^ 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.
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).
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:
The internal switcher uses PWM to regulate output current, all switchers do that and in most cases there is a filter on the output to remove the PWM and give a smoother current and voltage.
The internal switcher usual works at 300000Hz to 60000kHz, not the <100Hz that Opus and other analyzers uses for PWM.
@ HKJ: Thanks for explaining altough I don’t really understand it. @Gaus: well you mention safety, so I would say that putting a high current in a bad worn out cell might be dangerous.
My opus arrived and I’ve used to charge and test a few cells. I like it so far but I’m not sure bout the full test, I seem to be getting quite low mAh. But I have to play with it a little more. Some cells got warm on 700mA charge rate but not hot. They never got this warm on my VP2 or VC2 on a 1A charge rate. I won’t be using the opus to charge smaller cells unless I really have to.
Your Opus will not use your chosen charging rate if the cell cannot handle it. It will just automatically go down to what is the level it deems safe for the cell, which is a good feature when charging salvaged cells that has remained in low state-of-charge for quite a while. You will see the display not ‘follow’ your chosen rate, but will eventually go higher, or may not at all if the cell is really in bad shape.
The four individual displays of the Opus is one major advantage over the Littokala and Dragon, for you see what’s happening to ALL four cells at the SAME time, regardless of mode chosen in each bay.
I don’t worry about those pwm or pure CC/CV or whatever thing, for as I posted before, I have owned or am using those ALL those type of chargers and until now have not noticed any advantage of one over the other to my cells in real usage, just perhaps a smoother graph presentation of one over the other.
With salvaged cells, just be around ALL the time when charging them as some of them can and will suddenly get abnormally hot anytime. Most of these cells have had a tough life, or have stayed in a very dangerous low voltage already. It happened one time to me. I salvaged Sanyo cells that was given by a friend from an unrepairable laptop. It was 4.2v after charged, but suddenly got hot when put into the charger in a discharge mode.
In an open cell (SLA battery) environment this can matter, but in a sealed cell, humidity can only matter with hygroscopic flux residue present, or if the cell itself was defective so the seal, wasn’t one.
The world will need a mechanism for the change relative to humidity. This is science, not a social game of putting the burden on someone else who screwed up their findings.
Don’t be deluded by one study where the participants were desperate to show they didn’t waste the money spent on it. This happens all the time.
I like this charger however the one I have the fan is on all the time while powered on.
Occurred after I inserted the dc plug several times directly into the charger when the adapter was plugged into AC.
The ac/dc adapter having power apparently caused an electrical spark to occur between plug and charger, (while inserting the dc plug) causing damage to some of the fan control electronics of the charger’s PCB.
You shouldn’t ever plug in this type of charger when the AC/DC adapter has power as doing so may cause sparking between the DC plug and charger.
Charger seems to charge batteries ok, only the fans run all time never stopping or starting.
How do I get the fan to turn on and off via it’s thermistor or temperature sensor? Currently the fan hasn’t ever stopped running while the charger is turned on (plugged in) and charging batteries.
The fan began running all the time just after I plugged in the AC/DC adapter DC plug several times, afterwhich I noticed the sparking between the dc plug and charger.
IIRC, the Opus instructions state to first plug the dc plug into the charger before plugging the power adapter into AC.
