Here's my story. The Explorer dosn't have an issue but I do have an question that some one here must be able to adress.

Back ground. Good battery alt ect. Tested over time with various meters and proven in DB Drag. I just recently aquired an Escort X50 detector. One of it's options is to show continues voltage. In the mornings on start up it reads 15.1 to 15.2 volts. As the engine warms up the voltage comes down to the mid 14 range. This is what I had witnesed in the past. This 15 + seems to only happen when it's cold. Now it gets parked in the heated garage and all so it's not that cold.

Is this normal. And if so why?

 

I'm not an expert on alts, but I'm fairly sure it can pump out more when cold.

 

think of it as a ... um somthing electrical lol like a voice coil... as it heats up you lose performance. or something along those lines.

 

Maybe has to do with the fact that a lot of vehicles idle higher when cold?

 

All this is correct. Alternators put out more when cold. Always look for hot ratings when buying an aftermarket unit.

Plus, since the battery just puked a bunch of energy into starting the car, the alternator is going to be jamming to recharge it.

 

Starting an ice cold engine requires way more energy, thus the battery drain is more substantial, and the alternator's job is to recharge the battery plus run all of the electrical components in the vehicle. The engine, the oil, ignition system (spark) etc, when cold are more resistant to moving and/or more is required of, thus more energy is required, more spark, more fuel and air and more alternator output to make it all happen.

 

gret info here, though I would like to add, that even though you park in a garage, the engine is still 'cold'... consider it this way, if opperating temp is 180f then 10c isn't too warm for the engine...

Mark

 

Thanks for all the feed back guy's. Your information reflects what I thought. It seems the as the engine temp. gets to "normal" it levels of. So now all I have to do is replicate the colder temp to charge between Burps. Mmmm ice packs?

I didn't have any negative concerns as I already knew that every thing was working fine. Now how to replicate this in +35....

Dew I thought about the idle but when it's on higher idle no real change.

Duke yes it doescharge higher at start but again not in the 15v range.

SQ civic your right about the 10 to 180+ temp diference. Yet when I start it when it parked out side during my work day it doesn't seem to get such great voltage.

And for the record the Explorer is spoiled so I can be more comfortable. Heated garage to plug in. This detector is an neat toy/ tool. And a plus great learning tool.

Thanks again guys keep it coming!

 

(GrizZz here, wife's PC)

Yes, alternators will charge higher when cold. The colder they are, the more they'll put out. And with low resistance batteries (Optima, etc.), and extreme cold mornings like -25 or colder, it can get quite high, alarming even.

An easy starting engine, at +20c, will only draw 60 to 80 amps for 2 seconds (or less). The alternator will replace that charge on a good battery within 10 to 15 seconds, maybe 20 on an older battery/vehicle... usually before the idle returns to normal.

But give the alternator a couple minutes, and the voltage will start coming down. If you give it more of a load (heater, headlights), it'll come down more.

My Delco alternator (as always, using my own van as an example) will pump over 15v at -25. Within 3 minutes, it'll be around 14.8. It won't go below 14.6 if the ambient temperature is -10 or colder, unless I'm in Glenmore Trail traffic, where it'll heat up more, so it may come down slightly.

Give the alternator to much heat, like +35 and working it hard, It'd probably drop to 13.8, or even 13.5.

Batteries like the cold. Batteries self-discharge faster in the heat. This is why it's common for people to keep storage batteries in the cold, like a fridge or basement. As long as it's charged beforehand, you can safely store a battery to -40c for up to six months. Room temperature storage batteries should see a charger every two months.

Where it gets a "Huh?"... Yes, of course, at -30 it takes a lot more power to start a car. If your car draws 80 amps when starting at +20, at -20 it'll take near double that. -30 make it quadruple, and so on...

This is where you get "Why do I need 800cca if my car only draws 100?". That 100 is all things perfect, a new vehicle. Add a -20 temperature and now you need around 200 amps. Add the GM poor battery systems (they're great for the first six months...) and you need another 100 to compensate... Add corrosion... and the four year life span of the average battery in Alberta, and you need another 300 (a battery slowly gets less powerfull over it's life).... Gettin' a better picture now?

In other words, batteries like mild temperatures. If you could keep your battery between -10c and +10c for it's entire life, you'd get over 10 years out of it. Alberta batteries average 4 years. Arizona batteries average only 2. Alaska batteries probably last 5 or 6.