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

[VidPro]

Quick question: I see the term "hobby chargers" mentioned a few times. And these seem to be a step above the "normal" chargers like the WF-139 or IBC. What exactly are "hobby chargers"?

the chargers that the RC (radio control) people made popular
http://www.hobbypartz.com/lipochargers.html
often they will do ni-mh , ni-cd, and Lead Acid, and li-poly and li-ion, in series or singles, have charge and discharge , now have cool readouts and now balancing connections. sort of a All-In-One microprocessor controlled muti-alogrythm multi-current multi-cell possible charger thing.
even cheap ones now have CC CV , control of everything, safety max capacity or time cutoffs, and the whole gambit of charge and discharge capability.
Which just leave the HUMAN having to, and being able to, control all aspects of it.
can be made "safer than" or can be set "incorrectally" 101 ways to completly destroy something Versatility to the max.

 

[mdocod]

Hello JB,

Best way to explain is actually just to show them:

Hobby Chargers

Do a search for Schulze chargers if you want to see some really fancy stuff!

Eric

 

[JB]

the chargers that the RC (radio control) people made popular
http://www.hobbypartz.com/lipochargers.html
often they will do ni-mh , ni-cd, and Lead Acid, and li-poly and li-ion, in series or singles, have charge and discharge , now have cool readouts and now balancing connections. sort of a All-In-One microprocessor controlled muti-alogrythm multi-current multi-cell possible charger thing.
even cheap ones now have CC CV , control of everything, safety max capacity or time cutoffs, and the whole gambit of charge and discharge capability.
Which just leave the HUMAN having to, and being able to, control all aspects of it.
can be made "safer than" or can be set "incorrectally" 101 ways to completly destroy something Versatility to the max.

Thanks for the link. Wow's that opening up a whole new kettle of fish when it comes to chargers.

 

[JB]

Hello JB,

Best way to explain is actually just to show them:

Hobby Chargers

Do a search for Schulze chargers if you want to see some really fancy stuff!

Eric

Saw that link. Also did a search on Schulze chargers... fancy stuff indeed. Fancy price too

What I notice is that most of these have a fancy looking "controller" (if that's the right word). But I don't see any cradle to hold the batteries. Is that optional? Or some other connection to the battery is used? I see those black/red leads... are those used to "manually" connect to the batteries?

 

[VidPro]

But I don't see any cradle to hold the batteries. Is that optional? Or some other connection to the battery is used? I see those black/red leads... are those used to "manually" connect to the batteries?

and that is where the fun starts
there are many cradles hand made in the forum, and using that word "cradle" in the search with "li-ion" and "charging" or "hobby", is likly to find some of the designs. Also "magnet"ic bannana leads, and battery "tray"s and all discussed fluently.

 

[DM51]

Here's a link to a thread by sdnative, who makes various different-size cradles.

 

[mdocod]

Hobby chargers are normally intended for use with battery packs that are already all soldered or welded together and then shrink-wrapped up into a single unit with a bungle of wires coming out and a nice plug. Balance taps for li-ion packs are often pre-wired into the pack and right on the multi-pin plug.

Using these chargers for loose cells requires that the user either build apparatus for mounting and connecting or buy something to assist in this particular challenge.

 

[mr.snakeman]

Just thought I´d share my latest charging experience with you all. I thought I would measure the charging voltage of my UltraFire WF-139 (new model) charging an AW protected 14500 using the method mentioned in HKJ´s DMM user guide (see the link in post #265 above). The DMM used is a Caltek CM3900A. The voltage rose up past 4.2 volts before the diode turned green. From the time that the voltage rose above 4.2 volts until the charger diode turned green was only a few minutes, but when it did change the voltage measured 4.65 volts (remember, this was a one-off test). This was only for a few seconds as I terminated the charging process as soon as the diode changed color. The charging current fluctuated between 380-410mA. The 14500 measured 4.18 v. directly after charging and 4.17v. about ½ hour later. I think I´m going to order a Pila IRC and retire my WF-139.

 

[mdocod]

Hello Mr.Snakeman,

Very interesting results!

Something to consider:

It's possible to introduce substantially increased resistance from the charger to the cell when conducting tests with a DMM to monitor charging. Poor connections are generally the cause of this. When this happens, the charger naturally offsets this with higher voltage to maintain the charge rate it is shooting for. When the WF-139 does it's little "pulse" testing for cell voltage every second or so, the increased resistance has very little of any effect on the actual V-test because there is no significant load for the test.

It is very unlikely that the charge voltage is actually 4.65V under normal charging conditions. When the actual charge voltage exceeds ~4.35V, the protection kicks in and terminates the charge. Which is probably what actually happened, considering that your final resting voltage was below 4.20V.

It's also possible that if the contacts on your WF-139 or the ends of your cell are oxidized, that you could get these abnormal results.

Remember: V/R=I

In the case of charging a cell, the "V" in this equation is the voltage differential between the cell and the charger. A decent protected 14500 might have a total resistance of around 0.4ohm. Your 139 was running around 400mA so here's the equation:

V/0.4=0.4
V=0.16

Charge voltage differential = 0.16V required to maintain 400mA charge rate. Cell achieves ~4.18-4.19V SOC when the charge voltage reaches ~4.35V and the PCB trips, terminating the charge.

Hitting 4.65V charging voltage would require that your total resistance was over 1 ohm.

Eric

 

[mr.snakeman]

Thanks for your feedback, I´ll check all the contacts and try again when I have time and see if I get the same results (or not).

 

[march.brown]

Thanks for your feedback, I´ll check all the contacts and try again when I have time and see if I get the same results (or not).

