Slight digression: Your comments about average versus peak draw
reminded me of something I learned of long ago.
When an automobile engine is place in a boat, it is grossly *de-rated*.
Back in the old carburetor days, an engine that could be equipped with
a 2 or 4 barrel carb in a car might carry a 1 barrel carb in a boat --
and take the attendant power hit.
The reason is that in a boat, you operate the engine at full power, or
nearly full power, for extended periods. Boats don't coast (much), and
boats never go downhill. When the engine stops, the boat *stops* -- if
you've ever been in a cabin cruiser with good sized engines running
along at planing speed and switched off the engines, you know what I
mean: The boat almost instantly "falls off the plane" and reverts to
displacement mode, in which its top speed is far lower than what can be
achieved with a lot of power and some trim tabs. Folks who are standing
up in the boat when this is done may just fall right over (and then they
tend to get suddenly very rude -- it's not an experiment one tends to
try more than once, at least not without warning the passengers).
An automobile engine operated in this mode for extended periods burns up
in short order. So, when you drop a big V-8 into a boat, at least if
it's a factory conversion, it'll get a tiny carburetor stuck on it to
keep the owner from ruining it. (If it's a backyard conversion that's
something else again.)
And this really brings home the fact that automobile engines are just
*loafing* nearly all the time, and in fact their design *depends* on
that fact. You cannot operate a 250 HP auto engine in a mode where you
pull 250 HP out of it continuously and expect to get anything like its
rated lifetime from it.
With intelligent electronics which won't take the battery pack below,
say, half charge, you should be able to get away with a 30 or 40 horse
genset and *never* *ever* feel the lack, even if your electric motor is
a 150 horse monster -- because you'll never be drawing more than a
fraction of that power from it for more than short periods. I can't
accept Jed's implicit assertion that you need to be able to cruise up
hill at 106 MPH ("You have to have an ICE capable of carrying the entire
load up the steepest hill at maximum speed", he said) -- 99.9% of the
owners never do that, and 100% of them *should* never do that.
Furthermore, I seriously doubt even as many as 2% of the owners will
ever hold the pedal to the metal long enough to get it up to 106 MPH
even once. Short bursts of perhaps 20 or 30 seconds is all the time
normal drivers normally spend pulling full power out of an automobile
engine, unless it's a low-power 4 cylinder or small 6 cylinder engine.
BTW did you know that when you actually draw a good fraction of your
motor's power, the AC (probably) cuts out? This is pretty much standard
behavior these days - it's how you can have a pig of an AC unit and yet
never notice the power loss: Whenever you need the power the AC clutch
lets go and gives it to you. And yet most people never notice the loss
of AC, either, because the time one spends actually asking the engine to
work hard is such a small fraction of the time spent driving.
In short, the need to run at full power for extended periods with
totally dead batteries is a straw man.
