Difference between Opus BT-C3400 & BT-C3100 v2.1?

I’ve read the same, but apparently Opus doesn’t actually do pulse charging. It does PWM which is not the same…

This is strictly regarding Li-Ion chemistry, BTW.

[quote=Pete7874]

This is one of my main concern and I’m surprised it doesn’t get mentioned more. With those high pwm surges,2amps if I m not mistaken this charger is only useable with 18650 and other high capacity cells. So that would mean all those low current charge settings are completly useless except maybe for reviving dead cells. Also chargin aaa would not be recomended.

I have one on order and I am very much thinking of returning it when it arives. Maybe save up for the skyrc

PWM > high current pulses……harmful! Yes? No?

I know li-on is not li-poly, but in the RC world for a long time it was thought that charging lipos in excess of 1C was damaging. But a number of ‘battery gurus’ and at least one high end charger manufacturer FMA-Cellpro were charging at much higher levels. This was thought to be dangerous, stupid even. Now pretty much all RC chargers and li-polys are OK to charge at 1-5C, except maybe tiny ones.

Just to experiment I did some charging (hobby charger Accucel-6 and some others) at rates higher than 1C while I monitored them. The charge would start out high, then rapidly ramp down as the charge approached completion and at the end be essentially the same as the termination on a 1C charge rate. At no time ever did I get any cell that got hot or puffed, not even warm. Cell size didn’t seem to matter. It didn’t seem to hurt them at all.

OTOH, there are still people out there advocating charging at 1/2C for safety, reliability, and long term cell health, and say it with a profound conviction, as only men can do, that they, and they alone know the proper way to charge batteries. There seems to be nothing really to support that belief system.

I don’t KNOW it, but my strong suspicion is that in the myriad ways a cell can be abused and ultimately die, being charged with PWM is way way way down on the bottom of a very long list.

As you said liion is not the same as lipo. My limited understanding is that lipo can handle way more current than liion.
A hobby charger still usses a cc cv curve even if you charge at higher rates. Do you use the opus for small cells? How do they handle the high current pulses? I would not want to charge my eneloop aaa in the opus.
How do older, recovered laptop cells handle the pwm. It is an analyzing charger after all so that would be my main use: analyzing questionable cells.
What is the use of having an 100mA charge setting if it still puts 2A pulses in the cell?

I haven’t found any problem that I can determine using the Opus for any cell, AAA and recovered laptop included. I usually don’t use it for AAA unless I’m analyzing though. I have a Lacrosse I tend to use for that. I dislike AAA, I think it’s a poor size, but a lot of things do use them.

I guess ultimately it’s a question of control and the hated fan vs. PWM, and what you are primarily going to do with it. Both have their compromises. Try to be clear what is important to you when you chose. I like control.

In terms of current handling, there are lots of BLF users that are battery abusers :smiling_imp: , looking for current output in a li-on that some of my older, larger (2200mA 3S) lipos can’t match.

If I could charge some of my cells quicker I would.

The imalent 4400mAh cell is currently getting hit with 2A and its brand new.

I’ve had no problem with different size nihm or the 20is laptopbpulls I now have 9 were new unused others used. Charges just fine cells don’t get warm or act any different then liito 100 or vc2 charging them. New or old havnt seen any capacity decrease that isn’t average for cycle life. If it does affect cells its is so tiny I’ve seen no difference in aging in cells cycle wise then before I got one. Used only w vc2 and liito li 100 for a long time. Hundreds and hundreds of charges on each. Like 24/7 they was a line of batteries waiting to be charged for several months they never got a break. I had to upgrade. And I’ve put the opus through at least a month straight non stop duty when I first got it. To get capacity. I did my own non scientific expiriment. There are 4 cells that have been paired together one set I kept in the vc2 and the other in the opus. After around 100+ more cycles they both sets had roughly the same degraded capacity. There is no way you could tell which one hae been charged by which. So the opus damaging cell life I havnt seen it. I have some NCR b that get charged almost daily with the opus with over 200 for sure. But just under 300 cycles. Still have 3300mah. At the standard 500mah setting takes 8 hours from 3.0 volt every charge. 2 amp on the 26650s.

I use a lot of cells. When I take my daughters to the park its the high school ball fields that has a park its completely dark I make a circle of lights and light the plat structure up. 15+ cells in a night easy when we go. And for a stretch we were going 5-6 nights a week before it got bitter cold 6 lights on turbo for 2-3 hours. Pkus the one im walking aroubd with and my spare clipped to me anf a duffle bag of extra lights and batteries. Theb the light my wife walks around with. From 18650 to 26650 single and series. And with heavy use I habnt seen a difference in capacity that the other batteries with the same exact cycles because they are matched. So whatever the difference its less then 1%

Yeah, I don’t think PWM kills cells, USERS kill cells most of the time. :wink:
I’ll bet keeping a cell fully charged in storage is worse for it long term than storing it at 50% and charging it every time with 2C+ and PWM. But, those kind of tests are not done in any kind of controlled manner and would take forever anyway.

My take, don’t worry about it. Pick the charger you think suits you objectives, use pattern, and budget the best.

Well, I ignored that in my post because I am open to the idea of modding, have a few parts lying around. It would be no big deal to me to tack on some capacitors across the battery rails. I looked up the datasheet for the regulator, at least the IC model # used on past revisions of BT-C3100, and it does allow for an output smoothing capacitor.

