# Buck or step down converter question.

#### Bruiser

Joined Jun 4, 2019
10
If you use a 12V to 3.3V buck converter, for a 3.3V .30mA application.

Will it (the converter) drain your small ah battery fast?

#### BobTPH

Joined Jun 5, 2013
5,804
Buck converters are not at their best for small currents like that. If the draw is constant, a resistor might actually do better.

Bob

#### crutschow

Joined Mar 14, 2008
30,822
Do you mean 30mA or 0.3mA?

#### Bruiser

Joined Jun 4, 2019
10

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#### CharlesWMcDonald

Joined May 16, 2019
233
Are only willing to use a 12V battery? If a lower battery voltage is acceptable you could use a charge pump regulator. The cost is low and they are suitable for low currents.

#### Bruiser

Joined Jun 4, 2019
10
Are only willing to use a 12V battery? If a lower battery voltage is acceptable you could use a charge pump regulator. The cost is low and they are suitable for low currents.
I require a permanent outdoor weatherproof solar power supply solution to simulate/replace Lithium 123 Voltage of 3.3V

So far thanks to this forum I’m at:

10W solar panel
to solar charge controller
to small AH 12v battery
to 2A fuse
to 12vdc - 3.3v 2A stepdown
to 30mA fuse
to circuit

So far it makes sense to me. I just don’t know how much draw the device and step down will take from small 12v Amp Hour Battery

Currently one lithium 123 battery lasts only 5 days.

Last edited:

#### CharlesWMcDonald

Joined May 16, 2019
233
I found a suitable regulator, refer to attached file.

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• 6.3 MB Views: 5

#### mvas

Joined Jun 19, 2017
539
Search ebay using "3.3 volt buck converter"
They start at $0.99 with free shipping I can't build one, for that price ... Thread Starter #### Bruiser Joined Jun 4, 2019 10 Search ebay using "3.3 volt buck converter" They start at$0.99 with free shipping
I can't build one, for that price ...
But how much juice do these buck converters suck back from the battery. Can’t find those specs.

#### crutschow

Joined Mar 14, 2008
30,822
But how much juice do these buck converters suck back from the battery. Can’t find those specs.
Aye, there's the rub.
Many switching regulators draw a significant bias current that can cause poor efficiency at low loads.
You need one designed for high efficiency with small loads, such as this.