How to amplify two AA bateries?

[AviationElectrician]

Like the title says, I am trying to get more power out of two AA batteried, and I would like to know what the best way to do that is. Thanks.

 

[duffy]

Do you mean voltage? One simple, easy trick is to buy an "emergency cell phone charger". That will give you 5V from 3v with no hassle, and quite cheap.

 

[DerStrom8]

I've heard of a "joule thief" before. I've never built one, so I'm not quite sure if that's what you're looking for or not. You can find designs all over the internet. I'm thinking it's used to get more from AA and AAA batteries, but I could be wrong. Something to read up on, anyway

Good luck!

 

[AviationElectrician]

what i am doing is an engineering project, and the only stored energy I can use for the device is two AA batteries, so I am trying to see if I can get mor voltage out of them to speed up the motor I have to use.

 

[DerStrom8]

what i am doing is an engineering project, and the only stored energy I can use for the device is two AA batteries, so I am trying to see if I can get mor voltage out of them to speed up the motor I have to use.

Ah, I see. Well, I just did a brief search for a "joule thief" on google and found the following site (one of the first hits): https://www.evilmadscientist.com/article.php/joulethief
It does, as a matter of fact, boost the voltage slightly. It is a very simple design--definitely worth giving a try.

Der Strom

P.S. Welcome to ETO!

 

[audioguru]

If you feed more voltage to an electric motor then its current also increases. Its heating also increases.
1) Can the motor survive having more voltage and current?
2) Can the AA battery cells supply that much power?

 

[DerStrom8]

If you feed more voltage to an electric motor then its current also increases. Its heating also increases.
1) Can the motor survive having more voltage and current?
2) Can the AA battery cells supply that much power?

Agreed. I guess you should check that out first

Thanks AG

 

[Joe G]

you might want to read up on maxims max1674,1676 chips and also hendon om5448. i use the maxims frequently for led projects.

 

[Veraxis]

I agree with DerStrom's idea, with one slight modification:

Correct me if I am mistaken, but, as I understand it, the problem with an ordinary joule thief is that it only works on loads with a forward voltage, such as a LED or a zener diode. This can be used to power loads from sources lower than the needed forward voltage (such as with a half-dead battery, in this case), but little else. A similar design, which can be used to raise the voltage (and therefore power output) of a simple DC source is with a "blocking oscillator" (which has a very similar design to the joule thief). Like a joule thief, a blocking oscillator uses a transistor to create an oscillation, but the coil used also has a set of output windings, (creating a transformer) which, along with a bridge rectifier to convert the voltage back to DC, can be used to raise the voltage output as needed. I have tried this myself, and I easily managed to get 45V from a 9V battery with a transformer that I wrapped myself in a couple of minutes. I have seen videos of people getting hundreds of volts from low voltage sources this way.

https://en.wikipedia.org/wiki/Blocking_oscillator

https://www.instructables.com/id/high-voltage-joule-thief/

All that said, raising the power output to the motor will also appropriately increase the drain on your batteries, and, as stated above, you do not want to exceed the voltage ratings of your motor, either.

 

[RCinFLA]

Small MP3 players with a single AAA or AA battery have a boost switcher that increases voltage to about 3.5 vdc for the electronics.

The switcher works down to about 0.7 vdc on the battery. It squeezes the last few mAH's out of the battery. It's worth about 5% to10% of net battery mAH's compared to a normal device that fizzles below about 1.35 vdc of cell voltage.

The switcher has its own loss which probably amounts to equal or more then the small battery capacity yielded down to 0.7vdc but if the electronics are requiring the higher voltage then it would be necessary regardless of how low it can suck the battery dry.

 

[colin55]

It will be very difficult to get a circuit to increase the voltage AND be able to deliver the high current you require for the motor. You need 3v to 6v converter @ approx 500mA.

 

[tylernt]

It will be very difficult to get a circuit to increase the voltage AND be able to deliver the high current you require

Agreed. Especially with alkalines, which tend to fall flat on their face when you try to pull a lot of current from them. NiMH and NiCd do much better, an AA Ni cell can deliver up to 4A, and with high-quality cells even 8A.

There are a few boost ICs out there designed to supply high-power LED flashlights, up to 3A should be possible. Depending on the IC, you may be able to parallel them for additional current. No boost converter is 100% efficient, so an 8A load on your battery will get you somewhat less than 8A on the output.

Of course, at 8A load, your AA NiMH cell will last maybe 10 minutes.

 

[Veraxis]

It will be very difficult to get a circuit to increase the voltage AND be able to deliver the high current you require for the motor. You need 3v to 6v converter @ approx 500mA.

How big is this motor exactly? I would think a pair of alkaline AA batteries should be able to deliver 1-2A just fine. If it is just a small size DC motor and you want to get more power, raising the voltage to about 9 or 12V should be manageable even with AA batteries. Unless you intend to power a really big motor with this, I do not think that you should need to worry too much about the internal resistances of the batteries. They will, of course, drain much more quickly this way, but this will be the case no matter how efficient the circuit is.

However, if you need to make the blocking oscillator circuit more efficient, I have seen slightly more advanced designs which allow control of the oscillation frequency, possibly even with something like a 555 astable, but I cannot recall any specific examples from memory.

Of course, at 8A load, your AA NiMH cell will last maybe 10 minutes.

Also, the battery would probably explode from how hot it would get, but hopefully the poster will not need quite that much current .