What is the most important factor in choosing the perfect solar charge controller for your project?
The most important job of all solar charge controllers is to properly charge the batteries and to give them as long a life as possible. There are two types of charge controllers:
- Pulse width modulation (PWM)
- Maximum power point tracking (MPPT)
The difference between these two types of controllers is that the PWM is not as efficient the MPPT. The MPPT is the most common these days and can gain you up to 30% more power than the PWM controllers. The MPPT controllers also allow the strings of panels to be connected in series for higher voltages, keeping the amperage lower and the wire size smaller, especially for long-wire runs to the PV array.
Things to look for in a charge controller
It’s important to choose the right charge controller in terms of size and features. For remote systems, reliability and performance are very important considerations. Lower cost solar controllers are often not going to be the most reliable and may not meet vital charging requirements. Poor performance or reliability can end up costing many times over the cost of the solar controller in terms of replacement of the battery bank, site visits and loss of operating time.
Solar charge controllers must be designed to take a beating, since they deal with a lot of heat and have to manage it properly. Small charge controllers have the advantage of being fanless — they get rid of heat by simple passive cooling. By eliminating the fan they achieve three advantages:
- Higher reliability — Fans have moving parts, usually the only component with moving parts on a charge controller. Eliminate the fan and you eliminate one of the most common points of failure.
- Longer life — Fans pull in dirt, dust and even insects, which can clog the charge controller’s insides and shorten its life.
- Greater efficiency — Fans require electricity to run, and that electricity comes from the solar electricity flowing from the panels. Fans are a “parasitic load” in the system, diverting and consuming power that could be used elsewhere.
Some larger controllers (including all Solar Talkers controllers) also use passive cooling with no fans, incorporating very advanced thermal mechanical design and software. They are preferred in remote, mission-critical installations where maintenance is infrequent and replacements are difficult.
Smaller charge controllers will often only have preset charge settings. If the battery charging requirements are not sufficiently met with these presets, a controller with more settings options can be selected. Custom settings can be simple adjustments to voltage set points, particular applications or environments. For example, a system which does not cycle much can be set up with reduced daily absorption time, which is the amount of time before it puts the battery into float.
Selected Solar Talkers controllers also have custom settings options for daily lighting on/off control. This type of control automatically adjusts the lighting on/off control independent of the time of the year so lights will come on when it gets dark in the evening and/or in the morning before it gets light.
Whatever your application, location or budget, the most important step in controlling a solar + storage investment is spending time and care selecting the right charge controller. Solar Talkers has sold over +4000 charge controllers in Nigeria, over 7 years — and we’ve yet to have a single customer tell us they wished they skimped on this critical system component.
How to Pick the right solar charge controller
When picking a charge controller there are a few steps that you must follow to make sure that you get the right controller for the job. The best thing that you can do is to give us a call +2348164596107— our salespeople will usually be happy to help you to pick the best controller.
If you need to make some quick calculations, the following information will be needed to manually figure out the amperage of the controller needed:
- The wattage of the solar array
- The battery-bank voltage (12V, 24V, or 48V). Typical bank voltage because inverters are offered in these voltages.
- Now Ohm’s Law comes into play: Amps x Volts = Watts
Example: 1200-watt array/24-volt battery bank = amps, so you would need a controller capable of 50 amps. Most controllers out there are either 60, 80 or 96 amps so you would pick the controller with the next higher rating. In this case, it would be the 80 amp controller.
Now if you know the amperage of the controller, and you would like to figure out how the maximum solar array wattage that can go into the controller, you would also use Ohm’s law:
Example: 60 amp controller x 24 volt battery bank = 1,440 watts of solar panels. Note that most of the controllers will allow a bit more wattage to go into the controllers. This is where the sizing by a call to us can help out.
The next thing that you must ensure is that we do not exceed the input voltage the controller can take. Again the manufacturer will dictate what the input voltage should be included in the design. Temperature and open-circuit voltages have to be considered. Since PV open-circuit voltage (Voc) goes higher as temperature drops, you will need to make sure the controller’s input voltage ratings can handle this in the sun in Dry season.