On Thu, 13 Oct 2016 19:20:14 -0400, firstname.lastname@example.org wrote:
The average automotive starter today draws less than 100 amps under
normal cranking conditions. In extreme cold the draw may excede 150
amps. This is because the average starter today is a geared permanent
magnet starter. A direct drive series wound starter of yesteryear
could draw well in excess of 300 amps on a cold engine.
You need to remember the cranking voltage drops to well below 12
volts under cranking load. The actual voltage at the starter is much
closewr to 10 volts than 12 - so the current is closer to 100 amps
than 83 under full load.
Then again, starting a warm (but not overheated) engine can take
significantly less than the full 1000 watts of power. It is not
unheard of for an engine to start with the starter drawing less than
75 amps and the voltage dropping only slightly.. An overheated (tight)
engine ot a very cold (stiff oil) engine will draw more.
On 10/13/2016 7:12 PM, email@example.com wrote:
When an engine stops, the computer that controls it knows the exact position of each piston. And when you go to start the engine, it knows which piston is ready for its power stroke. So it injects fuel into that cylinder and then instantaneously commands
the spark plug to fire, which detonates the fuel, pushes down the piston and…starts the engine.
In other words, Ford has figured out a way to start an engine without a starter, and it’s going to incorporate that technology into its hybrid systems to hold down wear and tear and reduce the cost.
On Thursday, October 13, 2016 at 8:24:29 PM UTC-4, Joe wrote:
ion of each piston. And when you go to start the engine, it knows which pis
ton is ready for its power stroke. So it injects fuel into that cylinder an
d then instantaneously commands
and…starts the engine.
tarter, and it’s going to incorporate that technology into its hybr
id systems to hold down wear and tear and reduce the cost.
Now that is very interesting and could explain why it takes less energy to
start it when the computer has not been reset. It's not starting it withou
a starter, but it could lessen the power needed.
You would need a battery with zero internal resistance to maintain 12
volts at the amperage drawn by a starter. If you want to get the value
in Watts, you have to measure I and V and multiply them together.
You'll find that the lower voltage from the battery means that even
*more* current than you thought is needed to get the required power.
Just measuring amperage and multiplying by an assumed voltage gives the
On Thursday, October 13, 2016 at 1:43:31 PM UTC-4, RonNNN wrote:
And in the real world, power, which is what we are talking about,
is measured in watts. The claim was made that leaving the car
door open for the brief perios while
resetting the codes could have run the battery down enough so that
it would not start. Now we could either talk about the amps drawn
by the door open and for how long, how many amps the starter pulls
and for how long, etc or we could talk about power.
Power is more direct, so that's what I used.
Current draw is measured in amps but starter power is rated in watts.
(which is amps times volts)
Since under starter load the battery drops to roughly 10 volts, a 1000
watt starter draws roughly 100 amps.
Why not just address what I said.
Now, think of this. Does the starter draw *any* power when not in use, as
compared to a hand held scanner turned on and taking readings while
attached? Even at that, I doubt the scanner would draw more than 1/2 of 1
amp... likely much less.
I retired from automotive after over 45 years, and never measured starter
draw or battery draw in terms of wattage. Battery capacity is measured in
cranking amps and cold cranking amps, not wattage. Battery ability is
usually measured by how many amps it can maintain being loaded down to
9.6 volts for 15 seconds. Rule of thumb is the battery needs to be able
to maintain twice the cid of the engine in amps to be capable of
satisfactorily starting the car.
That WAS the rule of thumb. You won't go wrong using it today, but
your battery will be significantly oversized.. Today's starters are
significantly more "efficient" than the starters of yester-year.
The starters are rated in watts or kW. For instance some American
market Toyotas used to get 1kW starters, while the Canadian standard
was the 1.3kW "arctic" starter. A lot of diesel starters are upwards
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