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So a lightning strike seems to have blown my router adapter which had a 12v DC 2 amp output adapter.

I am currently (no pun intended) using a spare adapter with 12v DC 1.2 amp output. This works fine for now, and I've turned the second wireless radio off just to be sure it doesn't want to draw more amps than can be supplied.

So my real question is--suppose I used an adapter with 12v 10 amp? Do the devices draw only what they need, or would the 10 amps smoke the router? Taken a step further...if I had to in a dire emergency, could my car battery (12v DC 700 amp) be spliced to the router adapter plug and not smoke the router?

Thanks, James

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The voltage should be exactly the same. Amperage should be greater because the device will draw as much as needed. Of course the power supply must be able to provide the needed current by the device. The spare adapter of 1.2A you're using now may not work in all situations.

See this on electronics.SE: Choosing power supply, how to get the voltage and current ratings?

If you are replacing a previous power supply and don't know the device's requirements, then consider that power supply's rating to be the device's requirements. For example, if a unlabled device was powered from a 9 V and 1 A supply, you can replace it with a 9 V and 1 or more amp supply.

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  • Thanks! Yes, the 1.2A I think will work with just one radio on, but I eventually want to replace the adapter with one that can handle both radios, but was worried I'd smoke the router with too much Amps. That link explains it very well.
    – jimo3
    Commented Jun 21, 2014 at 13:53
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Well you should NOT be using that power adapter.

The current rating (amp) listed on the power adapter tells you what the power adapter is capable of supplying. In your case, the original adapter was rated at 2 amps, which tells me that the router may draw up to 2 amps, otherwise they wouldn't have provided a 2 amp adapter. The adapter you're using now is capable of supplying up to 1.2 amps. You're risking overloading the adapter and possibly starting a fire if the router draws more than 1.2 amps.

The current rating of a power adapter tells you what it is capable of supplying. The device being powered actually determines how much is drawn from the adapter. So, in most (all?) cases an adapter with a higher current rating is perfectly OK to use. It's capable of supplying more current, but the device determines how much is drawn.

It is NOT acceptable to use a power adapter with a lower current rating than the device requires. You will overload the adapter and could potentially start a fire.

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  • @joequerty, yes, I fully understand the implications of using the lower-rated adaptor, which is why I've turned off the other radio (actually both radios, as I'm using this as a router only), which are the high-drawing units. Either way, I bought a replacement of the proper amp rating in case I decide to power up the radios.
    – jimo3
    Commented Jul 17, 2014 at 13:10
  • would it actually start a real fire, or will it just burn the adaptor, probably the fuse inside it ?
    – Omu
    Commented May 25, 2019 at 16:48
  • A real fire? As opposed to what other kind of fire? Is there a type of fire that isn't real? Yes, it could burn the adapter... causing a fire... of a very real kind.
    – joeqwerty
    Commented Jun 21, 2019 at 21:23

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