# Can batteries provide alternating current?

1. Jun 29, 2009

### mherna48

I was just thinking about batteries and such after my brother asked me about AC vs DC current and their pros and cons.

2. Jun 29, 2009

### mherna48

Another reason why I was wondering is because my cell phone battery has three nodes. Which might just be for charging...

3. Jun 29, 2009

### mgb_phys

Batteries provide DC power - the third terminal is a temperature sensor that the charger uses to monitor the rise in temperature while charging.

4. Jun 29, 2009

### mherna48

So there's absolutely no way to get batteries to make AC right? Or has it just not been tried?

5. Jun 29, 2009

### mgb_phys

You could build a circuit to generate AC from a battery or any other DC source. But batteries are fundamentally DC sources.

6. Jun 29, 2009

### mherna48

What kind of components can do that? The only ones I would think could come close are capacitors and inductors. But those need alternating current to begin with.

7. Jun 29, 2009

### turbo

If you are willing to buy a DC-AC inverter, you can get AC in remote locations using DC batteries. I use one of these to power my telescope AC drives from the cigarette lighter of my vehicle. If you need smooth sine-wave AC you should know that these little inverters give you pretty notch-ey square-wave AC. Plugging my mount into real AC results in smooth quiet operation, but the 60-cycle buzz is noticeable when operating off the inverter.

8. Jun 29, 2009

### vk6kro

To supply AC from DC, you usually have to make an oscillator.

An oscillator produces AC from DC. The AC can then be used in a transformer to change the voltage of the AC.

See the following circuit:
http://www.elecfree.com/electronic/...6/circuit-inverter-100w-by-ic-4047-2n3055.jpg

This starts with DC and produces a much higher AC voltage suitable for small AC appliances.

The part marked 4047 oscillates and produces outputs which drive big power transistors which then drive the transformer.

Last edited by a moderator: Apr 24, 2017
9. Jun 29, 2009

### Phrak

Swap the wires on the battery back-and-forth really fast.

10. Jun 29, 2009

### Starwatcher16

Does your inverter advertise itself as a modified or pure sine wave inverter?

11. Jun 30, 2009

### turbo

No idea. I bought that little box about 15-20 years ago. My only requirement was that it put out 60 hz AC so I could run my drives.

12. Jun 30, 2009

### Andrew Mason

An "inverter" converts DC to AC. A Toyota Prius has DC batteries but supplies high frequency AC to the motor. See: http://en.wikipedia.org/wiki/Inverter_(electrical [Broken])

AM

Last edited by a moderator: May 4, 2017
13. Jun 30, 2009

### mherna48

That's really cool. What does IC 4047 stand for and what is that VR 250K component coming out of pin 2?

Last edited by a moderator: Apr 24, 2017
14. Jun 30, 2009

### MATLABdude

IC 4047 is an integrated circuit. A (more-or-less) standardized part produced by a bunch of semiconductor companies. Look for CD4047 or some such. For instance, Fairchild makes one:
http://www.fairchildsemi.com/ds/CD%2FCD4047BC.pdf [Broken]

VR 250k is just a 250 kOhm potentiometer (a.k.a. Variable Resistor) used to tune the duty cycle of the circuit.

EDIT: As per the notes that accompany this very similar design:
http://www.elecfree.com/electronic/100w-square-wave-inverter-by-cd4047-lm3582sc10612n3055/

Last edited by a moderator: May 4, 2017
15. Jun 30, 2009

### vk6kro

The CD4047 is a CMOS logic integrated circuit.
There is a whole family of such chips that all have numbers starting with CD4.... and they are very useful for making circuits like this one. They are a little slow for some things so there are other chip families for faster logic jobs.
In this case it is a multivibrator which produces two outputs that are 180 degrees out of phase with each other. It is adequate for this purpose.

The VR 250 K is a variable resistor with a maximum resistance of 250 K ohms. It would be used to set the frequency of the oscillator in combination with the capacitor Cx.

16. Jun 30, 2009

### cabraham

There was a nuclear cell which not only provided ac, but outputted constant current as well, unlike the constant voltage types in common use. If you google the word "nucell", you should find it. The main physicist who was developing it died in a car accident and I don't believe anybody picked it up. It should make interesting reading.

Claude

17. Jul 1, 2009

### mherna48

That's really cool. I wonder if they stopped developing it. Maybe they don't trust people with radioactive materials.