# Current and Voltage limits for circuit

Thread Starter

#### Snowfish

Joined May 11, 2017
42
Hi,

My circuit needs 11V and 1A . I would like to know if I could give him 12 V and 4 A from batteries. I would like to know if it's ok or is it it bad for my circuit to have higher voltage and current supply?
Would my circuit burn in that case?
what is worse a higher current or a higher voltage ?

Thanks

#### Dodgydave

Joined Jun 22, 2012
10,590
If your design can take 12V then yes it's ok, the current won't be a problem as the circuit draws what it needs.

#### falade47

Joined Jan 24, 2017
178
Hi,

My circuit needs 11V and 1A . I would like to know if I could give him 12 V and 4 A from batteries. I would like to know if it's ok or is it it bad for my circuit to have higher voltage and current supply?
Would my circuit burn in that case?
what is worse a higher cuhigher voltage
?

Thanks
Some circuits do have internal resistance to be able to limit the flow of current, so your device would just take what it needs..if at all it draws 1amp, it will only take 1amp..if again the voltage difference is just one or even two, it doesn't seem like a big deal as long as it is just a power supply, not a reference voltage ..

High voltage. And high current are both lethal, but very low voltage and high current has no shock effect

Thread Starter

#### Snowfish

Joined May 11, 2017
42
Some circuits do have internal resistance to be able to limit the flow of current, so your device would just take what it needs..if at all it draws 1amp, it will only take 1amp..if again the voltage difference is just one or even two, it doesn't seem like a big deal as long as it is just a power supply, not a reference voltage ..

High voltage. And high current are both lethal, but very low voltage and high current has no shock effect
How can I know if the circuit has an internal resistance to be able to limit the flow of current ? Should I take the risk to connect even if the current supply from the batteries is 4-5 times higher that what is needed ?

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
Some current limiting device is usually in place to protect wiring. e.g. 14 AWG circuits in a US home are fused at 15 Amps. It might be connected to a 200 A fuse and a primary transformer fuse that might serve multiple households.

The car usually has a fusible link on the alternator and each circuit is fused based on the wire size. The starter is left unfused.

Take transformer based devices for the home. They usually had their own fuse. In reality, that fuse protects the transformer wiring.

In newer stuff the fuses are non user replaceable or some other component sacrifices itself. Usually before that sacrifice occurs, the power supply may go into current limit.

#### #12

Joined Nov 30, 2010
18,224
My circuit needs 11V and 1A
How can I know if the circuit has an internal resistance
Keep your circuit a secret from us and we will guess.

#### AnalogKid

Joined Aug 1, 2013
10,173
How can I know if the circuit has an internal resistance to be able to limit the flow of current ?
Show us the circuit and ask.

ak

Thread Starter

#### Snowfish

Joined May 11, 2017
42
Show us the circuit and ask.

ak

I actually don't have the circuit of my device. All I know for the device's supply needs it's that the cable gives him 11V and 1A in it's input. I would like to know if I could remplace that cable by batteries without burning the circuit. After testing the batteries, I get the good voltage but the current that the batteries give is 4-5 times more and that is why I would like to know if I could use them for the supply without burning the circuit and also can you tell me how could I decrease the batterie's current to 1A, while keeping the same voltage?

#### WBahn

Joined Mar 31, 2012
27,863
There is no way for us to know whether your circuit can handle 12 V or not. You aren't giving use any information upon which to base an answer. There's probably a fair chance it can handle it, but who knows.

Why won't you at least give some hint as to what this "device" you keep referring to is?

The overwhelming majority of circuit need a power supply that provides a voltage within some specified range and maintains that voltage when supplying up to some maximum amount of current needed by the circuit.

It's like saying that your dog needs a water bowl that can provide one gallon of water a day. If your water bowl can provide five gallons a day, the dog isn't going to drink five gallons a day and burst (well, MY dog might, but then she's an idiot). But if your water bowl can only provide one cup a day, it won't be long before you don't need a water bowl at all.

Thread Starter

#### Snowfish

Joined May 11, 2017
42
There is no way for us to know whether your circuit can handle 12 V or not. You aren't giving use any information upon which to base an answer. There's probably a fair chance it can handle it, but who knows.

Why won't you at least give some hint as to what this "device" you keep referring to is?

The overwhelming majority of circuit need a power supply that provides a voltage within some specified range and maintains that voltage when supplying up to some maximum amount of current needed by the circuit.

It's like saying that your dog needs a water bowl that can provide one gallon of water a day. If your water bowl can provide five gallons a day, the dog isn't going to drink five gallons a day and burst (well, MY dog might, but then she's an idiot). But if your water bowl can only provide one cup a day, it won't be long before you don't need a water bowl at all.
You didn't read my last post. I wrote that the voltage is the same but that the current is different, and my question is if the device can handle the current which is 4-5 times more ''not on the voltage''?!

#### Ylli

Joined Nov 13, 2015
1,060
You didn't read my last post. I wrote that the voltage is the same but that the current is different, and my question is if the device can handle the current which is 4-5 times more ''not on the voltage''?!
And you don't understand that the device will most likely just draw the amount of current it needs. Does not matter if the supply can source 1 amp or 100 amps - it will only take what it needs. As long as the supply can supply that need. ^^That will be true for 99% of electronic devices. But to reiterate, unless you tell us what this device is, we can't advise you with 100% certainty.

#### WBahn

Joined Mar 31, 2012
27,863
You didn't read my last post. I wrote that the voltage is the same but that the current is different, and my question is if the device can handle the current which is 4-5 times more ''not on the voltage''?!
And you won't listen to what everyone has been telling you.

A supply that CAN deliver 4 A to a device does NOT mean that it WILL deliver 4 A. It will deliver what the device pulls UP TO a maximum of 4 A. If the device only needs 1 A, then it will only pull 1A.

A typical car battery can deliver hundreds, even thousands of amps. Yet if you connect it to a 12 V, 12 W light bulb you will not be forcing a thousand amps through it -- the bulb will only draw about 1 A of current.

The AC circuits in a typical household can supply 15 A of current (that is what the breakers are set for). Does that mean that everything you plug into a wall outlet is having 15 A for current forced into it? Of course not! It is a LIMIT on the maximum that it CAN provide.

Just how did you determine that the current was 4-5 times more? What did you connect to the battery to make that determination?

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
I had one thing, that I would not consider over-rating the supply. It was an CAT6 triple AB switch. I had no schematic, but did know the OEM's power supply rating. They wanted $100.00 for a$6.00 wall wart and another \$6.00 connector. I chose a wall wart that was 12 V current limited near the value of the OEM power supply.