VV overhead with nimh?

[Berylanna]

Hi.

I'm waffling back-and-forth between making a 3 AAA 3.6v Puck or else a 4 AAA VV Puck. My roomie and I usually vape 3.6v regulated X2s, and I have a Twist that I like, but it spends at LEAST half the time set at 3.6v.

We also tend to vape 4.5-6.5 watts.

So, since nimh AAA's from the store are, what, about 850 MAH, and expensive ones from a battery store 1000mah, I wonder...does making something VV require I either use something that does weird switching that will freak out a voltage display or else something that's going to chew up half the hours in my mah?

On the other hand, I thought I saw somewhere that nimh's, especially unregulated, see a significant voltage drop after about half of their mah is used up. If that is true, it argues against a 3-AAA design if we're used to our nice Volts.

Thoughts?

 

[Rader2146]

NiMh will see a significant voltage drop even at full charge. IIRC, a 4 cell puck is about 1 volt drop with a 2.0 ohm coil. For a VV buck regulator you wil typically need 1.5-2.0 volts headroom, that puts you at 6 cells if you want a decent runtime.

If you want to build a VV mod, a 2x 14500 OKR mod might be a more feasible option based on what you say you are looking for.

 

[Berylanna]

NiMh will see a significant voltage drop even at full charge. IIRC, a 4 cell puck is about 1 volt drop with a 2.0 ohm coil. For a VV buck regulator you wil typically need 1.5-2.0 volts headroom, that puts you at 6 cells if you want a decent runtime.

If you want to build a VV mod, a 2x 14500 OKR mod might be a more feasible option based on what you say you are looking for.

I want to build an nimh mod, and we use 2.4-2.8 ohms usually but sometimes 2.0

Sounds like I need 4 AAA w/o any other load than the leds, a 1-volt drop would give me about 3.8, which is in my neighborhood.

 

[Lonnie Lepp]

I am building a Puck with AA NIMH Batteries that are rated 2000mAh
I am using an N Channel MOSFET as a switch so that I can use a smaller momentary switch.
I used 2 each 2xAA boxes back to back for the batteries and 1 each 2xAA battery box glued to the side of the resulting 4 pack for the batteries.
Still testing things out on a bread board.

Good luck

Please keep me informed of your progress.
Be sure and check out the "Puck", lots of good info there.

Lonnie

If you can find a boost circuit that would run from 1.8 volts to about 3 volts you could use 2 batteries in series.

###
This is from a thread I started
http://www.e-cigarette-forum.com/fo...-1st-mod-progress-ti-ldo-way.html#post6788932

More progress. Got a new multimeter and I ran tests on a 4.8 volt NIMH battery pack measured volts and amps using two meters and a load test with a 2.7 ohm 10 watt ceramic resistor. Stopped testing at 30 minutes. I did not know how low I could take the batteries without damaging them. started out with freshly charged set of batteries.

No load voltage of 5.67 @ zero minutes
Minute 1 under load, voltage was 4.35, amps at 1.24 for wattage of 5.3940
Minute 17 under load voltage was 4.00, amps at 1.15 for wattage of 4.6000
Minute 30 under load voltage was 3.77, amps at 1.08 for wattage of 4.0716
No load voltage of 4.74 @ 31 minutes
30 minutes times 60 seconds equals 1800 seconds.
1800 seconds divided by 3 seconds equals 600 each 3 second vapes
The batteries seem to recover voltage after they rest.


No load voltage of 4.98 @ 50 minutes

These are 850 mAh AAA NIMH batteries

Did a stop watch test of a vape and averaged 3 seconds per vape

 

[Berylanna]

I am building a Puck with AA NIMH Batteries that are rated 2000mAh
I am using an N Channel MOSFET as a switch so that I can use a smaller momentary switch.
I used 2 each 2xAA boxes back to back for the batteries and 1 each 2xAA battery box glued to the side of the resulting 4 pack for the batteries.

Good luck! Sounds interesting.

Now I have to go back to Radio Shack and play with their boxes again! When I tried to hold 2 4-AAA battery boxes back-to-back, it was uncomfortably fat in my hand, and my hands are bigger than those of the intended recipient. Now I'm wondering how hard it would be to glue an ugly box out of wood, maybe by cutting down cigar boxes, and only leave about 1/2 the clearance of a battery box for components. I'd have to choose really low-profile components, but that sounds doable (especially since I intend to put the connectors on top of the box instead of inside.) But I'm thinking the wood would eat up a lot of space, still resulting in a too-big-for-hands mod.

But I'm also working, taking Mom to the Dr., babysitting grandchildren, and going to South Africa soon for a short vacation, so right now I'm not going to actually start anything, I'm trying to decide on parts and form factor.

But pricing commercial mods made up my mind for me, I gotta try this between now and Christmas.

Please keep me informed of your progress.
Be sure and check out the "Puck", lots of good info there.

Yeah, I read that through after watching Steeljan's $5.99 mod demo, she said to read Puck.

If you can find a boost circuit that would run from 1.8 volts to about 3 volts you could use 2 batteries in series.

I'm a software engineer, we don't even change lightbulbs, "That's a Hardware Problem!"

Minute 1 under load, voltage was 4.35, amps at 1.24 for wattage of 5.3940
Minute 17 under load voltage was 4.00, amps at 1.15 for wattage of 4.6000
Minute 30 under load voltage was 3.77, amps at 1.08 for wattage of 4.0716
The batteries seem to recover voltage after they rest.

These are 850 mAh AAA NIMH batteries

Hmmm, MadVapes is looking better and better.....or...the only way I can see the above working for me is if I get several mini-ViVi Novas and put different resistance heads in them so I can keep swapping as the voltage goes down.

