Results 1 to 8 of 8
Like Tree4Likes
  • 1 Post By fabricator4
  • 1 Post By fabricator4
  • 2 Post By LNB

Thread: A few question about Tesla Invader 3

  1. #1
    AVF Newbie | Be nice to me
    Join Date
    Oct 2016
    Location
    Canberra
    Posts
    15

    A few question about Tesla Invader 3

    Hey all!

    I've ordered in a Tesla Invader 3 (my first dual battery mod) and a pair of Samsung 25rs, there's just one thing about the mod that's confusing me, and I'm having a hard time processing my confusion into a simple post, but I'll try my best.

    I understand how a series mech mod works, but don't understand how the potentiometer effects the current being drawn from the batteries when the volts are regulated back.

    If I set the invader 3 to 4.2 volts, does this mean each battery is providing 2.1 volts?
    What happens to the amp limit of the batteries when the volts are set back?
    How do I calculate coil builds for the invader 3 on steam engine? (how is does it differ to a build for a single battery mod)

    Basically I want to know if lowering the volts on the invader 3 will give a higher amp limit, and if so by how much.
    Until I know for sure I'll stay under 15 amps :P


    Sorry for my confused words, and thanks in advance to anyone who can help me understand what I'm doing .

    Cheers,
    Kieran.

  2. #2
    AVF Regular
    Join Date
    Apr 2013
    Location
    Toowoomba (West)
    Posts
    7,897
    Quote Originally Posted by Kieran View Post
    Hey all!

    I've ordered in a Tesla Invader 3 (my first dual battery mod) and a pair of Samsung 25rs, there's just one thing about the mod that's confusing me, and I'm having a hard time processing my confusion into a simple post, but I'll try my best.

    I understand how a series mech mod works, but don't understand how the potentiometer effects the current being drawn from the batteries when the volts are regulated back.

    If I set the invader 3 to 4.2 volts, does this mean each battery is providing 2.1 volts?
    What happens to the amp limit of the batteries when the volts are set back?
    How do I calculate coil builds for the invader 3 on steam engine? (how is does it differ to a build for a single battery mod)

    Basically I want to know if lowering the volts on the invader 3 will give a higher amp limit, and if so by how much.
    Until I know for sure I'll stay under 15 amps :P


    Sorry for my confused words, and thanks in advance to anyone who can help me understand what I'm doing .

    Cheers,
    Kieran.
    None of the above, really.

    The batteries will always supply terminal voltage - 4.2 volts per cell when fully charged and 3.3 volts when the mod considers them to be flat. Series cells therefore give you from 8.4V full to 6.6V flat.

    The buck circuit changes the output voltage in the range 3.6 volts to 6.6 volts, which effectively allows it to deliver up to it's 45 amps output limit.

    What you need is to understand that the output current and voltage is not the same as the input current and voltage because the buck circuit is taking the power input and regulating the output depending on the pot setting and the coil resistance. The only thing that will stay the same between what the battery sees and what the coil sees is the power. Power in equals power out, less a little bit for losses in the circuit, call it 5% on that device.

    If you base your calculations on the battery nominal voltage, which is 7.4 volts you should be able work out what the batteries are doing most of the time.

    OK, working this again because I think I must have made a mess of it. Guess my brain had shut down about 2AM...

    0.15 ohm coil with 6 volts on it is 40 AMPS, not watts. 240 watts is about right.

    Now to see what the battery is doing:

    240 watt divided by the battery nominal voltage which we're taking as 7.5 volts, comes to 32 amps, so outside of the safety range of of the Samsung 25R which will be much happier not going over 20 amps.
    Last edited by fabricator4; 28-02-17 at 08:10 PM. Reason: Fixed the figures to reflect 5% losses
    Kieran likes this.
    Chris: Tobacco free since 17:00 15th March 2013.

  3. #3
    AVF Newbie | Be nice to me
    Join Date
    Oct 2016
    Location
    Canberra
    Posts
    15
    Quote Originally Posted by fabricator4 View Post
    None of the above, really.

    The batteries will always supply terminal voltage - 4.2 volts per cell when fully charged and 3.3 volts when the mod considers them to be flat. Series cells therefore give you from 8.4V full to 6.6V flat.

    The buck circuit changes the output voltage in the range 3.6 volts to 6.6 volts, which effectively allows it to deliver up to it's 45 amps output limit.

    What you need is to understand that the output current and voltage is not the same as the input current and voltage because the buck circuit is taking the power input and regulating the output depending on the pot setting and the coil resistance. The only thing that will stay the same between what the battery sees and what the coil sees is the power. Power in equals power out, less a little bit for losses in the circuit, call it 5% on that device.

    If you base your calculations on the battery nominal voltage, which is 7.4 volts you should be able work out what the batteries are doing most of the time.

    Example:

    0.15 ohm coil, output set to 6 volts.
    Power is 6/0.15 which is 40 watts

    The battery is supplying 40 watts plus a bit more, call it 42 watts due to losses.
    42 watts over the nominal voltage of 7.4 volts is just under 5.8 amps the batteries will be supplying.

    So you see the invader is able to run at much higher wattages, but to do that you have to build crazy low ohm coils.

    If you know what watts you want to run your coil at, you work the above steps backwards to find out what resistance and voltage setting you need to aim for, keeping an eye on the current drain on the battery side of course.

