Battery Voltages -- Surprise!

[Rocketman]

That is a very valid point Willy.

Wanna have some fun while you're probing your battery (under a load)? Earphones. Parallel a pair of cheapy 28 to 32 ohm earphones across your atty, or resistor, and listen to your e-cig "sing" to you (If it's chopped or PWM). Wear it when vaping out in public and hum while you vape. Sort of like whistle while you work, only different.

 

[MichelleDen]

Oh shute, sorry.. disregard my post..

 

[Scottbee]

I haven't put any real technical stuff into this thread in a while.

I was doing a "educational thing" thing the other day and picked up a new teaching toy. A popular vendor had also sent me some of the 900mAH eGo batteries to look at. So of course, I had to put the two together. Here is what I got:

There's some interesting stuff in here. Unlike the previous eGo and Riva batteries that I had tested, this unit runs at a fixed (84Hz) frequency. Completely uniform and repeatable pulse widths. I DO NOT know if this means they worked on the protection algorithm or not... I haven't tested it. You can also see by the peak voltage that this is a pretty healthy cell.... and unlike my other tests, this is actually running into a 1.6Ω LR atty, not the 2.5Ω dummy load.

There is some other REALLY interesting data in this screen capture.... but I'm not going to get into it right now. Those who know how to read a scope output and the attribute data might snap to it and furrow their brow. I'll leave my opinions on the data for a future post.

Enjoy!

 

[DC2]

There is some other REALLY interesting data in this screen capture.... but I'm not going to get into it right now. Those who know how to read a scope output and the attribute data might snap to it and furrow their brow. I'll leave my opinions on the data for a future post.

Thanks Scott, I'll be keeping my eye out for that future post!

 

[jimho]

I haven't put any real technical stuff into this thread in a while.

I was doing a "educational thing" thing the other day and picked up a new teaching toy. A popular vendor had also sent me some of the 900mAH eGo batteries to look at. So of course, I had to put the two together. Here is what I got:

There's some interesting stuff in here. Unlike the previous eGo and Riva batteries that I had tested, this unit runs at a fixed (84Hz) frequency. Completely uniform and repeatable pulse widths. I DO NOT know if this means they worked on the protection algorithm or not... I haven't tested it. You can also see by the peak voltage that this is a pretty healthy cell.... and unlike my other tests, this is actually running into a 1.6Ω LR atty, not the 2.5Ω dummy load.

There is some other REALLY interesting data in this screen capture.... but I'm not going to get into it right now. Those who know how to read a scope output and the attribute data might snap to it and furrow their brow. I'll leave my opinions on the data for a future post.

Enjoy!

I furrowed my brow for a bit- ... was wondering what was with the RMS...
Looks like the software doesn't know that it's looking at a square wave - thinks its a sine wave..... RMS should be 3.59 ...

Is that one of those hantek/protek usb scopes? Was thinking of getting one....

 

[Joseph112]

I furrowed my brow for a bit- ... was wondering what was with the RMS...
Looks like the software doesn't know that it's looking at a square wave - thinks its a sine wave..... RMS should be 3.59 ...

Is that one of those hantek/protek usb scopes? Was thinking of getting one....

RMS is not 3.59

It's a perfect square wave, the peak voltage is 3.92 then...
3.92 X 0.84 (duty cycle) = 3.2928 V

The real output voltage or RMS should be 3.29V and the software tell it as "mean" voltage.

There is a lot of great info in this thread but finally, anyone was able of find why Joye do this on 510/Ego batteries ?

 

[Scottbee]

I furrowed my brow for a bit- ... was wondering what was with the RMS...
Looks like the software doesn't know that it's looking at a square wave - thinks its a sine wave..... RMS should be 3.59 ...

Is that one of those hantek/protek usb scopes? Was thinking of getting one....

Wow... I lost track of my own thread! How embarassing!

