Boost Module

[u_couple]

Needing some help once again guys

I recently purchased a couple of these boost modules, with the intention of using in a box mod I was gonna build. I planned on using an 18650 battery, with the option of upping the voltage to between 4V and 5V. Last night I wired them up on the bench, just to test before I glued/epoxy`d them in the case, and I can`t get either of them to go below 5.2V !!

Am I missing something here, or is there any way to get them down to a lower voltage? My normal setup on the provari is around 4.4V, so I was hoping to get round about that voltage.

Here is the module :- Mini DC to DC Converter Boost Input 2.5-25V to 3-25V Step Up Wide Voltage Module | eBay As usual guys, any help greatly appreciated

 

[jhonutz]

When you tested before glued in boxes, hes work or not?maybe you miss something when you put in box.

 

[u_couple]

When you tested before glued in boxes, hes work or not?maybe you miss something when you put in box.

Yeah they work just fine, I can get anything between 5.2 and 14.6 V, but can`t get them to go lower than 5.2 !!
As far as I can see, it`s just a simple voltage in + & - , and voltage out + & -

 

[CraigHB]

Are you testing them with no load? Boosters do not always work well unloaded. Mine do, but I use a high end controller, unlike the eBay ones. Even so, they lose some regulation accuracy when unloaded. Check output voltage on your booster while powering an atomizer or equivalent load.

These are no-name modules from China. They may or may not work to specifications indicated on the item listing. People have reported issues with similar booster modules purchased on eBay, but that's the first time I've seen that particular module. You may want to check them over a wide range of voltages and loads before permanently installing them. Keep in mind, a booster can never go more than a half volt below input (battery) voltage. The most efficient boosters can't go below input voltage more than a tenth of a volt.

You said you planned on using "an 18650 battery". You'll need to use a high drain battery with a booster, specifically an IMR 18650. Even if not over-loaded, the protected 18650s can trip due to start-up inrush currents which, for a few milliseconds, can be multiples of normal currents.

 

[u_couple]

Hey Craig, thanks again for the info buddy,

So far I have just tested the output with "no load" I would really like to get the voltage down to around 4.4, and so I just assumed that even under load, it wouldn`t drop down to that, but I will certainly test it tomorrow.

And yes, I would be using IMR 18650

edit to add, unloaded it`s reading 5.2V, loaded it`s reading between 5.0 and 5.1V

 

[CraigHB]

Welcome,

Just for a reason why, boosters are not like buck or linear regulators in that they can only add to input voltage. They can't subtract from it. They really are a unique animal with their own set of pitfalls.

There are actually several transitions boosters go through in adding to input voltage. They have to be able to operate in three different modes, no load, DCM, and CCM. High end boost controllers are designed to operate in all three, but cheap ones may only be able to operate in one or two. Also, the engineer has to compensate for the various operating modes in the design. If you get a boost module from someone like Texas Instruments or Murata, you can be confident it will operate properly under all conditions. From some hack in China? Who knows.

BTW, the voltage below input depends on rectification, synchronous (uses a MOSFET rectifier) or asynchronous (uses a diode rectifier). As far as I can tell from the photos, it looks like that booster is asynchronous. So, you should get a half volt drop from the diode rectifier. In that case, you should be able run with a minimum setting of 3.7V. That would be peak battery voltage of 4.2V minus the half volt drop of the diode rectifier.

 

[u_couple]

Thanks again Craig, it looks like it`s back to the drawing board then, either that or just be prepared to forego LR attys on this mod !! Pity, cause I already have all the holes etc cut out to take all the other components.

 

[CraigHB]

If the specs are right, it says 4A max input so you should be able to get 13W out of it. Though, you're right, it's probably not enough to drive an LR atty much over 5V.

I haven't yet seen a booster you can buy off-the-shelf capable of putting out over much over 12W so that's probably going to be the best you can do. I make them myself capable of 30W (5A @ 6V) using a high-end TI controller driven by a 20C LiPo. Typically not something a person can do themselves without a good amount of experience in electronics design. Maybe I should do a co-op version to help out other booster lovers like you and me.

 

[rusalka]

If the knowledge and price is right, then go for the co-op.

 

[u_couple]

This probably sounds like a stupid newbie question but, would it be feasible to run a "drop down module" from the outputs of the boost ? just to get the voltage down a little !