GM's Electric Lemon

GM's Electric Lemon...

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...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson
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Anyone have any idea how many kWh of charge is required for the "electric range" of 40 miles? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

From the chevy web site, it looks like ~ 13kwh. That's from their $1.50 a day and 12c a kwh.

But, I hear the Prius's batteries tend to become unbalance after a few years, and they need to be painstakenly charged and balanced.

I'm not convinced yet.

BTW, the Volts battery capacity is rumored to be between 25% and 75% of the actual cell capacity. Otherwise the batteries will not last. Probably due to heating during discharge (25%) and heating during charge over 75%. Wonder if they are still having 'Thermal' Events' ;)

Cheers

Reply to
Martin Riddle

I smell a business opportunity for a younger Techie.

In a few years there will be a supply of these things around that will not have a market value that exceeds the cost of a new set of batteries. A replacement power system that costs less than a battery set may do well.

Watch out for new laws that may restrict such things. A niche may exist under all circumstances. Any one for Steam Power? After all the Stanley Steamer held speed records for a long time!

John Ferrell W8CCW

Reply to
John Ferrell

I suspect it costs more per mile to operate electrically than via gasoline. But I can't find anything on the Volt website other than obfuscated "specifications". ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

I would go with some figures for cost of energy and efficiency of converting energy from one form to another.

Gasoline appears to me to cost lately $2.65 per gallon.

I plug into Google gasoline btu gallon and I see figures mentioned in the hits to average-to-my-eyes around 120,000 BTU/gallon, and 115,000 BTU/gallon gives me the impression as reasonable for the modern stuff diluted by ethanol and sometimes MTBE.

A BTU is 1055.9 joules

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At this rate, gasoline has 121.43 megajoules per gallon, or 45.8 megajoules per dollar.

I do have the impression (no web work this minute to support it) that car gasoline engines achieve around 25% efficiency of converting chemical energy to mechanical energy into the car's transmission, and only at a rate that high when "the going is better". Car engines have to do a lot of work at RPM and mechanical loading far from their optimum, and they often have to burn fuel when they re not moving the car at all. As a result, I would like to think of 20% as an "average ballpark figure" for car gasoline engine efficiency of converting chemical energy to mechanical energy.

"At this rate", gasoline achieves 9.16 megajoules per dollar.

=============

Now, for the electric car alternative:

USA national-average residential electricity cost is nowadays probably about 12 cents per KWH. A KWH is 3.6 megajoules. Divide that by .12, and the result is 30 megajoules per dollar.

However, there are still the losses between one's electric meter and the motor shaft of an electric car:

1: Household wiring downstream of the house's electric meter. I expect a house with wiring to support an electric car to have a nice low loss there around 1%, for 99% efficiency. However, many houses that get electric cars will need wiring installations/upgrades whose cost needs to be considered for return_on_investment.

2: Efficiency of the battery charging circuitry: My impression based on my experience with a bewilderment of specific individual figures for efficiencies for modern electronic fluorescent lamp ballasts and modern line-powered lighting-grade LED drivers is that a reasonable figure is 93%.

3: Efficiency of the battery storing and releasing the charge: 3a: Hysteresis between charging voltage and discharging voltage of the battery: For sake of argument, I would take on a 12V lead-acid battery. I seem to think that a lead-acid battery charged at a mildly aggressive rate that appears to me necessary will have most of its charge pushed in at a voltage of close to 14 volts, and the average voltage per unit charge appears to me to be 13.6 volts (or slightly more) to push the charge in.

The average discharge voltage of this battery appears to me to be 12.1 volts. At discharge current low enough to make IR drop negligible and the battery being discharged and having discharged at least half a percent of its charge since last recharge, it appears to me that this is 12.7-12.75 volts at 90% charged and 12-12.1 volts at 10% charged. Average is probably 12.4-12.5, but there is IR drop in the battery and wires connected to it, and a motor to move a car appears to me to be a heavy load. I like to think that 12.1 volts is "charatable in favor of an electric car".

