get the batteries LOW enough and they will take upteen amps at 13v
that is NOT BOOST
BOOST is getting the battery voltage to 14.4 at what ever amps they will accept
and a full charge is when you get the batteries accepting about 1 amp PER battery or less
so when you get (3) batteries in parallel at 14.8v taking less than 3 amps
they are fully charged
bulk is high amps, boost is getting enough voltage to actually get to a fully charged condition
and getting a full charge is when they accept less than 1% of AMpHr capacity at full gassing voltage, which does shift slightly with ambient temperature
the peak voltage 14.4 to 15.0v varies with the construction of the battery, who mfg it, and for what design purpose
