Question About Battery Safety...

[aldenf]

Hi Gang,

Hope everyone's evening is swell!

I've been using an rda with a single coil, 1.0 ohm (2mm, twisted 28g) build on my VTR at 10-15w. Love the flavor! Even at 10 watts it blows away every clearo I've ever tried. Not looking to chase clouds. But considering picking up an inexpensive mech clone as dripping on the VTR is not ideal.

I have two Panny NCR18650PF hybrid batts that I use with the VTR. As long as I stay .5 ohm and above, shouldn't the 10 amp Pannys drive the dripper safely? I'm actually thinking of a 1.0 single or .8 dual coil build which should keep me right around what I've been loving. .5 ohm with a freshly charged batt (4.2v) is still only 8.4 amp. The .8 build would only pull 5.25 amp.

I understand the safety factor and am well aware of some idiots out there doing really stupid things. But am I missing something beyond stupidity?

Thanks!

~Alden

 

[HughDaHand]

Looks like you did your research. With that battery your going to get the best results above 0.8ohm as much lower and you will get alot of voltage sag. Its not a ideal mech battery but should be safe in the range you plan to use it. I use its older brother the NCR18650PD in my nemesis/kayfun combo at 1.1ohms quite often.

 

[aldenf]

Thanks Hugh!

Ahhhh.... Voltage drop. Something I didn't include in the equation. Drop changes not only with batt type but also age. I'll just plan on picking up a 20+ amp batt for the mech.

An rta is my next purchase. Still doing my research...

Have a great night!

 

[Baditude]

1.0 ohm = 4.2 amp draw
0.9 ohm = 4.6 amp draw
0.8 ohm = 5.2 amp draw
0.7 ohms = 6 amp draw
0.6 ohms = 7 amp draw
0.5 ohms = 8.4 amp draw (safe margin of safety)
0.4 ohms = 10.5 amp draw (over spec)
0.3 ohms = 14.0 amp draw (over spec)
0.2 ohms = 21.0 amp draw (over spec)
0.1 ohms = 42.0 amp draw (over spec)

Your battery has a 10 amp continuous discharge limit. You could build 0.6 ohm coils and still have a 0.1 ohm safety margin. This is assuming that your ohm reader is a reasonably accurate meter.

 

[aldenf]

Thanks Baditude!

I read your battery blog entry long ago. I thought my math was working out correctly. All the "you need a 30 amp VTC5 to sub-ohm" must really translate to if you "super sub-ohm". Last time I checked, .6 & .8 were sub-ohm.

I always triple check my RDA builds on my ohmmeter, VTR and digital multimeter. What does it take, 90 seconds to ensure I didn't mess up my build?

Anywho. Thanks again!

 

[Stosh]

If you like the RDA at about 10 watts on your VTR, then on a mech with the same RDA a 1.7-1.8Ω build will give you about the same 10 watts on a fully charged battery. On a mech the voltage is going to drop as you use it so a 1.4-1.5Ω build would be a bit hot to start (pulse the fire button till the voltage drops) and then drop the voltage to give about 10 watts.

With a mech for your RDA, adjusting wattage has to be dome with the resistance build.... If you keep the same wattage as you've been using the batteries won't be strained.