I think it makes more sense to just build a single (1S) cell charger. So for example, bulk charge to an average cell voltage of 4.10V. Some cells will be 4.13V, while others might be 4.07V. Individually charge them all to 4.15V. This would manually balance the pack. You’d only need to do this occasionally. Often the pack will stay nearly perfectly balanced with no maintenance
The problem I have is my BMS doesn’t seem to balance very well. Some cells consistently lag behind 0.05V at EOC
0,05V apart is well enough…
0.05V is not worth talking about. This is probably already in the range of the measurement error of your voltmeter.
the cool thing about this would be to simply choose how much cells you want, so a modular charging system, where you could charge your 6s board aswell as your 10s, without using a bms! To me that sounds really cool! Also cool for people with things like 9s Boards, where you normally have to use two rc chargers…
I don’t understand you guys. how is having ten chargers better than one that you need to hook up twice but ultimately takes less time? There are even wiring diagrams out there on how to split a >6S battery to charge it in parallel. This proposed mechanism (if you go for multiple cells at a time and not just one) will be a wiring mess, complicated to connect and can do more harm than good.
this can be easily achieved like I explained above with a simple boost converter - no explicit balancing but you can keep it hooked up until it reaches your desired current in the CV phase.
You build this thing by your own and throw everything in a cool housing, then you only have one cable with a few phases out. Different cables with different phases for different boards like 6s or 10s.
Hook it in the wall, hook it to your battery and you´re done. No BMS, no worries to overload your battery. Sounds cool to me 
@jmasta use this, TP4056 modules, they are limited to 1A max, but work quite well and are very cheap, now you only need 10 USB wall adapter, again, isolated with one USB each
Look what I found on AliExpress
Yeah, that would need a bit of tinkering, but is doable
0.05V is not a huge deal. 0.50V is a different story
If you have a welded pack and you find one cell group very out of balance… What do you do? Your BMS won’t take care of it if the voltage difference is significant. I have a 0.05V difference now. What happens when that grows to 0.10V?
The following scenario resulted in permanent cell damage
Tell me why it won’t work. Provide suggestions if you are so inclined. Not to be rude, but whether or not you see a use for the technology irrelevant. The need exists
We already have that. This thread is about balance charging individual cells simultaneously
I don’t know what to say. I told you multiple times that it will not be that easy (just think about how many power outlets you’ll need for 10 separate USB chargers). One RC charger does what you want - and is easier to use, faster and cheaper. There is no need for this because the solution already exists.
You need to start thinking what the benefit of your method will be.
Just as an example: I already have my battery set up as two 5S packs that I can charge individually on an 6S charger. This way I can test the individual voltages from time to time. Normally I charge with my DROK. This is as easy and cheap as it can get and I have full control over the voltages I charge my battery to.
yes, both…
if you absolutely have to buy something from aliexpress just get a BMS there
If the goal is to be cheaper I agree with both of you
But building a charger this way could be a fun project
As an electronics engineer, there’s a lot… interesting ideas presented here. Surely out of the box ideas for me, but how sensible? Not so much.
The easiest and best practical way would be to wire your S>6 pack so that it can be charged as two S<=6 packs and use RC chargers as @Maxid suggested. Otherwise you’re going to be babysitting your battery pack and checking cell voltages and adjusting your charging currents and voltages. A RC charger will lower the charge current once a cell hits 4.2 V and then trickle charge the rest of the way while discharging the 4.2 V cells so they don’t overcharge.
Other possibility is the @raphaelchang 's BattMan BMS module.
It pretty much comes down to these reasons: Not everyone uses quality cells. Not everyone uses quality welders. Not everyone has good soldering/welding skills.
Any of the above plus not having a BMS will ruin your batteries. As an example @denton had a battery pack in which welds failed and he was also using a charger with way too high voltage, but since he was using a BMS to charge and discharge no damage was ever done to his batteries.
Someone with a wrong charge voltage is kind of unfair to use though as an argument no? 
It is not hard to make a setup without a BMS work well, so I still feel like they are not really necessary.
His charger was not the reason his cells were out of balance, it was the bad welding tabs. Still a valid argument. Look at eboosted and all the trouble he’s having with drifting cells.
It’s not trivial… One, you have to buy or make a quality welder. If you are soldering, you have to have good soldering skills and even then by the fact that you’re soldering onto batteries, you will damage them some. Two, you have to buy quality cells. Three, you have to have very conservative settings. Have you looked at whitepony’s settings? He only uses like 70% of the available capacity in his cells and doesn’t discharge them at high currents either. Four, if vibrations work a weld/solder joint off a cell, your pack is F’d. (this is where my example came into play really)
There are plenty of reasons to use a BMS. If you prefer to baby your pack instead then fine, I do it that way just because I like to know the state of my batteries all the time.
Not sure what to say - as usual I get your point but am personally not convinced that a BMS is crucial. Put some balance leads on the pack and check from time to time and it should work fine. I used a DIY welder and have no problems with my packs. People with faulty packs will obviously benefit from a BMS but I’d rather pay attention when building my pack in the first place and make sure everything is well.
All I am saying is that when you know what you are doing they are not crucial.
