Problem when connecting two cartridge heaters in parallel

I wanted to know if there is any problem in connecting Cartridge heaters in parallel, as I have been facing this issue while testing the cartridge heaters in parallel connection with DC power source at 12V. Initially the voltage set on a DC power source was 12V but when the system was turned ON the voltage displayed on the DC source jumped down to 9.6V and current consumed was 4.78 amps. The same is the result when connected to a battery source. So I don't understand why is this happening every time.

Please Note: The capacity of these cartridge heaters are 12V 40W.

Batteries and power supplies have what is called internal resistance. Essentially this acts as another resistor in series with the load (your heater cartridges) and causes the supply voltage to drop as more current is drawn. Add to this the resistance of the wires and any connectors you have in your circuit and it's not that surprising that you're not seeing the performance you're expecting.

Idris

---

{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.

40W + 40W = 80W

80W/12V= 6.67A

Your power supply probably can't deliver 6.67A, so the voltage is dropping.

9.6V x 4.78A = 45.88W

Are you trying to use a 50W power supply?

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Where do you measure 9.6V? Directly at the PSU terminal? Or do you see a huge voltage drop due to insufficient cross section of the power wires?
Another point of concern might be the 5A polyfuse if you use a RAMPS board...