Lithium Ion Batteries

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acmotor
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Lithium Ion Batteries

Post by acmotor »

Does anyone have experience with the life expectancy of Lithium Ion Batteries ? Image
The cost is very high at present and the 'how long will they last ?' question must be asked.
Will they give up after 1000 cycles if you use them every day ? or give up after 3 years even if you only use them 10 times ?
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Post by RonS »

My generalised research indicates a realistic cycle life of about
300 - 500 cycles provided you don't discharge them below
50%. I have no practical experience to back this up,though.
Lithium Ion batteries don't mind being left in a state of
discharge for any period of time, unlike other types and their
storage life is not an issue, as far as I can tell.
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Post by RonS »

I've done some more searching and found this ... http://en.wikipedia.org/wiki/Lithium_ion_battery
which contradicts what I said in the previous post.
Dunno! Some say YES some say NO. You figure it out.
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Post by RonS »

Here's a contradiction of the previous contradiction (!!)
http://en.wikipedia.org/wiki/Talk:Lithium-ion_battery
This bloke appears to have somewhat better credentials than the other.
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Post by roddilkes »

Hi All,
This is my very first post!

LiFePO4 batteries have a life cycle of 1000-3000 deep cycles.
Suppliers are currently offering warranties of 1-3 years which is pretty good.
The only issue is the cost, about 3-5 times lead acid.
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Post by Thalass »

The lithium batteries I was looking into the other day claimed to have a life of 2000cycles, with a 100% DoD, which I think is pretty good. But man, are they expensive! heh.
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Post by Rob M »

There are a few things to consider when comparing lead acid to lithium ion.
Number of cycles claimed is five to six times lead acid but shelf life has not been determined yet. Lithiums are supposed to be less affected by heavy discharge. The Trojans I put in the Mustang did 12,500km and 460 cycles at an average of 40% depth of discharge. I guess you could reasonably assume that would be equivalent to 230 cycles at 80% depth of discharge. Very disappointing really. I think that the 400 cycles claimed was probably at a 20 hour rate and not relevant for ev use. I did flog them a bit but I am doing the same with the lithiums so it will be an interesting comparison.
The lithiums will only need to do 1200 cycles at 80% DOD to cost the same per km.
The up front cost should not be a deterrent if you borrow the money because it can be amortised over a longer period.(assuming long shelf life)
The other advantages worth considering are the weight reduction, which considerably improves performance, the low maintenance, the ability to fast charge (up to 3C)and the extended range which makes more difference than I thought it would. I no longer have to consider the fuel gauge if I am running aroung town. I start out with about a third of a tank of 'petrol equivalent' instead of about an eighth of a tank in which case I would be heading for the nearest fuel station in my petrol burner.    
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Post by zeva »

Yeah I'm with Rod Dilkes on this one..

The cost equation for Lithium Cobalt and Lithium Manganese chemistries just doesn't work due to their lower cycle life (500-800 cycles), but Lithium Iron Phosphates (LiFePO4) have a 2000-3000 cycle life so they do actually work out cheaper than lead acids in the long run!

A couple of important players in the EV world, namely Jukka Jarvinen and Rich Rudman, have been doing independent cycle testing of the ThunderSky brand and can confirm that they have very impressive cycle life - something like a mere 5% capacity drop after 1000 charges..

Go LiFePO4!
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Post by Thalass »

LiFePo4 seem to be the best, though I'll have to do more research. I'm interested in how people are doing their charging systems with the lithiums.
I'll drive an electric vehicle one day.
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Post by zeva »

In my case I'm using a Zivan NG3 with the TS90 battery management
system (BMS) from evpower.com.au.

For interest, the charging algorithm for lithiums is Constant Current,
Constant Voltage (CCCV), which basically just means the charger needs to
limit both voltage and current. It might be easiest to understand this from
a graph.. I did a report a while back on LiFePO4 performance which
shows charge curves:
http://www.zeva.com.a
u/tech/LiFePO4.php


The tricky part is where charging a whole lot of slightly different capacity
cells in series (no two ever are identical), means some hit peak voltage
sooner than others. As such you need a means of shunting off the charge
current to prevent this cell going above its max voltage while the other
cells come up to full. (This is a job for the BMS)

The other essential function of a BMS is to prevent any cell going below
minimum voltage. Weaker cells will will hit their low voltage cutoff sooner
than others, and you basically have to stop when the first cell hits its
minimum voltage.

To stop the BMS shutting down the battery pack due to voltage sag (under
heavy acceleration for example), the speed controller I built for the MX5
dynamically restricts its power output to keep pack voltage above some
programmed minimum voltage. (This way you can still limp home safely if
your pack is starting to get low!)
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Post by Thalass »

Ah. Interesting. Could you not shunt or otherwise bypass the cells that drop below their minimum voltage during discharge?


