LM2577 Fail

[Dougiestyle]

I bought this boost circuit from eBay LM2577S DC-DC 4-35V Adjustable Step-up Power Supply Non-isolated Boost Module 3A | eBay . Wired it up all purty and stuff in an awesome aluminum project box 3.15in X 2.17in" X 0.98in Aluminum Die Cast Box-MPJA, Inc. . Tested unloaded voltage @ 6V. Nice! Threw a 2ohm DC atty on it and tested loaded voltage @ 3.6V and watched the meter drop down as I puffed to 3.3. Waaaah!

Just posting this to prevent anyone else from this mistake.

Looks nice, tho!

 

[lynch]

Too late, I brought 3 of them and 2 other $3.00 ones. I hooked up 3 of them and all did the same thing, my first one lasted a few days befor it died out. Glad my cheap 18650 bats are ok.....so far.

Correction, the ones I got are LM2596 but same thing happened.

 

[breaktru]

Talk to TomCatt and see how he likes his:
http://www.e-cigarette-forum.com/forum/battery-mods/236779-first-li-ion-battery-mod.html

 

[TomCatt]

heh heh, yeah I got one of the LM2577 modules. Couldn't get more than ~4.9V loaded, I think that was it, with a 3.2ohm clearomizer, out of it off of a cheapy GTL 18650. I've since 'retired' that mod .

I did find a 3v to 5V 3A boost module on eBay which seems to work well. That's in my 3-2-5 mod which I posted. I plan on re-doing the 3-2-5 soon to use 2 18350 batts.

I've been vaping exclusively on my ACDC mod using the LM2596 buck module off of eBay for a few weeks now. No problems at all. But then again, I don't vape at high watts, 6-8 seems to do me fine. And hey at $2-$4 per module, if they last a month that's fine, give me something to do without breaking out all my supplies....the soldering iron, some solder and another module and the mod would be as good as new.

 

[Dougiestyle]

Highest resistance atty I have is 2.5ohm, so yeah lol. This chip is fail. The 2.5ohm needs at least 6.5V to hit my sweet spot. Oh well.

I'll probably ditch the circuit and turn this box into a 18650 bottomfeeder. Gotta find a source for the silicone tube and fab a squonker.

 

[TomCatt]

I bought this boost circuit from eBay LM2577S DC-DC 4-35V Adjustable Step-up Power Supply Non-isolated Boost Module 3A | eBay . Wired it up all purty and stuff in an awesome aluminum project box 3.15in X 2.17in" X 0.98in Aluminum Die Cast Box-MPJA, Inc. . Tested unloaded voltage @ 6V. Nice! Threw a 2ohm DC atty on it and tested loaded voltage @ 3.6V and watched the meter drop down as I puffed to 3.3. Waaaah!

Just posting this to prevent anyone else from this mistake.

Looks nice, tho!

Dougie, did you do any more testing of the 2577? Increase the output to 3.9 to see if you get 3.6 loaded? Any test for battery life? The module has some sag there; but if the run time is halfway decent, it could still be an option.

I don't have any high drain batts; but if (well, when) I do, I'll prolly re-visit my 2577.


Sent from my iPod touch using Tapatalk

 

[jhonutz]

Too late, I brought 3 of them and 2 other $3.00 ones. I hooked up 3 of them and all did the same thing, my first one lasted a few days befor it died out. Glad my cheap 18650 bats are ok.....so far.

Correction, the ones I got are LM2596 but same thing happened.

lm2596 work fine,i made mod with this IC.Anyway lm2596 it`s a step down regulator need 8.4V In (2 series Li-Ion) and lm2577 it`a a step up regulator works with 1 li-ion, but it`s no good for ecigarette. A step-up convertor not work well with 1.25 or 1.5 ohmi atty, it`s need to use 2 ohmi and higher.

 

[Dougiestyle]

I used a 2ohm DC atty and it still only went to 3.3V.

 

[jimbalny]

its got a 3amp limit, a 2ohm dual coil at 6 volts is bringing it right to that limit. 2ohm dc 2x 4ohm coils in parallel. So lets say you got 6 volts at each coil, 6volts / 4ohms = 1.5amps x 2 = 3amps (am i right?). maybe try using an imr battery or two 18650's in parallel to see if that has any effect?

 

[TomCatt]

I used a 2ohm DC atty and it still only went to 3.3V.

What was the unloaded voltage for this? In the first post you stated that you "tested loaded voltage @ 3.6V" and it dropped to 3.3V. So there was a 0.3V sag when vaping. That isn't really a deal breaker as long as you're not beating the battery up and you get a decent amount of run time. But then again, I started modding with NiMH batts (Puck mods) and with a 3.2ohm carto, you still get ~0.8 - 1V sag when vaping; but I can vape on a AAA Puck for at least 10-12 hours.

 

[Dougiestyle]

Unloaded voltage was 6V, not 3.6 lol. I dialed the voltage down to the range you posted in the Altoids can thread and still only 3.3.

 

[TomCatt]

OK, then pretty much a FAIL for lower res vaping definitely


ETA:
Guess I'll actually have to find my breadboard and check this module out, just have to watch for the dangling cap

 

[Dougiestyle]

It was a shot in the dark, really. I had a hunch it wouldn't put out the volts I like my DCs set at. I vape somewhere around 12W, so this circuit woun't cut the muster. I'm going to try installing a pair of 16340 AW IMR to see how it does. I dunno if the voltage will be low enough then tho. Probably not, as this doesn't step-down, as would be needed.

 

[TomCatt]

It was a shot in the dark, really. I had a hunch it wouldn't put out the volts I like my DCs set at. I vape somewhere around 12W, so this circuit woun't cut the muster. I'm going to try installing a pair of 16340 AW IMR to see how it does. I dunno if the voltage will be low enough then tho. Probably not, as this doesn't step-down, as would be needed.

If you could parallel the 16340s (or any larger cells you might have), it might give the LM2577 more umphh to work with.

Here's the 3V to 5V 3A module I used in another mod - DC-DC Converter Boost Step Up Voltage Power Module 3V to 5V 3A | eBay. It was running solid on a Trustfire 18350 with a 3.2ohm carto. I got mine on an auction for ~$4.50; this buy it now listing is probably the cheapest buy it now at $7.60. (Actually got a 2nd of these in the mail yesterday ).

 

[jhonutz]

try to find some step-up convert with lowest Vin, about 2.5V minimum to Vin.

 

[jimbalny]

That module is pretty dam big for the low capabilities of it.. u should consider the ptr08060, its basically the 6amp version of ptr08100 (used in vv evercool). Its 10 bux on mouser or u can get free samples from ti. All u need to make it work are 2 100uf tantulum capacitors, 220ohm resistor and 200ohm pot. You would need to use two batts in series but dang, this circuit could handle anything u throw at it.

 

[jimbalny]

2x aw imr 18490's (1100mah) in a radioshack 4x2x1" project box, thumbwheel on side.

Vaped my smoktek 1.5ohm dc tank carto all day at 3.6-4v yesterday and half the day before and the batts ended up @ 3.5v each last night so threw em on the charger. I do notice tho that 3.4v on this regulated seems to have more pep than 2x imr 18350's in parallel. My next one I intend on making the electronics take up even less space and adding a low battery indicator and whatnot. Got a pcb from mouser that's set up exactly like a breadboard, cutting that up would be perfect for this chip.

 

[TomCatt]

Nothing you said there isn't true, Jim . I've been playing investigating the dc-dc converters from eBay for the simplicity of use.

Sorry Dougie if I'm hijacking your thread - this does seem to be somewhat on topic, right?

 

[Dougiestyle]

Yeah, you're on topic, TC lol. My motivation was the compact size paired with the high mAh of an 18650. There doesn't seem to be a step-up converter capable of doing this, unless you dissect a Provari, and even then you're limited in amps.

My fiancee's son is almost graduated as EE, but getting him to design a circuit to handle step-up VV with higher amps and a small footprint is damn near impossible, especially when he's working on micro electronics for NASA lol. He's a very busy (student, musician, getting married, dance instructor and more) young man, and I really just hate to ask.

I'm guessing my only options are the step-down VV circuits from TI or the OKR-T. I built the OKR-T/10, but it never worked for me. Dunno what to do to get it operational, so it sits. Ideally, I could use it with the 18350s or 16340s in this box, but then I sacrifice high mAh, which was my biggest goal. I've built several dual 18650 wood boxmods with the MV VV circui and get 1.5days at 5V, but they are just slightly too large for comfort.

 

[jhonutz]

you are wright . Step-up module is good only ptn04050C and you have two options : buy ptn04050C from TI or build a boost convertor with IC .Or make a step down with 2 battery