Advantages\Disadvantages of the new WF-139

[joshconsulting]

A few weeks ago, I ordered the WF-149 from DX [http://www.dealextreme.com/details.dx/sku.1251]. Since then, I've been using it to charge my 14500s, and hopefully soon my 18650s (where are you, HK air mail?). I have a multimeter, but hadn't gotten around to testing it until recently. What I found:

Charging current: 390 Ma
Voltage of cells taken directly from charger after light turned green: 4.22v
Voltage of cells after 60 seconds off of charger: 4.20v
Voltage of cells in charger after light turned green: 0.00 Ma

My multimeter is only accurate to a hundredth of an amp at 300+ Ma, but goes out to a hundred-thousandth at 300- Ma, so I'm reasonably certain that the 0.00 Ma of the green truly represents a complete cutoff with no trickle charging.

The only thing I'm concerned about is that this charger uses a cycle on\cycle off method for charging to avoid overcharging. I noticed this while taking the charging current reading, but I've heard conflicting advice regarding the efficacy of this method; some say it shortens battery life, others say the cycling helps restore the battery chemistry and extend the life. I'm inclined to assume it shortens, but by how much? Is it a big deal?

Also, could this charger truely be used, in conjuction with high quality protected AW cells, as a 24\7 thing (drop it in the charger, grab it when you need it, put it back when your done)? If there is truely 0 current flowing to the battery when the light is green, it seems as if there would be no harm done. According to reports, it checks for voltage every 60 seconds when idling; does this mean after a certain period of time when the battery begins to degrade it will begin charging, thus keeping the cells permanantly fully charged? I ask because I've been having problems with this myself; my 14500 Trustfires have a tendancy to completely discharge in a few months, leaving me with dim or no light if I forget to charge them. Having a permanent, cool place (my basement) to store them in the charger would be REALLY helpful and was one of the main reasons I originally wanted a Pila, but the trickle charging would have made that impossible.

Thoughts?

 

[Black Rose]

Also, could this charger truely be used, in conjuction with high quality protected AW cells, as a 24\7 thing (drop it in the charger, grab it when you need it, put it back when your done)?

Do not leave Li-Ion cells unattended in a charger, any charger, after they have completed their charge.

It is dangerous to do so.

 

[joshconsulting]

Do not leave Li-Ion cells unattended in a charger, any charger, after they have completed their charge.

It is dangerous to do so.

Yeah, I kinda figured. They need to develop a charger with guaranteed cutoff, I'd gladly pay $100 for something like that with temperature monitors and an alarm etc.

Anyway, does anyone have more info on the effects of the on\off cycle of the 139? Other then that, I really can't see why I should pay 4 times more for the Pila.

 

[T0RN4D0]

Hobby chargers. You can set a few of cut-off measurements. (Voltage, time, charged capacity, temperature...) So for that 0.xxx% that the standard charge wouldn't stop, you can set it to stop charging when the charger put in 1100 mah in a 1000 mah cell, or in two hrs no matter what...

The negative part is that you don't get any cradles with them, but if you are paranoid that should be good, since you can design your own fire or blast proof cradles for you terrorist cells.

I have heard a few good things about Turnigy Accucel-6, as it offers alot of options, especially for the price. You can snoop out more about it and hobby chargers if you want to drift into those waters.

 

[Black Rose]

Anyway, does anyone have more info on the effects of the on\off cycle of the 139? Other then that, I really can't see why I should pay 4 times more for the Pila.

The WF-139 does NOT follow the CC/CV charging algorithm that Li-Ion cell manufacturers recommend.

The Pila IBC appears to be the only consumer cradle Li-Ion charger that truly does.
The Yoho-122 follows very closely, but is no longer available at an affordable price.

The other alternative would be a hobby charger, which costs more (unless you get something like the Turnigy Accucel-6), but really gives you a lot of freedom in charging cells.

 

[Elliot]

If any of my WF-139 chargers worked like yours, I'd be doing cartwheels!

 

[T0RN4D0]

I mentioned the accucel because it seems to get lots of positive feedback and almost no negative, which is surprising for that price.

Of course there are better chargers out there, but brand names quickly add up to 10 times as much as this one...

 

[rmteo]

I mentioned the accucel because it seems to get lots of positive feedback and almost no negative, which is surprising for that price.

Of course there are better chargers out there, but brand names quickly add up to 10 times as much as this one...

This is the same as with anything else including flashlights (think SureFire vs. xxxxFire, etc.). I have several hobby chargers, including the Accucel-6 and Accucel-8, and I will say that the positive feedback of the Accucel-6 is deserved. I do not use any of the "other", non-hobby chargers, as I do not see the value in them compared to the hobby chargers in terms of capabilities, features, price, etc. The only time I would recommend one of them is if your budget has to be <$10 - then pick your choice among the kind of stuff that DX sells for example.

