Why Is My Generator Not Charging My UPS?


The main work of a UPS to a computer is to retain the power in the computer during a breach or power interruption. The power it gives to the computer is essential for data saving. It gives you enough time to save your data and avoid data loss.

This essential role is why it becomes a problem if your power source is not charging your ups. You end up asking why is my generator is not charging my UPS.

Why Is My Generator Not Charging My UPS?

Your UPS may not be charging under a generator due to power instability, frequency fluctuations, poor or unstable voltage, fuel type, ups incompatibility, or high ups sensitivity setting. These reasons might be why your generator is not charging your ups.

A generator provides electrical power, which the UPS stores for emergency use. However, there is a huge difference between generator power and wall socket power. This difference can affect your power input and cause your UPS not to charge. Here are some reasons why your generator is not charging your UPS 

1. Unstable Generator Power

UPS units are picky and particular about the power coming into their system. Power instability is one effect it does not tolerate. If they are fluctuations in the current or voltage, It might reject the power, leading to the not charging issue. The UPS has numerous circuits that observe the incoming power.

Once it detects any instability from the current, it stops accepting the power supply. Hence the UPS will not be charging. Unstable power is often the major reason for UPS not charging on generators because generators can only sometimes provide a stable power supply.

The solution to generator power instability is simple—run maintenance on the generator. An erratic power supply is often a mechanical problem. Call a technician to fix the generator’s mechanical problem, and once the UPS receives stable power, it will start charging. 

2. UPS Sensitivity Settings

As mentioned, a UPS needs stable electricity flow and uses circuits to detect power instability. The circuits also protect the UPS by terminating the power supply end and continuing on battery mode. These circuits have sensitivity settings that allow you control over power fluctuations. The higher the sensitivity setting, the more sensitive it will be to fluctuations. You can easily reduce the sensitivity setting, but it does not come without risks. 

Your charging problem could be due to high-sensitivity settings that pause the power inflow to the UPS. These pauses can be very annoying because it causes your UPS to go into battery mode and not charge. You can fix the problem of high sensitivity settings by reducing the setting to low. The reduction will stop the UPS circuits from interrupting your charging process even during generator power supply fluctuations. 

3. Generator Fuel Type Or Source

Generators have different types, shapes, and sizes and have lots of fuel types and source options. Some run on diesel, natural gas, and propane. Yes, they all produce electricity, but the fuel type and source sometimes affect the generator’s performance. Different fuel types or getting fuel from a bad source will affect your generator’s power output and cause fluctuations.

Fluctuations will trigger your ups sensitivity and stop the incoming power use, causing the ups not to charge. Propane and gas generators have a higher tendency for slow fluctuation response. A diesel generator is the best because it provides a more stable power supply. But it is expensive. If you cannot run a diesel generator, consider reducing your UPS sensitivity setting. 

Consider buying a generator compatible with your UPS that can handle its needs and load. It is best to use a diesel generator, assuming your options are propane or natural gas. You should get one with a higher load capacity than your UPS. It will ensure lesser fluctuations and maintain a stable power supply. 

3. UPS Type

They are different types and models of UPS in the market. These different models have different compatibility rates with generators. These models include the standby, online double-conversion, and line-interactive ups models. The best model for generator power use is the online double-conversion model. The standby and line-interactive models are less receptive to generator power.

The UPS topologies affect the UPS’s ability to handle electrical power fluctuations. Remember, power fluctuations trigger the ups sensitivity setting and lead to incoming power supply termination. Hence, no charging. Before buying a UPS, it is important to consider your major power supply and get a receptive and compatible topology model.

The online double-conversion UPS is the best for generator power because it handles power fluctuations better. The major reason your generator is not charging your UPS stems from an unstable power supply. UPS is sensitive to erratic currents and voltage. It has sensitivity circuits that detect differences in current and voltage and terminates the power coming in before it can do any damage.

What Kind Of Generator Charges UPS?

All kinds of generators capable of generating electricity can charge UPS. The problems now stem from how high and stable the electricity output of the generator is. They are three different types of generators by fuel source. They include propane, diesel, and natural gas generators. The best generator type for UPS charging or usage is the diesel generator.

This quality is because diesel generators can handle erratic power output more than others. Diesel generators are often larger than other generator types. Your UPS generator choice should be almost 1.25 or 2 times higher than your UPS load capacity. The higher the generator capacity, the more fluid power delivery will be. Power supply fluctuation causes the UPS not to accept power and stop charging. Ensure you choose the right generator for your ups before purchase.  


UPS batteries are lifesavers. They ensure that you do not lose data during a power interruption. That is why it is critical always to charge them. In a situation where you have to use generator power, charging your UPS might become a problem. The natural logic is that the power source is electricity and should charge the UPS. But it only sometimes works that way.

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