"small 12V system" is not one that can power a heater unless the heater is VERY small.
Electric heaters are extremely demanding. You need to assess how much kWh the heater will consume and determine fewer than 2-3kW of panels is adequate.
Numbers:
445W/12V = 37A per panel
445W/24V = 18.5A per panel
445W/48V = 9.3A per panel (but you will need two panels in series, so back up to 18.5A you go)
For each battery voltage, you will need a charge controller rated for the stated amps for each panel.
For 12V, you must purchase a MPPT controller. A PWM controller will operate at about 1/3 the panel power.
For 24 or 48V, you have the option of a PWM controller operating at about 70-80% of the panel(s) rated power.