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Mon, 27 Feb 2012, 9:03pm Envia Claims ‘Breakthrough’ in Lithium-Ion Battery Cost and Energy Density »
Registered: Jul, 2009
Last visit: Sat, 31 Mar 2012
Posts: 1400

Dolphyn wrote:

Here's an interesting graph:
It appears to lose its 45ah capacity after just a few cycles, so it seems like a stretch to describe this as a 45ah cell. If you'll settle for 25 AH, it should be good for 450 cycles or so. This makes me think that for all practical purposes, they've only achieved 200 watt-hours per kilogram, but maybe the longevity will improve before it comes to market.


Actually it is just a bad graph. Apparently the first 3 cycles were 100% DOD - and rest were 80% DOD. So, obvioiusly they show 80% capacity. I know, bad presentation.

The capacity drops off in the first three cycles because the first 3 cycles were done at 100% DoD (C/20, C/10 and C/3 rates respectively). Cycles 4-400 were conducted at 80% DoD at C/3 which are typical charge/discharge profiles in automotive EV applications. By definition you'd get 80% of the original capacity. Hope this helps.
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