charging new STYLE batteries

I have solved my battery issues and found out older batteries were able to
be charged with lower voltage but newer batteries need higher voltage so as
we replace our batteries we run into issues of compatibility .
My Optima is working fine and charging well  with my I.P.D adjustable
regulator .I have been studying up on gel batteries as my mobility scooter
has two.That is a whole new field as we here in Australia pay a huge amount
for batteries that are available at less than half the price in America .We
pay double at least if not more for the gel battery and as for the mobility
scooters we pay $US 4300  FOR A SCOOTER COSTING $US 1750 .
Our dollar was au $1.07 to the US $ yesterday go figure .
As for Volvo parts we seem to do ok if we are careful .