Wednesday, March 8, 2017

Batteries for e bikes

100 kWh? LiFePO4

It's about time they manufactured large cells with bolt conections! These are bigger than 18650 cells. But I can't help wanting fire proof insulation between the cells.

The only problem is that you can't get these free out of old computer packs. 
And some people are telling me that these cells are not as potent as the sellers want you to believe.

These are considered safer when compared to lithium oxide or mixed oxide battery products. Punctured or short circuited lithium metal oxide cells will cause heating, oxygen release and the potential for thermal runaway.

Tesla is about to start manufacturing mass quantities of these new batteries to bring the price down a little. It looks like the chimistry of these bolt end cells are already old tech, not that it matters much. The Iron Phosphate LiFePO4 chimistry is safer to use than the magnisium, but heavyer. I would choose the weight over the danger.

What chemistry is the Tesla 2170 cell? LiFeMgPO4 Lithium Magnisium Phosphate?

By 2018, Tesla's new “Gigafactory” will produce 35 GWh/year of lithium-ion battery cells, nearly as much as the rest of the entire world’s battery production combined. And there are several other companies racing for the claim of .highest energy density/cheapest cell in the world” also.

But will they have bolt ends? Not likely! So how do they connect the cells in the cars?

The new ‘2170’ is 21mm (13/16th inch) by 70mm (2¾”). Smaller than these bolt end cells that are about a 1.5” diameter by 4” long. But larger than the old 18650 cells (17mm x 67mm).

Lithium batteries should regularly be recharged because high batteries lead to oxidation of the anode and low batteries leads to the disintegration of LiNiCoAlO_2. This makes lithium batteries very sensitive. Research has been showing that with two 50% depth of discharge (DOD) cycles, the battery lifetime is about four times longer than one 100% DOD cycle.

The Myth of Ebike Wattage

How to make an inexpensive Lithium-Ion Battery Pack

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