EverCool Variable Voltage Mod

[bigblue30]

Willy,
Thanks for keeping an "eye" on this thread. Between you and CapeCAD it looks like you have it covered.

I finely broke down and built a 4081 Evercool. "wink".

Bobrez and Warbdan, I am glad you like it.

Everyone please have a safe and Happy New Year.

 

[sgtdisturbed47]

I took a look at your variable voltage mod that uses a switching regulator, and I was wondering, what sort of resistor would I use on the switching regulator to achieve 5v, without using a pot? I don't want to build something that has adjustable voltage.

I tried building my mod using that switching regulator, and without a resistor on the 5th pin, nothing happens. I'm assuming that it requires a resistor. What resistor would I need, and how would I connect the resistor?

 

[bobrez]

From a previous post.

Maybe this will help. As biggie mentioned ignore the decimal point.

 

[givesuhe11]

you have to short 5th pin and 3rd pin with a resistor of the values listed in table one or two of the pdf... shown in previous posts or go to the pdf on TI's site and download it (if you haven't already)... ignore the decimal... so for 5.0 volts looks like 267-268ohm resistor... but you'll search forever for that exact value... so round up or down to the nearest you can find in that range... you'll hit somewhere in the 5.0volt range...

 

[sgtdisturbed47]

I can score 270 ohm resistors for dirt cheap, but they are 1/2 watt. Does it matter if they are 1/4 watt or 1/2 watt?

 

[CapeCAD]

The data sheet specifies a .05W (1/50) Watt may be used. 1/2 Watt will be much larger, and overkill, but will work.

 

[sgtdisturbed47]

My source has 270 ohm resistors in 1/2 watt only. Will this affect battery life?

 

[CapeCAD]

My source has 270 ohm resistors in 1/2 watt only. Will this affect battery life?

No, this will not affect battery life.

 

[sgtdisturbed47]

I went ahead and picked up a 5 pack of 270 ohm resistors from work, and after a couple hours of assembling, I got it to work. The 270 ohm resistor works perfect, giving me a nice, hot 5v vape.

I am having a lot of trouble with the soldering though. Not sure if it's my tip, but it doesn't always want to bind to the wires and to the copper on the PCB I tried to use. I gave up on the PCB and directly soldered the wires and connectors to the regulator's pins. Very frustrating. The solder just doesn't take to the copper on the PCB! I'm using a 40 watt soldering iron, and lead-free silver solder. Any tips on how to do this with a PCB? I'm sick of my mods looking like a spliced wire mess on the inside.

 

[WillyB]

Lotsa soldering vids on YouTube.

Not sure if it's my tip,

Well is it clean and in good shape? When you tin it before you start soldering is it nice and shiny with a nice even coat of solder?

Try cleaning the PCB with some steel wool till the copper shines. A little bit of flux often makes life easier.

 

[grantemsley]

If it's not sticking to the PCB, the PCB might be oxidized. Happens from them sitting exposed to air for awhile. Rub it with some light sand paper until it it shiny.

It may also help to switch to a lead based solder. It's a lot easier to work with (at least I find).

 

[sgtdisturbed47]

Lotsa soldering vids on YouTube.


Well is it clean and in good shape? When you tin it before you start soldering is it nice and shiny with a nice even coat of solder?

Try cleaning the PCB with some steel wool till the copper shines. A little bit of flux often makes life easier.

Flux. That's what I need. Thanks again WillyB, you're always spot-on with electronics.

 

[warbdan]

I just had the batteries in my Evercool decide they needed a charge. One of them was at 2.5(isn't this below the overdischarge limit?) volts and the other was at 3.4 volts. Is this normal in a 2 cell application? Shouldn't they have balanced each other somewhat? I could see them being a couple tenths of a volt different in charge, but we're talking almost 1 volt difference here.

 

[Java_Az]

From what i have read you want to keep them within 0.4 volts of each other. What can happen is the higher voltage one can rapidly charge the lower voltage one , That can cause overheating and or venting of the cell or cells. I would keep a close eye on them if your going to keep using them. Safest bet would be to put two fresh batteries in their place.

 

[WillyB]

Shouldn't they have balanced each other somewhat?

Nope, cells in a parallel configuration will do some balancing, but in series the top cell always gives up the ghost first.

at 2.5 (isn't this below the overdischarge limit?)

Yes but in some flashlight tests I've seen many times even the premium brands end up well below the 2.75V mark. In a way you are lucky, if the protection circuit had tripped you wouldn't be able to charge that cell. Sometimes they recover the next day, but not always.

It is generally a good good idea to let the cells rest a bit before recharging. It gives them a chance to stabilize (the voltage will usually creep up a hair)

Is it dangerous? Maybe? Does it shorten the cells longevity? Maybe/probably? Is your meter accurate? Maybe not. Were your cells actually well matched to start with? Maybe not.

After a rest and a recharge switch positions and go for broke again again. Check the voltages and see if you have the same voltage spread.

You should have your cells marked, and if you want them to age equally you should be switching their positions each time.

What voltage were you vaping at?

 

[warbdan]

I've been vaping at 4.0 to 4.2v with a 510 atty or 4.5 to 4.6v with a carto. Overdischarging is what concerned me and why I posted this. I have the batteries charging now, so when they are done I'll try them again. I'm watching the pair I have in my mod now. So far, the first battery(one providing the postive) is at 4.0v and the other battery(providing the negative) is at 3.97, so maybe the battery that had hit 2.5v wasn't fully charged when I put it in even though I thought it was. When I put it on the charger the light went red for 1 second, then green for 1 second, then orange for 2 or 3 seconds, then it went red again, so it is charging, but I was afraid I had ruined it when it went green for a second, so that's why I was asking here if any of you had seen this happen. I think what I will do is just change their position in the mod every few hours to kind of keep this from happening to begin with.

 

[WillyB]

So far, the first battery(one providing the postive) is at 4.0v and the other battery(providing the negative) is at 3.97

Well that seems odd, the lead cell should be lower. It's conceivable that one side of your charger charges to a higher voltage (many do, mine does). Check them right off the charger.

Although this may nitpicking, when you have freshly charged a pair set them aside for a few hours, then check the voltage and see how close they are.

You made 2 mods right? One with a switching reg the other linear, which one is this?

 

[warbdan]

The batteries in question came out of the evercool. The batts in the 383-adj mod aren't close to needing a charge yet.

 

[inkjet21]

ok i have my parts from ti and i found a nice thumb wheel pot i like but it is 200k ohms instead of 200 ohms will this work or will it mess up the output voltages? BTW this thread has made this mod pretty ez for a non electrical guy. thanks to all who posted all the good stuff

 

[rannox]

ok i have my parts from ti and i found a nice thumb wheel pot i like but it is 200k ohms instead of 200 ohms will this work or will it mess up the output voltages? BTW this thread has made this mod pretty ez for a non electrical guy. thanks to all who posted all the good stuff

you will basically go from the voltage you want to nothing really quick. I wouldnt get one higher than a 1k. Realistically you shouldnt even use one over 500ohms