DC Uninterruptible Power Supply (FAQ)
Is UPS output AC or DC?
UPS (Uninterruptible Power Supplies) are available with either an AC (Alternating Current) or DC (Direct Current) input and output. Standard AC voltages such as 115Vac and 230Vac are available in a wide range of output sizes and autonomy times. We offer a wide range of both AC UPS and DC UPS units.
What is a DC UPS?
UPS refers to Uninterruptible Power Supply, which means the output will not be interrupted in a mains failure by using a battery backup. We offer UPS units with either a DC or AC output, with a DC UPS having a DC output. More information can be found on our product focus page.
What does a DC UPS do?
A DC UPS (Uninterruptible Power Supply) uses batteries to provide backup power and ensure uninterrupted DC output during a power failure. It combines multiple electrical products into a single system, such as:
- A DC Power Supply/Battery Charger - Taking an AC mains input and outputting a DC voltage, it provides a battery charging voltage to both the DC load and batteries.
- A DC Battery - Usually added to the DC UPS, this is charged by the DC UPS and used in a mains failure to power the load.
- A Deep Discharge Protection Circuit - To stop the batteries from deep discharging, the DC UPS will stop supply of the batteries to the load.
What is the difference between a battery charger and a DC UPS?
The main difference between the two products is a battery charger only recharges batteries, while a DC UPS both powers devices and ensures backup during outages. Looking at this in more depth:
Battery Charger:
- Solely charges a battery by converting AC or DC power into the required voltage and current.
- It typically does not supply power directly to devices during operation.
- It has no deep discharge functionality, so if you use the battery to power a load, it could overdraw and damage the battery.
- Provides uninterrupted power to devices by simultaneously powering them and charging the battery.
- Automatically switches to battery power during a power failure, ensuring continuous operation.
- It has deep discharge functionality, so the load is turned off to protect the lifespan of the batteries.
Do DC UPS have an internal battery?
Unlike AC UPS units, DC UPS typically use external batteries which should give you more flexibility on the autonomy options available.
Do DC UPS have an AC or DC Input?
We can offer options that use either an AC or DC input, but most of the units we typically suggest take an AC input to a DC output. The DCH for example, uses mains power to charge batteries and power a load. Redundancy modules are available if you already have an existing system that needs added redundancy.
What is the output voltage on a DC UPS?
The output voltage is the same on both the battery output and load output. So as an example on a 24Vdc DC UPS system, during normal operation your battery and load will receive ~27.3Vdc output. In a mains failure system, your load will see the battery voltage until the low voltage disconnect is reached, as an example 21.5Vdc.
If your load voltage is sensitive, you can use a DC/DC converter on the output to stabilise this voltage. You can find more information on DC/DC converters in our FAQs, or feel free to contact us for advice on your DC UPS requirement.
Why does my DC UPS turn off when power goes out?
Your DC UPS should be providing power from the batteries in a mains failure, so there are a few reasons why this may not be happening.
Firstly, the batteries may be old or faulty. Discharged, damaged, or just aged batteries are the first thing to check with your DC UPS. All batteries have a lifespan, and it could be that it's time to replace them.
If your batteries seem okay, check the physical connections between your batteries, DC UPS and load. In some circumstances you could see a failure due to loose or faulty connections.
Finally, check the DC UPS itself. Is it charging the battery correctly? Are any conflicting settings switching the battery off prematurely?
So, there are a number of aspects that could cause your issue, but we would always advise you check your batteries first before delving deeper into the DC UPS.
How do I battery back-up my power supply?
If you have a DC power supply, you can easily add DC functionality with one of our "add-on" modules. This uses the DC output of your power supply, whilst adding DC UPS functionality. These are great for existing applications where DC power supplies are already installed.
If you have an AC supply, we can offer DC UPS systems for a wide range of output voltages, you don't necesarilly need a DC input. Solutions are available for AC and DC input voltages.