Voltage drop? What voltage drop?

[dchest02]

When I started to look at voltage drop on my Grands I found that my voltage was dropping about .9 volts with a fully charged battery on a .65 ohm coil.

Soon after I employed Pdib's brass shim, and my voltage drop decreased significantly. After brass shim it was about .35-.4 volts. I decided that wasn't good enough, and Rob answered my prayers by saying that he was coming up with a sub-ohm kit soon. I, being impatient, couldn't wait. Here is what I came up with



What you're looking at is my brass firing pin. I had a firing pin go bad (point flattened out from overuse, at least that's what I am going to call it), and I used that as my template. Bought some .007 thick brass shim stock, cut to size, drilled the hole, and in it went.

I was kind of scared to hit the button at first, but then I remembered buying at least 6 extra hot springs since my first Reo experience. With my tankometer on my baby I hit the button



3.93 volts, and no melting spring (also no Noalox on firing pin). So far, so good. Screwed my RM 2.0 with a .65 ohm coil onto the tankometer, and VOILA!



3.74 volts! That is a voltage drop of .19 volts.

It worked so well that I made a second one for my other Grand, and that had a voltage drop of .2 volts. Also, the picture in this post were from about 24 hours ago, I just changed the battery, tested again, and the voltage drop was .22 on the black Grand. Consistent enough results for me to call this a success. Now I need to make one for my Mini 2.1.

 

[pesky_human]

Homie - what is that voltage meter and where can I sell a kidney... err I mean buy one.

 

[dchest02]

I bought mine from Empire mods

I would provide you with a link, but their website seems to be down at the moment.

 

[Krazirob]

i would be willing to purchase a couple of these from you........thats pretty impressive........having a .2 V drop is as good as you can get it.......

 

[malkuth]

For those that are interested....

Here is a link on ECF that might help.

 

[Cavere]

I did something similar which helps with the drop I've noticed. I used. 006 brass feeler gauge but I doubled it over and rolled the tip for a larger striking surface. The only issue I've noticed and I don't know if you did as well dchest02 but it's not as springy so my button doesn't return all the way back up so sometimes I have to pull my button to lock it.

I don't have a simple meter to test my drop but I notice the difference. Nice write up.

Sent from my SM-N900V using Tapatalk

 

[dchest02]

I did something similar which helps with the drop I've noticed. I used. 006 brass feeler gauge but I doubled it over and rolled the tip for a larger striking surface. The only issue I've noticed and I don't know if you did as well dchest02 but it's not as springy so my button doesn't return all the way back up so sometimes I have to pull my button to lock it.

I don't have a simple meter to test my drop but I notice the difference. Nice write up.

Sent from my SM-N900V using Tapatalk

Both of mine actually work the same as using the stock firing pin. The stock one measured .006, but I went for the .007 because I thought the extra .001 of thickness would help with the rebound of the button. Also, you can't see it in the first picture, but the new firing pin is bent up slightly which also helps with the button rebound.

As far as performance goes, where I notice the most improvement is longer battery life, I can usually vape my batteries down to 3.6-3.4 before I notice the lack of performance and have to change them out. One downer though is that I have scorched the cotton wicks in both of my Grands on fresh batteries since I did this. More voltage getting to the coil, quicker wick drying out. Now I squonk after every drag. Used to get two or three good pulls before I needed to. Small price to pay.

 

[SeaNap]

Very impressive! Doing some maths with your numbers the total resistance of your Mod+Batt+Coil = .683ohm. That means you only have .033ohm of resistance between your Batt and your mod. The aw 1600 is rated at .05ohm so there may be a slight fudge factor on your coil ohm. But over all you have essentially a 0.0 Voltage drop mod. I do not think you can squeeze any more performance out of the REO.

Comparatively, I just replaced the spring with a fuse (no firing pin mod yet), and my total v-drop across a .5ohm coil is .7V, and using the same maths from above I get a total resistance Mod+Batt+fuse+Coil = .602ohm. Batt = .05ohm Fuse = .0075ohm therefore my Mod = .0425ohm. So I have quite a bit of room for improvement, and by nature of me having a fuse I will not be able to replicate your results of having the bypass shim. I'm excited for Rob to release the sub-ohm kit.

 

[pdib]

Very nice! I've been using the .010" brass. It seems to be the thickness that compensates for the difference in springiness compared to the SS. I found the .08" to be a bit flimsy (didn't feel reliable on the springback) and the .012 is just too stiff. I also find that I get comparable v-drop from sheathing SS in .001" brass shim; but those stainless pins are of my making and have the better shape. I did find some improvement in v-drop with shape too.

this is the shape I borrowed from darkzero's tinkerings



and here's the flat buttontop battery version I'm using

 

[Ian444]

Good work guys.

There is IMO a factor that is left out in many voltage drop measurements, concerning the battery itself. Seanap has allowed for this with the internal resistance of the battery in his math, but not all cells are the same, even within the same batch of same type cell, or the same age (internal resistance increases with age), and manufacturer's specifications are often optimistic.

