Can You Use A 12v Power Supply On A 9v Product?

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If you survey your home, you will find dozens of devices and their corresponding power supplies.

From smartphone chargers to power supplies for internet routers and AC adapters for household devices, there are different means at our disposal to power a device.

People often wonder if they can use an alternative power supply or adapter for a devices if they output less or more voltage than the original.

So, can you use a 12V Power Supply On A 9v product?

You can’t use a 12V power supply on a 9v product, as less voltage means the device will work erratically and more voltage can cause damage. Overvoltage may also lead to overheating.

Let’s go through three basic concepts before we proceed.

  • Polarity: (+) or (–) indicated via a diagram on the device and output plug.
  • Voltage: How much power can be drawn from the source
  • Current Rating (m/mA): Refers to the max. current that can flow continuously

So a 12v 1.5A power supply has 12v voltage and a 1.5 amp rating.

In other words, the power supply can draw 12v power up to 1.5 amps and supply it to your device.

As for polarity, you can check the output plug to ensure that the polarity is correct.

I won’t dive deep.

You can read more about polarity, voltage and rated current in what does 12v power mean.

In this post, we try to understand 12v power supplies with a few real-world scenarios, but the larger idea is to learn how to figure out what will and won’t work.

Safely swapping out the power supply of a device

Power supplies such are wall adapters are typically unregulated.

The voltage produced by an unregulated power supply varies with load. For example, the voltage can be 12v for a wall adapter rated “9V” with minimal load.

Manufacturers anticipate some of these problems. Therefore, most appliances have internal voltage regulators. They protect the electronics to some extent from overheating and damage.

However, you may notice that the product becomes hideously hot to touch.

Compared to the original power supply, a replacement power supply should follow these 3 rules to avoid any issues or damage:

  • The tip polarity of both power supplies or adapters should be the same
  • Output voltages of both power supplies should be equal
  • Output amperage of the replacement should be identical or higher than the original

Will 12v power supply work on 9v device?

You should not use a 12v power supply on a 9v device.

A power supply should always have the exact voltage, matching tip polarity, and an equal current rating  (amperage) to operate a device safely. A higher current rating is fine but you could fry your device if you mix tip polarities or use a power supply with higher voltage.

Let’s take an example of an internet router. The router typically ships with an original adapter, which may need replacement at some point. One of two scenarios may be possible –

a) You cannot afford the original power supply sold by the manufacturer or

b) The product or adapter is phased out and no longer available.

  • You can’t use any adapter outputting more voltage than the original.

This means you can’t use a 12v power supply on the 9v router. 

Many electronic devices are sensitive with fragile architectures. Some of them may tolerate a tiny increase in voltage above what they are rated.

Nevertheless, this will shorten their lifespan if you do not add a resistor to regulate the voltage.

But in most cases, devices won’t even tolerate a tiny bump in voltage. The device will get heated and will burn out due to the higher supply of voltage.

Here are some things you can do:

Get a Universal Power Adapter:

Let’s say the product is taken off the market and you can’t find a replacement. What should you do?

Go to the nearest electronics shop and look for a universal power adapter, preferably one with selectable voltage.

Universal power adapters are also sold in kits with several plugs to connect a power supply to any device without endangering it.

Add a resistor

A resistor is an electrical component added to a circuit to reduce the current by reducing current flow or diving voltage.

In simple words, it reduces the voltage to the appropriate level for your device. For instance, you can power a 9v product with a 12v power supply if the resistor can bring the voltage to 9.

Check out this YouTube video that explains travel adapters!

Can you use a 12V 2A power supply for a 12V 1.5A product?

It is perfectly safe to use a 12V 2A power supply instead of a 12V 1.5A.

In other words, you can use a replacement with a higher current (2A) and identical voltage (12V).

This is actually desirable because the power supply has a surplus. It’s less work for the power supply compared to a 12V 1.5A, which would run hotter because it is pushed hard.

Let’s take another example. Let’s assume you use a 19V/8A adapter as a replacement for the old 19V/5A adapter for a laptop. Higher current works fine and poses no threat of damage. The device is designed to draw the current it needs – 5A in this case. This is permissible and safe.

Can you use a power supply with a lower current rating as a replacement?

It’s not advisable to use an adapter with lower-rated current.

For instance, you should not use a 19V 5A adapter in lieu of a 19V 8A DC power supply or a 12V 1A for 12V 2A. Both adapters have identical voltage but the replacement’s rated current is lower than what your device needs.

This can lead to a few unwanted scenarios:

  1. The lack of current will push the power supply and cause damage.
  2. The device works but it will function erratically due to undervolting.

Many people have tried running a laptop with an adapter that has a lower-rated current.

The laptop may not power on at all or the battery may not charge efficiently. It’s not a proper replacement and you should avoid doing it.

Can you use a 12v power supply on a 19v or 24v device? 

In this case, the voltage of the power supply (12v) is lower than the voltage your device needs (19v).

It’s the equivalent of using a 9-volt power supply on a 12v device. The device may work if the current is the same, but it won’t work efficiently.

Although, that is far from any thumb rule. It depends on the internal structure and complexity of the device.

Some devices are designed to turn off when they detect low voltage.

Other devices may work unreliably i.e., you can power a speaker but the volume will be lower than usual. Either way, there won’t be any damage to your device if the voltage is low (under-volting). 

Takeaway: You cannot use a 12v power supply on a 19v or 24v device as it will result in under-voltage. It will not damage the device, but the device will not work efficiently.

Can I use a 12V 2A power supply adapter for a 12V 1A router?

You might face a situation where you have a 12v replacement power supply at hand that you wish to substitute for the 12v original.

Check the rated current of both power supplies. It will be mentioned on the product plate or adapter. Two things are possible – the replacement’s current rating will either be higher or lower than the original.

Any power supply with the same output voltage (v) and a higher current rating (A/mA) than the original will work.

A replacement with lower output voltage should be avoided.

For example, you can use a 12v 2A adapter (replacement) instead of a 12V 1A (original). On the other hand, do not use a 12v 1A power adapter on a 12v 2A device.

Can you use a 12v power supply on a 5v or 6v device?

It is dangerous to connect a 12v power supply to a 5V max-rated product.

At best, it will burn out the product, but based on the capacity of the 12v supply it could even result in a fire or other safety hazards.

The input voltage of a power supply should strictly adhere to recommendation

In this scenario, you might try to use a 12v power supply on a 6v product.

If the current is the same, the device can be seriously damaged or may run for a while before it is damaged. It shortens the lifespan of the device, which gets painfully hot when used.

Some appliances and electronic devices have a mechanism to prevent such damage.

They have a power trip for when the power exceeds a predetermined level. However, it is overvoltage and that’s not safe. Refer to the aforementioned tips to find an appropriate replacement.

In Conclusion

We have gone through a handful of real-world scenarios for those who need a specific answer.

At the same time, I have explained the underlying principle so that you can resolve similar issues in the future.

To sum it up, you can use a power supply for a device if the voltage is the same, the amp rating is identical or higher, and the polarity is correct.

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