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Old 03-30-2019, 02:48 PM   #1
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Nickel Cobalt Batteries

The largest user of electric vehicles is quickly turning out to be China. They are altering battery designs in favor of Nickel - Cobalt percentages which possibly will affect LFP usage. It will be interesting to see if this becomes a cost effective application for boats. For sure, nickel is currently easier to come by than lithium, but these industries are changing fast.

Chinese electric vehicle makers are gorging on nickel | MINING.com
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Old 03-30-2019, 04:15 PM   #2
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The NMC chemistries are one of the variants of lithium chemistries. The article below compares several of them. There are pro/con for both it and LFP (and the other chemistries).

https://batteryuniversity.com/learn/...of_lithium_ion

You can pick some of the six attributes they list that fits your application, but you can't have everything!

Yet to emerge are good off-the-shelf complementary components. eg for LFP you would ideally be able to isolate them once fully charged. Vehicles and boats that are still charging an Li battery bank at 14.4V (or whatever was set in the reg) even when it is fully charged is detrimental to the bank's long term performance.

Perhaps two banks? One for loads (isolated from charging), and one that is being charged, but then isolated when fully charged. Maybe even three banks? With auto switching for isolation when fully charged or discharged. Of course costs would preclude that for most of us at present - one Li-bank still costs an arm and a leg.

Are we there yet?
No, but real soon now!
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Old 03-30-2019, 05:45 PM   #3
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I'm not sure how these different NMC blends act, but so far LFP is the only chemistry that I would consider for a boat, simply because it's so much safer than the others. And a house bank doesn't require the ultimate in power density, or power to weight ratio - things that matter dearly for portable applications, and for cars.
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Old 03-30-2019, 06:59 PM   #4
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Yes, at present LFP are best for boats. Lithium titanate are equal or better for safety and life span, and are a bit better performing but are double the cost of LFP.

The benefit of NMC is cost, they appear to be about 80% of LFP cost/kWh. But a big problem is that, like some other chemistries, they can get thermal runaway. From the table in the link I posted above, NMC spec for this is:
210C (410F) typical. High charge promotes thermal runaway.

So, don't park you EV under your house whilst it is on the charger all night!

Of course, knowing the threat, good mitigation can be built in. Lets hope so anyway.
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