The measurement of battery voltage before firing and then subtracting the voltage across the coil while firing is generally unreliable as far as being useful for different owners to compare the internal voltage losses in their mods IMO.

A more useful measurement would be the battery voltage at the battery terminals while firing and then subtract the voltage across the coil while firing. This would eliminate the internal voltage drop of the battery, and give a real idea of the voltage drop within the Reo itself. But to allow an apples to apples voltage drop comparison for different Reo's owned by different people, the current being drawn by the coil would also need to be known, which could be worked out from the voltage across it and its resistance. This is because the voltage drop is proportional to resistance x current drawn, so a lower resistance coil will always cause a higher voltage drop from battery to coil in any given device.

Just food for thought.

oh by the way, hi guys, and gals, this is my first post in Reo's mods, I know little about Reo's but sure hope they are as good as all you good folks say, as one is on its way to me...flying fast I hope! Also throwing in something technical for a first post is not usually a good way to start, but I hope for the best.

 

[pdib]

Hi, Ian. Wad'ya get? Hammertone Silver Grand?


When I was doing some modding on my REOs to decrease V-drop, I wasn't overly concerned about being "accurate" the way you describe. It would certainly make sense to be more accurate when comparing different devices, or batteries. I, however, was using one device, one set of batteries. So, whatever readings I was getting under load at the atty posts only needed to be accurate as far as whether it was + or - in relation to the pre-tweaked readings. Meaning, if I got (for example) a V-drop of .15V with a 1Ω coil, I didn't care how much of that was battery internal resistance and etc. . . .. I just cared that it was .1V lower than before I did X,Y or Z.

 

[Ian444]

Dibs, you're a friggin mind reader! It's not here yet though, and I'm chimpin (oops chompin) at the bit for its arrival. Been reading too many monkey posts I think.

Yeah, the way you did it is fine, with known batteries and repeatable experiments on your own setup, A1. I was sort of worried that some peeps might see one person getting say 0.15V drop on their Reo, and the reader at home measures say 0.25V and goes ... whats wrong with my Reo. But the difference in batteries and coil resistance could easily account for many variations from one Reo owner to the next i.e. no apples to apples comparison. In your case on your own Reo, that is definitely apples to apples and a very good way to do it

 

[pdib]

Dibs, you're a friggin mind reader! It's not here yet though, and I'm chimpin (oops chompin) at the bit for its arrival. Been reading too many monkey posts I think.

Yeah, the way you did it is fine, with known batteries and repeatable experiments on your own setup, A1. I was sort of worried that some peeps might see one person getting say 0.15V drop on their Reo, and the reader at home measures say 0.25V and goes ... whats wrong with my Reo. But the difference in batteries and coil resistance could easily account for many variations from one Reo owner to the next i.e. no apples to apples comparison. In your case on your own Reo, that is definitely apples to apples and a very good way to do it

Well tell that Aussie mailman to rattle 'is dags!

Pics when you get it!

 

[Filthy-Beast]

congrats on the your soon to be Reo. I loved your first post. Welcome to Reoville.

 

[mackman]

Homie - what is that voltage meter and where can I sell a kidney... err I mean buy one.

Tankometer at IN STOCK: THE TANKOMETER (Ships From the USA) | VAPEHAPPY

 

[SeaNap]

Good work guys.
the internal resistance of the battery in his math, but not all cells are the same, even within the same batch of same type cell, or the same age (internal resistance increases with age), and manufacturer's specifications are often optimistic.

Absolutely! To clarify, I was using AW IMR 1600, and I did not measure the resistance I just went off of spec sheets. If you don't have some of these batts, you should consider them, they are the official batts of the REO and they work fantastic for sub ohm because they have a 15C discharge rating and are IMR so they are chemically safe.

Also, to be technical, my fuse resistance was not measured either I took the figure from the spec sheet which listed its "Cold Resistance so naturally there will be more resistance in the fuse the more amps (hotter) it gets. And I'm sure most of you know this but with the brass shim spring mod on the Grand there is NO protection against shorts, so fire the grand with the shim "disengaged" first incase there is a short after you screwed the cap to the RM2 on.

Welcome to Reoville!

 

[dchest02]

fire the grand with the shim "disengaged" first incase there is a short after you screwed the cap to the RM2 on.

This is something I need to do more often, but don't sorry to say.

 

[pdib]

I used to do that, before the auto fuse days. I fired without the shim engaged every new build, and every atty replacement or retighttening. Dropped a spring too! Glad I took precautions.

 

[BlaqueJezus]

I just got my first Reo last night(hello everyone ^_^) and I have a .58 voltage drop from a fresh battery over a 1ohm coil. where oh were do I find brass shim stock? The only place I could think of was a hobby shop that sold airplanes/cars. I gave them a call and the person told me he has brass, but isn't sure it is exactly what I'm looking for. And they close at the same time I get out of work here

 

[Krazirob]

do you have noalax on your bottom spring?