There are a lot of interesting points, but I still have concerns about
charging capacity, both for the generating network to supply it when we
all have electric cars, and for the wiring involved.
Some of the comments at the end of Part 3 are interesting. One in
particular is worth repeating as a practical constraint to fast charging:
"VOLTAGE kills. AMPERAGE requires copper. WATTAGE is Volts times amps.
I’m trying to imagine a world where 500 kW can be “pumped” over a 3
meter charging cable that’s long-term safe, using cable that is light
enough to be handled by my fiancé, and has an exactly ZERO chance of
accidentally electrocuting the operator in the middle of a rainstorm,
with wind, in the dark, near the sea.
There is a reason why 400 volts is considered the top limit to
industrial use for staff without special training and permits. It, just
like 240, 220,120 and so on can kill you, but with way less ability to
percolate thru invisible cracks in insulation, or with the nominal
conductivity of flying rain water.
500 kW at 400 volts (if we stick to the safe voltage) requires 1,200
amps. On 2 wires AC or DC. Or 800 amps on 3 wires, if AC. Power loss
(cable heating) is “ohmic”. E=IR … P=IE … P=I²R = E²/R. Cable heating in
turn depends on power loss and thermal wicking. If a cable is actively
cooled (having either a hollow center or jacket with flowing non-ionic
coolant), the power loss can be quite high. High power loss is high
resistance, which is minimal copper, which is light weight. But if you
want durable, “10 year” outdoor flexible cables, power loss must be low,
because insulation is thick, heat conductivity, low.
My fiancé won’t be able to man-handle a 35 lb, 10 foot power cable.
Period. yet, this is exactly what 1,200 amps (x 2) or 800 amps (x 3)
conductor cable would require, for passively cooled cable that can work
up to Las Vegas ambient heat levels.
Moreover, tho’ the “easy solution” is just to raise the voltage (to 600
or 800 or 1,000 volts), this in turn puts rather outrageous safety
requirements on the whole under-the-hood car battery and energy
management subsystem. And it becomes exponentially harder to make a
10-year-safe outdoor power cable.
While I don’t doubt that there are 300 and 500 kW
constant-current-source chargers now envisioned, they’re also in the
realm of having 10 gallon-per-minute gasoline pumps. Over-filling
becomes a life-and-limb threatening petrol-gusher problem, when ANY
component goes awry. Its one of the reasons (at least in USA) why
conventional pumps are limited to 4–5 GPM. “Fast enough”. Only the Big
Truck diesel stations get away with 10 GPM. And only those on Big
He justifies the viability of electric cars for the times when you need to
do the long distance trip on the premise that they can (or will in future)
be fast charged when you stop for your toilet break.
well in order not to have to join the queue of 50 other people all stopped
for their toilet break that would mean that every single parking place at
the motorway services will have to have a charge point
1) how is that additional cost going to be paid for
2) where the heck is that all that concentrated power requirement going to
reasonable point, but one that is solvable by sane engineering I think
Liek a replaceable standard sized battery that simply gets swapped out
at a service station.
The paradigm has to change for electric cars, and the direction it
changes in is not fully established
Microsoft : the best reason to go to Linux that ever existed.
This can only work if you purchase about half the value of the car and
lease the battery from the manufacterer, seller, or specific leasing
company. Then what you are leasing is access to a workable battery, the
leasing company being responsible for old or failed batteries.
The biggest problem with this scenario is the waste of space and weight
involved in making the battery a separate module rather than using all
the nooks and crannies in the car structure to place battery cells.
Well I was speaking loosely. But I hear that the battery in a Tesla,
for instance, is hardly modular in the sense that the labour costs of
replacing it are high enough to make a car with a failed battery
virtually valueless out of warranty.
In a Tesla, the battery /is/ the floor. See the picture in the article.
(obviously there's a framing structure too, but the 'skateboard' battery
takes up the entire space between all four wheels). The best way to swap
that is to get out of one car and into another.
It's like an electric drill. All it is, at the most basic level, is a
battery and some motors, plus a bit of plastic trim to make it comfortable.
When the battery in your drill goes, that's more than half the value gone.
It's still a bit early to say, but it seems that the cooling and the charge
management means the lifetime is a lot longer than you typically get out of
laptop or drill batteries (that get hot and abused).
That said, used Tesla batteries are actually not terribly priced. A Model S
module from a scrap vehicle is about 800 pounds on ebay for a 5.3kWh,
24V pack (weighs 55kg, there are 14 in the full skateboard). That will
probably come down as more vehicles have accidents and end up in scrapyards.
There are DIYers with software that talks to the charge manager and plumbing
to plug into the liquid cooling circuit.
Just think, what could you make with a 5kWh battery pack...?
All Teslas (up to the Model S at least, don't know about the Model 3)
were designed to allow a battery swap, and the ability to do it in a
couple of minutes has been demonstrated (video somewhere) but they've
now chosen not to provide battery swaps as a service.
On Mon, 13 Nov 2017 08:45:42 +0000, The Natural Philosopher
Or a 'normal' model aircraft for competition use. The F5B class uses
up to ten Lipo cells with motors pulling hundreds of amps. They are
really impressive in flight. See this video for an example of this
multi-task competition where the first task is shown ( max number of
legs of a 150m course in 200seconds.
They had to introduce energy limiters (1750 Watt-minutes) in 2008
because batteries were exploding.
But Tesla also recently patented ideas about a removeable, battery
replacement system didn't they? Unfortunately, they seem to be looking
at a 15 minute swap by a combination of a machine and technicians -
rather far away from their abandoned idea of a 90 second, automated swap.
The sort of idea promoted by one with their head in the clouds.
A battery pack is by far the most expensive part of the car. And likely to
remain so. With also a finite life.
So you change your fooked one for a good one for the cost of the
electricity. Or even more likely get given one which will just take you
down the road before failing.
And it hardly sits nicely in with one who wants to 'bring back control' It
would require compulsory cooperation between car makers world wide.
*Geeks shall inherit the earth *
Dave Plowman email@example.com London SW
That's dealt with later in the comments thread by the same guy who wrote
the comment about 500kW charging issues:
"Only battery swap tech can beat the 15 minute-to-charge barrier
reasonably safely. And only that can be done thru robotics. And “20
minute charge”, is full of a canard’s feathers: 80% of how many kilowatt
hours? Oh… it depends. A very light-weight car, getting way better than
1 mile per megajoule (i.e. 5+ mi/kWh) and having “only” a 200 mile range
battery will have 40 kWh battery of which 80% is 32 kWh. Divide by ⅓
hour (20 min) and you get 96 kW charge rate.
See, that’s doable. Already in service, actually, at some specialized
SuperCharge Tesla stations. 72 kW is more typical though. (30 min
charge). But oh… only Tesla may use Tesla supercharge stations. Monopoly.
But what of a nice premium car – 400 mi range for non-stop convenience.
Necessarily (today at least) heavy due to the extra-large battery. And
all the supporting struts and so on to keep everything aloft. A 2,000 kg
car, empty. Its mileage is closer to 3 mi/kWh. 400 ÷ 3 = 133 kWh
battery. 80% is 106 kWh. This baby requires 1.5 hours of charge at a 70
kW SuperCharge station to fill up.
Thats not 20 minutes. More like 90."
What fun, how many acres of storage space would you need how do you move
the batteries from point A to point B (fork trucks ?),tesla batteries
weigh 540 kg don't know size as they are built in.
How many refills (changes)per day
Sounds easy for engineering to solve,(I need a sarcasm symbol)
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