All Genasun controllers protect against reverse current (the battery sending power through the panel at night, or during a shaded condition). If you have one controller per panel, you should omit the blocking diodes from the system to achieve better efficiency. With multiple panels in parallel running through one controller, blocking diodes are generally recommended to prevent panel damage, unless the panel manufacturer recommends otherwise.
There are two scenarios here – something is broken or wired incorrectly, or the system is assembled correctly and under-performing compared to customer expectations. Genasun performs 100% testing and inspection on the controllers prior to shipping. Your controller worked when we shipped it. Unless the box got run over by the UPS truck, hit by lightning, or was recovered from the bottom of the ocean, it will work correctly when installed. Please read the manual to ensure it was installed correctly.
Here are the most common causes of system output not meeting expectations:
Panels are rated at “Standard Test Conditions” which should be viewed as a best case scenario. For example, a 20W panel will produce 20W under bright light, on the equator, pointed directly at the sun in cold weather. If you’re not on the equator with temperatures of 5°C, if the atmosphere isn’t crystal clear, if your panel isn’t pointed perpendicularly to the sun at all points in the day, it will not produce the “rated” power.
Power from the panel changes over the course of the day. The panel output is a direct function of how much light is available. The maximum output will be during the middle of the day. The further you get from the equator, the smaller that window for maximum light output.
It’s OK (and common!) to use multiple charging sources, and no special precautions are required. When the battery is low, both chargers will be charging according to their capability. As the battery becomes charged, whichever source is set to charge to a higher voltage will “win”, and the other will cease charging.