Seriously another alternator question.

^^This is a pretty good write up but one caveat, and that is "be careful" when making comparisons because those old chargers ARE NOT voltage regulated. You said you "adjusted the output" which is a key phrase here. Otherwise, just leaving the charger connected at the higher setting would result in overly high system voltage AND overly high charge rate AS THE BATTERY comes up in charge.

This is a dramatic and key departure from an auto system, where the system is VOLTAGE regulated.

"In theory" you could build a '"test fixture" using an alternator and regulator, and use a 100A+ alternator to charge the smallest "minibike" battery you can get your hands on, and the lash up would in theory, NOT damage the battery BECAUSE it is voltage regulated.

I basically agree, tho...........the main reasons for high charge rates after a cold start is that the battery is simply down.