Examples of a Charge Controller as a Load Controller
Examples of a Charge Controller as a Load Controller
When a Charge Controller is used as a load controller, the device simply protects the batteries from discharging too far. This is especially useful when using large motors, or things that use an abundant amount of power when they start, or run for long durations. Let's look at each separately.
Runs hard, eating power now (like a motor at startup):
A farmer wants to run his pumps on solar power. He incurs solar power in his batteries for 2 days, and then he irrigates. If there is no sun, he prays for rain, or has a gas generator as a backup. Now his solar panels charge the batteries through 1 charge controller, but he needs another to control those large motors. Large motors for example, need nearly 2x as much power to start as they do to run. This can cause the open circuit battery voltage to drop to as low as 10.5 volts. A good charge controller will allow this to continue for 15-30 seconds out of the box, longer if programmed, and then start monitoring the batteries. When the batteries get to 50% discharge, roughly ½ way spent, the controller shuts off the power to the pumps. This simple installation safely monitors the system, allows for automated shutoff, and protection of the batteries lifecycles in day to day operation.
Runs a long time, and eats power:
The same farmer wants to have another getup in his horse barn. He wants to have the lights come on from 6am until the sun comes up, and 5 pm until the sun goes down, every day. In the winter, he was charging the batteries at the end of the night, and again around 7am. He couldn't figure out why, and then he had to replace the battery bank twice in 4 months. The power situation, when left to a simple clock, was eating batteries every 60 days. WHY? Well he had no load control.
The on and off part was easy, a clock, a photo sensitive cell, and double circuit. The lights, although not very sizeable in terms of wattage, were on for many hours of the day, and it CHANGED ON HIM. To boot, a bunch of lights compounds the changing time. The math worked out like this....
34 lights, 15 watts each, 6 hours a day in the winter = 3060 W = 3+ KW
34 lights, 15 watts each, 2 hours a day in the summer = 1020 W = 1+ KW
Now he receives 5 hours of sun a day, and he has a 1.8 Kilowatt system on the barn.
Why was he eating batteries every month in the winter? He was running them all the way dead, freezing the dead batteries, and then recharging them every morning too. They were hot charging (A.K.A. as fast as possible) the batteries in 30 minutes by running the generator in the morning and again midway through the evening when the lights would dim. The batteries would accept the amperage, but after that many cycles, (4/day x 60 days = 240+ cycles from dead to full under the harshest conditions when he should expect 1000+).
With a load controller, he now has the ability to monitor the batteries, and auto start that generator. When the batteries start to get low, the system has a choice, start the generator, or turns off the lights. The generator start switch is plugged directly into the charge controller for autonomous operation until the fuel is exhausted.
