I am building the circuit listed on page 5 here:
http://focus.ti.com/lit/ug/sluu023b/sluu023b.pdf
Resistors R12, R14, and R19 are part of a divider that specifies the Bulk charge and Float charge characteristics. I am shooting for a bulk charge voltage of 14.7 volts and a float charge voltage of 13.5 volts. The resistor values are based on equation 1 and 2 on page 6 here:
http://focus.ti.com/lit/an/slua017/slua017.pdf
My question is this. I am using 1% resistors. If I consider all of the different permutations of the three resistors being +/- 1% of their stated values I end up with Vblk having a maximum and minimum possible value of 15.2V and 14.7V respectively and Vflt having a maximum and minimum possible value of 13.94V and 13.48V respectively.
First off is this amount of variation acceptable for charging a 12V SLA battery? Second, if this amount of variation is not acceptable does it make sense to stick a trimmer pot in series with either R12 or R14 to sort of tune the circuit?
http://focus.ti.com/lit/ug/sluu023b/sluu023b.pdf
Resistors R12, R14, and R19 are part of a divider that specifies the Bulk charge and Float charge characteristics. I am shooting for a bulk charge voltage of 14.7 volts and a float charge voltage of 13.5 volts. The resistor values are based on equation 1 and 2 on page 6 here:
http://focus.ti.com/lit/an/slua017/slua017.pdf
My question is this. I am using 1% resistors. If I consider all of the different permutations of the three resistors being +/- 1% of their stated values I end up with Vblk having a maximum and minimum possible value of 15.2V and 14.7V respectively and Vflt having a maximum and minimum possible value of 13.94V and 13.48V respectively.
First off is this amount of variation acceptable for charging a 12V SLA battery? Second, if this amount of variation is not acceptable does it make sense to stick a trimmer pot in series with either R12 or R14 to sort of tune the circuit?