I have traced the Service Doc's schematics of several of my cars and
many of the power circuits are no longer directly connected to the
battery via the Ignition key contact, but instead are relay-controlled
(which is enagaged by the ignition key directly or by electronics that
is triggered by the "Start" Button for newer cars without actual
ignition key lock).
If the battery voltage is too low to allow pulling in the relay or if
the electronics controlling the "ignition" relay cannot boot from the
weak battery, then there will be no alternator output, even though the
battery voltage itself might be enough to excite the alternator - if the
power cannot get to the alternator, then you cannot push-start the car.
Maybe have an emergency override where you power only the alternator
exciter from a push button without the car turning on?
Problem is that many modern cars have an electronic parking safety that
needs battery power to disengage, so jumping is the better approach in
those cases.

Regards,

Cor van de Water 
Chief Scientist 
Proxim Wireless 
  
office +1 408 383 7626                    Skype: cor_van_de_water 
XoIP   +31 87 784 1130                    private: cvandewater.info 

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-----Original Message-----
From: EV [mailto:[email protected]] On Behalf Of Ing. Marco
Gaxiola via EV
Sent: Thursday, August 18, 2016 8:20 AM
To: Robert Bruninga; Electric Vehicle Discussion List
Subject: Re: [EVDL] Pop-starting a stick shift?



 In my opinion, you may be half right. My logic says You can not start a
new vehicle with a pop-start with a 'completely ' dead 12v battery. 

 But thinking a little more i also have my doubts; since the alternator
once is spinning due to pop-start, is ready/can to produce electricity,
which in both cases would energize the entire electronics on board, by
consequence produce sparks and start the ICE machine. But me doubt comes
with a completely dead battery (0volts) not sure if the alternator
control cable (exite cable) could induce any curret so it start
producing energy. 

   If that is not true, it would only take more time to start a newer
vehicle. Also, usually batteries never get to 0v and it would depend on
how fine and robust the car's electronics is, by letting all this
process to happen with very little voltage (power)

    Just like you said: the only power needed to produce a spark. On
newer vehicles would be: ...to produce the spark and efficiently power
all the needed electronics to make the engine work properly.  And that
some times may be a considerable amount of power. 


Marco

Sent from my iPhone

> On Aug 18, 2016, at 7:27 AM, Robert Bruninga via EV
<[email protected]> wrote:
> 
> This is the only car group I know.  So pardon the off-topic post.
> 
> 
> 
> A young kid with a minicooper flagged me down to jump start his car.
I
> told him, I'd be happy to if he could figure out how to use my 400V
pack....
> 
> 
> 
> Then I asked, well, have you tried just rolling it and popping the
clutch
> to get it started.  He looked at me with blank stare.  I smugly said,
sure,
> it's a stick shift, so we just get it rolling and pop the clutch and
it
> will start.
> 
> 
> 
> It wouldn't.  Then I began to realize, that all the cars I have done
this
> with in the past DID NOT HAVE ANY CPU's in them.  IE, all you have to
do is
> get a spark, not power up and entire network of computers before the
motor
> will even begin to consider the "starting process".
> 
> 
> 
> So is this true?  That we can no longer pop-start a modern car with a
dead
> battery?
> 
> 
> 
> My son (too cheap to buy a new battery) still does it frequently with
his
> pre-cpu Geo-Tracker, in fact we just did it last week.
> 
> 
> 
> I'm just too old for all these newfangled hurdles...
> 
> 
> 
> Bob
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