Heh, I hate vagueness in posts so I should elaborate. EUP3484 regulators (or just stamped “P3484”) are on each charging bank. A datasheet for that shows a typical app circuit with 22uF on the output, but goes on to elaborate with equations and alternates like tantalum or lower ESR electrolytic, so you could choose the capacitance and ESR to arrive at the ripple reduction you want. It’ll never be a purely linear charge, but at some point you could consider it shades of gray how little ripple there is.

However, I must confess that I have not reviewed the details of HKJ’s analysis, so I don’t know how bad the pulse is.

You might find that eventually it needs some capacitor attention anyway, as the generic little 220uF caps they have on each bank could be considered a “wear item” with a finite lifespan shorter than the otherwise viable life of the charger. I mean something is going to fail first (after the !@#$ fan) , and if it’s something you can fix for a couple bucks cost…

I don’t agree about any 25mm x 10mm (or thinner) fan being adequate for (any) use, unless we’re talking about the highest precision fan that mankind could build at extreme cost. I’ve bought top shelf fans in the past and no brand or model that tiny has good lifespan. Granted I tend to think in terms of extreme duty, for someone running a charger only a handful of hours a week, it may not matter, but I am very much a fan (pun intended) of “fix it once then forget it”, to do a mod that never fails again, or at least not for a couple decades.

This mod you did is similar to some mod thoughts I had, except I would either use a lower diameter fan and cut an open hole in the bottom, OR make a reinforcement plate out of aluminum so a larger fan didn’t structurally weaken it too much, so there was a larger opening instead of little holes that catch dust and restrict airflow, and then I could just fold down the sides of the aluminum into an inverted “U” shape to form two leg-rails to elevate it.

However I have several fans of different sizes lying about, so almost too many options if I’m willing to fabricate a plate too. I’m leaning towards two 50mm x 10mm or one 50mm x 20mm fan on the bottom. The 10mm thick have a shorter lifespan, is the main reason I’d go with two 10mm thick instead, as one moves enough air if there’s an unobstructed opening to allow it, well that and I have about 4X as many new 10mm thick.

I get the concept but the electronic specific is out of my league. Are you willing to be a more specific about a cap? I can solder and have replaced bad caps in motherboards and TV’s but I just put in what is recommended.

^ Depends on if you’re trying to only fix a failure and promote longer life, in which case you could just do similar, pick the same voltage rating, capacitance value in a major brand with “very low ESR” and 105C temperature rating, like a Panasonic FM (or whichever newer series they came out with that lowers ESR even more), or for higher cost, one of several brands of polymer capacitor. NCC, Rubycon, et al make suitable models of capacitor. I would advise against use of a generic (or any, really) Chinese brand, though some people have had luck with those too, but I don’t see the point for a few cents cost difference, and the higher quality major brands tend to have lower true ESR.

Larger diameter, height, and voltage rating (up to a point) will give beneficial ESR reduction but as it is the cap is already shoehorned in there at an angle instead of proper mounting on a PCB. For best results a ruler may be needed to measure clearance.

As far as changing for performance, the conservative answer would be choose same diameter, taller since lying sideways that could fit, and go with a higher voltage rating to drop the ESR and no more than double the capacitance. At some point the capacitive load could be too high but I don’t know what that limit might be. If you’re measuring with a scope you can experimentally arrive at an ideal capacitance value to get closer to your ripple target.

You may try the 40mm fan like mine first, as in my experience it’s just powerful enough to keep the batteries just lukewarm, needed for nimh termination just in case…and as to durability, our charging needs is just way shorter than the time a ‘normal’ psu fan is subjected in its lifetime. And you can always pull out the 40mm and go for a bigger fan as you see fit.

And btw, those rectangular protrusions in the base surrounded by the holes I drilled have openings in its entire length as original design for air to pass through.

Ha, here I was nagging bout the pwm charging of the opus turns out my xtar VP2 also uses pwm :person_facepalming:.

l have yet to see someone declare with certainty and with concrete evidence that a cell NOT charged through pwm outlast or outperform a cell charged through other means.

I also have 2 vp2 chargers, iCharger, Pila, MC3000, C9000 and some really cheap ones and l for one never noticed any advantage of one over the other except the user-friendliness of the Opus (and the C9000).

Xtar do not use PWM in any of their chargers.

Hmmm ok wel maybe they mean something different but in the manual they state that the charger uses pulse-width modulation.

Whooo…

Euhm Xtar or what do u mean with “Whooo….”

Sometimes I wonder if pulse charging is just an evolution in marketing, a throwback to the NiCd era where people used pulses to blow away dendrites that shorted out cells, that if a charger did that for you automatically, it could create the perception that it was a more versatile charger in being able to charge near dead cells that others refused to.

I’m not suggesting that it should be avoided, only that like any other circuit, the level of peaks to the pulses are higher current that requires the whole circuit to be more robust to handle it, though I question if it’s a good idea to pulse past 4.2V/etc on lithium chemistries since their lifespan so dramatically drops the closer you get TO 4.2V, let alone going over it.

It’s another thing that makes me wonder how far a mad modder would go… they do make a thing called zeners that could shunt voltage, but then how far do you want to go to fix a design? It does make sense in that it saves a lot of time to get something with a custom display and features built in, then you just correct its shortcomings. Heck, half the time when I do a project, it takes me as much time to figure out and fab a custom enclosure that doesn’t look ghetto. :laughing: