Maybe look it up. It’s literally what you are looking for and more.
@Friskies I’m aware of DieBieMS and I have commented on it above. I like it but it just seems a complete waste to use it as a balance charger only.
Why charge only? It can handle more than most will be able to throw it it in regards to discharge too… You’re talking about bulk etc buy how many relays were you going to wire together??
@Friskies Bulky is only an issue if you were to put the thing inside the enclosure. That was never the intention.
The issue with DieBieMS is that either you put it inside the enclosure, in which case you have to make a lot of space for it, or you use it outside of the enclosure as a balance charger, in which case you’re wasting a nice product.
Meanwhile i use a 80A bestech BMS for daily use. it is so easy to use and trustable. every 2 month I use my “frankenstein charger” to charge the cells independent from the bms. therefor I have to open enclosure, unplug the BMS and plug the charger instead. Not a big deal to do so…
It just seems a little counter intuitive. If you are that worried about unbalanced P groups then you are probably just better off finding a way to incorporate a discharge BMS. There are still some really compact 60a discharge units around. LHB recommended one from batterysupports which seems to be pretty tiny…
This looks like a good option, especially with the link that @deucesdown has shared. I will get one too for experimenting. Which one are you getting? The cheapest one to bypass or the 60A one?
Sure the cheapest one.
I anyhow use it only in time of charging and I think I will not charge with more than 20a 
I ordered a pc module too, but not sure if it’s really needed.
Sounds good. I just ordered the same. If it works, that’s an easy way to implement a 12S balance charger. If it doesn’t, I’ll just have to build my binary relay tree. 
that bms is great, in the pc software you can edit more things you can even imagine!
Did you notice that you get one for LiIon? The one I linked is for lifepo4 cells. I was speaking with the shop and they said they will set it up for lipo/LiIon. If you didn’t, better write them a message too.
Ah, I didn’t notice there were multiple versions. I ordered from this link, so I should be good. Thanks for the warning though.
Now I have to figure out how do I install their Windows app on my Mac. 
Could anyone help me choose an appropriate relay for that binary relay tree? Ideally it would possible to switch it with 5V and it would be rated at least 5A at 5V DC. I guess some solid state relay would be best? Oh, and it has to be 2 pole. Does that even exist?
The one you linked is for 13s. That’s ok for you?
Uh, good point. Do you think it won’t work with 12S only?
Not sure. Normal bms usually work if you just don’t wire the last pin. Maybe @Acido know if it would work.
I messaged the seller. They actually don’t offer a 12S for li-ion. Only the lifepo4. Weird.
Strange, than let’s see what i‘ll get 
i didn’t read the full thread but with what i read i understand that he doesn’t trust the bms to do the balancing and that he want to be able to check on the voltages
this bms has an app and you can see the exact voltages in it and its not that big either so i see no point of making the “charger” when the bms has all he needs