@hummie I love and hate your rabbit hole tangents. But I think this might help people, and someone can shout me down if Iâm full of shit
[quote=âHummie, post:97, topic:36797â]it still seems a bare psu will not in any way be more damaging to cells. Is this true?
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Okay, Iâm still putting this together in my mind, but I think there are a few categories of power supplies.
vanilla normal power supply â will supply around the voltage specified, will vary with load, and will be able to supply specified voltage until the wattage is exceeded, at which point it will brown out, then pop a breaker or burn out or catch fire. Similar to how battery packs behave.
regulated power supply â will attempt to hold the voltage more accurately but otherwise similar behavior as #1. If your load exceeds the wattage limits, will brown out, then pop.
CC/CV power supply â the CC acts as a current limiter (cap on the max), the CV acts as a voltage limiter (cap on the max). Since it limits the output, you can put as big a load as you want on it. The PSU will limit current to the max and voltage will drop proportionate to the load.
So your questions/thoughts about PSUs need to be against one of above. And all of above can have different behaviors as to voltage/current spikes at turn on, dirty output, etc.
For example, the flashlight nuts charge single cell 18650 usually in 4 channel chargers. Reviewers will graph the output to make sure voltage doesnât spike, remains 4.20v or under, has a more-or-less CC/CV shape, and terminates charge when full. Many many chargers fail this test. A lot of chargers go to 4.25 or above.
As for your question about bare PSUs harming cells, I would think youâd have to graph the output while charging a pack, to answer the question. Likely no, but itâs quite possible the voltage overshoots, perhaps just for an instant, perhaps more.
Why would you buy those lol? There $50 for 250W of power??? Just buy a 12V 700W server PSU for $20 and add a boost converter and itâll be cheaper and higher power.
I have the hlg-320h-48a. I like it because itâs still sort of portable and can charge my 12s7p at 6 amps and my smaller pack at lower amps. The only thing is it gets so hot at 140f on the high end. Is that normal, did you add any cooling?
Boosting 12v to 50v at 250w is not supposed to be cheap. I donât think any of the $30-50 boost things will hold up. Youtube reviews indicate most of them have poor regulation or are in some other way crap.
I think itâs a better strategy to get 4-5 computer PSUs and wire them in series (after lifting the DC ground on 3 of them). Iâve actually done this, sweet! HP DPS-1200FB is the best value. But even at $20/psu, this adds up. Itâll be cheaper/safer to just get a 60v PSU.
The âwhyâ for the meanwell led driver:
good brand, likely to work as specified, likely to last
every time I look up the dangers of lithium charging I find another article contradicting what Iâd read before. This tells of how even float charging isnât a danger or even much wear on cells:
Also waiting for someone to tell me if Iâm wrong but hereâs a recap of what it seems to me:
We want the supply regulated and thatâs easy to come by, vanilla
The next important thing is not to put too high a voltage to the cell and thatâs why I feel safer with a cv supply. The manufacturerâs stated max current limits are much higher than any of us are doing for the cells we use. Weâre all looking to get something we can discharge at high amps and with that comes the ability to charge at high amps without the cells getting hot also. Logically then cc isnât needed as we arenât going anywhere near the current that would be truly damaging. so with this supply I linked above:
https://www.amazon.com/LM-High-precision-High-stability-Certification-Communications/dp/B06ZYDZCG9/ref=pd_sbs_328_4?_encoding=UTF8&psc=1&refRID=3AH9XHNXSP2T286R6732
which has an adjustable voltage I can set it toâŠit still limits the current to about 8 amps regardless, and even if it didnât somehow keep current to 8amps, and I were to be doing double that, thatâs just faster charging and not a problem for my 4p 30q.
but I put a wattmeter on to see the current come out anyway.
Hummie, these research papers are like a decade from reality, and are specific to the research being done. They cannot be generalized to, for example, the Samsung 30Q cell. You gotta trust what the manufacturer says, or do your own experiments, on a sample size much greater than one.
I like the PSU you linked, and I bought one. I donât see any wording that itâs a CC/CV supply, so I think itâs simply an adjustable voltage PSU. Weâd be quite lucly if thereâs a current limiting circuit in there.
Hereâs the difference between regulated voltage vs constant current. If your load wants to pull 200 amps, the non-CC PSU will try to supply it, and either pop a breaker or burn itself out.
The CC PSU will limit the current to what itâs set at (and voltage will drop to obey ohmâs law).
If you plug a pack into a non-CC PSU, the thing thatâs limiting the current is the internal resistance of the pack and all the wiring and connectors. If this resistance is low, itâs gonna pull hella lot of current. Analogy: connect an empty 18560 cell to a full cell in parallel.
On the other hand the CC PSU will keep things in a sane range. If you direct short the outputs of a CC PSU, you should see the voltage drop to just about zero and the current will max out to whatever it is set to.
