Hello everybody,

I would like to ask, what is in your opinion the best way to boost voltage from around 2.3V to 3V-3.3V?

Knowing that:
- Circuit would be powered with two AA 1.5V batteries in series
- Consumption current of the output of 20mA maximum
- Lowest noise produced by the boost
- Adding an extra AA battery is not an option

 

Define best.

If I had to get this done quickly and cheaply, I'd hack the boost circuit out of one of my solar lights.

 

Replace the batteries. They're worn out when a 1.5V battery gets to 1.35V
You're trying to run them at 1.15V and it isn't working?
No kidding!

 

Knowing that:
- Circuit would be powered with two AA 1.5V batteries in series
- Consumption current of the output of 20mA maximum
- Lowest noise produced by the boost
- Adding an extra AA battery is not an option

Use two 1/2 AA size batteries.

Or one 3 volt lithium AA battery.

 

Define best.

If I had to get this done quickly and cheaply, I'd hack the boost circuit out of one of my solar lights.

The chip/inductor from a 2 cell LED flashlight would probably shift more current than a solar garden light.

They don't cost all that much more.

 

The energy source is not changable, its two AA 1.5V batteries and I want to boost that voltage using current

Related to what #12 said; from my experience one the batteries are totally charged they should be around 1.6 even, buy higher than 1.5; once they are discharged, voltage drops to 1.4V from then the voltage starts dropping faster

 

What will the load look like? (How much current?)

 

The energy source is not changable, its two AA 1.5V batteries and I want to boost that voltage using current

Related to what #12 said; from my experience one the batteries are totally charged they should be around 1.6 even, buy higher than 1.5; once they are discharged, voltage drops to 1.4V from then the voltage starts dropping faster

True, and a good argument for using fresh batteries. Are you trying to extend the life of the near-dead batteries? There's not a lot of energy left once the voltage has sagged that far. That's why the voltage drops quickly.

 

I used it:

 

I used it:
View attachment 122259

The PR4401 is much easier, and probably cheaper.

 

The energy source is not changable, its two AA 1.5V batteries and I want to boost that voltage using current

That makes no sense. If you have two AA batteries you already have the capacity to get 3 volts.

Do the math and think about it.

1.5 volts @ 3000 mAh X 2 = 9 Watt Hours. Vs 3 volts @ 3000 mAh = 9 watt hours and zero energy lost in a booster circuit either to get it.

 

That makes no sense. If you have two AA batteries you already have the capacity to get 3 volts.

Do the math and think about it.

1.5 volts @ 3000 mAh X 2 = 9 Watt Hours. Vs 3 volts @ 3000 mAh = 9 watt hours and zero energy lost in a booster circuit either to get it.

Not if they're nickel chemistry - I have a collection of gadgets that won't put up with the slightly lower voltage.

 

That makes no sense.

It does, only if you read between the lines. He apparently needs to power something that needs a minimum voltage, like an LED, and he's using rechargeable cells instead of alkaline. Gaaa, Ian beat me.

 

It does, only if you read between the lines. He apparently needs to power something that needs a minimum voltage, like an LED, and he's using rechargeable cells instead of alkaline. Gaaa, Ian beat me.

Speaking of voltage and LEDs - a lot of cheap LED keyfob lights rely on the internal resistance of a coin cell to limit the current. I even have a 3D LED flashlight with no circuitry or resistor - its seriously bright with fresh cells and doesn't give much warning before sinking to a pale glow.

When the wire to the Cree puck broke, I coiled as much wire as I could round the inside of the housing to give it at least some resistance.

 

It does, only if you read between the lines.

I tend to not read between the lines when given conflicting information. If The OP can't be bothered to provide enough or correct information I can't be bothered to put much effort into speculating on what he wants.

He said he needed 3 volts with AA batteries and never mentioned them being rechargeable so that's what I went by.

 

He said he needed 3 volts with AA batteries and never mentioned them being rechargeable so that's what I went by.

He talked about charging in #6. Sort of.

 

What will the load look like? (How much current?)

Load will be around 15mA

I used it:
View attachment 122259

I dont know of it, I read the datasheet, thank you

The PR4401 is much easier, and probably cheaper.

As I said to Bordodynov, I dont know about the PR4401 either, I liked that you gave me some references that I can check and compare

Even if cost is to be considered, I am more worried about additional components associated and about the noise related to boosting voltage as far as the circuit will have associated a radio system

It does, only if you read between the lines. He apparently needs to power something that needs a minimum voltage, like an LED, and he's using rechargeable cells instead of alkaline. Gaaa, Ian beat me.

I dont think I mentioned to use rechargeable cells, I will be using alkaline 1,5V batteries that have around 3000mA (standard ones). I need to power an IC that needs 3V, but a have a diode in serie with the power source (it is totally needed), so I need to boost the voltage drop plus some extra volts (not to be so close to 3V that could risk a malfunction)

He talked about charging in #6. Sort of.

Did I? I wanted to say that the battery decision is changeable (I skept and "e"), maybe you missunderstood there? I meant that I the power source are two AA batteries and I wont be using any other power source that can supply me more volts


Regards and thank you to everybody

 

He said he needed 3 volts with AA batteries and never mentioned them being rechargeable

I interpreted this to mean they are not rechargeable:

Circuit would be powered with two AA 1.5V batteries

Are there any rechargeable batteries rated at 1.5 volts? I just checked some Ni-cads and NiMh batteries and they both say 1.2 volts.

Oops. He already answered that.
"I will be using alkaline 1,5V batteries" (post #17)

 

Hello again,

I´ve been digging around and I found Texas intruments (a bit overpriced I would say) and Microchip boost regulator

Let´s see what you think about theese parts

The TI: http://www.ti.com/lit/ds/symlink/tlv61224.pdf
The Microchip: http://ww1.microchip.com/downloads/en/DeviceDoc/40001420D.pdf

 

... from my experience one the batteries are totally charged they should be around 1.6 even, buy higher than 1.5; once they are discharged, voltage drops to 1.4V from then the voltage starts dropping faster

Sorry, I read that as a hint you were using rechargeable batteries since you hadn't specified the chemistry. I misread the hint.

...I will be using alkaline 1,5V batteries that have around 3000mA (standard ones). I need to power an IC that needs 3V, but a have a diode in serie with the power source (it is totally needed), so I need to boost the voltage drop plus some extra volts (not to be so close to 3V that could risk a malfunction)...

Ah, now we learn the specifications. I believe you'll need a solution that includes a regulated voltage output. Something like my solar light hack or the LED driver ICs (same thing, really) don't do that - they're designed to pulse a current through an LED and give the appearance of being continuously lit. Your IC probably wouldn't like that and would "see" the pulses. So you'll need to smooth it out AND get it into a narrow voltage range for your IC.

I think you just need a DC-DC boost converter with an adjustable voltage output. There are tons of these cheap on eBay.