***************Updated April 2017 for 800 cycles*****************
Both cell models are the current state-of-the-art in terms of high capacity 18650 Li-ion.
Although 18650GA gained popularity in the ebike community due to better pricing/availability (true in 2016, not in 2017), the LG MJ1 has been found superior by NASA in their applications (safety, cycle life and impedance)
Samsung 35E is a very promising cell also, but not included in this comparison because of its higher price back in Sept 2016.
In spite of extensive bibliography, I couldn't find any relevant or comparable information about how they would behave in a proper electric vehicle application (commuting ebike, motorcycle, cargo lift...).
I decided on the following parameters, which I think represent a pessimistic scenario of someone educated to battery care but also placing high demand on the batteries because of the application.
- Charge voltage 4.01V (yields 3.98V rest voltage, should enhance cycle life greatly. Satellites use 3.85V)
- Charge current 1.3A to 75mA (full charge in a little less than 3h)
- Discharge current 6A continuous (imagine climbing a hill with a DH ebike, or cells in the middle of the pack which cannot cool down properly)
- End of discharge : 5A at 2.8V (yields 3.2~3.3V rest voltage)
- 30-minute pause after charge and discharge operations (to let the cells cool down and stabilize the chemistry, which Sony has found to slightly improve cycle life)
Unfortunately SD card crashed during the first cycles, so initial capacity is not known. Paper and pen used for the data shown.
I tested a new 18650GA in the same conditions and found 2451, 2400mAh for the 2 first cycles. I don't have any new LG MJ1 cell yet.
If I had to do it again I would probably chose Kokam's recommended parameters for cycle life (4.1/3.3V), because these results are disappointing
- This cycle represents a ~70% DoD scenario for the Sanyo cell, and ~66% for the LG cell
- After 300 cycles, 18650GA performs better in this scenario despite being a C rank cell. It's not being aged faster in spite of being discharged more.
- After 800 cycles, the GA suffers from increased internal resistance, reducing its capacity in this usecase. The LG is more steady but loses more capacity under slow discharge.
- Both cells are disappointing in terms of cycle life, having lost ~15% of their initial capacity after only 50 partial cycles. Things calm down and the trend becomes linear after that but past that the cells premium price becomes less interesting. A 18650PF still holds 2500mAh after 300 cycles @ 100%DoD, 4A (according to datasheet)
Will keep updating the results and hopefully reach 1500+ cycles !
- GA vs MJ1 20161129.jpg (148.16 KiB) Viewed 561 times
- GA vs MJ1 20161210.png (88.92 KiB) Viewed 557 times
Last edited by youyoung21147
on Apr 19, 2017 12:48 pm, edited 2 times in total.