You can own a Li battery pack NOW!

[terry.kane]

Here's the link: scroll about 1/3 down the page to "Lithium Batteries"
http://www.evporsche.com/

<excerpted>
"Lithium in the new Porsches (99-'08) also offers a close final weight with the gas '08 and with rear trunk to boot.  The front trunk is untouched, more overall.

Cars above may be converted using new High Energy cell technology.  Up charge depending on KW hours requested.

16KWH - 225 lbs. with  75 mile range per charge.........................................................................................$16,000

32KWH - 445 lbs. with 120-150 mile range..................................................................................................$26,000

64KWH - 890 lbs.  capable of over 300 mile range........................................................................................$49,000

Any size pack from 100-1000 lbs available. Lithium batteries come in aluminum cases with Battery Management System."

This is presented in the context of substituting Li batteries for standard AGM in their EV sports cars.  I haven't spoken to him but I intend to.  I'm hoping he'll sell me raw cells and I'll do the series/parallel configuration to reach the voltage & capacity I need for my planned conversion ('73 FIAT 850).  Alternatively, he might give me the name/contacts of his source for raw cells.

I'm still learning about batteries & the jargon, stats, specs and indexes.  Can anyone comment on the weight of flooded/lead-acid packs delivering 16KWH, 32KWH or 64KWH? (say @144 volts - the evporsche cars are 336V)

-TK

[terry.kane]

Can someone help me with the numbers here?  The packs quoted below are rated in KWH and we typically discuss packs in terms of Ah @ voltage.  So Ted's truck, for instance, is 200+Ah @ 120V = 24kWh, right?  Ted - what is the weight of your truck with this pack installed?

The evporsche 16kWh/336V pack would be just 47.6Ah, right?  Yet he claims 75 mile range; I'm not sure how it all works out.  Perhaps they are making many assumptions about Wh per mile, regenerative braking and useable pack capacity based on DOD, etc?

My Fiat is 1600 Lbs GVW with the ICE installed.  Perhaps with a Li pack I would have a very low Wh per mile and could get the range I need (fully 50 miles round trip with a rest at 25 miles).

I will continue this thought on the other LiIon thread.

[robert.wood]

I'm no expert, but I've been looking into the issue.

It seems that Lead-Acid battery lose alot of there amps if discharged quickly, say in 1 hour.

Trojan T-125 batteries are rated at 240 amps if discharged over 20 hours, but only 195 amps discharged over 5 hours and 150 Amps @ 2 hours 12 minutes.  The loss gets even worse when discharging over 1 hour, with my guess at around 100 amps.  To increase life cycles, Lead Acid Depth of Discharge (DoD) is normally recommended to fall between 50%-80%.   So taking DoD into account, running around 40MHP, on flat ground during a nice spring day, you might expect to get 75 amps usagable.  Once again, I'm no expert, I'm just studing differnet websites.   

Expect life cycles: 750 at 75% DOD
Weight 66 lbs x 20 =  1,320 lbs
6 watts per lb


Other factors:
Let's also not forget that Lead Acid will loss something like 60% of it's charge @ 32 degrees F.

Lithum Ion batteries, such as Saft's VL 34 P module (called Military grade) can discharge 250 amps in 6 minutes at 45 to 40 volts.   Saft's NiCd STM 5-140 MR is 6 volts at 136 amps.  Not sure about DoD here.   

Expected life cycle of Lithium?  5,000 - 10,000 ?
Saft pack 43 volts
200 + amps
35 lbs
3 pack 105 lbs
245 watt/lb
cost ??

Expected life cycle of Ni-CD?  2,000-3,000 ?
Saft pack 6 volts
136 amps
37 lbs
20 pack 740 lbs
16320 watts
22 watts per lbs
cost ??

I have a call into Saft to locate a dealer for these products.


   

[larry.backes]

Let me know if Saft replies.  They told me to pound sand.

Larry

[matt.kenigson]

The effect that causes the true Ah rating for lead-acid (and to a lesser degree, other chemistries) to drop as you discharge faster is called the Peukert's law:

http://en.wikipedia.org/wiki/Peukert's_law

Here's a great write-up about it:

http://www.smartgauge.co.uk/peukert_depth.html

Here's also a great spreadsheet to figure out more precisely what you can expect out of your batteries:

http://www.smartgauge.co.uk/calcs/peukert.xls

The rule of thumb most folks on the EVDL use, though, is based on Peukert and bolstered by usage data.  It comes out to around .56 or .57 of the 20hr rate if I recall correctly.  I've always mentally thought of T-125's as having around an effective, usable, 120Ah because of this.

Matt

[robert.wood]

You say T-145's have ~120ah effective, usable.  Are you accounting for 80% depth of discharge? 

[matt.kenigson]

No.  I was just talking about what you *can* figure as a more realistic figure to base all other calculations upon.  It certainly helped introduce a bit of reality into range calculations.  You should, of course, figure in your optimal DOD.  My advice is to actually figure on a 60-70% DOD to give your batteries a good, long life. 

Which reminds me of a question I've had.  I've seldom had the chance to opportunity charge during the day (although a past employer did put in a plug for me on a light-pole once).  I always wondered whether my pack would last longer with fairly shallow discharge (30 - 40% DOD) and twice the charging cycles or with regular 60-80% DOD cycles.  It seems like taking it easier and having more cycles would be better but if there's one thing I've learned about having an EV it's that things are not always as you might expect.

Anyone have any real-life experience with this?

Matt

[john.emde]

Would someone care to elaborate on what "80% depth of discharge"  means ?
It can be confusing to some of us.

John

[ted.karson]

"Would someone care to elaborate on what "80% depth of discharge"  means."
Here you go!
http://www.batteryuniversity.com/print-partone-16.htm