Anyway.. yes, the RMS voltage of this particular waveform is what furrowed my brow. I haven't tried their older software version to see if this is something that was born out of the latest revision... or if they've had it wrong all along. I have sent the manufacturer an EMAIL regarding this, but haven't heard back from them yet. But... it is.. after-all.. the holiday season.

This specific USB unit is from "Parallax". Great little educational tool (assuming you're smart enough not to believe everything it tells you!)... but ti's only good for "small signal" stuff.. unless you want to build your own dividing probes.

 

[Scottbee]

RMS is not 3.59

It's a perfect square wave, the peak voltage is 3.92 then...
3.92 X 0.84 (duty cycle) = 3.2928 V

Ummm... no, I don't believe that is correct.

 

[BradSmith]

If I plug my PT into my USB while using VOIP my friends get to hear my PV hum. Does that count?

 

[jimho]

RMS is not 3.59

It's a perfect square wave, the peak voltage is 3.92 then...
3.92 X 0.84 (duty cycle) = 3.2928 V

The real output voltage or RMS should be 3.29V and the software tell it as "mean" voltage.

There is a lot of great info in this thread but finally, anyone was able of find why Joye do this on 510/Ego batteries ?

3.29 is the average voltage diplayed a mean- that is correct... However, that is not the same as RMS-
For a square wave, Vrms= Vpk*sqrt(f*T) = 3.92 * sqrt(84.03*.0101)=3.6


If you go back to the OP, Joye employed a mosfet working as a switching regulator giving you the voltage off the ego. The interesting observation/prediction was that it opened to door to PWM as an effective means of controlling output- it's been a bit overhyped recently though...

Wow... I lost track of my own thread! How embarassing!

Anyway.. yes, the RMS voltage of this particular waveform is what furrowed my brow. I haven't tried their older software version to see if this is something that was born out of the latest revision... or if they've had it wrong all along. I have sent the manufacturer an EMAIL regarding this, but haven't heard back from them yet. But... it is.. after-all.. the holiday season.

This specific USB unit is from "Parallax". Great little educational tool (assuming you're smart enough not to believe everything it tells you!)... but ti's only good for "small signal" stuff.. unless you want to build your own dividing probes.

That looks like the same device I was eyeing- they seem to be manufacturing under several different labels. ..... from what I gather it's got a limited capture buffer... but it's good enough for what I need, cost effective and compact enough too.... definitely let us know how they explain the RMS-

If I plug my PT into my USB while using VOIP my friends get to hear my PV hum. Does that count?

Only if your usb port isn't current limited ;-)

 

[Scottbee]

OK... this is getting kinda interesting for me again. I recently got two new devices (thank you "secret-Santa"!) for review.... a 900mAH eGo and a USB passthru eGo. Both of them intrigue me since it looks like Joye has changed their control algorithm. Previous units had a non-repeatable waveform (as you could see on my old Tek trace) and the new ones have "repeatable" waveforms. Much, much easier to analyze.

And then I saw something else as I played around with various load resistances. I don't have enough data points as of yet to make a definitive claim.... but if my supposition is correct.... ;-)

Anyway, since we now know that I can't trust the RMS calculations from the Parallax USB scope, I went back and threw my USB eGo onto another lab scope that we have laying around. Below you will find two captures:

The image above is the USB eGo feeding a 2.5Ω dummy load.

And now this image is the same USB eGo feeding a 1.5Ω load.

The astute observer will notice some interesting changes between these two traces when it comes to peak voltage, duty cycle, and delivered RMS voltage.

Like I said.. I don't want to come to an unfounded absolute conclusion here.... but I'm certainly going to try and come up with a few more data points!

 

[Scottbee]

I took a couple of more data points late in the work day..... I'll be staring at them and will probably put them up later tomorrow.

I have a very funny feeling that some clever Chinese Engineer has been following this thread for the last 11 months or so, saying to himself: "Stooopid Round-eye....". ;-)

 

[jimho]

I took a couple of more data points late in the work day..... I'll be staring at them and will probably put them up later tomorrow.

