Best 18650 battery at 0.2 ohm or 16-21A pulsed loads

One question we get particularly from the e-cig crowd is which battery will show less voltage sag and perform better under pulses at a specific ohm level, for example in a mechanical mod device.  The results are very applicable to someone using a regulated (constant watts) device as well.  So we decided to do a comparison test of the voltage drop under this significant constant resistance load, comparing the Samsung 25R vs Sony VTC4 vs Sony VTC5.

The Contestants

The batteries under test are the Samsung 25R  (full part number INR18650-25R), the Sony VTC4 (also known as VCT4, full part number US18650VTC4), and the Sony VTC5 (also known as VCT5. full part number US18650VTC5).  The test will be at the top end of the rating of the Samsung and the VTC5 (they are rated 20A continuous), while being mid-way through the rating for the Sony VTC4 (pretty much the only battery that's truly rated for 30A continuous).  The Samsung 25R is the new green Samsung, the 25R5.  All batteries we tested at least one new one as well as a couple that had been lightly used and stored for a bit.  After verifying there wasn't a huge difference, the data for the new ones will be shown below.

So how do the 25R, VCT4, and VCT5 perform with 0.2 ohms?

The Test:  3 second load pulses of 0.2 ohms

This test simulates a mechanical mod or other constant resistance load of 0.2 ohms with one lithium ion cell (3.0-4.2V).  The device is fired for 3 seconds, then turned off for 8 seconds, then repeated.  This is done from full charge (4.2V) until the voltage goes to 3.2V.  This will mean current levels will vary from 16-21A and power will vary from 51W-88W, per battery.  Both power and current decrease as the voltage drops as the test goes on since it's constant resistance.

Here's an overview chart of how the test turned out:

As you can see from the overview, the 25R lasts the longest, followed by the VTC5, followed by the VTC4.  So let's look at the first part of the test in more detail.

As you can see in the very beginning the VTC4 and 25R are right on top of each other.  The VTC5 starts at a very slight disadvantage being at 4.18V instead of 4.2V like the others but still even with that considered it sags further than the others and drops in voltage quicker than the 25R.  After a few pulses though the VTC4 starts to show its lower mAh and by 8-10 pulses in you start to see a bit of a difference at max voltage with the 25R winning.  However it shows less sag in this region than the 25R so under load they're about the same.  The VTC5 continues to be just slightly worse than the others both under load and off load.  

Around the 20th pulse or so a clear difference starts to emerge.  Let's look at one pulse close up, 200 seconds in.  You can see the 25R has the highest voltage, followed by the VTC5, followed by the VTC4.  

Here's a table of the voltage sag under load and a calculation of the internal resistance at this point.  As you can see from the table, the voltage sag from the different batteries are all pretty much identical especially when converted to internal resistance.  The only reason the 25R and VTC5 show better voltage numbers is because they still have more charge left in the battery.  At this point it's worth considering that the slightly lower performance of the VTC5 is simply because of the lower charge it started with.  

Now let's look at the middle part of the test.

The same trend is continuing here.  Let's zoom in on 700 seconds similar to how we did before.

And similarly we'll build a table:

Again we show amazing performance by all 3 batteries.  Internal resistances all significantly below 20 mOhms is great!

And here's the end of the plot:

Keeping with the trend, the VTC4 hits 3.2V first and shuts off, followed by the VTC5 11 pulses later, followed by the 25R another 9 pulses after that.

So how many total pulses did we get?  Keep in mind the VTC5 had slightly lower charge so take its results with a grain of salt, I would guess it should have had 1 or 2 more pulses.

So what about temperature, did any of the batteries get hot?  No, temperature wasn't even measured because they all stayed room temperature plus or minus a couple degrees.  Impressive.

Conclusions

All three batteries are awesome.  The VTC4 has a little bit better performance in terms of pure voltage sag but it's pretty small difference.  The 25R clearly wins in terms of being able to hold voltage the longest and provide the most pulses per discharge cycle.  The VTC5 lost voltage quicker than the 25R in the beginning of the test so it might not give as hard of a punch with a fully charged battery but after a while mostly ran the same.  It also gave a few less pulses before needing a recharge but not a huge difference.

So what would the best 18650 battery be for a mechanical 0.2 ohm device?  I would say the 25R, unless you also expected to run even lower resistance.  That's where the VTC4 will really shine.

And how does this compare to a regulated device that puts out constant power instead of a simple mechanical device?  It will be a little bit different, check out the regulated mod test here.  Be sure to subscribe to our newsletter at the bottom of this page or like our facebook to see all our newest updates.