Hi Williamson! I made a basic 6kW charger design and am in the midst of prototyping a single bms node for LiFePO4 batteries. With lithium batteries, you can't make a charger who's voltage output is too sloppy voltage wise, because if the voltage goes over the 3.75v limit (or so), you will be destroying the batteries. In my case, that meant having a good sized inductor and big input filter capacitor. You want to charge the whole pack so that you stop the constant current as soon as a single battery hits like 3.8v. You need pretty fine control of large current at high voltage, and it's not terribly cheap. In my case it's about $600-$700 for the parts. But the good news is, if you go buy a 6kW charger with CAN interface, it's like $6000 haha. so maybe that's not so bad.
The bms will be very noise tolerant because it uses CAN for the communication with the charger and controller. There are some other good open source designs like Greg Fordyce's.
Hey, I soldered my first surface mount components (in my whole life! for the bms):
This is a 1.25v reference (+/- 0.2%). It costs like $2.80 just for that microscopic little sucker! I thought it was a piece of dirt when it was on my desk.
This is for a mosfet that turns completely on with gate voltage of only like 2.5v! haha! ya!
Here it is with the mosfet attached:
I had to make little adapters with the mill for prototyping. And that meant tuning that sucker so it didn't have the slop anymore! ya! I bet it's +/- 0.001 or +/- 0.002 now! ya! I did a tiny plus sign that showed how much x and y were off, and then corrected for that. It took a few plus signs before it was tuned really good! Now it's perfect! ya!
By the way, an expert in the industry is going to make a "how to build a reliable pcb" to help people reliably put together their own stuff. I'm starting a thread for him, so check it out. ya!