# Question about voltage Answered

I am brand new here and have a question about voltage. I was reading the Instructable about how to run battery operated devices with ac power.

https://www.instructables.com/id/Run-any-battery-powered-item-through-AC-power./

If I have a device that uses, for example three 1.5v batteries ill need to find an adapter that will push 4.5v. Is that correct? If that is correct, what would I do in this case? I have 20 of the same device, each of the devices take three 1.5v batteries. I want all 20 of these devices to be run on one wall plug(if possible). Does this mean that I need to get a wall plug that will push 90v? If thats the case, is that even possible? Thanks in advance

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## Comments

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The lamps would all be run in parallel, not series. So, they would require just 4.5V to run instead of 90V. However, each lamp would add to the total amount of current drawn. If each lamp required 100mA, the total current would be 2A. So, you would need a power supply capable of supplying 4.5V at 2A.

Can you post the link to the lamps you have? I'm confused by the 5 LED/ 3W thing. I highly doubt that each LED is drawing 3W, it's probably the sum of all five. If the LEDs are actually drawing 3W, that means the current is about 660mA (or a bit over 120mA each) which is an awful lot for AAA batteries. Do you go through batteries really quickly?

If each lamp really does need 4.5V at 660mA, you'd need a power supply capable of supplying 4.5V at 13.2A, which is HUGE. In a case like that, I'd suggest doing a series/parallel setup which would increase the voltage but decrease the current (say, 18V at 3.3A)

I suppose a lot of this is a bit confusing to someone new to electronics. So for now, just send the link for your lamps and we'll go from there.

I cant find the site that I was looking at with the info for my lights. Chances are, I read something wrong. Not sure though. The lights that I have are just cheap dollar store lights so I cant imagine that they use some above standard high quality, high wattage bulb, but again I really dont know.

What you said about the 5 LEDs being 3 watts is probably right. So assuming that each 5 LED lamp is running 4.5V at 3W, How many A or mA would I need the adapter to be?

Lol, I am very confused. Thanks for your help

You are correct about needing 4.5V to power the device which ordinarily uses 3 1.5V batteries.

If you are powering multiple devices, each with the same voltage requirements, the necessary output voltage will remain the same. However, the current rating of the power supply will have to be multiplied by how many devices you are powering at once.

You don't specify what type of devices you are powering. However, for the sake of an example, if each one needs 0.1 Amp at 4.5V, then the power supply to power 20 at once will need to be able to supply 20 X 0.1Amp = 2Amps at 4.5V.

I just found this on another site.

Watts=Volts X Amps, so Amps = Watts / Volts

I also found some info out about the lights that I have. The LEDs are 3 watts each, and each of the 20 lights that I am using has 5 LEDs. Does that mean the each of the 20 lights are 3 watts or do I have to multiply the watts of each LED by the amount of LEDs per unit to get the wattage to fill into the equation.

Also for the equation, do I use the voltage that each light draws or do I use the voltage that will be coming out of the wall?

Arggh!!! I wish I knew more about this stuff. Thanks for the help