    The only other safety issue I'd mention is that I'm not sure the Invader monitors each cell individually. I think it just monitors the total battery voltage. You might want to keep an eye on the cell voltages when it's getting close to flat. Might be easier just to charge the batteries before they get that low. I think that is the thinking behind picking the 6.6V (series total) endpoint point for the cells - to give the cells a small safety margin if they are not balanced.
    Thanks for clearing that up for me, I really was taking stabs in the dark.

    I'm having a hard time understanding the example you gave me though, there must be something I'm still not taking into consideration.
    I plugged it into steam engine and 6 volts through 0.15 ohms came out to be 40 amps and 240 watts?
    Should I be using the formula you showed instead of steam engine?
    Maybe I'm still stuck in single battery land, but I'm still a little confused.

    I won't be using this device until I can understand it properly, I'm starting to think I don't have the brain power to handle a second battery lol.
    I appreciate your help though, thanks again

  4. #4
    AVF Regular
    Join Date
    Apr 2013
    Location
    Toowoomba (West)
    Posts
    7,897
    Quote Originally Posted by Kieran View Post
    Thanks for clearing that up for me, I really was taking stabs in the dark.

    I'm having a hard time understanding the example you gave me though, there must be something I'm still not taking into consideration.
    I plugged it into steam engine and 6 volts through 0.15 ohms came out to be 40 amps and 240 watts?
    Should I be using the formula you showed instead of steam engine?
    Maybe I'm still stuck in single battery land, but I'm still a little confused.

    I won't be using this device until I can understand it properly, I'm starting to think I don't have the brain power to handle a second battery lol.
    I appreciate your help though, thanks again
    Yep, I used a stupid ohm wheel for the formulae instead of working it out, because it was late at night. I didn't check anything. LOL

    It sounds wrong. bear with me while I go over it...

    OK, I've changed it, and well done for seeing that it was wrong Keiran. My advice was so wrong it was unsafe.

    Do you want to have a swing at working out what the safe voltage would be to run that coil? Hint: You have to work it from the battery first, find out what a safe wattage is for the series battery nominal voltage, then work out what voltage on that coil will give you that power or less.
    Last edited by fabricator4; 28-02-17 at 08:12 PM.
    Kieran likes this.
    Chris: Tobacco free since 17:00 15th March 2013.

  5. #5
    LNB
    LNB is offline
    AVF Regular
    Join Date
    May 2014
    Location
    Sydney
    Posts
    4,208
    I usally run a .18ohm build in a mini buddha rda ontop of the tesla at the max 6.5v...gives around 230odd watts and drawing 36odd amps from the batteries...vapes pretty good but not as good as a mech...the tesla is a tough mod, mines been dropped of window sills, lived in my tool belt with screws,nails,etc and fallen out of said tool belt quite a few times...its taken a beating but still goes and has yet to fail...
    fabricator4 and Kieran like this.

  6. #6
    AVF Newbie | Be nice to me
    Join Date
    Oct 2016
    Location
    Canberra
    Posts
    15
    Quote Originally Posted by fabricator4 View Post
    Yep, I used a stupid ohm wheel for the formulae instead of working it out, because it was late at night. I didn't check anything. LOL

    It sounds wrong. bear with me while I go over it...

    OK, I've changed it, and well done for seeing that it was wrong Keiran. My advice was so wrong it was unsafe.

    Do you want to have a swing at working out what the safe voltage would be to run that coil? Hint: You have to work it from the battery first, find out what a safe wattage is for the series battery nominal voltage, then work out what voltage on that coil will give you that power or less.
    Ahh, that makes more sense now :P

    I think I can figure this out...

    So to find out the max safe wattage, I multiply the amp rating of 2 25rs in series (20 amps) by the nominal voltage of 2 25rs in series (7.4 volts) which would be 148 watts... (I think?)

    Then to find out how many volts I would need to run through a 0.15 ohm coil to be at 148 watts or under, I need to... use steam engine? lol.

    Steam engine says 4.7 volts would be 147.27 watts on a 0.15 ohm coil...

    Does this seem right?

  7. #7
    AVF Regular
    Join Date
    Apr 2013
    Location
    Toowoomba (West)
    Posts
    7,897
    Quote Originally Posted by Kieran View Post
    Ahh, that makes more sense now :P

    I think I can figure this out...

    So to find out the max safe wattage, I multiply the amp rating of 2 25rs in series (20 amps) by the nominal voltage of 2 25rs in series (7.4 volts) which would be 148 watts... (I think?)

    Then to find out how many volts I would need to run through a 0.15 ohm coil to be at 148 watts or under, I need to... use steam engine? lol.

    Steam engine says 4.7 volts would be 147.27 watts on a 0.15 ohm coil...

    Does this seem right?
    Yep spot on, you've got it!

    These things are adjust to taste anyway, but now you know what your safe limit is if you're using 25Rs.
    Chris: Tobacco free since 17:00 15th March 2013.

  8. #8
    AVF Newbie | Be nice to me
    Join Date
    Nov 2017
    Posts
    1
    Hi...i am a new user here. As per my knowledge series cells therefore give you from 8.4V full to 6.6V flat.The buck circuit changes the output voltage in the range 3.6 volts to 6.6 volts, which effectively allows it to deliver up to it's 45 amps output limit.

    pcb assembly
    Last edited by JardCrocker; 13-01-18 at 08:51 AM.

 

 

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBulletin® Version 4.2.4
Copyright © 2018 vBulletin Solutions, Inc. All rights reserved.
Search Engine Friendly URLs by vBSEO 3.6.0
All times are GMT +11. The time now is 12:59 AM.