ... I did have a digital multimeter to check it with though ... So, I don't personally trust this particular model.

If you live close to a Maplins shop, they have Digital Multimeters at £3-99 and that is great value for money ... It comes with test leads and prods ... It is accurate to better than 0.8% on the 20 volt range ... You probably won't need a better one as you might only use it on DC volts ... I have one of these plus a more expensive £9-99 one which really is no better ... I wanted two so that I could monitor both the charge current and the cell voltage at the same time.

A voltmeter is the only easy way to see what percentage of the cells capacity is stored ... If the meter reads 4.2 volts then it is 100% charged (approx) ... If it reads 4.0 volts it is 80% and if it reads 3.7 volts then it is only 20% ... There is a chart showing all the figures from 100% (4.2 volts) to Empty (3.6 volts) in one of the threads ... I take my cells out of the charger to check their progress then pop them back in to continue the charging ... You will find that the last little bit of charge takes ages to complete, so a meter really is the only way to know when the magic figure of 4.2 volts is reached ... If you read more of these threads on CPF, you will realise that it can be dangerous to overcharge ... At the very least you would be reducing the cell life by overcharging.

I wouldn't try banging the Li-Ion cells either, as they can be damaged to the point where you might get in internal short circuit and this is one fairly certain way to get a visit from the Fire Service.

I would highly recommend that you get a cheap digital meter for your Li-Ion cells ... It is also handy for other jobs such as checking fuses etc.

Good Luck.
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Thanks, i bought one of those maplin's digital multimeters for £4.99 today :thumbsup: so i've been testing all my lithium cells from when they come of the charger. I'm glad to say that my other ultrafire chargers seem to be cutting of betwen 4.2 and 4.23 volts pretty accurately. But the wf-137 seems to keep charging, at a slow rate well after the cell has reached 4.25 volts.. :thumbsdow so i guess ill have to moniter the voltage manually from now on. At least i know what the problem is now and can deal with it though so :thanks:

However, i do have one other problem, i have two trustfire 2500mah protected 18650's from dx (blue wrapper) and while both coming off the charger at the same voltage, one only lasts for half of the time than the other. I don't think i have a way of measuring current draw within the torch, but one lasts for two hours while the other only for about 55/60 minutes.. I guess it's just a lack of quality control on some cheap chinese batteries really, but i am slightly dissapointed all the same..

RedForest UK said:

Thanks, i bought one of those maplin's digital multimeters for £4.99 today :thumbsup: so i've been testing all my lithium cells from when they come of the charger. I'm glad to say that my other ultrafire chargers seem to be cutting of betwen 4.2 and 4.23 volts pretty accurately. But the wf-137 seems to keep charging, at a slow rate well after the cell has reached 4.25 volts.. :thumbsdow so i guess ill have to moniter the voltage manually from now on. At least i know what the problem is now and can deal with it though so :thanks:

However, i do have one other problem, i have two trustfire 2500mah protected 18650's from dx (blue wrapper) and while both coming off the charger at the same voltage, one only lasts for half of the time than the other. I don't think i have a way of measuring current draw within the torch, but one lasts for two hours while the other only for about 55/60 minutes.. I guess it's just a lack of quality control on some cheap chinese batteries really, but i am slightly dissapointed all the same..

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Does the WF-137 LED change to green, to tell you that the cell is charged ?
You should take the cell off charge as soon as possible after the LED goes green and test the cell voltage ... If the voltage is 4.25 straight after the LED goes to green, then the charger voltage is a bit too high ... Just take the cell out every so often during charging and check the voltage ... When it gets to 4.2 volts you can assume that the cell is charged ... If it drops a few millivilts off charge don't worry ... If it drops to 4.15 volts, the cell is still 95% full.

As far as the Trustfire cells, I would be inclined to get a new one to replace the one that discharges too quickly ... If you are using the same torch to test both the Trustfire batteries then it must be one cell that is defective.

As far as checking current flow, If you remove the end cap and put an ammeter between the negative pole of the battery and the torch casing, you should read current ... This is easier with a single mode torch ... To check the charging current, I use two paperclips with a thin piece of plastic (as an insulator) between the negative end of the cell and the contact on the charger ... The ammeter goes between the two paperclips ... Don't forget to put the meter back onto volts afterwards.

I hope this makes sense.
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Yes, it does go green eventually, but i only ran it until it went green once and now that i know that it still isn't going green when the cells reach 4.26 volts i don't really want to run them all the way through again to be honest... I'll be monitoring them myself from now on and removing them when they reach 4.2 volts or so i think.

And yes, i tested both batteries in the same torch so i think one is just faulty, i'll ask dx for a replacement but probably order some new ones too just in case.

Thanks i've worked out how to measure the current draw, and it appears to be 1.45 amps, which is a bit higher than i had hoped really, but again it was only one of those cheap $23 xp-g torches from dx, so i guess you get what you pay for really..

Thanks again for your help anyway, i'm now set up for reading voltages on my batteries and current draw on all my torches, which i couldn't do before :thumbsup: