Many customers asked me this question. The answer is “yes”, but not every type of pumps can work. And it does not indicate that the pump has a reliable life expectancy.
We have lots of solar pump customers in Africa and New Zealand. They have been using our 12V, 18V, and 24V DC water pumps for a simple solar irrigation system without battery.
Before choosing us, they usually purchased DC water pumps on eBay or Amazon directly. In the title or descriptions, the pump is often claimed to be suitable for the solar panel. When they first got the pump, yes, the pump works. But the problems came soon, the pump did not work automatically at dawn the next day, you have to reconnect the wire and start it manually every day. To make matters worse, after a week or two, the pump was burned completely.
Therefore, it can’t be simply said: “will a DC water pump work if directly connected to solar panels without a battery?”. It usually depends on two aspects: 1. The solar panel’s parameters and quality; 2. What types of DC water pump. Both are very important.
First, you should choose a suitable solar panel for your pump.
If the solar parameters are not suitable or the quality is poor, your water pump may be burned or will not be able to achieve the best performance. For example, for a 80 watts water pump, you should choose a 100 watts ~120 watts solar panel for it (because the solar panels have about 30% energy loss), and the output voltage should match. We know that the output voltage of the solar panel does not exactly equal its rated voltage, which is strongly related to the light intensity. When the light is very strong, the solar panel may provide a high output voltage exceed its rated voltage. If we did not limit the wattage of solar panel, when overvoltage, the working current of the pump will exceed its rated current, then the pump will be burned. If we limited the wattage, the actual working voltage and current will be balanced to a suitable level. On the other hand, if the solar panel wattage is not enough, or the solar panel quality is poor, it can’t provide enough power for the pump, so the pump can’t achieve its best performance.
Second, you should choose a suitable DC water pump.
Most of common DC water pumps can work directly connected to the solar panel, but their biggest problem is stuck. At dawn, the sunlight begins to change from weak to strong, when the output voltage of solar panel achieves the starting voltage, the pump will start to work. But at this time the solar panel can’t provide its full performance, the voltage will decrease significantly because of the load. If it drops to a voltage which can’t maintain the pump running, the pump will get stuck.
For the first point, you only have to solve it by choosing the right solar panel. For the second point, common DC water pump is certainly not suitable. For some special models of BLDC PUMP, we can manually set up a larger starting voltage and add an overvoltage protection function. For example, most of DC water pumps can maintain work at 5 volts, for common pumps, they will start to work from 5 volts and then maybe stop because of voltage drop. If we set up the starting voltage to 10 volts, the pump will start to work, then even if it decreases, it is hard to drop to less than 5 volts. So the pump could maintain running, this will greatly reduce the stuck problems. The overvoltage protection can protect your water pump from being burned to the maximum extent.
In summary, if you need your pump work directly connected to the solar panel and have a long lifespan with no stuck problem, you should choose a suitable parameter and good quality solar panel, and a starting voltage controllable DC water pump.