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Expand All Questions
Do Genasun controllers prevent "back feeding" the panel with reverse current?
Do I need blocking diodes?
What does the controller do when the pack reaches full charge?
Why am I getting less power than expected?
- 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.
How do I know my controller is working?
What if I have two charge sources connected to the battery in parallel?
What the heck is "Passive" or "Nominal" MPPT?
Can I charge from a DC Source?
What are Blocking and Bypass Diodes?
Don't MPPT Controllers use PWM?
Yes. All Genasun controllers prevent reverse current to the panels. This keeps the battery from running current through the panels at night.
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.
The controller will throttle back the current to keep the voltage at the specified float voltage, keeping the battery fully charged even if you have some loads drawing from the system.
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:
100% testing.
Our controllers include LED indicators which give detailed information about system status. Please read the product manual for detailed instructions about your controller. The manual can be downloaded from the product page that describes your controller.
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.
We were confused too. There are a number of golf-cart boost controllers that are advertised as MPPT controllers . . . until you read the fine print. Some clever marketers or lazy engineers came up with the idea that you can “passively” track the Maximum Power Point by operating at a fixed voltage. This is a joke. Tracking is the essential part of Maximum Power Point Tracking. Why? The Maximum Power Point changes. Tracking is the way you adapt to that change, and collect more power. “Passive” turns out the mean that the controller manufacturer took a guess and picked a voltage that will provide the maximum power for one specific panel, at one specific angle, in one specific lighting condition, at one latitude, at one specific time of the year. With this type of controller, you’ll be lucky to get the the maximum potential power a few times a year. The rest of the time, you’ll be loosing a lot of the panel power you paid for. In our own tests in with a competitor’s buck controller advertising “Nominal MPPT”, we found that the performance was often significantly worse than even a PWM controller.
Genasun solar charge controllers, can charge from a DC source PROVIDED that the input voltage is within spec and the input power is limited such that the rated output current (input current for the GVB series) of the Genasun controller is not exceeded. For most efficient operation, we recommend a power supply in the 15-18V range for typical 12V applications. The Genasun controller will operate the input power source at its maximum output power, and the power source must be able to sustain this output continuously. Most laptop-style power supplies will not stand this type of operation.
For OEM or volume applications requiring charging lead-acid batteries with controllers other than the GV-4 and GV-5, or from input sources that cannot be power-limited (such as batteries), please consult Genasun for custom programming.
If the power supply is very stiff, the large inrush current may trip the short circuit protection on the controller. If this happens, add a resistor in series with the input to reduce the stiffness of the power supply.
Blocking diodes are connected in series with panels, are conducting during normal operation, and do introduce a voltage drop. Blocking diodes are not normally built in to panels. Blocking diodes do not provide any performance improvement in partial shading, but will eliminate the possibility of damage from one solar panel feeding into another if they are connected in parallel.
Bypass diodes are connected across cells within a panel, are not conducting during normal use, and do not introduce a voltage drop. Typically, 12V nominal panels may include 2 bypass diodes, which can sometimes be seen inside the junction box or within the panel laminate. In principle, blocking diodes can aid in partial shading by allowing current to flow around a shaded cell. In practice, there is no benefit in 12V and 24V systems, as losing 1/2 of a panel will not allow enough voltage to charge the batteries.
Yes, technically speaking they do, but that’s about where the similarities end.
A PWM controller is 100% on (panel directly connected to battery) during normal charging. Once the batteries are full, it reduces the charging current by pulsing the panel between on and off at a low frequency, often ~300Hz. The pulses are observable on the panel input. The current coming out of a PWM controller when the batteries are not full is always a little less (due to control losses) than the current a panel would deliver when directly connected to the battery. The ONLY charging functions of a PWM controller are to prevent overcharging, and to prevent reverse current flow from battery to panel at night.
In contrast, while an MPPT controller uses a PWM-type power conversion technique internally, this function is active all the time, whether the battery is full or not. The frequency is typically much higher, 20kHz and up, and is not directly observable outside the controller; the panel input is a steady DC voltage. Most importantly, the power conversion technique used in MPPT controllers can INCREASE the power delivered to the battery compared to a direct connection to the panel, in addition to preventing overcharge and reverse current flow. The function is analogous the the ability of an automotive transmission to maximize the power delivered by an engine by allowing the engine and
wheels to turn at different speed ratios. By contrast, the function of a PWM controller is similar to regulating vehicle speed by leaving the transmission in 5th and quickly pulsing the clutch from fully engaged to fully disengaged.
