camasleaf
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Delivery Date: 17 Jun 2011
Location: Camas, WA

Re: All "Future" battery technology thread

Sat Dec 06, 2014 11:30 am

http://www.ebay.com/itm/261625724561

"2013 CHEVY VOLT BATTERY LITHIUM-ION BATTERY PACK" for $280. The price really has come down!

I emailed the seller two weeks ago to correct it. Yesterday ebay emails me that the price dropped.
2011 SLe 06/17/11 Over 71000 miles, GID 213 49.88 AHr; 76%SOH; 16.5kWh
2015 SV 09/02/14, Over 15000 miles, GID 287; 61.12AHr; 98%SOH; 22.2kWh
5.7kW DC System:

donald
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Re: All "Future" battery technology thread

Sat Dec 06, 2014 1:35 pm

Heh..... Just a charger. "Batteries not included", as they say.

donald
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Re: All "Future" battery technology thread

Sat Dec 06, 2014 1:48 pm

JRP3 wrote:Anyone who knows anything about the actual parameters of NiMH chemistry vs lithium chemistry has no need to try because it's already known.

hmmmmm..... the chemistry of batteries is known, but the physics of cars in the hands of drivers with varying demands and psychological profiles is what counts.

What I mean is that there is no problem building a car with 30kWh of NiMH for less than a Li car. It would be heavier, and it would get worse mi/kWh in the hands of someone who will 'use' it (abuse it) in a manner that is not sympathetic to the weightier technology.

But give me the opportunity to buy such a car for my slow 50 mile commute everyday and I'll be laughing after 10 years of use when I see my li-battery owning neighbours pouring $1,000s into buying new batteries for their lighter faster cars. I don't need 'light' or 'fast', I want 'robust' and 'best value'.

Don't decide what I want for me, please.

In any case, I'll repeat, if I have said it before, that I believe the real future for EVs is super-fast charging. Once that is mastered then distance becomes no object if it a case only of stopping for a few minutes every hour or two to charge up. I am not knowledgeable enough to know if some Li tech holds the key to that, or if some other chemistry might fare better.

JRP3
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Re: All "Future" battery technology thread

Sat Dec 06, 2014 2:58 pm

Whatever techniques you use to get more range out of your NiMH pack will get you more range out of an equivalent Li pack. Additionally the better Li chemistries will last the life of the vehicle, so your neighbors won't be replacing anything. Tesla's NCA packs have been tested for over 2K cycles, which in a 200+ mile pack is 400,000+ miles. Other Li chemistries have even higher cycle lives.
I also don't think lithium is any more expensive than NiMH now, so your imagined NiMH car won't be any cheaper. Remember, all automakers are aware of the NiMH patent situation yet they are all investing heavily in lithium ion. There is a reason for that. Continued ongoing advances in Li chemistry will make the gap even larger.

donald
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Re: All "Future" battery technology thread

Sat Dec 06, 2014 4:15 pm

JRP3 wrote:Tesla's NCA packs have been tested for over 2K cycles, which in a 200+ mile pack is 400,000+ miles.
hmm.... there are 'tests' and there is 'real life'. I do not have enough information on tesla pack life to comprehend it. I have heard of pack failures, but don't know what those involved.

I don't think NCA is well suited to large capacity cells, and many parallel cells create reliability issues - i.e. they might last longer, but when one cell goes in a module of parallel cells it brings the whole module, and/or pack, down. So we might be seeing lower degradation out of tesla packs but possibly lower reliability too. If that can be picked up early and fixed cheaply then that's not necessarily a problem, but if there's a chance I might break down and never know that's about to happen until it does, I'd worry about that sort of tech.

JRP3
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Re: All "Future" battery technology thread

Sat Dec 06, 2014 4:51 pm

donald wrote: hmm.... there are 'tests' and there is 'real life'.


True, but the tests were also full cycles, which the car never allows.

