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Why is voltage drop unsafe?

ghh3rd

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How do you know when it's time to recharge or swap out your battery on a mechanical mod?

I was researching possible safety issues with a mechanical mod, and am confused. I read about watching that battery voltage doesn't drop too low... or it gets unsafe. But:

If I have a battery at 4.0 volts with a .5 ohm coil, I should be drawing 8.0 amps.
If I have a battery at 3.0 volts with a .5 ohm coil, I should be drawing 6.0 amps.

I thought that the only reason not to draw down the volts too low was to keep from ruining the battery. Why is voltage drop on a mech mod unsafe?

Thanks,

Randy
 

M5amhan

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first off measuring ohms law based on the current battery voltage is unsafe, you should calculate at a full charge 4.2v but other than that voltage drop isnt unsafe. you could ruin a battery by discharging it completely though so try to keep it above 3.2v or 3v at a minimum

knowing when to recharge you could go from taste after some experience with it. to be more sure use an inline volt meter or an ohm meter with a voltage connection
 

Pauly Walnuts

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first off measuring ohms law based on the current battery voltage is unsafe, you should calculate at a full charge 4.2v but other than that voltage drop isnt unsafe. you could ruin a battery by discharging it completely though so try to keep it above 3.2v or 3v at a minimum

knowing when to recharge you could go from taste after some experience with it. to be more sure use an inline volt meter or an ohm meter with a voltage connection
With a mech, Im not sure how anyone gets below 3.7 without noticing a HUGE drop in performance.
 

nightshard

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The battery cell gets damaged when dropping below a certain point (around 2.5v).
Regulated devices prevent you from doing so, mechs don't
 

UncleRJ

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Also sometimes when talking about voltage drop in mechs it has to do with the construction of the device.

The better ones have little voltage drop due to construction and the materials used like copper, silver and even gold.

I got the ball rolling on this so now I just need a mech wizard to drop by and explain what I am trying to say correctly!
 

State O' Flux

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Why is voltage drop unsafe?
I'll keep this short, not overly technical... and just hit the most relatable points. First, "It takes a village" of false assumptions, low quality products and even poor maintenance to cause a runaway battery overheating condition.

High voltage drop values not only reduce the amount of wattage available for the atomizer... in turn reducing performance, but can create Joule (resistive) heating, typically concentrated in a poorly designed and executed firing button.
A 510 connection, particularly an uninsulated hybrid type, can also produce the right conditions for Joule heating, but far less likely.

Battery quality of construction, along with overly optimistic, inaccurate manufacturer ratings can be contributors to failure as well.

You may need a few more "conditions" to produce an actual battery "failure". Anything from a scary but non life threatening mild venting (the reason for mod pressure vents), to runaway overheating and explosion, are a few definitions of failure.

The aforementioned suspect quality mech mod is a prime and frequent contributor, but not an absolute necessity.

Deep sub-ohm resistance, and/or sufficiently low resistance to apply a load near or above the battery actual MCCD. People think they're safe if the resistance is a mild 0.5Ω or so... but if an 18350 battery is used, you can still get resistive heating, and/or exceed the batteries MCCD... if the right conditions are met.

Speaking of battery ratings... these high (35, 38 & 40A) 18650 ratings are not in fact MCCD ratings, but rather pulse or "momentary" ratings. Granted, they are relatively modest pulse ratings within a time limit likely exceeding even a deep draw vapists usual application... but they are still a lie, and not the Maximum Continuous Current Discharge. The same applies to the the smaller popular vaping batteries, where the listed amperage is above the norm.

An inaccurate read on the net atomizer resistance, where the actual resistance is lower than the measured... a poor quality Ohm meter will be the main source of inaccuracy.
For example, an assumed 0.2Ω, where the true value is less... the battery discharge can rise dramatically, not only beyond the MCCD, but beyond any reasonable pulse discharge, time to excess. Remember that battery discharge doubles as resistance is halved... so at 0.2Ω, an error of 0.1Ω means that discharge can go from a safe 21 amps to a not so safe 42 amps, in the press of a button.

If there's enough resistance in the mod when fired, independently or in combination with an extreme discharge... the localized Joule heating can also raise temperatures in the battery, causing it to fail.
 
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UncleRJ

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Thank you for explaining far better than I could!
 

State O' Flux

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Thank you for explaining far better than I could!
Ah well... thanks Uncle. Some will get a useful bit from it... and some will think me an blathering idiot.

I'm well use to it going either way. o_O

Off to workies.........
 

UncleRJ

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Ah well... thanks Uncle. Some will get a useful bit from it... and some will think me an blathering idiot.

I'm well use to it going either way. o_O

Off to workies.........


Credit where credit is due!
 

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