Ratio of 12.1/13.6 is 89%, a figure that I consider to be somewhat "charatable to electric cars". So, I now want to back that down to 88% for efficiency for the battery storing and releasing energy.

4: Efficiency of motor control circuitry: Such as likely-needed PWM-based switching motor driver circuitry having simulated output resistance. I am guesstimating efficiency of 96% on a good day, due to lack of AC-DC conversion in electronic fluorescent lamp ballasts and "lighting grade LED drivers", and to a lesser extent lack of fully converting pulsed output to AC.

5: Efficiency of the electric motor: That one I have checked out less, other than on the nameplates on a few motors in the near-one-HP range (~~ ?? 80%). I would like to think that the electric motor in an electric car is 85% efficient.

Total efficiency in an electric car:

.99 * .93 * .88 * .96 * .85, totalling 66.1%, probably optimistically, for efficiency of converting billed electrical energy to mechanical energy from the electric car's motor.

This appears to me to be 19.8 megajoules per dollar for cost of moving an electric car, in comparison to 9.2 megajoules per dollar for cost of moving a gasoline-powered one. "So far at this rate", the electric car costs about half as much to drive as a gasoline-powered one does.

However, an electric car has further disadvantages:

  1. Initial cost is higher, and initial cost of getting an electric car also includes whatever cost of home wiring upgrade needed for charging it.

  1. A practical electric car nearly-enough-inherently requires a large rechargeable battery, likely to need to be replaced more often than "similarly-big-ticket" items in gasoline-powered cars need.

  2. The amount of energy stored in a fully charged battery in an electric car will not move it as far as can be achieved by the gasoline in a typical gasoline-powered car.

  1. Ratio of peak motor horsepower to loaded vehicle mass so far tends to be less with electric cars than with gasoline-powered ones. That wil impair an electric car's acceleration, especially acceleration after achieving a speed around 30-35 or whatever MPH. That slightly impacts ability to handle some somewhat-common emergency driving situations, slightly impacts ability to accomplish merging operations and lane changes on higher speed roads, and to many people greatly impacts enjoyment of driving the vehicle in question.

Even if an electric car achieves as much acceleration at 60 MPH or whatever as a fully-loaded 18-wheeler achieves, 18-wheelers are big and have a higher rate of achievement of getting fellow motorists to accomodate their movements than dinkier energy-efficient cars have. (Although that becomes some argument in favor of mandating "usual cars" to be "dinkified", but then-again that appears to me likely to "not sell well" in USA anytime soon.)

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Reply to
Don Klipstein

As someone has noted, a boiler and a steam engine can be small and very powerful, especially peak power. The problem is the condenser.

John

Reply to
John Larkin

Electric vehicles can often be charged outside peak hours, which reduces the production cost in power stations.

During peak demand, the peak power is typically produced with simple gas turbines burning expensive fuels, such as gas or oil.

Extensive use of electric vehicles will reduce the peak/average ratio, the need for peaking gas turbines is reduced and power plants using cheaper fuels can be operated 24 hours each day.

The reduction of the production cost is not necessarily reflected into end user prices (taxes, "Enrons" :-(

Reply to
Paul Keinanen

Actually a diesel engine does much better. A good diesel like found in a BMW will have a 50% efficiency.

You forget that the engine can also work as a generator to re-use energy otherwise lost while braking.

But these costs tend to go down.

Clutch and timing-belt replacements aren't cheap.

Don't forget most combustion engines found in cars only achieve their rated (peak) power output at unusable high RPM. Cars with an engine which produce a flat power output graph over a wide RPM range are rare. If you have a 100HP car you might actually use 50HP to 60HP max or even less if you are a relaxed driver.

An electric engine with switchable poles ('electric' gearbox) can output its full power at almost any RPM.

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Reply to
Nico Coesel

Electric cars usually have the ability to use regenerative braking to recharge their batteries so they should be particularly advantageous in city driving. Gas cars need to add much of the overhead of a full electric car (just a smaller battery) to get the same advantage.

