Friday 3 February 2017

Using the Nitecore SC2 superb charger

Superb charger

on Nitecore's web pages for the "SC2 superb charger", there is no shortage of superlatives. Charging with "Infinite Intelligence" certainly is the boldest claim.

See for yourself >>> HERE <<< in my review video on YouTube.

Infinite intelligence

So I tried to find out more about the limits of this "active charging with infinite intelligence" thing. Gearbest sent me a unit for review and I put it through a few tests to see how it performs.

First impression

The charger feels quite tough & beefy to the to touch. The kind of plastic that doesn't feel plasticy, but rather reminds of high quality power tools. A good start.

Second impression

But why-oh-why are the settings for the current and max. charge voltage printed on what looks like a sheet of protective film that easily comes off the display.
I'm sure if I don't constantly use that charger, I'll have forgotten what which LED means what after a few days. Nitecore has to do something about that in the next iteration of the SC2.

Automatic battery capacity detection

Now this should be what is at the heart of this ominous infinite intelligence. The traditional way to determine the battery's capacity is to discharge them and measure the capacity that they charge to, possibly adding another discharge/charge cycle. Nitecore's web pages claim that it automatically detects the battery's capacity and sets the charge current accordingly.
So come on SC2, impress me!

Test setup

First, I have to know about my cell's actual capacity. To find that out, I use an improved version of my previously published Arduino battery tester.

Makeshift battery tester

I use four cells for testing:
  1. AWT 18650 35A 3000 mAh IMR cell 
  2. Ultrafire 18650 3000mAh (Really is only 300mAh)
  3. KeepPower 14500 800mAh 
  4. Ultrafire 14500 1200mAh (Really a little over 200 mAh)
With automatic battery capacity detection, The good quality cells AWT and KeepPower cells should charge at a higher rate than the Ultrafires (who in all tests had only a fraction of their nominal capacity, regardless of the charger.)

Size matters

As cells with the same size charge at the same current, I wondered what happened if I make the 14500 appear bigger. So I inserted a spacer with the 14500 cell.
14500 to 18650 converter :-)

Nut&bolt spacer inserted
It charged at 2A. Way above the recommended 0,4-0,8A (Unconfirmed, from reseller pages)

The assumption that bigger cells hold more capacity might on the whole be correct. But we all know that there are good and bad cells and that makes way more of a difference than the size.

The limits of infinite intelligence

There is more that will confuse the charger:
  1. LiFePO4 cells: The charger can't distinguish LiFePO4 cells from Li-Ion cells and would overcharge them. So the maximum charge voltage has to be set manually
  2. 3,8V Li-Ion cells. I've never had or seen any of these, But as they are indistinguishable from a 3.7V cell, The charge voltage needs to be set manually.

Example Charge

While I had initially observed some brief overvoltage conditions, All the voltage (and charge curves I took) did not exhibit that phenomenon.
0,5A charge curve
I did many of the long-term measurements with PC on the USB-Port of the bside ADM20 Multimeter that I quite like. I also got from Gearbest to get a better grip on some problems I suspected with the SC2 charger.
bside ADM20 at work with a current shunt resistor
The multimeter turned out to be quite hackable. But that will be a whole new blog entry & video.

Final word

  • Great charger if you're in a hurry. Very fast and reasonably safe.
  • Supports all currently available battery chemistry types.
  • Sometimes has trouble disabling the protection circuit in KeepPower batteries.
  • Needs help choosing the right battery chemistry.

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