Step up voltage regulator

[johnny bravo]

I was looking at battery holders for doing my own 5v mod, and came across some that had a built in 5v regulator that steps up the voltage from 1 or 2 batteries and regulates the voltage to 5v, or some that are adjustable from 2.5-5.5v.
Here is an example Pololu - Bodhilabs VPack5.0V 2-AA Battery Holder w/ 5V Regulator

I saw that the amperage was limited on this one (200mah) so i searched for a standalone step up/regulator and found this
MAX1703 Datasheet - 1-Cell to 3-Cell, High Power (1.5A), Low-Noise, Step-Up DC-DC Converter

it is rated at 1.5 amps. What do you think? I thought maybe 1 C battery stepped up to 5v, @ 1.5 v its ~4500-8000mah, so @ 5v would that be 1350-2400mah?

Got my battery info from List of battery sizes - Wikipedia, the free encyclopedia

Any thoughts or criticism?

[kinabaloo]

I was looking at battery holders for doing my own 5v mod, and came across some that had a built in 5v regulator that steps up the voltage from 1 or 2 batteries and regulates the voltage to 5v, or some that are adjustable from 2.5-5.5v.
Here is an example Pololu - Bodhilabs VPack5.0V 2-AA Battery Holder w/ 5V Regulator

I saw that the amperage was limited on this one (200mah) so i searched for a standalone step up/regulator and found this
MAX1703 Datasheet - 1-Cell to 3-Cell, High Power (1.5A), Low-Noise, Step-Up DC-DC Converter

it is rated at 1.5 amps. What do you think? I thought maybe 1 C battery stepped up to 5v, @ 1.5 v its ~4500-8000mah, so @ 5v would that be 1350-2400mah?

Got my battery info from List of battery sizes - Wikipedia, the free encyclopedia

Any thoughts or criticism?

Current output would be limited by the internal resistance of the cell. So for high current apps like e-cigs, nothing to be gained with voltage step-ups. It might work, but it won't work much, if at all, better than using the cell directly (if it was 3.7v; 1.5v will not work at all).

In other words, one can't step up the power (no free energy).

[johnny bravo]

Ah, oh well, thought maybe i had stumbled upon something great

[Scottbee]

Kinabaloo is mistaken on this one. Step-up DC-DC converters (boost) work exceptionally well in this application (the internal resistance of the cell doesn't come into play.. unless you are using watch batteries). The problem is going to be the 1.5A current limit. Running 5V into a 2.3 Ohm (510) atty requires over 2A.

Higher current version of the same concept (high frequency DC-DC boost switchers) are already being used in some custom mods.. and I believe an introduction is imminent on at least one main-stream mod.

[johnny bravo]

So i need to be looking for something in the 2.5A+ range? Also, when you use a USB PT, is it pulling 2+ amps from the usb port? Thanks for the input

[Scottbee]

Yes.... 2.5A would be good.... 3A would be better (for margin).

As far as the PT is concerned... it really depends on what kind of PT you have. Many (if not most) actually have a 3.7V battery in them... and all the USB power is doing is keeping the 3.7V battery "topped off" in-between vapes.

There are others that don't have the battery. They try to pull the current out of the USB port.. and if the USB port can deliver it... then great. But since USB 2.0 is only rated for .5A.... it's a crap shoot. Some USB ports will literally shut down when you try to exceed their capabilities.... others will give all the current that they can, but the resulting voltage across the atty will be lower (Ohms Law).

[johnny bravo]

Just found this one @ 4A MAX1709 Datasheet - 4A, Low-Noise, High-Frequency, Step-Up DC-DC Converter

Not sure how large these are though, anyone have any idea? I'd hate to order one and find out it was on a 6" square board lol.

[Scottes]

In the middle of that page is:

MAX1709 Datasheet and Application Notes

* MAX1709 Datasheet

Click on the "* MAX1709 Datasheet" link to open a PDF. Dimensions are on the last page.

[johnny bravo]

Thanks Scottes, if it were a snake it would have bitten me No better place to hide than in plain sight.

[WillyB]

Yes.... 2.5A would be good.... 3A would be better (for margin).

As far as the PT is concerned... it really depends on what kind of PT you have. Many (if not most) actually have a 3.7V battery in them... and all the USB power is doing is keeping the 3.7V battery "topped off" in-between vapes.

There are others that don't have the battery. They try to pull the current out of the USB port.. and if the USB port can deliver it... then great. But since USB 2.0 is only rated for .5A.... it's a crap shoot. Some USB ports will literally shut down when you try to exceed their capabilities.... others will give all the current that they can, but the resulting voltage across the atty will be lower (Ohms Law).

I don't think that's correct. USB2 specs (Battery Charging Specification) say up to 1.8A can be be provided. The D+ and D- pins come into play, for signaling.