Samsung 25r or vtc5 in box mod.

[Mrez]

So I just ordered a pair of vtc5 and 25rs. I have had the 25rs before and was always happy with their performance in the .25 - .4 range. My question is my builds are starting to get more intricate and I don't really want to push <.25 on a mech mod and 25r. I recently ordered a Snowwolf 200 watt which places batteries in series from what I understand. So would it be more beneficial to use the Sammy's in the Snowwolf with the extra levels of protection, and the vtc5 for mechanical use? Or vice versa? If the Sammy's are used in the box..what are my limitations in builds and wattage?

 

[Mooch]

I'm only about halfway through my testing of new VTC5's but at 20A they are running several degrees hotter than 25R's. The VTC5's also have a slightly lower voltage than the 25R's at 20A. As of now, the 25R seems to be a slightly better cell overall, for any use.

 

[Mrez]

I'm only about halfway through my testing of new VTC5's but at 20A they are running several degrees hotter than 25R's. The VTC5's also have a slightly lower voltage than the 25R's at 20A. As of now, the 25R seems to be a slightly better cell overall, for any use.

Thats not exactly encouraging for .2 ohm builds I'd been considering. Perhaps i'll be better off keeping them in the Snowwolf and keeping the 25rs at a .25 ohm build. If im understanding this correctly, then at equivalent low resistance, the Vtc5 will run hotter and have a great risk of going into thermal runaway?

 

[Mooch]

Thats not exactly encouraging for .2 ohm builds I'd been considering. Perhaps i'll be better off keeping them in the Snowwolf and keeping the 25rs at a .25 ohm build. If im understanding this correctly, then at equivalent low resistance, the Vtc5 will run hotter and have a great risk of going into thermal runaway?

I haven't finished the testing yet but the VTC5 was running at 82°C at 20A versus about 75°C-78°C for the 25R....a small difference. While the VCT5 does seem to run a bit hotter, it's not by a lot, and both temperatures are a long way from that needed to vent and/or go into thermal runaway. Both the HG2 and 30Q run at the same temperature as the VTC5.

The VTC5 should be as safe as any other good 20A cell, to use at 20A. But with the slightly higher voltage of the 25R (at 20A) it all added up to the 25R being a slightly better choice between the two in my opinion. It's not because the VTC5 is a poor performer or dangerous. The VTC5 is still a darn good 20A cell. It's just that, with all other things being equal, I would choose the cell that had a bit more voltage and ran a bit cooler.

If you wanted a bit more headroom, use a VTC4. Its 30A rating should result in a lower cell temperature than the 25R or VTC5. Not by a huge amount, but it would be a better choice if you plan to take your Snowwolf to high wattages.

For your mech, your 0.25 ohm builds will run the 25R and VTC5 hard, but within their ratings. Either cell can be used.

 

[Mrez]

I haven't finished the testing yet but the VTC5 was running at 82°C at 20A versus about 75°C-78°C for the 25R....a small difference. While the VCT5 does seem to run a bit hotter, it's not by a lot, and both temperatures are a long way from that needed to vent and/or go into thermal runaway. Both the HG2 and 30Q run at the same temperature as the VTC5.

The VTC5 should be as safe as any other good 20A cell, to use at 20A. But with the slightly higher voltage of the 25R (at 20A) it all added up to the 25R being a slightly better choice between the two in my opinion. It's not because the VTC5 is a poor performer or dangerous. The VTC5 is still a darn good 20A cell. It's just that, with all other things being equal, I would choose the cell that had a bit more voltage and ran a bit cooler.

If you wanted a bit more headroom, use a VTC4. Its 30A rating should result in a lower cell temperature than the 25R or VTC5. Not by a huge amount, but it would be a better choice if you plan to take your Snowwolf to high wattages.

For your mech, your 0.25 ohm builds will run the 25R and VTC5 hard, but within their ratings. Either cell can be used.

I'll keep that in mind when I get them in. One follow up question, and maybe I'm missing something. I thought the current generation of Sony VTC5's were rated for 30 amps continuous? Is testing finding that not to be the case?

 

[Mooch]

I'll keep that in mind when I get them in. One follow up question, and maybe I'm missing something. I thought the current generation of Sony VTC5's were rated for 30 amps continuous? Is testing finding that not to be the case?

The August 2013 Sony tech info document only shows discharges up to 20A, with a temperature about the same as what I got...hot. I think there was earlier Sony documentation that showed a 30A discharge but it was removed. If there was a 30A test in it, I can see why it was removed because the temperature would have been way too high for safe operation.

To my knowledge, the VTC5 has never been a 30A cell. It has been tested at 30A, but either the temperatures were crazy high or temperatures were never recorded. And any graphs I've seen show the VTC5 (along with any other cell) having very, very short running times down to the minimum voltages we vape to, around 3.2V-3.5V.

The VTC5 is just a 20A cell. A good one, but just 20A.

 

[Mooch]

With your Snowwolf, at lower battery voltages, you'll be pulling 25A to over 30A from the batteries. It's pulsed current, so it won't heat them up as much as my tests do, but you should be aware of how hard 150W and higher is on a battery.

 

[Mrez]

With your Snowwolf, at lower battery voltages, you'll be pulling 25A to over 30A from the batteries. It's pulsed current, so it won't heat them up as much as my tests do, but you should be aware of how hard 150W and higher is on a battery.

But staying at 100 watts or below should be in a safe zone for 20amp batteries?

 

[Mooch]

But staying at 100 watts or below should be in a safe zone for 20amp batteries?

Absolutely.

 

[Mrez]

Absolutely.

Great..hopefully that works out well for the builds I have in mind.

 

[Mrez]

Absolutely.

Looks like, as per usual when learning something new for me, I was unduly concerned. My Snowwolf arrived today, so after I got the Vtc5s charged up, and loaded up some new builds in the .25 - .3 range (clapton's of various sizes with kanthal cores instead of nichrome), i tried out a few and I can't push them past 70-75 watts without scorching my mouth. So, assuming i'm using the steam calc correctly, .25 ohms, at 75 watts, is pulling 17.32 amps from the battery, at 4.33 volts. That should be within the upper limits of the safe range for me, if I've followed the discussions correctly. Also within safe ranges for mechanical use (though fire up time is a bit slow). The only thing I was a little confused about on first use is the Voltage on the mod is reading lower then I expected (in the 1.3ish range or something like that). Not sure about that one. In any case, I pulled the batteries and shut it off for the night...all nic'ed out after a few good pulls. Thanks for the help Mooch, and the info.

 

[Mooch]

No problem, glad things are (mostly) working out!

 

[Mrez]

Follow up, the VTC5's are preforming well, getting a good solid day out of them in my regular builds. They seem to take a bit longer to charge then the 25r's presumably because of the little bit of extra mah. Thinking about picking up a pair of those 3000 mah LG's to run in the Snowwolf.