The Elusive Holy Grail of Batteries

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Mik
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The Elusive Holy Grail of Batteries

None of the various battery types which have been developed so far seem likely to be able to get around all of the difficulties that need to be solved for use in a high performance, mass produced and sell-able EV, not without being inefficient and extremely expensive.

There are similarities to the main problems of the internal combustion engine (ICE) in a vehicle:
It needs to produce torque across a wide range of revs, and power, and low emissions, and low noise levels, and low pollution, and have low weight, and last a long time, and need little servicing, and not be too complex...
Of course the ICE will therefore have severe limitations, or an extreme price and/or extreme servicing requirements, you know the story.

But a specialized ICE, which always runs at it's optimum speed and load, can be much more efficient, simple, free of service requirements and extremely long lasting. The oil in such an engine needs to be perfect for just one set of circumstances; the vibrations can be almost eliminated at the typical constant running speed, parts don't heat up and cool down and fatigue unduly etc., you know that story, too!

Now take the leap and apply this kind of thinking to batteries:

I propose that for a high performance advanced EV it would be beneficial to install several different types of battery in such a way that they support each other synergistically! A "specialist battery' for each of the attributes that are hard to combine into just one battery type!

A) A large, high energy density battery capable of producing a constant base load current.

This battery constantly recharges the other battery types in the system, at the most efficient, constant rate, with minimal losses, allowing for minimal heat production, exceptionally long life, and large energy storage for the weight and volume used. This battery needs to be able to provide a constant current sufficient to maintain vehicle speed at highway speed for long periods without straining or suffering any damage. It does however not need to be able to produce the currents needed to accelerate, go up steep hills or burn tyres. It also does not need to be able to absorb massive amounts of regen breaking energy. These are the jobs of the other parts of the system. It's constant power rating would be similar to the motors constant power rating.

B) The next part of the system could be a smaller battery of a chemistry type that is capable of rapid charge and discharge.
It would provide the energy needed during normal acceleration, during fast uphill driving and during faster than normal highway driving for fairly short periods. It must have a high C rating for both charging and discharging and a high cycle life expectancy, because it provides the immediate energy source and energy dump for stop-and-go city traffic including normal (but not emergency) regenerative breaking. This battery does not need to be able to provide the extreme power needed to do a full power acceleration, or absorb the power of an emergency regen breaking maneuver; that's the job of the next part! It's constant power rating would be higher than the motors continuous power rating, but much lower than the motors peak power rating. The capacity can be fairly low.

C) The third part would be a small battery (and/or super-capacitors) with low capacity, but capable of producing and absorbing phenomenal currents during hard acceleration and emergency regenerative breaking.This battery and/or capacitors must be able to absorb the maximum regen currents without getting damaged, and to produce enough power for a single acceleration from zero to top speed, even uphill into a headwind, but this is only needed for a few seconds at a time.

I think we already have suitable battery types for the roles of A), B), and C)!

As long as we try to find the "Holy Grail Battery" that combines all the attributes needed in an EV into just one type of battery, we are reproducing the inefficiency problems of the internal combustion engine as described above. It will likely fail.
There will probably never be a battery that can do it all and still be affordable, recyclable, non-toxic and durable!

Of course, this synergistic battery combination needs a complex battery management system.
But again, I think this could be designed and built by using already existing components.

Paul
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Re: The Elusive Holy Grail of Batteries

I like Mik's battery model, where are all those battery engineers?
CSIRO has been working on a device called an Ultra-battery, which is a combination of lead acid battery and ultracapacitor in the same case. This seems to go some way towards Mik's battery combo model. The website has had no more new info for about 12 months, but I hope it comes off.
A Texas company EEStor has made progress towards large capacity ultracapacitors for the EV market, they have a deal with ZENN Motor company who seem to be bankrolling until production begins.....'soon'.
So there seems to be work out there towards the 'perfect' EV storage device, but I have not seen any mention of a combo such as Mik is suggesting.
wish I was smart enough to sort such a system!

Paul

jdh2550_1
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Re: The Elusive Holy Grail of Batteries

Interesting idea.

I think if I were choosing A, B & C then I'd go with

A = LiFePO4 from someone like Altair Nano (apparently good for 12,000 cycles)
B = A123 LiFePO4's which I think are good for 20C or more.
C = super caps (the real kind, not the mythical EEStor kind)

But I'm not sure. It seems to me like one would probably be better off with "the best" LiFePO4 for both A+B and supercaps for C. It would be expensive - but is likely to come down in price.

LiPo is good for high C but I don't think the cycle life is there.

Is there a better choice?

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

MikeB
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Re: The Elusive Holy Grail of Batteries

It's a good idea, and people are already working on it, or at least some flavor of it.

Here's a lead-acid battery buffered by supercapacitors:
http://www.technologyreview.com/energy/20105/

My electric vehicle: CuMoCo C130 scooter.

jdh2550_1
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Re: The Elusive Holy Grail of Batteries

It's a good idea, and people are already working on it, or at least some flavor of it.

Here's a lead-acid battery buffered by supercapacitors:
http://www.technologyreview.com/energy/20105/

But lead-acid is bad for energy density nor cycle-life - so I'm not sure I'd choose it for the bulk-storage option (A in Mik's post)

John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.

MikeB
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Re: The Elusive Holy Grail of Batteries

But lead-acid is bad for energy density nor cycle-life - so I'm not sure I'd choose it for the bulk-storage option (A in Mik's post)

I agree that lead-acid isn't the best choice for A, I'm just showing that the basic concept is being worked on already. I think you're right, LFP is a good choice for A, and some sort of capacitor setup might be best for B and C.

My electric vehicle: CuMoCo C130 scooter.

myocardia
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Re: The Elusive Holy Grail of Batteries

Hey, Mik, were you inquiring about what a person could do themselves? If so, there's a guy here in Texas that has added a bank of supercapacitors in addition to the LiFePO4 batteries in his CRX. IIRC, he was saying that he got at least 100 miles per charge, with good acceleration. I'll see if I can dig up his website.

antiscab
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Re: The Elusive Holy Grail of Batteries

thats the guy at metric mind.

the batteries are (were) lithium cobalt.
that setup is no longer used (as in 2-3 years ago)

Matt

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myocardia
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Re: The Elusive Holy Grail of Batteries

thats the guy at metric mind.

the batteries are (were) lithium cobalt.
that setup is no longer used (as in 2-3 years ago)

Hah, what would you expect? That's always the case with EV's, and it seems to go double for home-builds.

edit: Thanks for reminding me where I saw that. For anyone that's interested, here's the homepage: http://www.metricmind.com/ac_honda/main2.htm The ultracapacitor link is on the left side.

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