Idea for a mod using a step-up power module. Am I nuts?

[Fronkey]

Hi, I'm a new member but have been lurking for several months.

I am interested in building a vv mod that will go up to ~5 volts, but can't seem to find a battery that will fit in the form factor I am envisioning that will put out more than 3.7 volts. In order to get around this, I have "designed" (in my head) a system that would use a 3.7 volt battery run through a step-up power module to raise the voltage to the 6-7 volt range, then wire a pot in between the negative terminal of the power module and the atomizer connector (possibly with a volt meter in there as well) to regulate the voltage to the atomizer.

I understand that the step-up module will suck some power, but have found a small module that claims to operate at 80% efficiency, and a battery that would fit my envisioned form factor with a 6000 mAh capacity and a 2C discharge rate.

Has anyone tried anything like this? Is there something I am missing that would prevent a setup like this from working well?

Thanks for any input.

 

[Java_Az]

bunch of mods that do this. provari lava tube darwin the new ego- twist and so on. there is a Texas Instruments module that a lot of modders in here use ptn04050c can be set up for variable voltage output. it can handle 12 watts and has better then 80% efficiency. 6000 mAh battery is going to be big unless you go on ebay you can find one that says it is 6000mAh but in real life it will be more like 2000mAh. But yeah for sure has been done and works quite well if you use quality Japan made 18650 batteries.

Edit: The pot idea would work but it will make it even less efficient then 80%. Plus you would need a pot that can handle at least 10 watts and those are big and expensive. Your much better off getting a booster chip that can be set up variable voltage.

 

[WillyB]

I understand that the step-up module will suck some power, but have found a small module that claims to operate at 80% efficiency, and a battery that would fit my envisioned form factor with a 6000 mAh capacity and a 2C discharge rate.

Post links.

 

[BJ43]

LM2577 DC-DC Adjustable Step-up Power Converter Module | eBay

I built one with this regulator

 

[Fronkey]

Post links.

The power module:

LM2577S DC-DC Adjustable Step-up Power Supply Module - Free Shipping

The battery:

Polymer Lithium Ion Battery - 6Ah - SparkFun Electronics

ETA: As far as the battery goes, it's more the shape that I am worried about than the actual size for the form factor I envision.

 

[Fronkey]

LM2577 DC-DC Adjustable Step-up Power Converter Module | eBay

I built one with this regulator

Looks like the same module I was looking at. How's it do in use?

 

[BJ43]

Looks like the same module I was looking at. How's it do in use?

It works ok for me but I hardly ever use a battery PV since I normally vape a VV PT, so really can't rate it's efficiency.

 

[Para]

bunch of mods that do this. provari lava tube darwin the new ego- twist and so on. there is a Texas Instruments module that a lot of modders in here use ptn04050c can be set up for variable voltage output. it can handle 12 watts and has better then 80% efficiency. 6000 mAh battery is going to be big unless you go on ebay you can find one that says it is 6000mAh but in real life it will be more like 2000mAh. But yeah for sure has been done and works quite well if you use quality Japan made 18650 batteries.

Edit: The pot idea would work but it will make it even less efficient then 80%. Plus you would need a pot that can handle at least 10 watts and those are big and expensive. Your much better off getting a booster chip that can be set up variable voltage.

You got me thinking with that one....with the new Evolv DNA going up to 12.7 watts....what's the pot that would handle that look like? Any recommendations of what to use?

Thanks

 

[Java_Az]

You got me thinking with that one....with the new Evolv DNA going up to 12.7 watts....what's the pot that would handle that look like? Any recommendations of what to use?

Thanks

Really it is not a good way to do it. The pot would be burning off the extra voltage as heat so it would basicly be just like a linear regulator. Really a linear reg would be better since it would be cheaper. The best way would be to just use a switching booster that has variable voltage. But if you really wanted to it would have to be a low ohm rheostat to be able to handle the watts. something like this. Note the price and it is one of the cheaper ones REL1R0E Ohmite Rheostats

 

[meatsneakers]

If you're looking to have a max of 5v, then this would be a good option: http://www.ebay.com/itm/DC-DC-Boost...326?pt=LH_DefaultDomain_0&hash=item1e6dd9295e

The less voltage difference between your desired voltage and the input = less heat. A linear reg wouldn't work in this case because the dropout voltage would leave you at a max of ~4.4v.

A couple of power resistors could work, perhaps using a selector switch or a DIP switch to select a few different values. They would dissipate less energy than if you stepped up to 6 or 7v.

If you look at the dimensions on that battery pack you linked to, you're better off using stacked 18650's and a step-down regulator. The pack is 19x54x54mm while 2x18650 is 18x36x65 (give or take a few mm). Two of these: PANASONIC 18650 PROTECTED NCR18650A 3100mAh FREE Shipping from Florida-USA. 18650 cell-Made in Japan, Protection IC's-Made in Japan would equal the capacity (roughly) of the poly cell you posted, + they have protection... and you would be using at least 90%+ of the cells energy with a switching regulator compared to burning it off as heat after boosting it.

Just some things to think about.

 

[WillyB]

If you're looking to have a max of 5v, then this would be a good option: http://www.ebay.com/itm/DC-DC-Boost...326?pt=LH_DefaultDomain_0&hash=item1e6dd9295e

A couple of power resistors could work, perhaps using a selector switch or a DIP switch to select a few different values. They would dissipate less energy than if you stepped up to 6 or 7v.

