There is a common misperception that charging one's battery banks faster is better or worth throwing more money at. 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 up. 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.

However:

charge current affects the SOC transition point from bulk to absorption charging - MaineSail²⁾

MaineSail found that

• charging AGM at C/2.5 (max rate) resulted in the battery being 63.3% “full” at Vabs and being fully charged in 5hrs, 30 minutes
• charging AGM at C/5 (min rate) resulted in the battery being 77.4% “full” at Vabs and being fully charged in 5hrs, 42 minutes

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.

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.

• solar charging - sunlight is only available during a short window, as when camped in a forest canopy with a clear overhead view. Note that poor insolation calls for increased harvest / overpaneling, not faster charging necessarily
• generator charging - for efficiency purposes the generator is shut down after Vabs is reached. Generators run most efficiently when fully loaded.
• shore charging - if you only have a certain amount of time on the extension cord
• alternator charging - if you will driving for short periods only