I disagree with the article- I think GM made a reasonable choice for a first offering in the US. Who would buy a car like the Nissan that didn't have a backup gas engine? What if you forget or are unable to charge it? What if you want to take it on a long drive? And it's silly to try to connect the bail-out with the Volt. GM's problems are more to do with their current unexciting and (in some cases) award-winningly ugly product lineup.

As far as it being cheap to operate- watch out for laws that would require separately monitored outlets, perhaps for off-peak charging or some kind of bogus safety reason, so that extra road taxes can be tacked on to the electrical rates at a later date.

Best regards, Spehro Pefhany

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Spehro Pefhany

: : :"Jim Thompson" wrote :in message news: snipped-for-privacy@4ax.com... :> On Fri, 30 Jul 2010 14:14:05 -0700, Jim Thompson :> wrote: :>

:>>GM's Electric Lemon... :>>

:>>

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:>> ...Jim Thompson :>

:> Anyone have any idea how many kWh of charge is required for the :> "electric range" of 40 miles? :>

:> ...Jim Thompson : : :From the chevy web site, it looks like ~ 13kwh. :That's from their $1.50 a day and 12c a kwh. : : : :But, I hear the Prius's batteries tend to become unbalance after a few :years, and they need to be painstakenly charged and balanced. : :I'm not convinced yet.

Me neither....

All of the DIY electric vehicles I have inspected employ a cell equalisation circuit on every lithium-ion cell in the string. I guess that would be just too expensive for GM.

: :BTW, the Volts battery capacity is rumored to be between 25% and 75% of :the actual cell capacity. Otherwise the batteries will not last. :Probably due to heating during discharge (25%) and heating during charge :over 75%. :Wonder if they are still having 'Thermal' Events' ;) : :Cheers : :

Reply to
Ross Herbert

Got to be done if you want best life out of the battery pack, they just need to cover warranty period? People buy on price, don't look at the cut corners manufacturers make to meet the low price demand.

Like the older new cars that one had to remove original plugs and fit grease nipples in order to perform normal maintenance? You wouldn't guess the proper part cost much more?

Grant.

Reply to
Grant

ion

st too

ANY modern battery pack that does not charge the battery on a per cell, fully managed basis, is NOT a 'modern' battery pack.

It is NOT expensive at all. Battery watchdog chips and charge management systems have been around for a long time.

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Nunya
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amdx
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amdx

I don't think so, at least in the country where I am living. Gasoline is sold with much more taxes as electricity, so you can drive about a few hundred miles for just $50.00. It's about ten times cheaper to drive elecrtical.

BTW: you don't need as much energy as with fuel, because you only spent energy when you move. It doesn't make a dirty smell in our small streets, so it's better for our health.

We only need better solarcells to load the batteries, loading batteries by burning fuel is a bad option. Driving an electric car is preferable in all ways, except the low sound it produce. You need to look around better when you want to cross the street.

KB

Reply to
Koning Betweter

The warranty is 100K miles or 8 years. That's quite a long life to not have equalization, I agree. Of course the fine print in the warranty could have such a low threshold of operation that it doesn't matter. Yeah, my wife's 3+ year old laptop battery works, but not for a useful amount of time.

Except that greasing the linkages wasn't considered "normal maintenance". They were "permanently lubricated".

Reply to
krw

You don't think they're going to replace that lost revenue somehow?

Ban diesels. Modern gasoline engines are quite clean, forgetting the CO2 hysteria.

Complete nonsense.

Reply to
krw

Koning Betweter wrote in news:2010080116430434228- Koning@Stumpernl:

newer cars don't make that "dirty smell".(US cars,perhaps..)

in your country,they might make sense. In the vast USofA,they don't. They don't have the range.

I note your country gets more than 1/3 of it's electric power from oil,another 45% from natural gas.

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Jim Yanik

Europeons seem to bloviate a lot over things they know so little about. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Jim Thompson

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