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Old 04-04-2011, 05:41 PM   #16 (permalink)
3dplane
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Quote:
Originally Posted by jamesqf View Post
Start with 35 lbs rather than 7 for the gallon of gas, because you have to carry both reactants around with you.

Then tell us exactly why you're doing the comparison against lead-acid batteries. I mean, to begin with, the stuff's about as heavy as, well, lead. If you're doing weight comparisons, it's not really a good idea to start with something that's a metaphor for heaviness, now is it?

Nor is lead particularly energetic, chemically. Look at a lump of lead: what's it do? Just sits there, like thy nuncle, no? (If you remember your Tolkien.) So why not use something that's a) light, and b) energetic, like for instance lithium?
I'm talking about driving down here on earth where we don't have to carry our own oxygen.

I'm doing the comparison with the metaphor for heaviness because....that's what my batteries are made out of.

Lithium looks about 4-5 times better than lead but other than a few RC lipo packs,I don't have any significant amount of them.

I'm not bashing lead acid nor the efficiency of ICE powertrain.
I'm simply trying to come up with an answer to what is a fair/realistic way to relate to the amount of battery pack power available in an EV to certain amount of gallon used in an ICE powered car for the same distance driven under similar driving conditions,similar car etc.

Let me put it this way. There is an employee at my work who comes up to me once in a while and asks me when are they coming out with the electric car? (he does that about once a month)

I reply it's already out. He would then ask how far does it go?
I reply 200 miles. Then he asks why only 200 and not 400 miles?
This is where I wish I had a simple answer for a simple man and say: Because it would require X amount of lead acid or X amount of NiMh or Lithium to match the energy contained in the amount of gas the ICE used up to drive 400 miles!

I clearly understand that due to the efficiency of the EV, to drive X miles we do not need the crazy amount of batteries that my stupid energy comparison shows but that's besides my point.

Or this question. If my electric golfcart is powered by a 72 volt 100 Ah pack...( all used/murdered mismatched auto batteries 2p 6s) What size is my "gas tank"? (400+ pounds of lead)

I can drive it for 10 miles before the weakest battery will go below 12 volts (and stay there with no load) while the rest of them are around 12.2V (no load)

So I got a 7.2 Kw/hr pack. Can I say that I have a .2 gallon "gas tank"?
(7.2/36.6=0.19)

Sorry for the long babble.
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