I have a very funny feeling that some clever Chinese Engineer has been following this thread for the last 11 months or so, saying to himself: "Stooopid Round-eye....". ;-)

I have a feeling you are right- although I'm not sure they will have been laughing since Feb.... the traces and RMS is quite different here....looking at the two screens it sure looks like they have it locked in for ~3.6V RMS and they are indeed using PWM to keep it there. I hope your additional data confirms that.

These are passthrough or passthrough/battery (650mAh)? not to be condescending but make sure what you are seeing is the passthrough and not the supply clipping off of the usb port- I recently spent alot of time trying to explain to someone why his brand new USB hub with a VV passthrough was giving him a cooler vape than his pro-vari @5V - he didn't realize the specs limited each port to 500mA and he didn't seem to want to accept that there was no way of knowing exactly what the hub would do if you exceeded the spec.

 

[ManicMaurice]

I know I'm new here, I want to cast a vote for this thread to be stickied.

Also, the info in here should probably be repeated in the ECigarette Technical Issues > Battery Issues sub-forum.
Maybe start a new thread in that sub forum that could cover all battery, atty, carto specs? I know I've been searching for something like that and I have yet to find it. It would be an asset to the community. Just my 2 cents.

 

[Scottbee]

These are passthrough or passthrough/battery (650mAh)?

It's the eGo passthrough/battery (650mAH). Time permitting I'll run some more traces today with it "off of life support" so I can watch the battery voltage sag, and observe the PW.

 

[Scottbee]

That looks like the same device I was eyeing- they seem to be manufacturing under several different labels. ..... from what I gather it's got a limited capture buffer... but it's good enough for what I need, cost effective and compact enough too.... definitely let us know how they explain the RMS-

I did get an EMAIL from one of the techs at Parallax. He wanted to know what I thought the correct equation was for calculating RMS voltage from that waveform.....

FWIW, I'm happy that he replied and is entering into a dialogue. Far too many don't these days.

 

[br5495]

It's the eGo passthrough/battery (650mAH). Time permitting I'll run some more traces today with it "off of life support" so I can watch the battery voltage sag, and observe the PW.

Scott, have you tested your eGo passthrough/battery using the same rig as your original post? If so, what are the differences? I've been using one of these batteries for a while now and can't tell that the voltage is any different than the other 510 type batteries.

 

[jimho]

I did get an EMAIL from one of the techs at Parallax. He wanted to know what I thought the correct equation was for calculating RMS voltage from that waveform.....

FWIW, I'm happy that he replied and is entering into a dialogue. Far too many don't these days.

Just ran into this - mathematical derivation of RMS for a square wave:
MasteringElectronicsDesign.com : How to Derive the RMS Value of Pulse and Square Waveforms
you might want to share it with them....

 

[Scottbee]

Just ran into this - mathematical derivation of RMS for a square wave:
MasteringElectronicsDesign.com : How to Derive the RMS Value of Pulse and Square Waveforms
you might want to share it with them....

Thanks.... that's good information. I had already sent them the specific (simplified) equation for that specific waveform.

I ran a bunch of tests yesterday and got some interesting results as I "sagged" the cell in an eGo 900mAH. Not exactly what I was hoping for.. but still interesting. I have about 9 traces that I can put up, but I think I will re-run them with a different timebase so I can get better granularity on the measurements. Time permitting..... <sigh>

 

[Scottbee]

Scott, have you tested your eGo passthrough/battery using the same rig as your original post? If so, what are the differences? I've been using one of these batteries for a while now and can't tell that the voltage is any different than the other 510 type batteries.

BR... good to hear from ya!

Yes, I did run the eGo900mAH and the USB eGo on that rig with just the DMM on the DC scale (giving the DC mean voltage). On a freshly charged 900mAH and USB units (which have the "newer" waveform) I did see a slight increase in the mean DC voltage.. but not enough to write home about. Your "taste test" doesn't surprise me at all.