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Re: [EVDL] Press release on Firefly "Oasis" battery

Thanks for the link on the theoretical chemistry. However, hang with me for a moment and I think you'll see the real world energy density could be much closer than you would have ever guessed. It surprised me.

Bill Dube's pack on the Killacycle weighs about 200 lbs, is 374 volts, and has 9 * 2.3 Ahr = 21 Ahr. Two of these packs would be 42 Ahr and 400 lbs.

An Orbital XCD is 41 lbs and has 50 Ahr. It would take 31 of them to get 374 Volts (actually 372 Volts nominal). So it would take 1300 lbs of Orbitals to have 50 Ahr and 372 Volts nominal.

OK, so you don't want to run batteries to 100% DoD (Depth of Discharge), so let's design to discharge each to 50% to account for things like Peukert, temperature, better cycle life, etc. Then we get:

A123: 374 Volts, 21 Ahr, 400 lbs
Orbitals: 372 Volts, 25 Ahr, 1300 lbs

Now, big if here, but if Firefly can get their lead acid batteries down to 1/3 the weight of conventional batteries, and scaling from the Orbitals:

A123: 374 Volts, 21 Ahr, 400 lbs

Orbitals: 372 Volts, 25 Ahr, 1300 lbs
Firefly: 372 Volts, 25 Ahr, 1300/3 = 433 lbs (Theoretical number!)

Wow, the theoretical Firefly numbers are nearly identical to A123! Of course, these are vaporware numbers at the moment, but shows there is some hope. Also, there are other lithium batteries with better energy densities than A123. Firefly batteries should be far cheaper than lithium, so this could be a very exciting battery breakthrough for EVs.

So while it is hard to compete with the inherent lithium voltage advantage (2 to 3 times that of nickel or lead chemistries), it is also hard to compete with the lightness of carbon compared to metal. Lead acid batteries are only at about 1/4 of their theoretical capacity. Firefly is basically replacing the interior structural and inactive part of the lead electrode with lightweight carbon foam.

Switching to power, the A123 batteries can supply up to about 800 hp! The Orbitals can provide "only" about 400 hp worth of power for a few seconds. The Firefly batteries are unknown on power, but theoretically there are reasons to believe they could have power comparable to Orbitals.

Final caution: The first batch of Firefly batteries will just have one carbon electrode, so won't be as light as the later ones with 2 carbon electrodes.


----- Original Message ----
Quoted anonymously:

> "...Hopefully they'll have similar energy density to A123..."

Cough.

I am sorry but a little thing like the laws of physics kinda messes
that
one up. There is a theoretical maximum if you were able to fully charge
and discharge every gram of active material.

spend a few seconds on google and you will find stuff like :

http://www.doitpoms.ac.uk/tlplib/batteries/battery_characteristics.php

It is hard to compete when the voltage alone is 3x




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