I do not have enough information on tesla pack life to comprehend it. I have heard of pack failures, but don't know what those involved.


All the ones I'm aware of entailed a failure of one or more high voltage contactors inside the pack. The quick fix is to drop the pack, put in a new pack, send the customer on their way, and then open up the pack and replace the failed part.

I don't think NCA is well suited to large capacity cells, and many parallel cells create reliability issues - i.e. they might last longer, but when one cell goes in a module of parallel cells it brings the whole module, and/or pack, down.


Larger format cells are made up of paralleled layers internally. If one of those layers goes bad it brings down the whole cell/module, and pack. If a large format cell goes bad you lose a larger portion of the pack.

So we might be seeing lower degradation out of tesla packs but possibly lower reliability too. If that can be picked up early and fixed cheaply then that's not necessarily a problem, but if there's a chance I might break down and never know that's about to happen until it does, I'd worry about that sort of tech.


If a pack module is having problems the BMS will catch it, and that data will be sent back to Tesla, who can take action long before it strands you. Again, the benefit of many smaller cells is that any individual cell problem will have a smaller impact on the pack as a whole. Of course there is the tradeoff of greater complexity and a higher number of potential failure points, but I've never heard of a Roadster or Model S being stranded because of individual cell failures.

donald
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Re: All "Future" battery technology thread

Sun Dec 07, 2014 12:24 pm

JRP3 wrote:Larger format cells are made up of paralleled layers internally. If one of those layers goes bad it brings down the whole cell/module, and pack. If a large format cell goes bad you lose a larger portion of the pack.
If that is an argument to say multiple parallel smaller cells are in some way more reliable for high power work than one large cell, I'd have to take that on advice as I'd doubt it.

But in any case, let's look at NiMH tech versus Li like this:- I buy plenty of those 'eneloop' type batteries, the NiMH with thicker separators that stay charged for a couple of years in the packet. I believe they are ~50c each wholesale, capable of delivering 2Wh each and weighing 27g. A 22kWh battery pack of those would cost $5,500 and weigh 300kg. They are very robust, last a very long time, and, as mentioned, can be left for years with only minor self-discharge.

Show me a 22kWh Li pack for $5,500 (real commercial price, not the loss-leader Nissan is offering on an exchange basis), and show me one that can be left unused for YEARS and still be charged up.

Let me buy 22kWh of eneloop AAs for my car, please!!

JRP3
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Re: All "Future" battery technology thread

Sun Dec 07, 2014 12:38 pm

Long term storage is not really an important spec for a vehicle, and comparing cheap cells with an EV pack is a bit ridiculous. For one the price of bare cells does not include connections and packaging, nor does the label necessarily reflect real world performance. In other words battery labels often lie. I'm sure I could spec out a lithium pack fairly cheaply using label data only, but it wouldn't reflect real world performance.
As for storage, I have some "new" LiFePO4 cells that have been sitting in storage for about 3 years, they are still around the same 50% SOC they were left at 3 years ago, and are charging up as we speak.

I guess I look at it this way, if you want a less expensive EV with limited range, buy a used LEAF or similar vehicle, but I would not expect to see a new factory EV using NiMH.

donald
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Re: All "Future" battery technology thread

Sun Dec 07, 2014 12:47 pm

I'd just prefer to use my money for what I choose to use it for, but it's common practice for the auto industry to only provide what IT thinks customers want. Why change just because they are EVs? I don't expect to see what I want, but one can but dream.

At least give me an option for LiTiO, people!

LiPos have a good shelf life, but don't take too many recharges. You go find me some LiPos at 25c per Wh and post the link. They are usually over $1.

Being lucky with batteries doesn't mean they are good batteries.

JRP3
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Re: All "Future" battery technology thread

Sun Dec 07, 2014 1:12 pm

I'm talking about LiFePO4, lithium iron phosphate, not LiPo, lithium polymer. LiFePO4 has very high cycle life.

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