BATTERIES LITHIUM OR LEAD ACID
Excerpt from The Next Best Ebike Battery.
There is a recently introduced battery chemistry that we will likely be seeing a lot of soon. Lithium-Nickel-Manganese-Cobalt-Oxide, or LiNiMnCoO2/NMC. Since Asian battery manufacturers have been working on a wide variety of alternative chemistries, a manufacturer standards group has chosen the abbreviation NMC for this chemistry (although one wholesaler stubbornly calls it NCM).
Nissan, Imara, Microvast, and Zero E-Motorcycles are now using NMC after extensive testing. Let’s take a quick run down memory lane to show how battery chemistry has evolved in just a few short decades. The following is not the order of their invention, just what my foggy memory recalls as seeing them used in E-bike battery packs.
NMC/LiNiMnCoO2/Li-NMC-O2-Lithium Nickel Manganese Cobalt Oxide
Battery manufacturers are continuing to research for developments in dozens of battery chemistries, and a couple of years ago, a big improvement to LiPo/LiCo chemistries began to be produced. A high-Cobalt cathode (LiCo) provides very good power density, but how can we make it more stable and reliable? Here’s a quote from batteryuniversity.com
“The secret of NMC lies in combining nickel and manganese. An analogy of this is table salt, in which the main ingredients of sodium and chloride are toxic on their own but mixing them serves as seasoning salt and food preserver. Nickel is known for its high specific energy but low stability; manganese has the benefit of forming a spinel structure to achieve very low internal resistance but offers a low specific energy.
Combining the metals brings out the best in each. NMC is the battery of choice for power tools and powertrains for vehicles. The cathode combination of one-third nickel, one-third manganese and one-third cobalt offers a unique blend that also lowers raw material cost due to reduced cobalt content“
Some of the NMC sellers are advertising their chemistry as 5C, but real-world use by E-bike builders has them calling NMC a solid reliable 3C chemistry, which can provide a continuous 30A from an affordable and compact 10-Ah battery (temporary peak amp-draws can be higher, as it is with any of these chemistries). This may sound only as good as the most recent LiFePO4, but NMC is smaller, and is not as fussy about keeping the individual cells balanced.
A recent quote from ES member SamTexas on claimed max C-rates: “…I have in front of me Samsung’s own Nickel (Manganese) 18650 cells….I have tested these cells at 3C continuous and they do deliver full capacity at that rate. Push it to 5C and they become hot and capacity is greatly reduced…“
You can actually buy an E-bike NMC pack right now, but it remains to be seen which retailer will prove to be the most reliable. An NMC pack will be about 25% smaller and lighter than an equivalent LiFePO4/LiMnO2 pack. The extensive testing done by Zero, Tesla, and Nissan gives us a great deal of confidence in the safe and effective use of NMC over the next year…