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Single 18650 Regulated Mod & Max Battery CDR

Discussion in 'Batteries and Chargers' started by lamensterms, Dec 27, 2019.

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  1. lamensterms

    lamensterms Senior Member ECF Veteran

    Dec 28, 2012

    Long time built-in battery mod user.. Trying to get educated on external battery mods.

    Finding it a bit hard to find definitive info with the sea of information online.

    Is exceeding the Max CDR possible on a regulated mod?

    I think I understand ohm's law and the relationship between voltage, power, current and resistance. But I don't have my head around how much it applies (or doesn't apply) to regulated mods.

    I've got the Falcon 80w kit and trying to figure out if I need to be wary of the atty resistance and the Max amp capacity of my battery.

    I'm using Samsung 25r with Max CDR of 20A.. Are these safe to use at any power with builds as low as 0.1 ohms?

    Thanks for any help
  2. AvaOrchid

    AvaOrchid Super Member

    Sep 19, 2019
    I did have a response here but I don't feel it was particularly helpful especially since someone else has answered in a much better way :)
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  3. Punk In Drublic

    Punk In Drublic Vaping Master ECF Veteran

    Aug 28, 2018
    Toronto, ON
    You can absolutely exceed the CDR rating with a regulated mod. But that would be due to your prescribed power, not coil resistance.

    A regulator circuit separates coil from battery, the battery never sees the coil resistance, it only sees what the circuit is requesting in terms of wattage. As battery voltage depletes due to use, current draw increases to meet you power demands. So we always use the low voltage cut off of the device to determine the max current draw. Device efficiency also draws a bit of power in addition to what you prescribed.

    The math behind this would be Battery Current = Wattage/Number of batteries/Low Voltage Cut Off (usually 3.2 volts)/Device Efficiency (90% is a good estimate). So if you were to use the Falcon at 75 watts that would be 75/1/3.2/0.9 = 26 amps

    To determine the max power a battery is able to handle while reducing risk, multiply it’s CDR rating by 3. So the Samsung 25R would be good for up to 60 watts.

    That said, depending on your wattage and coil resistance, you could exceed other limitations of the device. At 80 watts with a 0.1 ohm coil, the regulator circuit is required to deliver 2.83 volts and 29 amps. Could be wrong but I believe the circuit’s limitations is max 7.5 volts and 25 amps. So this coil resistance would exceed the current limitations of the circuit when attempting to operate at max 80 watts.
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  4. AvaOrchid

    AvaOrchid Super Member

    Sep 19, 2019
    I should have just tagged you the minute I read the ops post I thought of you!
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  5. lamensterms

    lamensterms Senior Member ECF Veteran

    Dec 28, 2012
    Thanks for the replies guys.

    Awesome answer Punk In Drublic, pretty sure I've got my head around my batteries limits now (also got some help from Mooch over at Reddit). Looks like I'll need to get some higher CDR batts to open up the power range for this mod.

    In that scenario you describe above.. Would you expect the mod's safety feature to intervene or would you expect battery damage? I don't really wanna test it out haha, but interested in that the consequences would be.

    Thanks again man.

    Ps: PID is one of the greatest albums of all time
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  6. Punk In Drublic

    Punk In Drublic Vaping Master ECF Veteran

    Aug 28, 2018
    Toronto, ON

    I’m going to assume by battery damage you mean causing it to vent or enter a thermal runaway? By exceeding the cells CDR limits, you pose that risk. The device does not know these limits of your battery and there is no safety feature implemented. Use a 10 amp battery at 60 watts, the device will attempt to draw 20 amps from that cell, and in doing so will pose a higher risk of the battery venting or entering a thermal event.

    Every device will have its limitations in terms of applied voltage and current which means its max power may only be achieve with a very small window of resistance. HorizonTech does not reveal these limitations, only it’s max power, but looking at DJLsb Vapes measurements, we can get a good idea of what its limitations are. The device seems to have a max output voltage of 7.5 volts, and a max current of ~26 amps hence why some resistances is unable to reach 80 watts. There maybe other variables involved, but a max 7.5 volts/25 amp output is pretty normal for a single cell device. The device may allow you to set 80 watts, but due to these voltage/current limitations it will deliver a lower output. We do not know what that output is, therefore we do not know what current draw on the battery is so we assume a unknown risk. So it is best just to conclude 80 watts will draw the calculated 28 amps.

    I brought this up to make you aware that you may not achieve 80 watts with that resistance coil. This is not just an issue with the Falcon, but all regulated devices.

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  7. lamensterms

    lamensterms Senior Member ECF Veteran

    Dec 28, 2012
    Awesome, thanks a lot for the info and taking the time to explain
  8. sonicbomb

    sonicbomb Vaping Master Verified Member ECF Veteran

    Feb 17, 2015
    1187 Hundertwasser
    Exceeding a battery's known CDR is a poor choice.

    As a rule of thumb and assuming a 90% efficiency and a 3.2 volt cutoff -

    10 amp CDR = 30 watts
    15 amp CDR = 45 watts
    20 amp CDR = 60 watts
    25 amp CDR = 75 watts
    30 amp CDR = 90 watts

    We are blessed to have a resident battery guru Mooch who provides reliable information on in house tested battery specs. As opposed to the works of fiction that some companies choose to print on their cells.

    Always consult his test data before buying or using a battery

    List of Battery Tests | E-Cigarette Forum

    There is also a wealth of other useful data within his blog

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  9. classwife

    classwife Admin Admin Verified Member ECF Veteran

    Supporting member
    Moved to Batteries and Chargers

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