i use battery supports BMSs and ebike chargers. That will likely change sometime in 2018 if these new BMSs wortk out and i can find some nice quiet 4 amp chargers.
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@Hummie Thanks for linking those articles, read them all.
Okay I think mostly you have it right. The current in a circuit is dictated by the load (resistance). Since battery pack IR is very low, ohmās law says packs will basically pull a metric shit-ton of current from a supply if not limited.
Math example: charger/psu is supplying 50.4v. pack is 12s1p with 20mohm per cell (spec sheet says DC IR is 20mohm), 240mohm for the pack.
ohmās law: V = IR, or V/R = I
50.4v / 0.240 ohm = 210a
210a should pop the psu and torch the cellsā¦ Actually I think what would really happen is your 8a psu will supply 12a for a while then either pop its internal protection or fuse, or catch fire. 
The way CC/CV works, first, current is limited (which forces voltage down), then if you reach that current, voltage is limited, forcing the current down.
So CV stage comes after CC.
Youāre right that CC is to limit the rate at which energy is entering the pack. Youāre also right that most cells can probably handle more than the spec sheet says. But cells can handle what they can handle, going above that will damage the cells. You canāt pour 10C into a cell rated for 1C charge and expect them to hold up. This is where itās best to follow the mfg spec sheet. Theyāve done tons of tests and know what their cells can take.
None of the articles you linked contradict this. Actually all the articles you linked were interpreting the same research study on a made-to-purpose cell, and draw some reaching conclusions. I donāt think itās relevant to the 18650 cells weāre using.
As the cells get fuller, the voltage rises. When you hit the CV voltage limit, the charger keeps the voltage from rising further by cutting current. A PSU with adjustable voltage is probably okay here. But going too high on voltage is REALLY bad for the cells so you want to be sure the PSU is behaving as you expect/wish.
Dude wtf!
How did you get 8ah pack??
Spec sheet says capacity is 3ah. standard charge 1.5a (0.5C), max current 4.0a (1.3C). Going with this weird 8ah, that means the pack is 2.67p. Standard charge rate would be 4a (2.67 * 1.5a), max charge is 10.68a (2.67 * 4a).
If this were something like a more normal 10s4p pack, 4p makes it 12ah (4 * 3ah). Standard charge rate is 6a (4 * 1.5a), max charge rate is 16a (4 * 4a).
If samsung says 4a is max charge rate, going higher than that WILL shorten life.
Generally true, trickle charging is bad for most lithium ion cells. But there are differences! A123 for example can trickle charge (at lower than max voltage) with little ill effect.
CC/CV Power Supplies do not cut power and continue to trickle charge.
CC/CV charger have a cutoff current, below which it cuts off power. Usually C/10 (for a 4a charger, 0.4a).
If you havenāt noticed, most things that have lithium ion batteries (cell phones, etc.) donāt trickle charge. They terminate the charge when full, then perhaps will begin the charge cycle again if/when the voltage drops lower than some threshold (topping off charge).
So yeah I think a CC/CV PSU is an incomplete solution. Iād advocate putting a timer on the wall plug if using a CC/CV power supply to charge.
https://www.amazon.com/gp/product/B014SGCIR4/
https://www.amazon.com/gp/product/B014SGCN88/
https://www.amazon.com/gp/product/B01D3QEK4E/
Oh btw that 60v 8A PSU you found, nice, gone! 
The thing thatās different about the regulator @scepterr is linking and your PSU, your PSU is not adjustable CC.
Constant Current really means max current limit.
Most PSU have rated max current, but does not limit and hold current to the rated max. Rather, it allows some brief excursions above the rated max, then pops some protection or a fuse, or blows. From the description, āOverload protection: 105%-150% cut off outputā
Holy crap wrote all thatā¦ Iām supposed to be BF shopping. I guess itās all good though, writing this kind of stuff out forces me to be precise in what Iām thinking and knowing.
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Depending on your setup that could be too strong current
can u confirm if itās a 4amp max charge current per cell with the ones I have and iām doing 12s 4p with themā¦thatās 16amp max charge they recommend?
sorry I shouldāve written I have an 12ah pack and charge at 8amps with cells that can do 4amps each
I think with the ohms law equation you wrote you need to incorporate the pack voltage so itās not 50 and a minimal resistance but the difference between the supply and the battery
a123 arenāt li-ion
I see your point with the timer. but itās vague the ātrickleā as to how long it can be on. with my supply it will slowly creep up to 50v at the end doing maybe half an amp. I wonder if thatās a problem
Click on the spec sheet link. Itās worth a careful look.
