WF 139 and rcr 123

[bcool]

I thought this would charge my aw 123. It looks like it needs a spacer, any ideas?

 

[darkzero]

You can get spacers from AW or from 4sevens.com. Or you can use magnets for spacers.

Or you can do this:
http://www.cpfmarketplace.com/mp/showpost.php?p=2162154&postcount=5

 

[bcool]

so you just bend the clips, also for the magnets are they rare earth type magnets or just normal magnets? Thank you very much.

 

[mdocod]

so you just bend the clips,

???

If you are referring to the modification that darkzero pointed out, you need to solder those wires in, THEN bend out those clips a bit to make contact.

Spacers will probably be easier, another option is to build your own spacer.

Wooden dowel, a hunk of small wood, a hunk of plastic, a machine screw, a hole drilled, maybe a nut, I can think of about a hundred ways to make a 15mm electrically conductive spacer with common household tools and junk laying around here. Don't be afraid to invent something.

Eric

 

[ackbar]

haha.. I rolled a aluminum foil cylinder as a spacer.. works well thus far...

 

[dealgrabber2002]

Can the WF139 charge lifepo4 RCR123? I think the lifepo4 voltage is around 3.0~3.2...and the WF139 charges 3.7V.

 

[darkzero]

Can the WF139 charge lifepo4 RCR123? I think the lifepo4 voltage is around 3.0~3.2...and the WF139 charges 3.7V.

No. You would need the WF-138 with the switch for those.

 

[cheetokhan]

haha.. I rolled a aluminum foil cylinder as a spacer.. works well thus far...

Me too. An aluminum foil ball works fine and cost nothing.

 

[Shrigg]

Piece of .45 ( or most any other caliber) brass makes a very cool spacer!

 

[Black Rose]

When using the WF-139 with 16340 cells and spacers (AWs spacers in my case), is it at all possible that the use of spacers could prevent the cell from ending with a higher voltage?

I have a pair of TrustFire 16340 cells (sku 19627) that come off the charger at 4.07 & 4.09 volts.

My pair of AW 16340 cells come off the charger at 4.12 volts.

When charging full size cells in the WF-139, they come off the charger at 4.18 volts.
That makes me wonder if the spacers are "getting in the way" of the charging current.

I wonder if I would be better served by the WF-138 instead, since there doesn't seem to be an affordable dedicated CC/CV 16340 specific charger.

 

[mdocod]

When using the WF-139 with 16340 cells and spacers (AWs spacers in my case), is it at all possible that the use of spacers could prevent the cell from ending with a higher voltage?

I have a pair of TrustFire 16340 cells (sku 19627) that come off the charger at 4.07 & 4.09 volts.

My pair of AW 16340 cells come off the charger at 4.12 volts.

When charging full size cells in the WF-139, they come off the charger at 4.18 volts.
That makes me wonder if the spacers are "getting in the way" of the charging current.

I wonder if I would be better served by the WF-138 instead, since there doesn't seem to be an affordable dedicated CC/CV 16340 specific charger.

Hello Black Rose,

Allow me to try to clear up this issue...

I have pointed out the reason for this phenomenon in at least a half dozen places but I'll be happy to repeat it because it's very interesting and also important information...

The lower voltage termination on the RCR123 size cells in the WF-139 has absolutely nothing to do with the added resistance from using spacers, in fact, removing resistance would have no effect on the termination anyways...

Before that can be explained, we first have to look at how the WF-139 charges and terminates.

The WF-139 uses a constant current charge that shuts off every ~1.x seconds or so (that's the slight blink to green you see in use) to take a cell voltage reading with no charge applied.

The charger has no true constant voltage stage, it just ramps up continuously at the ~350mA or so that each charger actually runs at. When it takes a cell voltage reading of 4.20V in-between it's charging "pulses" it terminates the charge.

On large cells, like a 17670 or 18650, charging voltage will reach ~4.25-4.29V towards the end of the charge before the cell reaches a resting 4.20V that triggers a charge termination.

On small cells, like a RCR123, or sometimes a 14500, the same charging rate is applied, but since the cell is smaller, and has a higher effective resistance, the differential between charging voltage and resting voltage is larger. The result is that, the charging voltage reaches the 4.35V cutoff of the PCB. Rather than the charger terminating the charge, the cell terminates the charge. Different effective internal resistance or PCB limits will have different effects on final charge voltage.

Without PCBs on these cells, we would likely be seeing charge voltages of ~4.4V before termination.

This is one of many reasons I do not like the WF-139 and don't recommend it.

-Eric

PS: in regards to the WF-138, it uses the same charging method with a slower speed, so it will reach higher termination voltages on protected RCR123s, but I still don't have anything really good to say about it. I would suggest a DSD over a WF-138 or WF-139 if you want to keep it cheap. A Pila IBC is however, the only charger I am aware of at this time that can safely charge RCR123s and uses a fully "proper" charging algorithm. The nano has termination problems, the ultrafires use crummy algorithms, the yoho-122 charges too fast for RCR123s, bleh.... just not many good options.

