# Forum

Unisciti allacomunità

Fun Facts - 85kWh

Looking at this thread on regen I got to thinking about just how much energy is in an 85kWh battery. So, plugging it into Wolfram alpha we find out that 85kWh is:

• equivalent to 305MJ
• about \$9.83 in typical electricity prices
• 10% of the annual energy use of a standard clothes dryer
• 16% of the Planck Energy
• 20% of the energy of a typical (?) lightning bolt!
• 3.6% of the total magnetic field energy in all the magnets in the LHC
• 3.4µg relativistic mass equivalent

Any other interesting/fun/crazy equivalencies?

2.6 gallons of gas ;)

It's more like 20 gallons in my current car!!

Enough to drive a Model S Performance at FULL POWER for about 15 minutes. Who will be the first to try that?

Steve_P445:
I don't think it would work... I think the software would limit power output to protect batteries, discharging them in 15 minutes would harm them I guess...
In owners manual (or was it warranty paper?) is written that car is not meant for racing (driving fast and racing are two completely different things), I have no idea how would it react... I guess only Tesla dev team knows :-)
But if somebody is going to try it, I absolutely want to know what happend :D

Just wait for Volker to get his car :)

Whity Whiteman presents himself as an even better candidate for this experiment :-)
http://www.teslamotors.com/forum/forums/model-s-autobahn

Gasoline energy content ~36MJ or 10kWh / liter, so 85kWh is 8.5 liters of gasoline which is ~2.2 gallons. With that you get 265 EPA defined miles, so 265miles/85kWh = 120 mpg of gas. About six times better than equal (heavy, large & fast) ICE car.

Timo, that is the exact formula I think should be used too. This whole weird math of cost comparison that is used is ridiculous considering everyone gets billed a different amount for gas and electricity and can charge using whatever power source they choose.

and something like 7100 cells to make up the battery

@Timo - and as the cost of gas rises the equivalent mpg of the MS will go up. :-)

...if you use \$/kWh and \$/gallon in the calcs.

nickjhowe, it does not calc. Gas here in the mid-west is a little over \$3. I think around \$5 in California. That is an extreme cost difference that significantly changes the EPA rating. The guy in Calli that is charging with his existing solar array is paying a completely different price. Ameren (my electric company) charges anywhere from 4.5-7 cents a kilowatt depending on the time of the year then they add on a fuel surcharge depending on the going rate for coal.

Timo's method which is the one I use it pretty much direct conversion using joules. No costs are involved since they are completely arbitrary.

Yes, Timo's system is cross-currency, too. The cost calcs differ in Norway, Germany, UK, US, and Canada, and can be applied after getting the true MPGe that way. In your own "market", though, that final step is the one that matters.

Ah, but how many gigawatts is it? At 88 mph does it reach near to 1.21? May need to test it near a clock tower or something... I hear the TM brand flux capacitor is better than the old DeLorean model.

I only wish that Tesla offered the Model S in a raw brushed aluminum unpainted finish. (Not a fan of the silver, I know many others are).

Cheers.

I hear Elon is really an alien trying to build the tech needed for him to get home...... oh wait that was a cheesy TV show.

Ceilidh;
There's always DIY brushed aluminum. Step 1: acquire a selection of steel brushes ...

@Sudre - my point was based on an assumption that the price of gas will outpace the price of electricity, so \$-for-\$ the model s mpge will increase over time.

By the end of next year--and certainly 2 years the EV industry will be using Super Capacitors to drive your car. They weigh a fraction of the battery weight. Capacitors have a huge advantage, in that they practically never wear out--charge instantly, and some of the new super caps are holding substantially greater charge. I ordered mine with a Flux Capacitor so I could jump forward a few years get a battery of super caps and have all their advantages.

@nick
It's a bit more complex than that.
From real driving experience (about 1,600 miles now) in CA:
My average is 377Wh/mile and I drive about 30 miles a day during the week and more on weekends.
Assuming 30 miles a day that's 11.3kWh/day.
The chargers are not 100% efficient, so let's assume ~5% loss.
Now you're looking at ~12kWh a day extra (to your normal electricity use).
If it pushes you to tier3 or tier4 pricing that are unregulated (it does push me into those rates), you're paying \$0.34 per kWh or \$4 a day for charging your car.
If you drive an ICE car with 19MPG (also a real life number) using Premium gas that's 1.6gal or \$6.2 at \$3.89 a gal (that's what it is here today).
So it's still about 50% less than gas but not that much in absolute value (\$2 a day of savings) considering once I'm in tier3 or tier4 pricing I'm paying \$0.34 for *all* kWh I use, not just 12kWh that I use for charging.
If you had a more efficient ICE car, the math could be in ICE favor altogether, e.g. if you're over 30mpg you're even or better than me driving a Tesla.
The best case scenario I'd be paying \$0.11 per kWh (tier1 pricing) and that changes things a lot since instead of \$4 a day it would be
\$1.32 a day or about 5 times cheaper than gas.
Staying in tier1 is pretty hard though, you need a PV system on your roof to offset most of your use.
At least we have that option in CA since we get a lot of sunny days here, and incentives are pretty good too.
That's pretty much the only way to guarantee your pricing long term as both gas and electricity prices will go up.

