OT: New but interesting car battery issue

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Scott Lurndal presented the following explanation :

So that's 83 1/3 amps then? ;)
I doubt that very much.
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On Thu, 13 Oct 2016 17:00:07 -0400, FromTheRafters

Why? Starters are power hogs and we wire them with 2ga or larger wire. When they rate batteries the CCA is hundreds of amps.
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On Thu, 13 Oct 2016 19:20:14 -0400, snipped-for-privacy@aol.com wrote:

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.
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On 10/13/2016 7:12 PM, snipped-for-privacy@snyder.on.ca wrote:

From: http://www.autoline.tv/journal/?pq0
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.
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On Thursday, October 13, 2016 at 8:24:29 PM UTC-4, Joe wrote:

ton is ready for its power stroke. So it injects fuel into that cylinder an d then instantaneously commands

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 t a starter, but it could lessen the power needed.
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On 10/13/2016 8:28 PM, trader_4 wrote:

That makes a lot of sense. If the code reader was taking the energy it would be very hot when you unplugged it.
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snipped-for-privacy@aol.com expressed precisely :

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 wrong answer.
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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.
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Now we could either talk about the amps drawn

Actually Watts x time would be Energy with units of Joules.
One Joule of energy is 1 Watt of power for 1 second.
m
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(which is amps times volts) Since under starter load the battery drops to roughly 10 volts, a 1000 watt starter draws roughly 100 amps.
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snipped-for-privacy@snyder.on.ca says...

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.
--
RonNNN

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RonNNN wrote on 10/13/2016 :

I think it's thirty seconds, and for CCA the voltage is 7.2 volts.
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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 of 2.5kW
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On Thursday, October 13, 2016 at 10:50:17 PM UTC-4, snipped-for-privacy@snyder.on.ca wrote:

Can't be, R stays that starters can't be spec'd in watts.
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snipped-for-privacy@optonline.net says... <snip>

<snip>

You really do have a reading comprehension problem, don't you?! Reread what I actually said instead of playing "twist and shout".
--
RonNNN

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On Thursday, October 13, 2016 at 8:36:17 PM UTC-4, RonNNN wrote:

I see, so whether a battery or other energy source is capable of delivering 600 amps for 1 sec or 1 hour doesn't matter?
Battery ability is

I see, so it's more than just the amps delivered for an instant.
Rule of thumb is the battery needs to be able

None of which has anything to do with using watts to measure a starter.
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On 10/13/2016 10:39 AM, trader_4 wrote:

I've got a ScanGauge II plugged into the ODBII port permanently. It's been there for over 5 years on this car, and 4 on the previous one. Both cars only had the OEM battery.
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On Thursday, October 13, 2016 at 10:26:24 PM UTC-4, rbowman wrote:

Which fits into what I've been saying, that the code reader doesn't use power in a few minutes that's significant compared to the starting power needed.
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On 10/12/2016 03:55 PM, trader_4 wrote:

There's no mystery. Time for a battery funeral.
And after you replace the battery, check the charging system for proper voltage output.
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On Thursday, October 13, 2016 at 4:37:24 AM UTC-4, Bubba wrote:

You missed the mystery part. I clearly said that I immediately diagnosed it as a bad battery. THAT wasn't the mystery.

Given that the car made it from NC to NJ just fine with a bad battery is proof enough for me that the charging system is OK.
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