One for the elec.techs Forester

[BOB HOLLOWAY [ UK].]

I am given conflicting "advice" from "experts"about the battery charging on
my 03 Forester, because I only do low miles..
One says the battery is only charged when cruising,the other says it only
charges when a load is applied or on over-run[free running down hill]
The second guy suggests running with the lights ON to keep the battery fully
charged.
Seems whacky to me , but if it is so , is there a way of wiring the side
lights via the ignition switch auxillary so that they go off with the
ignition. All this stems from a moonlight that will not work properly, will
only travel 3 inches with each button push, and low volts are suspected, a
it clears itself after a run.

 

[mike]

The battery charges when the engine is running. Check the battery with a
multimeter, when the car is off you would read about 12 volts. When the car
is running you should read about 14 volts.



If you meant moonroof (as opposed to moonlight) it should work fine when the
car is running unless your battery and/or alternator are a little dodgy
(check by using a multimeter as mentioned above)

Note often the sunroofs (or moon roofs) have intermediate stages.

My legacy the sunroof will open fully with one press (and hold) of the
button, but when you go to close it the roof stops halfway until you release
the button then repress it. This is normal.

Hope this helps



Mike

 

[Guy Macon]

I am given conflicting "advice" from "experts"about the battery charging on
my 03 Forester, because I only do low miles..
One says the battery is only charged when cruising,the other says it only
charges when a load is applied or on over-run[free running down hill]
The second guy suggests running with the lights ON to keep the battery fully
charged.
Seems whacky to me

They are both wrong, but the first fellow is almost right, while the
second one should never be allowed to give anyone advice ever again.

Your battery gets charged whenever the engine is turning. More RPMs
means more charge, but it still charges at idle.

Load has no effect unless it changes the RPMs. All the generator
cares about is how fast it is spinning.

Having the light on makes it charge a tiny bit slower, but the effect
is too small to worry about.

Your battery gets discharged when it supplies electricity with the
engine off. The domelight discharges it slowly, the headlights
faster, and cranking the engine fastest of all.

If you want to see whether I know what I am talking about, see
my webpage at http://www.guymacon.com/

 

[nothermark]

I am given conflicting "advice" from "experts"about the battery charging on
my 03 Forester, because I only do low miles..
One says the battery is only charged when cruising,the other says it only
charges when a load is applied or on over-run[free running down hill]
The second guy suggests running with the lights ON to keep the battery fully
charged.
Seems whacky to me

They are both wrong, but the first fellow is almost right, while the
second one should never be allowed to give anyone advice ever again.

Your battery gets charged whenever the engine is turning. More RPMs
means more charge, but it still charges at idle.

Load has no effect unless it changes the RPMs. All the generator
cares about is how fast it is spinning.

Having the light on makes it charge a tiny bit slower, but the effect
is too small to worry about.

Your battery gets discharged when it supplies electricity with the
engine off. The domelight discharges it slowly, the headlights
faster, and cranking the engine fastest of all.

If you want to see whether I know what I am talking about, see
my webpage at http://www.guymacon.com/

Pretty close but.... at idle it's marginal. There are stories of
people caught in traffic jams having their car die from running the
air conditioning and hi power stereo while sitting for long periods.
The battery runs down and the car dies even though there is no
indicator light.

 

[John Varela]

Your battery gets charged whenever the engine is turning. More RPMs
means more charge, but it still charges at idle.

I agree with nothermark: running the heater/air conditioning blower, the
lights, and one or two other things can draw more current than the
alternator can supply at idle.

Having the light on makes it charge a tiny bit slower, but the effect
is too small to worry about.

I recall that many years ago--and by that I mean 60+ years ago--before all
cars had voltage regulators it was common belief that on a long trip it was
wise to run with the lights on in order not to overcharge the battery.
Whether that was ever necessary or just an old wives' tale, I dunno. But
some of these beliefs die hard and advisor #2 may have been delivering
advice that is no longer good if it ever was any good. I suspect it was
already obsolete by the 1940s.

 

[tom klein]

I am given conflicting "advice" from "experts"about the battery charging on
my 03 Forester, because I only do low miles..
One says the battery is only charged when cruising,the other says it only
charges when a load is applied or on over-run[free running down hill]
The second guy suggests running with the lights ON to keep the battery fully
charged.
Seems whacky to me , but if it is so , is there a way of wiring the side
lights via the ignition switch auxillary so that they go off with the
ignition. All this stems from a moonlight that will not work properly, will
only travel 3 inches with each button push, and low volts are suspected, a
it clears itself after a run.

i am *not* an electrical engineer, but the charging system, even on
today's cars, is very simple.

the alternator is driven by the engine, and produces electricity; the
faster it spins, the more electricity it produces. as far as i know,
most alternators are designed to work best at more than 2,000 rpm, so
normal driving (not idling or stop-and-go) will charge your battery,
and staying in a lower gear will also increase charging (easy to do on
a manual transmission).

unlike older cars, most models today have lots of "features" that will
drain a battery, even while the car is parked. you should either make
a habit of driving your car more often, or consider using a trickle
charger to maintain the battery while it's parked.

i'm not sure what the one person meant by "cruising", but the key to
charging is engine rpm, so that doesn't sound right. and to the best of
my knowledge, there's no control involved other than a simple
solid-state voltage regulator, so any "load" would only waste some of
the electricity, thereby reducing the power available to recharge the
battery. likewise, "free-wheeling" would also just decrease the
alternator's output.

i wouldn't just "suspect" low voltage - a voltmeter is a cheap (under
$20) and useful piece of gear. get one and use it!

 

[ed]

Had an alternator that showed proper voltage and amperage when running, but
would slowly discharge the battery in city driving, turned out 3 of the 4
diodes in it were burned out, but the one good one was enough to fool even
the alternator testing machine.
Have the amperage/voltage output checked at idle speed.
Ed B

I am given conflicting "advice" from "experts"about the battery charging on
my 03 Forester, because I only do low miles..
One says the battery is only charged when cruising,the other says it only
charges when a load is applied or on over-run[free running down hill]
The second guy suggests running with the lights ON to keep the battery fully
charged.
Seems whacky to me , but if it is so , is there a way of wiring the side
lights via the ignition switch auxillary so that they go off with the
ignition. All this stems from a moonlight that will not work properly, will
only travel 3 inches with each button push, and low volts are suspected, a
it clears itself after a run.

i am *not* an electrical engineer, but the charging system, even on
today's cars, is very simple.

the alternator is driven by the engine, and produces electricity; the
faster it spins, the more electricity it produces. as far as i know,
most alternators are designed to work best at more than 2,000 rpm, so
normal driving (not idling or stop-and-go) will charge your battery,
and staying in a lower gear will also increase charging (easy to do on
a manual transmission).

unlike older cars, most models today have lots of "features" that will
drain a battery, even while the car is parked. you should either make
a habit of driving your car more often, or consider using a trickle
charger to maintain the battery while it's parked.

i'm not sure what the one person meant by "cruising", but the key to
charging is engine rpm, so that doesn't sound right. and to the best of
my knowledge, there's no control involved other than a simple
solid-state voltage regulator, so any "load" would only waste some of
the electricity, thereby reducing the power available to recharge the
battery. likewise, "free-wheeling" would also just decrease the
alternator's output.

i wouldn't just "suspect" low voltage - a voltmeter is a cheap (under
$20) and useful piece of gear. get one and use it!