Question about building a custom 12s BMS power supply

I am building a custom charger for my batteries. It’s a 12s setup and I ordered a drok cc cv step up module. I will be using a 12v power supply as input and output will be 50.4v. My question is how will I know when all the cells are charged and balanced?

This is what I ordered: DROK Numerical Control Regulator DC 8-60V to 10-120V 15A Boost Converter, Constant Step Up Module Adjustable Output 48V 24V 12V DC Power Supply with LED Display

I am curious about this answer too, after cc cycle usually the Amp goes down, that might be the indication. I may be completely wrong but, if anyone has done this can answer better,

Eev blog has video on this i guess

Im doing something similar, @Hummie suggested I use an inline watt meter. If you set a constant voltage when your battery comes to full charge (At that voltage) there will be little to no potential difference between the supply and the battery therefore current will drop to a very small amount.

Just dont set your voltage too high (I.e 4.2v per cell) and leave it on full charge for a long time as it might be bad for the cells. Read here:*

What if I use a 12v power supply with a light on it. Will the light turn green at 12v or will it turn green or whatever color when the cells are all balanced for a total of 50.4v??

Or maybe just keep a multimeter in the xt60 and when it reaches 50.4, stop it. Just throwing out ideas.

You can do the light thing, but that would require a separate circuit (Either design or buy) and Im not going to bother. I’ll charge my cells with me beside them so I can monitor them, one day Ill build a cutoff but for now its good enough.

Most of the time you wont be charging from a flat battery (Or atleast I wont be) so waiting beside them shouldnt be too bad…

do you know how I would build a cutoff for each cell

There’s single lipo cell chargers but never have I seen one that did a decent current. U could do one of those going into each cell’s balance leads and the other sides all in parallel into some power supply. U could have it all off the board and just a 13 prong plug into the board.

is there a way for the drok module to cutoff at a certain voltage

I read this on the questions section of amazon, someone wrote this as an answer to something: This is a constant voltage & constant current converter. Which means it will supply the regulated current value until the constant voltage is reached. Thus if the voltage is set properly it will not overcharge an AGM battery. Just be aware that the battery will likely have to be isolated in some manner while charging or you will create a feedback situation where the converter runs & runs but never gets any charge to the battery. For a 145AH battery heed the note to provide additional cooling (a fan) when operating over 100W

does this mean I can just wait until the voltage is reached and the module will shut off automatically?

Regardless of if it shuts off or not it doesn’t matter. Similarly a psu without the drok thing will not shut off as it never gets quite to the voltage its set to

so what do you recommend I do so I don’t overcharge my packs??

Just get the bulk power supply that does 8amps and adjustable 0-60 with the golden knob n has aoltage screen. Amazon or eBay . set it so ur cells only hit 4.15 to be safe, n balance on the side at any time w “lipo discharge balancer”. This is the cheapest and fastest charging method. No bms. N rely on the vesc low voltage cut-offs.

the problem is I already ordered the drok thing and I have a BMS. What should I do??

U have a power supply to go w drok?

yes I have a 12v power supply which I will up with the drok

U have nothing to worry about. Just don’t overcharge any cells. Even if u set the supply to put 4.2 and the cells sit on that for days that’s not a danger. It’s not trickle charging and its a misunderstanding. Think it’s float. its the same as if the cells are at 4.20 n not on a charger

it doesnt supply to each cell, you just set it to the total voltage no?

Yea it just does the full pack n the bms likely does discharging of any cell that hits 4.2 simultaneously. Danger there is all the bms I see have a very low n slow discharge current when balancing so maybe slowly charge to full voltage the first time.