If you have another meter (or can borrow one), try measuring the resistance of your ammeter plus its leads on the different ranges ... Each ammeter range will measure a different value in ohms ... This is why some CPF'ers measure the voltage across a resistor inside the charger and work the current out from that (ohms law) ... I tried to measure charge current and had a different reading on each current range of the meter ... I gave up in the end and just check the cell open circuit voltage nowadays.

As a matter of interest , if you know the resistance of the ammeter plus leads and you know the current as measured on the ammeter , you can calculate the voltage across the ammeter and leads ... The actual voltage across the cell will be reduced by this amount.
.

 

[HKJ]

As a matter of interest , if you know the resistance of the ammeter plus leads and you know the current as measured on the ammeter , you can calculate the voltage across the ammeter and leads ... The actual voltage across the cell will be reduced by this amount.
.

Why not measure the voltage directly across the cell? It is much easier.

 

[JB]

Thanks for all the feedback on hobby chargers and their accessories. Opened up a new perspective for me.

 

[recDNA]

Hello recDNA,

I prefer the Pila IBC for all cells from RCR123 (16340) size and up regardless of whether they are IMR or not.

Honestly, given that the small cells you are charging are IMR16340s, which are inherently more abuse tolerant and safer, and the large cells you are charging are not exceeding 4.25V during charging, I would have felt pretty comfortable just sticking with the WF-139 for your purposes. The Pila will give some nice piece of mind and will charge faster than the WF139 so all in all not a bad investment regardless, and if you ever need to top up more cells at once your 139 can be on backup duty.

Eric

Well my PILA arrived and I've tested it a few times now I like it. It only charges to 4.17 volts (IMR or protected 18650 or 16340 all quit at 4.17 volts) that's OK with me. I know I could hit reset and pack a little more energy in the cells but would the runtime at 1.5 amp be significantly increased by jacking the voltage up to 4.2 volts?

Thanks Eric

(BTW, I'll still use the WF-139 with protected 18650 when I'm charging more than 2 at time. I actually thought it was a great charger until reading this thread and I still feel pretty comfortable with it. I just find myself charging more often so in the long run I thought the PILA would be a good investment)

 

[old4570]

Well , I did one to completion ..

Batt 4.2v Voltage from charger 4.24v , with green light , I get no current ...

My test set up seemed for some reason to restart the charge cycle , which does not seem to happen with just a 18650 in place ..

Just uploading the video now of the 139 completing the charge , as I said , my test rig seems to kick start the charge cycle ... Anyhow , if you like watching a AMP meter , gratuitous action video .... http://www.youtube.com/watch?v=1Gk6vevQnBY

Update : Well I was able to measure current @ 200mA setting and 20mA setting when the green light came on and there is no trickle charge ...

So , if you have a 5v open circuit WF-139 , then it does not [ mine dont ] trickle charge on completion ..

I tried it with an unprotected cell , both channels and no current on green light ...

So as near as I can tell , there are two issues ... Open circuit voltage / stand by voltage / and the way it charges [ pulsing ]

I made a separate post as I captured the pulsing on video [ 1A meter ]

I dont think the open circuit voltage is anything to worry about . as once the cell goes in it changes to charging voltage ...

 

[JHCANDLEPOWER]

WF139 reading 0 volts on open circuit

Hi,
Bought the WF139 before reading this forum....doh!
It came with two Ultrafire 18650 blue labels. The battery both had a voltage reading of 3.8V. Just to examine the charger regarding the old vs new concept, I connected one lead from the meter to the positive terminal and the other lead on the negative sliding terminal. The meter read 0.09. Has anyone seen something other than 10-11v and 5v? I haven't seen a mention of ~0v during open circuit. By open circuit, I attached the leads as described and plug the charger into the wall (no batteries). The light flickers from red to green very quickly. I know the charger is working as the batteries are now at 4.1v after a two hour session.

Is this possibly another revision?

 

[old4570]

Re: WF139 reading 0 volts on open circuit

Hi,
Bought the WF139 before reading this forum....doh!
It came with two Ultrafire 18650 blue labels. The battery both had a voltage reading of 3.8V. Just to examine the charger regarding the old vs new concept, I connected one lead from the meter to the positive terminal and the other lead on the negative sliding terminal. The meter read 0.09. Has anyone seen something other than 10-11v and 5v? I haven't seen a mention of ~0v during open circuit. By open circuit, I attached the leads as described and plug the charger into the wall (no batteries). The light flickers from red to green very quickly. I know the charger is working as the batteries are now at 4.1v after a two hour session.

Is this possibly another revision?

Could be , I had a feeling that a another revision may have been made .
It would be nice if Ultrafire actually marked the chargers with the production revision .

 

[Bullzeyebill]

Re: WF139 reading 0 volts on open circuit

Could be , I had a feeling that a another revision may have been made .
It would be nice if Ultrafire actually marked the chargers with the production revision .

Yes, that and use a CC/CV algorithm. What keeps these folks, all of them that produce so called Li-Ion chargers from doing that?

 

[45/70]

Re: WF139 reading 0 volts on open circuit

Yes, that and use a CC/CV algorithm. What keeps these folks, all of them that produce so called Li-Ion chargers from doing that?

Profit margin ($$$). In order to accomplish this, they would have to upgrade the quality/tolerance of the components used. I wouldn't be surprised If dealers are paying $2-$3 for these chargers now. If the dealer's price went up $5, they'd have to charge $30-$45 for them to keep their margin.

I can hear people complaining now, about how they'd have to pay as much for a Li-Ion charger as they do for a NiMH/NiCd charger. Makes sense to me, but......

Dave

 

[rocled]

My WF-139 has an open voltage of 4.9V. I purchased it 1 year ago. I only use protected cells, so will this charger be safe for me as long as I remove the batteries as soon as they are charged? Thanks for any input.....