DBR;
And fill half a room for the charge you'd need, and lose charge 10X+ faster than a battery, and can fry you in a microsec if they short. Which they really enjoy doing. Good plan!

34 cents per kwh in CA?? OMG, that's like 6 times what we pay in AZ!!

@timo- you said "Gasoline energy content ~36MJ or 10kWh / liter"
I could be wrong but...
The figure I have is 1 gallon of gas produces 36.6 kWh with 80% being heat loss (-29.28kWh) so you would only get about 7.32kWh usable energy out of that gallon. not sure how that equates to MPG figures.
(Just guessing) that 10kWh is enough for about 34121 BTUs

If you get only 36kWh / gallon you are using a very inefficient gizmo to get energy out of it (like ICE). What I wrote is direct energy content figure without conversion inefficiencies (like the heat loss you mention). Gasoline (and hydrocarbons in general) have very high energy densities, far greater than any batteries. Problem is to get it out of them efficiently.

@cstull - PG&E's E-9 rate schedule goes from 3.74c/kWh (baseline) to 19.8c/kWh (top tier/300% of baseline) during off-peak hours.

If you're using a Supercharger, however, you must be in a hurry and are more likely to be charging during peak hours. PG&E's summertime peak-hour rate can hit 54c/kWh, and other providers may charge even more.

Arizona exports a lot of electricity, much of it to California, so I expect that lets them lower the rates at home - to a certain extent, some of what you're buying is surplus capacity that Southern California didn't need this week. We also have a high renewable energy purchase mandate on providers and virtually no in-state coal power generation; Arizona has coal from the Kayenta mine and the Glen Canyon and Hoover damns.

Arizona residential electricity cost is 3% below the average for the country, while Californians get charged 37% above average. On the other hand, you pay 41% above average for natural gas and we pay 36% below average. (Data from EIA.gov.)

Some CA providers offer steep discounts for charging EVs at night. You can use net metering to offset any electricity you use with energy you generate (e.g. from solar PV). If you produce more than you use, they will write you a check (something like \$0.04/kWh).

CA power supply is so pooched that the bind moggles. And it's getting worse, by fiat. Quite a spectacle!

Parts of CA are unable to meet demand during peak hours. SoCal Edison has even had scheduled rolling black-outs to miser energy. Therefore they charge customers a premium who use a lot of energy and give incentives to reduce demand during peak hours.
You could be referring to any number of things when you say it is getting worse by fiat, but the things I mentioned are implemented by SoCal Edison, not their big brother. Regardless of the possibly myriad causes underlying their behavior, it is working out ok for me, because I'm getting paid to drive electric.
To me what is bind moggling is why more people don't take advantage of the situation. Solar City takes advantage of it by giving people "free" solar panels while reducing their electric costs. I think that demonstrates there is at least enough margin in electricity costs for 3 parties (home, Solar City and the local electric company) to profit. it is possible for the home owner to take nearly all that margin for themselves.

MB3 -- it is possible for the home owner to take nearly all that margin for themselves.

It is, but there is also the risk of high maintenance costs. Solar City can average the maintenance costs over the number of installations so it's no big deal for them if a few have "problems". If you're a homeowner and are unlucky...

I didn't actually think of catastrophic failure, and they probably will occur at some rate. I'm not too worried though and perhaps there are ways to mitigate. I purchased micro-inverters so a single failure will not affect the whole set of panels. There aren't any moving parts though, so I'm not sure what kind of other failures to occur, but the panels and inverters have 20 or 25 year warranties. I suspect existing home-owner's insurance might cover other failure modes (e.g. tree falls).

MB3,

Hail damage too. If you use your homeowner's insurance for something less than a major fire or similar catastrophic event, your rates will go up far more than what you receive in an insurance payment.