 

[joshconsulting]

Actually, I have a very nice hobby charger I purchased a few years ago to charge my custom battery packs. But it would be inconvenient to try and rig a system with the charger, as it's already set up.

Again, I know that the 139 doesn't follow the specs; it does cycle on, cycle off charging. But I haven't heard anything definitive about it beyond "it might shorten the lifespan" or "it might help the batteries regain life". Does anyone have solid evidence of it decreasing the battery lifespan in charge cycles?

I'm quite impressed with the regulation on mine. 1, 5, and 30 minutes after charging, it registered exactly 4.20 - not bad for a $12 charger.

 

[rmteo]

Just to give you an idea, a low current (up to 500mA), true CC/CV, single-cell, Li-Ion charger can be built around a tiny SOT23-5, $0.40 chip and 5 passive components. All you need to do is to supply it with 3.75-6V DC.

 

[joshconsulting]

Building my own isn't as high of a priority at the moment - without several saftey cutoffs that I'm not prepare to build at the moment, it wouldn't be a real 24/7 solultion, and would be a pain to set up. My 18650s will probably see 20-30 cycles per year, so unless the 139 really kills cells, the question of what to use is purely academic.

 

[rmteo]

I wasn't suggesting that you DIY your own charger - if I did then that was not my intention. I was just showing that safe, accurate/proper charger designs for Li-ION's are available. All the safety that you need is already built into these things - no need to add any additional safety cut-off's etc.

 

[joshconsulting]

I mean safty features that allow you to leave batteries in 24/7. I really don't see any reason to build your own with a 12$ 139 doing such a good job, unless you are a serious diyer (which I am, but not with this type of work) unless there was a big disadvantage to the switching circutry.

 

[TooManyGizmos]

24/7... Un-monitored use is not advisable with any charger .

Even Drill pack chargers and such .

A good precaution you can use on each of your chargers ... is to get reliable , free-standing turn off timers for the AC outlet each is plugged into.

That way , if you get distracted and forget about it , the timer will disconnect the AC feed.(Don't use a timer that repeats on-off times... as some do. It has to shut off permanently ! )

Don't set the timed period for TOO long.

A good idea on Soldering Irons ... TOO .
.

 

[joshconsulting]

I like the turn-off timer idea. Setting it to, say, 8 hours should leave a decent gap - I could have a button timer that you simply drop the batteries in, hit the timer button, and come back days later to pick up your charged batteries.

 

[kramer5150]

I don't think theres anything advantageous about 18650 charger that tops cells off at 4.22V. The difference between a ~4.15 top off and a 4.22 is negligible in any flashlight application I can think of (LED or incan), while being a step down in reliability, cell longevity and safety.

FWIW, my cells are 4.16V hot out of my version 2.

 

[joshconsulting]

I don't think theres anything advantageous about 18650 charger that tops cells off at 4.22V. The difference between a ~4.15 top off and a 4.22 is negligible in any flashlight application I can think of (LED or incan), while being a step down in reliability, cell longevity and safety.

FWIW, my cells are 4.16V hot out of my version 2.

Quite frankly, I expect to lose or kill both batteries long before the 400+ cycle lifetime ends, and I don't think a few dozen extra cycles from the higher voltage are a big deal - I'd rather have the slightly longer runtime. I just wanted to make sure it didn't end at 4.25+; at that point, the shortened lifespan starts to outweigh runtime.

 

[kramer5150]

Quite frankly, I expect to lose or kill both batteries long before the 400+ cycle lifetime ends, and I don't think a few dozen extra cycles from the higher voltage are a big deal - I'd rather have the slightly longer runtime. I just wanted to make sure it didn't end at 4.25+; at that point, the shortened lifespan starts to outweigh runtime.

It could very well be charging your cells at 4.25+ if you cells are coming off at 4.22.

Either way there is an element of safety that you should think twice about, and leaving them in the charger 24/7 unattended would be a safety risk too.

 

[joshconsulting]

It could very well be charging your cells at 4.25+ if you cells are coming off at 4.22.

Either way there is an element of safety that you should think twice about, and leaving them in the charger 24/7 unattended would be a safety risk too.

I agree on the safety issue; I will install an AC switch before I go for 24/7. However, 4.22 was very literally hot off the charger - I watched the light turn green, yanked them off, and measured them within 4 seconds. In another 20 or so seconds they dropped to 4.2 and held steady there.

 

[kramer5150]

I agree on the safety issue; I will install an AC switch before I go for 24/7. However, 4.22 was very literally hot off the charger - I watched the light turn green, yanked them off, and measured them within 4 seconds. In another 20 or so seconds they dropped to 4.2 and held steady there.

Regardless, 4.22V at any given time is beyond what the cell manufacturers recommend for safe usage. You can't deny this, or justify any level of safety so long as your charger overloads the cells in this fashion.

It would be safer to reconfigure your fore-mentioned hobby charger, than to continue use of the WF-139.

**EDITED** Per request from the grammar police