Charging batteries from the grid

I'm working on a diy12S powerwall that will be both charged by the gridand discharged into the grid.

System would have a max voltage of 12 * 4.2 = 50.4V
ButI willbe limiting it to 4.0v per cell (48V) for extra cycle life.
(System will have a hard life, it willcycle once per day in the summer and twice per day in the winter)

I can easily come up with a cheap, high power, high efficiency 48v PSU.
But the only circuit I know of to limit current would be a simple linear regulator,
And that would kill my efficiency.


Could I use a PWM solar charge controller limit the current into the battery from a 48v dc psu?
What are some other frugaloptions?

EDIT:
Reading some more about what pwm charge controllers actually do, I don't think my first idea would work.

"PWM Controllers - When charging, these controllers feed the power from the panel straight through to the battery until
the battery voltage reaches a predetermined Acceptance level. It will then keep the voltage at that level by pulsing
the panel voltage on and off to keep the battery voltage constant."

Use a 24/36V PSU and a boost converter.

PWM will not work because they work like a slow manual switch (on/off) at times.

Most efficient option, buy a used HE flatpack2 unit but you would need to change the output voltage with a separate computer controlling the flatpack.

12s is not 48v and you Will have issues finding Gear supporting it. Use 14s. Secondly is it legal where you live?

Easiest is just a PSU straight into the battery via the bms. Just det the psus voltage to the battery.