There is a common misperception that charging one's battery banks faster is better or that having more charging capacity guarantees faster charging. Here are some reasons it is not always true:
Lead batteries have a maximum amount of current they will accept, typically C/3 for AGM and C/5 for flooded. So if you have 100Ah of AGM the most it will want to take is something like ~33A. Once the battery's limit is hit throwing more charging capacity at it can't charge it any faster.1)
Deep-cycled lead batteries have a lengthy Absorption stage that cannot be sped up2). Depending on use, Absorption typically requires several hours.There is a saying that “it takes 9 months to make a baby, but two women cannot make a baby in 4.5 months”. Same with absorption - it takes what it takes and you cannot hurry it in the normal sense.
charge current affects the SOC transition point from bulk to absorption charging - MaineSail3)
MaineSail found that
Note that the using 2x the charging current only sped up the whole process by 12 minutes (3.6%) due to Vabs starting earlier but taking longer. Getting to Vabs faster could be preferable on PWM controllers.
Lithium batteries can slurp up current wildly, but shouldn't for their own health. Lithium lasts longest in sub-C use (ie, less than 100A for a 100Ah Li bank). C/2 (50A) is a more common limit to keep from stressing them. In commercial examples the BMS will limit current to protect the cells. A small DC-DC charger can help protect bare cells from their own greediness.