You can try to satisfy yourself by actually measuring voltage and current when you hook up that PSU you linked to a mostly discharged pack. Get one of those volt/amp/watt meters and put it inline. Maybe a 200amp one to make sure it doesnât blow up.
We need to really prove this. I mean if they work decently and not going from 12V to 50V but maybe something more tenable like 24V to 55V then we can get past this 5A charging and get to maybe 15A.
I see the following (3) components as a good basis for a test to get 15A 12S chargingâŠ
4.2 * 12v * 15a == 756watt. So you need a bigger PSU.
15a is starting to be a lot of current. Need somewhat beefy wires and good connectors, otherwise youâll have a decent voltage drop, and potential melt/fire issues.
The DPS5020 is supposedly 50v 20a, but itâs really a lot of power! Dave at EEVblog managed to blow his up:
(EDIT the psu is not unsafe! But perhaps itâs good to check it over before putting max power through it)
Most of what I know is what Iâve read and not what Iâve done, but buck is supposedly way more efficient than boost.
My guess would be that DROK boost will be either badly regulated, not deliver full power, or blow up quickly under full power without adding a bunch of heat sinks, etc.
There might be a good model out there, or one that was put together nicely that can take a beating. But Iâd be wary of putting hundreds of watts though those things. The DPS buck PSUs seem to have fairly consistent quality and good basic design (from what Iâve read/watched).
Iâd say youâre better off getting Hummieâs 60v PSU and the DPS5020. Settle for about 8 amps. At least I havenât found a cheap way to do better.
While youâre mentioning eevblog. Did you watch the video and videos after that? Reason of the failure wasnât âtoo much powerâ but the ceramic capacitor cracking due to mechanical reasons. Just sayinâ.
Yeah I watched it. Design problem, fixed perhaps in later revisions. (Fixed as in layout compensates for delicate parts, or was it a diode that prevents the boom) Donât know what version youâll receive.
But the point I was actually trying to make was that if you watch the video, itâs a LOT of power! So any little thing goes wrong, poof or BOOM!
And these random china designed/built poorly QCâed not UL-tested electronics mostly do not perform to spec and often fail, sometimes terribly, so the onus is on us to test and be careful.
For sure! Always know the limits and expect anything.
I just wanted to make sure the video wasnât taken out of context for a casual reader. Daveâs vids are loooong
Also, the reaction speed of the maker of the module shows that he cares and continues to improve the design. Itâs a rarity for manufacturers in China.
Iâm just confused why people bother with these drok things which being a buck down or boost up are more inefficient than pwm and you can get the adjustability from 0-60 for cheap in the psu we have. CC seems a waste of time unless you have cells that are made for a laptop or something and thereâs no problem charging at around double if not triple the rate of what people typically do. its said they will last longer.but its not a safety thing and within the manufacturers stated fast charge rate, and Iâve also found many recent studies/articles stating that the charge rate isnât what damages a cell and just the voltage itâs put to and if it gets hot.
Iâll grant you that was an old article and trickle charging is no good at full capacity of a cell according to everywhere else, the details of what that means lets forget but does the drok even have an auto shut off when its at the end of a charge and just trickling anyway?
the psu we both have I think we could define as a constant voltage in that you set it to a voltage and it stays charging at that voltage and brings the battery up to it.
Iâve hooked up different very low batteries to different psu all of which are hooked up with a wattmeter too so I can see the current and voltage. In this low battery situation with usual CV psu such as linked they most often will stutter and do an on-off of current until the voltage is lowered manually or they very slowly bring the battery up (meanwell), or if theyâre cheap they just try to do a higher amperage then theyâre stated to do get hot and blow((cheapo that they sent a higher rated replacemen and no problem), or they limit themselves to around the stated amperage somehow, not following ohmâs law, and that seems the norm so in a way theyâre current limited in that it wont go much over 8 amps.
CC is not really constant current. Itâs current limiting. So it really really is a safety thing, and required. Mucho danger to connect a high discharge battery pack (low internal resistance) to a PSU without something that limits current. Rates will not be triple, but potentially hundreds of amps, like connecting a dead lipo to a full lipo. Granted, the PSU will likely pop a fuse or something first.
I donât think itâs responsible to say your 60v 8a adjustable voltage (non constant current) psu is safe to hook up to packs, without having done a bunch of testing to verify.
Iâm thinking most people use these to feed BMS? And depend on BMS to cut the charge when full.
And Iâve been reading and thinking about this. I donât think itâs the BMSâs job to terminate charge. Charge termination is different from over voltage protection⊠Still thinking and learning about this one.
This behavior is critical, in contrast to your âget hot and blowâ behavior, and needs to be verified. Iâd say this type of supply is constant current.
But I think this might help people, and someone can shout me down if Iâm full of shit 
