Off-grid power systems often have several sources for power generation to augment and support the optimal charging of the battery bank. A solar panel array can be duplicated and extended to create more power when needed, or wind and hydropower generators can be added to the system.
Multiple charge controllers can be wired in parallel to regulate the power flowing to charge the battery bank. Charge controllers should be dedicated to one power source to govern the charge output to the optimal voltage and current required to manage the battery bank efficiency and longevity.
The conditions for using multiple charge controllers arise when:
- The solar array output exceeds the required input parameters of the battery bank;
- If separate solar arrays with mismatching power outputs need to be connected to the battery bank;
- Separate solar arrays that are affected by different light conditions due to orientation to the sun or shadows;
- If additional sources of power generation are used to augment the charging of the battery bank.
In systems where several solar arrays or power generation sources are used to provide optimal battery charging efficiency and redundancy, smart MPPT charge controllers are ideal.
Let’s look at how two or more charge controllers are installed to provide the best battery charging efficiency and protection.
Why Is Wiring Two Arrays To Two Charge Controllers Smart?
Not all solar systems are installed all at once. As the energy demand of a household, workshop, RV, van, or yacht changes and becomes more complex so additional sources of power generation can be added.
The battery bank can also be extended and converted from lead-acid to Lithium-ion type batteries changing the optimal charging parameters for the battery bank significantly. Installing multiple smart MPPT charge controllers in parallel is the only way to maintain your overview and control of the system.
Basic Solar Array Setup
In a simple solar setup where one solar array is used to charge the battery bank and a simple PWM charge controller with a balanced voltage output between the solar panel and the battery bank will suffice.
The energy demand on the battery bank often exceeds the original design capacity, and the battery bank needs to be converted to more efficient Lithium-ion batteries or additional deep cell lead-acid batteries.
The original solar array can still be used, and an additional, more powerful solar array is added to increase the power generation potential. The solar arrays can have different power outputs and voltages, and it would not be possible to wire them into a single charge controller.
How To Wire An MPPT Charge Controller
Each solar array will be wired into a dedicated MPPT charge controller, and the two charge controllers will be wired in parallel to the battery bank. The charge controllers can be set to communicate wirelessly to one another to manage the state of charge optimally.
Wired in parallel, the output current from the charge controllers will be combined, but the voltage will be governed to the ideal voltage required for optimal battery charging and longevity.
Smart MPPT Charge Controllers
Smart MPPT charge controllers are designed to communicate with one or more similar charge controllers on the network and provide the user with full system transparency via wireless communication to cell phone applications or visual displays.
This system power overview shows the user how much each source of power generation contributes to the replenishment of the battery bank.
As wind and weather conditions change during all times of the day and night, the state of charge of the battery bank can be monitored.
Why Do Multiple Charge Controllers Make Life Easier?
Being fully reliant on an off-grid power system can be a matter of life and death. If your critical control and life support systems depend on the availability of power at all times, building some redundancy into your power generation is essential.
For homesteads in remote off-grid locations where weather conditions can rapidly change the power generation capability of the solar, wind, hydro, and other renewable power sources built-in redundancy is critical.
A sailboat crossing the Pacific cannot lose power to critical systems such as navigation and weather warnings. In such power systems, planned redundancy saves lives.
On a sailboat, there are multiple potential sources of power generation:
- Solar panel
- Wind generators
- Engine alternator
- Feathered propeller generator
- Gasoline or diesel generators
These power generation sources can be integrated to supply AC and DC power to the electrical appliances and devices onboard the yacht. Typically the house battery bank and the engine started battery bank are managed separately.
Smart MPPT charge controllers are wired parallel to the house battery bank to maintain the optimal state of charge and manage the battery chemistry to extract maximum life from the batteries.
Each power input source is connected to a dedicated MPPT controller, and the controllers are programmed to charge the battery bank in an integrated manner.
The captain can monitor the current draw on the battery bank and how much charge each of the power sources is providing to replenish the battery bank.
In the worst-case scenario, when solar, wind, and water propulsion power generation is insufficient, the generator or engine can be started to provide power to replenish the battery bank.
An online view of all the power sources and draw can assist the captain in managing the state of charge of the battery bank to an optimum. Without the use of multiple MPPT charge controllers with functionality will not be possible.
How Do Multiple Charge Controllers Sense The SOC?
Each charge controller senses the state of charge (SOC) of the battery bank at the charge terminals individually. The smart MPPT charge controllers must be integrated to communicate with each other and manage the flow of power into the battery bank.
Only smart MPPT charge controllers can communicate as a network and make the charging parameters visible. It is best to stick to one brand of MPPT charge controllers to facilitate these networking capabilities.
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Victron Energy and Renogy are the best-known brands of power system components for off-grid applications.