 

[unloaded]

I made a Puck using 4x AAA's unregulated. Had two sets of batts but got pretty good runtime on a set. The nice thing is you can get by with them as they get low, they don't just quit all of the sudden. Also I used RadioShack parts. I hollowed out a 4x AA box and put a 4x AAA box inside. A bit of solder and hot glue and it was good to go. Try one without VV or boost, it might surprise you.

 

[Lonnie Lepp]

I made a Puck using 4x AAA's unregulated. Had two sets of batts but got pretty good runtime on a set. The nice thing is you can get by with them as they get low, they don't just quit all of the sudden. Also I used RadioShack parts. I hollowed out a 4x AA box and put a 4x AAA box inside. A bit of solder and hot glue and it was good to go. Try one without VV or boost, it might surprise you.

I would love to see a picture of that setup. I kinda have an idea how you did it.

I put 2 AA boxes back to back for my batteries and 1 AA battery box on the the side of the previously mentioned battery boxes. It measure out like 2 each 3 AA battery boxes glued back to back.

 

[unloaded]

Here's a pic of it before i added push button switch. I tried it with just the on/off switch first to see how it would work:

You can see it fits nicely, just a bit of notching out and filing. I placed the button in the space between connection and on/off switch. I don't think I ever took any pics of it like that. I gave it to a buddy who is still using it. Made it almost 1 year ago.

 

[Berylanna]

Here's a pic of it before i added push button switch. I tried it with just the on/off switch first to see how it would work:

You can see it fits nicely, just a bit of notching out and filing. I placed the button in the space between connection and on/off switch. I don't think I ever took any pics of it like that. I gave it to a buddy who is still using it. Made it almost 1 year ago.

Do those boxes take paint if they are primed etc?

Has anybody ever made a leather box mod?

 

[unloaded]

If you use Krylon paint with Fusion in it, it does a good job on plastics. I've painted tons of stuff with it.

Edit: You don't need primer with that paint either.

 

[Berylanna]

OK, got some mosfets only to read that I can't use them in a 3.7v mod, even though I got the IRL3103 ones they say you can use in a 3.7v mod. Something about needing 1 volt difference between gate and the vaping voltage.

And I got 10M-ohm resistors because that's all the M-ohm that came in a pack with several at my local Radio shack. And I got some MadVapes nice little tactile switches rated at like .1 ohm

So, now I have to take back the resistors and save the IRL3103 for a 4.8-volt 4-nimh mod? I'm so confused.

I also don't see any 2+ amp switches that aren't either huge or reviewd as crap. How do y'all do this with small flashlight mods?

 

[Java_Az]

OK, got some mosfets only to read that I can't use them in a 3.7v mod, even though I got the IRL3103 ones they say you can use in a 3.7v mod. Something about needing 1 volt difference between gate and the vaping voltage.

And I got 10M-ohm resistors because that's all the M-ohm that came in a pack with several at my local Radio shack. And I got some MadVapes nice little tactile switches rated at like .1 ohm

So, now I have to take back the resistors and save the IRL3103 for a 4.8-volt 4-nimh mod? I'm so confused.

I also don't see any 2+ amp switches that aren't either huge or reviewd as crap. How do y'all do this with small flashlight mods?

A irl3103 mosfet should work fine in the 3 volt range. Gate voltage is rated up to 16 volts. The gate threshold voltage is 1 volt. The threshold voltage is the one you have to watch out for. If you used 1 volt to the gate to turn it on it would not fully saturate the mosfet which will cause it to heat up. 3 volts and above should be fine for that mosfet specially since vaping is not a always on activity.

gate voltage does not need to be 1 volt below the source voltage who ever said that is wrong.

 

[Rader2146]

The IRL3103 will work fine on a single batt mod. There have been many of mods build with that MOSFET. If you are looking to save a little space, IRLU3114 is a smaller package size. Your 10M resistors should be fine too. In a simple MOSFET circuit, the resistor value shouldn't make too much difference.

Just in case you need it, here's a good MOSFET switch schematic.....

Edit: Well, Java beat me to it. Haven't seen you around much lately and I've been meaning to ask you a question. PM coming your way tomorrow after I hunt down the thread in question.

 

[Lonnie Lepp]

Radar thank you for the simple circuit.

I have been making myself crazy trying to figure this N Mosffet thingy out.

Lonnie

 

[Java_Az]

Edit: Well, Java beat me to it. Haven't seen you around much lately and I've been meaning to ask you a question. PM coming your way tomorrow after I hunt down the thread in question.

Send away , still not around too much. I moved from AZ to Colorado so been pretty busy trying to settle down. But i will get back to you as soon as possible

 

[Berylanna]

Thanks for the schematic! With yours I now have 3! One with mosfet and switch, one with switch and LED, and one with mosfet and led. If I combine all 3, I have what I need, except....coordination. And a safe place to solder. And the right putty. I'm seriously considering Shoe Goo instead of JB weld.

Someone said the mosfets eat 1 volt, so I'd be vaping at 2.7 volts. That seems wrong, if I'm using it as
a switch.


http://www.e-cigarette-forum.com/forum/battery-mods/181976-1-aa-touch-modbox.html#post3071009

 

[Java_Az]

.

Someone said the mosfets eat 1 volt, so I'd be vaping at 2.7 volts. That seems wrong, if I'm using it as
a switch.

As long as the mosfet gets good saturation they add very little resistance to the circuit. The data sheet has it @ 16 milli ohms with a gate voltage of 4.5 volts. So say your atomizer plus circuit is 2.410 ohms it would only make the total go up to 2.426 ohms. You will actually find that push button switches add more resistance to a circuit then a mosfet this push button here adds 50 milli ohms PV5 anti-vandal switch | elevator switch | anti-vandal | round pushbutton