Custom build a current throttling resistor for your own battery bank. For a pair of GC 220's series parallel 200 watt of capacity would allow perfect amperage throttling for equalization. It would take a Meanwell RSP-400-15 to achieve 16.0 volts.
Naio, for example could easily make throttler for her AGM batteries and another for her gelled battery setup that in the case of the gel permit a one amp regulated flow.
Control of amperage has been the missing element for proper care of flooded batteries. using the 5% rule and watching voltage climb to 16.0 is magic for flooded lead acid battery management. Because of the lack of control devices I grit my teeth when I read about people doing it wrong then complaining about lack of results.
State battery bank size, and someone will calculate the number of resistors you will need.
The price of resistors such as these used to be TEN TIMES HIGHER.
