I tested the camera on my table in house using only my laptop and 12 v battery.
Example: Using Sharpcap I set the cooling temp to -20 degrees. The censor temperature will reach approximately -18 degrees, the cooler power will reach 100. Then the Temperature will gradually increase. The temperature will not maintain at or near -20 degrees.
I have downloaded the current software to run the ZWO camera, Also, monitoring the VDC to 12VDC.
I tried setting the cooling temperature to -15 degrees and censor temperature will reach -15 degrees with cooler power of approx. 74. The sensor temperature will remain near -15 degrees and the cooler power will gradually increase to 100 after 15 minutes. When the cooler power reaches 100 the sensor temperature will start decreasing.
Do you have any suggestions why the temperature won't maintain at the se temperature?
Sorry for this.
Could you tell us what is your ambient temperature?
When the cooling power reaches to 100%, it will generate more heat so the temperature will go up a little.
You can try cooling the camera gradually.
For testing purpose I had the ASI 1600 MM C camera sitting on table in the house ambient temperature of around 78 degree F.
Set target temp = -15 degrees C 67 cooler power
-14.7 degrees C 76 cooler power
-14.6 degrees C 76 cooler power
-14.6 degrees C 79 cooler power
- 14.6 degrees C 89 cooler power after 10 minutes
-14.5 degrees C 100 cooler power after 14 minutes
-14.3 degrees C 100 cooler power
This shows how the temp varies when set target temp at -15 degrees. (Note: the cooling fan was running the entire time)
I hope this helps.