How to charge this (SLA) battery?
Ideally:
CC using C/4 rate = 1.3A /4 = 325mA max whenever Vbat drops below 70% SoC or ~2.1V/cell or 12.6V in your case.
two-stage CV, if outdoors, apply a -4mV/˚C/Cell temp compensation for Vmax charge voltage above room temp. This is to charge the absorptive layer capacitance which has a much longer ESR*C time constant.
Use pulse float charge followed by measurement of no load decay rate in 1hr.
it is not a deep cell voltage battery. Sealed lead acid battery manufacturers do not recommend deep discharge, as this damages the battery (greatly reducing its life)
Absorption Charge Voltage 1
V OUT1 ‡ 14.2 14.4 14.6 V (min typ max)
Absorption Charge Voltage 2 & Float Charge Voltage
V OUT2 ‡ 13.5 13.65 13.8 V (min typ max)
Battery Capacity Threshold Voltage V TH 12.9 V After 2 mins