LG 18650 D1 changed?

For a caving light project I need a battery for a single cell light with buck or linear driver. The lamp will drain up to 3A on turbo. Most batteries do not deliver enough voltage under such high current drain.

As far as known from HKJs battery comparator LG 18650 D1 @ 4,35V should be best suited for those lights, because voltage holds highest even when most of charge has been extracted.

But the measurements from HKJ were carried out early 2012. I made now another measurement with two samples of the actual version of LG 18650 D1 and found this battery has changed internally.



The model E1 was developed later than D1 and LG specifies its capacity 200mAh higher than D1. But E1 is not really better than D1, since it shows larger voltage sag under load.
The recent version of D1 seams to have an increased capacity of 100mAh with respect to the earlier version. The capacity is now 100mAh below E1 only.
But the internal resistance has increased too, resulting in lower voltage at high drain currents: The voltages under load are now only slightly above those from E1 but much lower than those from earlier D1.

No good information for owners of single cell lights with buck or linear driver!

Keeppower offers now LG D1 and E1 cells with PCB . Akkuteile sells those batteries.

Be aware that the PCB of Keeppower does not allow to charge up to 4,35V completely. The overcharge protection jumps in at just below 4,35V. So you should use these batteries with 4.3V charger only. The protection adds about 13 to 16 mOhm.

Lot to lot variances? Differences in testing equipment?

I have both D1s and E1s from a year ago, which I run naked and don't know if the minor differences in your chart matter a whole heck of a lot in the real world?

Chris

Hi Chris,
If the light needs 3,5V to drive the LED with 3A, than LG ICR18650E1 will hold this for 33 minutes (the blue curve crosses 3,50V at 1650mAh).
The "old" D1 hold this situation for 43 minutes (the red curve crosses 3,50V at 2100mAh): This is 10 minutes longer or about +30%
The 'new D1 hold this situation for 35 minutes.
Sometimes small differences cause big effects!

How did you perform the measurements? I only see a difference of around 50mV, that can easily be wire or contact resistance.

If you tested a protected call, those 16mOhm @ 3A are 50mV...

To keep things in perspective, the tailcap spring of my Eagletac TX25C2 has 100mOhm resistance or a 300mV voltage drop at 3A. So there there is likely quite a bit of room for improvement elsewhere as opposed to worrying about that potential 50mV difference between the D1 versions.

The difference between "old" D1 and E1 is about 50mV. Both curves are measured by Henrik K. Jensen (HKJ). I trust his measurements.
I do not know the level of contact resistance he achieved, but his contact mechanism seams reasonable.

I used batteries with tabs and soldered all wires directly to the tabs. There was no common path for load current and voltage measuring on a wire.
Therefore I can guarantee that I always measure voltage directly at the unprotected cell and that there is no significant voltage drop.

The voltage measurement was done with a LabJack U3-HV, wich was cross-checked by three different high quality digital voltmeters.

The constant current sink is selfmade: MIC29502BT with selected resistors in parallel as load. The sink was calibrated and crosschecked by the same three high quality digital voltmeters.

I am sure my measurements are accurate enough for differences lower than 10mV.

ChrisGarrett said:

...don't know if the minor differences in your chart matter a whole heck of a lot in the real world?

Click to expand...

I'm pretty sure they don't. If you compare to a typical 3400 mAh 4.2 volt cell, the difference in voltage is enough to matter (and I can tell in real world use, with some lights)...but the D1 and E1 only differ by a few HUNDREDTHS of a volt. I'm confident that for my purposes, this will make no difference at all.

I'm not arguing that the performance is identical, but I do think the OP is making a mountain out of a molehill. Interesting result, and kudos to him for the accurate testing, but let's keep it in perspective.

I agree with you, thedoc007!

Indeed, I have overrated the effects of such a small difference.

The ICR18650D1 is still a very good battery and holds up voltage much better than most others.

Re: LG 18650 D1 changed? Added test of E1

I got now a LG ICR18650E1 and measured it at room temperature with 3A dc discharge.



Here is a larger image

The measurements of Henrik K. Jensen some years ago showed a difference in voltage sag between model D1 and E1: D1 had less capacity but holds the voltage a little bit better than E1.

The more recent versions of models D1 and E1 show nearely identical voltage sag.

If you trust both measurements (HKJ and mine), than the conclusion may be:
Nowadays D1 and E1 are identical with respect to voltage sag (that means internal resistance). Both have increased the capacity slightly.

Added information:
Formerly the original shrink tube of LG E1 was seagreen (bluish green), now it is violet (bluish purple)!
The latest datasheet I could find is Rev. 2 from 2012-09-03: This one still contains a seagreen image.