Volts and amps combine to confuse.
by Leo A. Notenboom
Yes with a couple of caveats, of course.
If its not made specifically for your particular computer, getting the right power supply is important and involves matching voltage, amperage, and polarity.
Each has different constraints.
Volts & Amps & Compatibility
In general, for power supplies or chargers:
- The output voltage must match.
- The output amperage must match or be greater than that required.
- The polarity of the output connection must be correct.
The input line voltage [wall or mains power] must be supported but is unrelated to compatibility with the device being charged or powered.
Voltage
The voltage provided by your charger must match that expected by the device being charged.
When replacing a charger, this is easy to determine: itll be listed on the old charger. In your case, the old charger supplied 19 volts, so your replacement must also be 19 volts.
Its very important to get the right voltage. Some devices are tolerant of variations and work just fine. Others, unfortunately, do not. Depending on how different the supplied voltage is from whats required, the device may simply fail, it may work kind of, or it may appear to work at the cost of a much shorter lifespan.
If the voltage is off by enough, it can damage your device.
And heres the problem: theres no way to say whats enough or too much. It varies from device to device. Some may tolerate a wide range of input voltages, while others are extremely sensitive to even the smallest error.
Sidestep all those unknowns and make sure to get exactly the right voltage from the start.
Amperage
Amperage Provided versus Amperage Required
| Power Supply or Charger Amperage Rating | Result |
| Greater than the devices requirement | Device works. |
| Matches the devices requirement | Device works. |
| Less than needed by the device | Device may fail, may run or charge slowly, power supply may overheat, may damage the device being charged all depending on the magnitude of the difference. |
The amperage provided by your charger must match or exceed what the device being charged requires.
The amperage rating of a charger or power supply is the maximum it can supply.A device being charged will only take as much amperage as it requires. If your device needs 0.5 amps to charge, and your charger is rated at 1.0 amps, only 0.5 amps will be used.
The problem, of course, is the reverse: if your device needs 1.0 amps, but your charger is rated at only 0.5 amps, then any of several problems could result:
- Charging may not work at all.
- The device may charge extremely slowly.
- The power supply may overheat.
- The device being charged may be damaged.
Thus, as long as you replace your power supply with one capable ofproviding as much or more amps than the previous, youll be fine. To be clear: there is nothing wrong at all with having a charger capable of providing more amps than needed.
Polarity
The polarity of the connection between your charger and device must be correct.
Most power supplies provide their output on two wires: one labeled [+] or positive, and the other [-] or negative. Which wire is which is referred to as polarity.
Polarity must match.
Heres the catch: just because the physical plug fits into your devicedoes not mean that the polarity is correct.
Particularly when it comes to popular circular power connectors, make sure the expectations match. If the device expects the center connector to be positive and the outer ring to be negative, your power supplys connector must match. Theres no getting around this.
Failure to get it right at best just doesnt work, but at worst can damage the device.
Look carefully for indicators on both the power supply and the device.
The good news here is that there are some standards where the polarity is always correct. USB power supplies, for example, are the same no matter what.
Input voltage
Input voltage aka mains or line-voltage is, of course, critical. Plug a device expecting 110 volts into a 220-volt socket, and youll probably see sparks followed by darkness as the circuit breaker trips. Youre also likely to damage the device.
Most of the time.
When it comes to modern power supplies, however, almost anything works.
If you look closely at the small print on many power supplies, youll see theyre rated for anything from 100 to 250 volts. This means most can work worldwide with nothing more than an adapter to account for the physical plug differences no voltage transformer needed.
Check your power supplies before you travel, of course, but its very,very convenient.
Important: the input voltage and amperage ratings are unrelated to the chargers compatibility with your device. What matters for your device are the output voltage and amperage ratings.
Related Questions
Do amps have to match?
No, amps do not have to match, but the power supply or charger must be able to supply enough amps as required by the device being powered or charged. In practical terms, that means the amperage rating of a power supply or charger must match or exceed that required by the device it is connected to.
Does more volts mean more amps?
Electrically speaking, higher voltage causes more amps to flow. This is one reason why getting the voltage correct on a power supply is so critical, because it can, in a sense, push too much electricity through a device and cause it to overheat or be damaged.
Can too many amps damage a device?
As long as the correct voltage is used, a device will draw only the amperage it needs, meaning there will not be too many amps. If an incorrect voltage is used say a higher voltage than the device is rated to accept then yes, too many amps may be drawn and the device can be damaged. This is why its critical to use the correct voltage.
Can I use an AC adapter with higher amps?
As long as the voltage matches that expected by the connected device, then yes, you can use an AC adapter capable of providing higher amps.
Can I use a 5V 2A charger with a 5V 1A device?
Yes. Because a] the voltage matches, and b] the amperage provided is greater than that needed, you can use a 5v-2A charger with a 5V-1A device.
Is 500ma the same as 0.5 A?
Yes. 500ma [or milliamps] is the same as one half, or 0.5, amps. A milliamp is just 1/1000th of an amp, meaning that there are 1000 milliamps to an amp.
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