270v DC current limiting circuit
If you don't need an adjustable current limit value and you don't need to cut off all charging when a specific terminal voltage is reached, then the classic two-transistor circuit will work with appropriately beefy parts.



At 20 A you'll dissipate about 14 W in Rsense, and much more in T1 depending on the initial terminal voltage.  A switching circuit will be much more efficient, but also more complex.