 

[Black Rose]

Thanks for that explanation Eric. Makes a lot of sense when all the variables are known :thumbsup:

 

[Black Rose]

PS: in regards to the WF-138, it uses the same charging method with a slower speed, so it will reach higher termination voltages on protected RCR123s, but I still don't have anything really good to say about it. I would suggest a DSD over a WF-138 or WF-139 if you want to keep it cheap.

Well, even though you advised against it, I did pick up a WF-138.

And what you said is true (not that I doubted what you said).
I topped off all my 16340 cells and they all had higher voltages hot off the charger than when charged on the WF-139.

My Trustfire 16340 cells were around 4.08 with the WF-139 and are at 4.15 with the WF-138.
My AW cells were 4.12 with the WF-139 and are at 4.17 with the WF-138.

Not a huge improvement but an improvement nonetheless.

The main reason why I went ahead and got the WF-138 was because it can also charge LiFePO4 cells.
I want to get some LiFePO4 cells for my lights that are being overdriven by the regular 16340 cells.

I haven't determined yet if going with a hobby charger is worth it for me at this point, so this charger fills that gap until I determine if it's worth the investment.

 

[sadtimes]

the only charger I am aware of at this time that can safely charge RCR123s and uses a fully "proper" charging algorithm.

Hi, You seem to really know your chargers, with that being said is this charger capapble of charging the cells correctly?

http://www.electrifly.com/chargers/gpmm3155.html

 

[325addict]

There's another charger on DX that follows a TRUE CC/CV method, but actually NEVER SWITCHES OFF COMPLETELY!!

So be warned....

It is all about the SKU 4151 or SKU 12594 (in grey, or in black respectively)

What's good about it?

A: it has a fairly good charging algorithm. It is in fact a constant voltage source of 4.22V with a kind of "foldback" current regulation for the first part of the charging. This charger will charge your cells full to the brim. When inserting deeply discharged batteries however, you can actually see that the internal power supply can't handle this: both the LEDs nearly went out, and came back a few seconds later. The charger survived this, as well as the AW 16340 IMR batteries I discharged to 1.4V and the other even lower :thumbsdow

B: it has two slots with a sliding negative contact, just like the WF-139, but with one big difference: this one accepts 16340s without a spacer!

C: it has clear communication with the user: a LED under the slot will turn from red to green when the battery is full.... and that is, when current has fallen under, maybe, 30mA or so.

D: it has a 12V DC input, so it can be used in a car! It even has a reverse polarity protection (I saw a diode in series on the PCB).

What's BAD about it?

A: it NEVER switches off! The fact that the LEDs turn to green doesn't mean, that the charger shuts off completely. It just keeps your batteries at 4.22V which will shorten life significantly.

B: it gets rather hot during the first hour or two when charging two empty 18650's. The combination of long-time, high-current charging creates quite a lot of heat inside... the batteries, however, stay fairly cool. No worries about that.


BOTTOM LINE:

If used correctly (that is, switched off after the LEDs turned green, and have the batteries removed from the charger) this one is as good as it gets for under $9,- !!


Timmo.

 

[travelinman]

So has anybody figured out how the little "universal" charger from DX (sku # 14885) terminates yet? It seems to take my 16340 cells up to ~4.18v. and they stay there even if left in for hours.

 

[325addict]

I think this charger will NOT switch off, although intelligent ICs exist today to build such "multichemistry" chargers. I don't expects these ICs to be in such a cheap Chinese charger however....

Most likely it has about the same specs as the one I mentioned above. In this case, with a better constant-current feature when voltage is forced well under 4V (after all, it seems to be able to charge NiMH).

Timmo.

 

[wapkil]

So has anybody figured out how the little "universal" charger from DX (sku # 14885) terminates yet?

I measured it and described the result here.

 

[travelinman]

Thanks Wapkil...I didn't measure current, but on mine the voltage is nearly identical to the charger in your test. With that little current going in after termination, I wouldn't be worried about overcharging. Especially since the current is pulsing. Very strange! :thinking: I can't think of any charger on the market that does that at the end of the cycle. Some do it all the way through, and some do it at the beginning, but I can't think of any reason to do it at the end.

 

[mdocod]

Hi, You seem to really know your chargers, with that being said is this charger capapble of charging the cells correctly?

http://www.electrifly.com/chargers/gpmm3155.html

I have never actually tested a full blown expensive hobby charger. I own numerous cradle chargers, some have been sent to me for evaluation, and some even gifted to me. My gut tells me that those expensive chargers are very likely going to use proper charging methods, ESPECIALLY if they are balancing style chargers for series packs of li-ion cells, because the only way to balance a li-ion pack is by using a true CV stage at the end of the charge on each cell (or bank of parallel cells). I think it's pretty reasonable to assume that any well respected hobby style charger will work fine for most of the stuff we do provided you have a cell-cradle solution figured out and it has a slow enough charge rate option for the smallest cells you plan on charging with it. The triton in that link can go as slow as 100mA, so could safely charge a li-ion a small as ~100mAH in size. Being able to charge at up to 5 amps would also be very handy as you could set up a bank of 4 18650s in parallel as charge in a few hours. Not bad.

-Eric