Two of these: PANASONIC 18650 PROTECTED NCR18650A 3100mAh FREE Shipping from Florida-USA. 18650 cell-Made in Japan, Protection IC's-Made in Japan would equal the capacity (roughly) of the poly cell you posted, + they have protection... and you would be using at least 90%+ of the cells energy with a switching regulator compared to burning it off as heat after boosting it.

Have you actually tried that assembly? I don't think they work for us. At least the couple examples I've seen on these forums didn't..

I would go as far as saying that none of those eBay boosters seem to provide enough current for our uses at our voltages. I have tried two, a simple booster and a buck-booster (step up/down). Total fail using our input voltages of about 3.4-4.2V.

The popular TI 04050 seems to be the best option for modders, 12W/2.4A is pretty much attainable, but obviously will need a few additional components.

Too many folks seem to recommend the over rated Panasonics. A better performing and less expensive cell would be these.

x2 XTAR 18700 2600mAh 3.7V PROTECT RECHARGEABLE BATTERY | eBay

Take a peek at this.

That's the essentially similar AW/Panasonic 2900 vs the Sanyo.

Xtar also re-wraps a 3100, avoid it and stick with the 2600 Sanyo. Panasonic's mAh is based on a useless to us 2.5V cut-off. Most will never drag their cells even to 3V.

Here's one more.

The protected Xtar2600 on top vs the unprotected (an advantage) Panasonic 2900 on the bottom.

I've marked when they hit 3.5V and then 3.25V. The Panasonic manages a measly 1600mAh @ 3.5V while the Xtar/Sanyo nearly 2400mAh. A rather amazing 50% more.

Food for thought.

 

[meatsneakers]

Willy, I love the AW 2600's but most places come out to around $31 shipped (edit- make that $39, it's been a while) and that was a bit too rich for my blood lol. The 3100 Panny cells seemed like a good deal from Orbtronic and they've treated me well thus far. I use them in series and rarely get them below 7.5v after 8 or 9ml (2+ days) - I just like that they're cheap and built using good cells + they handle a high drain situation and keep a good amount of their capacity. I always had trouble with the cheaper cells (*fire) barely getting to the end of the day. That eBay listing looks enticing though - if they are the same Sanyo 2600's then I may have to pick up a set.

 

[Fronkey]

If you're looking to have a max of 5v, then this would be a good option: http://www.ebay.com/itm/DC-DC-Boost...326?pt=LH_DefaultDomain_0&hash=item1e6dd9295e

The less voltage difference between your desired voltage and the input = less heat. A linear reg wouldn't work in this case because the dropout voltage would leave you at a max of ~4.4v.

A couple of power resistors could work, perhaps using a selector switch or a DIP switch to select a few different values. They would dissipate less energy than if you stepped up to 6 or 7v.

If you look at the dimensions on that battery pack you linked to, you're better off using stacked 18650's and a step-down regulator. The pack is 19x54x54mm while 2x18650 is 18x36x65 (give or take a few mm). Two of these: PANASONIC 18650 PROTECTED NCR18650A 3100mAh FREE Shipping from Florida-USA. 18650 cell-Made in Japan, Protection IC's-Made in Japan would equal the capacity (roughly) of the poly cell you posted, + they have protection... and you would be using at least 90%+ of the cells energy with a switching regulator compared to burning it off as heat after boosting it.

Just some things to think about.

I agree that it would be much more efficient to stack batteries (in series) and then use a step-down regulator. However, I had wanted to build a charging circuit into the mod along with a microUSB port to give me the ability to charge while I vape (and with the same cable I use to charge my phone and bluetooth headset). From what I have read, it's quite complicated (and also a bit risky) to try to charge batteries stacked in series.

Thanks everyone for all the info posted. I might just go with the battery WillyB linked to (though I would use 2 wired in parallel so that I can build in my USB passthrough). Also, Willy, do you have a link to a good place to get that TI power module you mentioned?

ETA: While not mentioned on the main page, a quick look at the datasheet (and in the comments section) reveals that the battery (pack) I linked to is, in fact, protected.

ETA2: Another feature I am considering is throwing a switch in there somewhere so that in a pinch my mod would be able to charge my phone.

 

[TomCatt]

I've used the 3V-5V 3A eBay module. A Trustfire 18350 lasted about 4 hours; so I'm sure a battery with more oomph would last much longer. I didn't pursue this very far cause I'm not really a fan of 5V vaping - 4.5 is more in my range for my ADV.


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[WillyB]

I've used the 3V-5V 3A eBay module. A Trustfire 18350 lasted about 4 hours; so I'm sure a battery with more oomph would last much longer. I didn't pursue this very far cause I'm not really a fan of 5V vaping - 4.5 is more in my range for my ADV.

As I recall you were pulling 1.6A for about 8W. You also mentioned that it started it's low current whining after only 1.5ml of liquid using an 18650. Pretty dismal efficiency for a paltry 8W.

Certainly not something most vapers would be happy with.

 

[TomCatt]

It was an 18350 Trustfire, Willy; not a very good battery to be boosting from. The whining would be a failing of the battery not the module. And yeah, was (and still do) using a 3.2 ohm clearo, which is 8 watts. I don't know about what ejuice you use; but, anything over 8 watts for my ADV and it's toast.

I'm not saying this module is great; but I would say that for anyone who vapes at 5V, it's a viable option.



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