With respect to fast charge/discharge, I believe what actually hurts cells is temperature. If you can monitor temperature and perhaps do active cooling, you can charge/discharge at faster rates without hurting the cells.
The true answer of what these cells can take will be from someone doing repeated abusive charge/discharge cycles while monitoring temperature (characterizing the cell). Havenāt seen this yet.
Take a look at this pdf, itās A123 but thereās some hardcore information about lithium ion in general.
Yeah it was just rough math to illustrate a point (to myself mostly).
Respectfully disagree. Li-ion, lipoly, lifepo4 are all subtypes of lithium ion. Within the 3.6v 18650s weāre used to, there are many different chemistries as well.
Yeah how much it hurts is gonna be a sliding scaleā¦
Hey so bringing it back to what you said about CC/CV, this guy below argues the case against CC/CV quite reasonably.
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Nice thread ā I have some 24V and 12V PSU supplies (server mods) that deliver like 750W & 1500W respectively. Question I was thinking of this unitā¦
https://www.amazon.com/gp/product/B0744BT79M/ref=ox_sc_act_title_2?smid=AFHAE9RJVUMB&psc=1
Now despite the language of it saying step downā¦ it is also step-up (i.e. can work like a boost converter as well?) ?
My plan is to buy one these and use it charge all my lipo and li-ion packs thru the BMSās charge port wiring (using 2.1mm DC female and male jacks). I have a couple of 10s and some 12s so I think this will solve all my needs. Also, it avoids me from buying that stupidly expensive $60 power brick.
https://www.amazon.com/gp/product/B015OCV5XY/ref=ox_sc_act_title_1?smid=A26VCHUIBE4PN9&psc=1
Gonna a do a For Idiotās thread on this [ mainly to remind myself too:) ]
I built myself a 3 amp charger from a Evolve charger, just bought a nice regulator and set the cut-off, itās super easy and you can make a charger from a regulator very easily, I want to make another one now from a 45amp power-supply I have, see how high I can get the ampsā¦I think I can charge my long range board near 15a if I please and cut down on the 48 hour charge time, lol
Iām currently using this regulator: https://www.amazon.com/gp/product/B01MSJQAKY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
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It wonāt boost unfortunately, there is a boost/buck version but I think itās 32v/5a
Ok so noob question incoming ā do I need to boost up or step downā¦ I am trying to connect either my 12V or 24V PSU (I have linked it below) thru the buck booster / converter to the BMS routed charge port? (assume 10s and 12s configurations).
Ahh poopā¦ I think ordered the wrong oneā¦ lolā¦ I can change quickly before they ship ā I think I need a boost up converter because 10s and 12s batteries will require 37V and 44.4V respectively.
Yes and the only boost version goes to 32 For your needs only a 55-60v psu + the stepdown would work
Man I so much extra junk I gotta sell or get rid of.
Anywaysā¦ I think this guy would work well:
Thanks!
Yeah the 60 would work, only 5A max though
Only 12v though?
I have thoseā¦ no good though. They are only at 12V or 24V (two in parallel). The problem is that one needs between 37-44V to charge 10s or 12s batteries via BMS.
One could perhaps take one of those PSUās you linked and put it thru a step-up boost converterā¦ see belowā¦ but the problem is the amps might destroy the boost converterā¦ itās not rated to handle 75amps.
@scepterr correct me if I am wrong.
Exactly, you combine it with a good regulator with a cut-off, like this: https://www.amazon.com/gp/product/B01MSJQAKY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
The voltage doesnāt matter when you have that much amperage to convert, lol
Iām concerned about how much loss theres gonna be going down-up-down
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Dude let me know how your project goesā¦ I have one of those 12V 75A power supplyā¦ also a 24V 60A. These are remnants from days of refusing to go the BMS route. So I have a 12S RC balance charger. Kind want to get back to just plug and play tech.
I see @scepterr idea with a lab bench power supply (60V) feeding his step-down its cool BUT since I already have partsā¦ I kind of want to see if your cutoff regulator works. I mean it shouldā¦ but I think that thing will get blistering hot.
https://www.amazon.com/gp/product/B071LGTTRN/ref=oh_aui_detailpage_o01_s00?ie=UTF8&th=1
Heck I can probably even send you my 12V power supply for free or close to free + shipping if you want itā¦ for science 
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