Tech A says that batteries should be charged as fast as possible. Tech B says that the ideal charging rate is the CCA divided by 70. Who is correct?

Neither A nor B

Explanation:

The charge rate of a battery is the rate at which charge is added to the battery in a given time unit. The unit of charge rate is Coulombs/second or amps

The time to charge a battery, is given by  the battery charging formula which is given as follows;

Battery charging time, t = Battery Ah(Ampere hour)/(Charging current, A)

T = Ah/A

Where;

T = Time (Hours)

Ah = The rating of the battery in Ampere Hour

A = The Current applied given in Amperes

The charging current should 10% of the Ah battery rating, such that a 120 Ah battery requires about 12 Amperes charging current

However, due to losses in the system, the current can be set at 13A

the time for charging will then be t = 120/13 = 9.23 hours

a and b sometimes have a positive value

c. magnitude and direction