> But the Tesla is old news! There's one just up the block.
I forgot that you need to keep up with the Jones.
> As a practical matter, that's what we should do. Well, other than keep the
> '95 Protege until the wheels fall off* or engine packs it in. Only about
> 65,000 miles on it, as I recall. Far the cheapest, and most environmentally
> friendly, option.
I've put 4500 miles on my X5 in the past five weeks. All three of our
vehicles range from about 120,000 miles to 180,000 miles and are going
strong.
> All our long distance road travel is diesel already.
My next SUV needs to get 28 mpg at a minimum. My X5 will get that at
55 mph if I am being a good boy. 21 mpg if I'm not being a good boy on
the interstate. But it has a big V8 to feed. I'll go diesel only if
it's BMW.
> I know you've been a big exponent of the Prius 'old' battery tech. The
> Toyota guy yesterday said they are using various battery types in their
> hybrids. The Mirai uses a controller and battery type from an RX something,
> I think. What's your take on the BMWs that makes you prefer them to others?
The RX's controller and battery are a joint development with Tesla, I
believe. It's been aging well.
There are three distinct styles of hybrids:
1. ICE (internal combustion engine) as primary and charge with
electric motor for acceleration/boost.
2. Electric motor as primary with ICE for acceleration/boost and charge.
3. Electric motor for all propulsion and ICE for electrical charge and
electrical generation for electric motor.
Most of the systems are a variation of the first style. The Prius is
the second style and GM's feeble efforts follow the third style.
The advantage of the first two is that the ICE is much smaller and is
all about horsepower with zilch torque. Honda has usually doing the
first style, but Honda is on at least the fourth version of hybrid
technology and the previous three have eaten batteries alive. Part of
the problem is that the first method requires distinct mode switching
with active engage/disengage mechanisms for the electric system. When
the electrical drive system is engaged for propulsion, it is using the
battery for the drive and will work down through the battery capacity
until it reaches a threshold and is gone.
The second system is generally more dynamic and especially as
implemented by Toyota in the Prius and some Camry models doesn't
actually switch modes but is always electrically seeking an
equilibrium. Under acceleration, the ICE and electric motor are
working together to propel the vehicle, but the battery contributes
electricity to the motor until a certain point where the ICE will
change RPM and will actually generate enough bonus electricity to
power the electric motor as well as feed surplus energy back to the
battery. As a result, the Prius doesn't go deep into the battery cycle
at all and will stay withing a 100Wh range. It doesn't deep cycle the
batteries like the other systems do. Where the Prius/Camry will "deep
cycle" the battery is when you are sitting at a long stoplight on a
hot summer day. Instead of running the ICE, it will use the traction
battery to keep the air-conditioner running as well as all the rest of
the electricals. After a couple of minutes of sitting, the ICE will
kick on to prevent the battery from going flat, but it will cycle off
right away and then when you are in motion again, it will get the
battery charged up a couple notches. It always saves a little bit at
the top of the battery charge for the unexpected long downhill coast.
(Our second-gen Prius will save enough battery capacity for about four
60-0 mph coastings or 200Wh).
The third system is really where I would prefer most system go, but
requires heavier motors and deeper cycle batteries. We're heading that
direction and the vehicles which are primarily battery-drive with the
ICE hidden in the trunk fit this description. We'll eventually see
some SUVs and 4wd vehicles which are 100% electrical drive that don't
have a normal drive-train, but actually have the electrical motors in
the hubs.
So, what about the BMW system? It depends on which mode setting you
are using. BMW is using a variation of the second method like the
Prius for lower speeds, and a variation of the first method for higher
speeds. Where it crosses over from one system to the other is
dependent on your mode setting and driving style. Instead of a
one-size-fits-all approach, BMW has opted for a system where either
the ICE or the electrical drive system will motivate the vehicle
nicely down the road. To REALLY motivate the vehicle does require both
propulsion systems, though. Porsche's system is very much the first
system style.
BMW is not really seeing the huge mileage gains with hybrid that we
would expect, as compared to the normal models because BMW has been
very aggressive in implementing power recovery and non-traction-drive
hybrid technology in the vehicles. For example, all the alternator and
air-conditioning compressor will kick in when the engine is producing
excess energy, and will kick out when it isn't. Ford has also been
aggressive in implementing this technology too and it shows in the
effective mpg. Pull up to a stop light and the engine will shut off.
Having electrical air-conditioning compressors, power-steering and
other doodads like that do make a difference. While unnerving to have
the engine shut off at the stoplight, you get over it by the time you
fill the gas tank for the second time.
I would be amiss if I didn't mention the ultra-drool-worthy BMW i8.
All I can say is "wow". I want one of those. It's form of "hybrid" is
unusual in that it's a split drivetrain system. Technically, it's in
the second category of hybrid systems, but crosses over a bit into the
third category.
If we stay here in Iowa past next summer, we're going to do some
upgrading on the house. It needs a new roof and siding as well as some
new windows and probably a new furnace/air-conditioner. Other than the
shingles, everything is original to the 1983 construction. It was a
state-of-the-art solar house when it was built and it may not take
much to bring it up to PassivHaus certification. Anyway, the thought
is that since we are going to replace the roof anyway, why not go PV
across it? We only need 1/3 of the south-facing roof for our housing
needs, and we could go ahead and add more panels to take care of
plug-in hybrids. Between and i3 and i8 we could be set to avoid just
about all energy costs for the house and travel.
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
--
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