I might have to talk to the evpower guys before I start building. I'd be interested if it would be possible to have a BMS/Charger that had two power input connectors - 3 phase for fast charging, and single phase for slow charging.
I'll drive an electric vehicle one day.
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Post by zeva »

The trick with bypassing cells as they discharge to their minimum voltage
is that the bypass mechanism would need to be rated for very high
current, certainly several hundred amps. This would basically require a
contactor per cell - pretty expensive!

And if the cells are reasonably well matched, their capacity should all be
within about 1% tolerance of each other so you're not gaining much by
making use of the extra 1% in the strong cells.

(OTOH charge current is usually only about 10-20 amps so the
bypass/shunt system for charging does not need to divert all that much
power.)

Re 3-phase charging, the main catch here would be finding a three phase
charger! I've never seen one (thats available to the public, anyway)..
Would be great though, being able to charge the car in an hour or so.
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Post by Thalass »

That's a point, it might be hard to find. I definately think it'd be beyond me to design. At the moment, at least.

It would make the car that much more useful. Come home from work, with the batteries nearly dead, plug in the car and by the time you're showered and dressed you're ready to go out for dinner the car is fully charged again!
I'll drive an electric vehicle one day.
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Post by Rob M »

I have two three phase chargers in the Triton, off the shelf Zivans, and they charge from "flat" in a couple of hours. The availability of three phase power is more of a problem I find.
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Post by Thalass »

Which is why I'd like to have single phase input as well as three phase. I'm building a house soon, so I'll put at least one three phase plug in the garage - I'll need it for aircon in the house anyway. But you'd need the single phase input for when you're out and about.
I'll drive an electric vehicle one day.
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Post by Rob M »

Anyone interested in being part of a bulk purchase of lithium ion batteries, please email me, robertmason6@bigpond.com
Hopefully under $1.60 per Ah
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Post by Lahzie »

My question is for Rob M. I saw you're Mustang at the Sunfair back in April (very impressive and very popular). It looked like it had Thundersky's in it is that correct? You're Sep 07 post mentioned changing to Li batteries. Is that when you put the Thundersky's in and how have they performed so far? Is it looking like performing to manufacturer specs?
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Post by Rob M »

Hi Lahzie
I am quite happy with the lithiums so far.
They have done more Km than the Trojans and are not showing any signs of weakening.
I haven't run them down below 90% DOD for a couple of months though (118 km trip).Safe to say they are better than 90% I guess.
The power output is unchanged at 600A at 2.6 volts per cell.
I now have 75, 200Ah cell in the ute. It still has a set of 20 yellow tops in it making it the same weight as before so I can get a feel for the change in performance. It is definitely slower running on just the lithiums and still pushing 2.4 tonne. When I remove the yellow tops it will drop in weight by 0.5 tonne, improving the acceleration by about 25%.
Still thrash a certain MX5 I reckon!

Rob
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Post by Rob M »

I would like to finalise the bulk purchase of lithiums by this Wednesday.
The price quoted above is in Aussie dollars, including GST, landed in Perth assuming we can get over 24,000Ah in this order. The exchange rate seems steady at the moment at around 95 cents.
The price does not include copper bars to connect cells. T/S want $3.20 each for them. A 3 metre length of 20mm by 3mm copper bar costs about Aus$30 from which you can get 12 or 15 bars depending on cell size.
Those interested please email me on Monday so we can discuss terms. I would suggest 50% on order and 50% on delivery.
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Post by acmotor »

I'm in , talk to you Monday.
Re bus bars... do consider using copper sheet in three layers bent in the middle rather than solid as this places less strain on the battery terminals. A bit like stranded cable.

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Post by antiscab »

"Still thrash a certain MX5 I reckon!"

haha just till my mr2's finnished:p

its good to hear the triton goes well with 110kw of electricity pushing 2400kg.
hopefully 110kw (im pushing my pack alot harder) pushing my 1100kg mr2 will be similarly successful:p

btw, confirm me on the bulk buy.
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Post by bga »

A useful Battery technology report:

"Battery Technologies for Cars"
June 11-12, 2007
IEA Headquarters, Paris
International Workshop on Technology Learning and Deployment
Here
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Post by Johny »

Thanks bga, good read. A fourtieth of the cost in 20 years... sigh
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Post by Richo »

yeah they completely over look LiFePO4.
So it was no good 2 years ago Image.

Go the Li-PO Image.
So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!
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Post by Richo »

Battery Uni is always a good read too.

So the short answer is NO but the long answer is YES.
Help prevent road rage - get outta my way!
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