[nazali]

Someone pls school me on Alternators.

So different people say different things and want to just understand on tis subject

Alternators:

I thought, that alternators charge the battery and also deliver v, DC for the electrical system. A friend of mine point blank said "you cannot charge a battery by driving a car" (as in, if the battery is low)

so I'm confused, as, we drive our cars and unless there is a problem, we don't always plug the car in ? Unless the demand is high (like short trips in winter) or a short in the electrical.

The message does come up saying "battery discharged or low while stopped, start engine" or similar putting on the Ctek overnight did the trick, but a 100km round trip didn't fix it.

So pls skool me yall !

[nazali]

also to add, anytime, I've needed a boost or a jump from an autoclub, they also ask or tell you, "take it for a long drive to put a charge in it OR if your going to be driving to work/home and it's a highway drive that should do you"

[Glen e]

The main difference between an alternator and a generator is an alternator charges the battery at idle. A generator does not. And whether a drive will recharge your battery, it depends on how low your battery is and how long the driver is. But certainly a long drive will charge a battery, unless the battery is defective.

[TheWatchGuy]

if your battery is defective it wont charge it since the battery cant hold a charge.

As for alternators, they absolutely charge your battery while on, as well as provide some voltage stability for the car. Thats why when your battery is dead and you get a jump, you dont need to get another jump after you let your car run for a little bit. the alternator charges the battery back up so it doesnt need another jump to get going.

If youve ever been big in to car audio and specifically big subs and bass competitions, youll notice that all the guys with big power systems have bigger alternators and multiples of them to provide more power draw for the amps, and provide the additional batteries with quicker recharging.

[nazali]

txs guy's that kinda jives with what I thought,
as said, I did a 100km round trip, the battery was actually showing 12.xx volts 12.50 I think
but was getting the "battery discharged or low while stopped, start engine"

txs for the confirmation

[HighlandPete]

Originally Posted by nazali

txs guy's that kinda jives with what I thought,
as said, I did a 100km round trip, the battery was actually showing 12.xx volts 12.50 I think
but was getting the "battery discharged or low while stopped, start engine"

txs for the confirmation

Our BMWs have energy management, which does mean at higher battery SoC, the alternator only supports the electrical demands and doesn't actually charge the battery. It is only when at lower SoC, that the alternator charges the battery. There is always capacity/allowance for over-run charging.

So it depends... several factors involved including the health of the battery. The battery has to be very low, to run 'conventional' charging. But even then, when thresholds are met for the management stages, the charging backs off.

[nazali]

ahh ok I get it

BMW damn you, you win again,

[nazali]

this car is begining to feel like an i3 more and more,
if I wanted to keep it plugged in all the time, I'd a not got it,
wifes stupid caravan, no problems, move it a few feet , leave it on the drive for weeks on end, dashcam on park mode, remote start, starts first click every click.

Actually my old 1'er was like that as well, only major winter did I have the odd cold start, damm

I may invest in an older BMW instead, I don't mind mechanical things that break, but when your car won't start because there's too much "electronics" in it, it's too cold, or you have'nt driven it in 5 hours GOD,

I am so dreading winter, cold starts and mainly trying to get to work, I'd better get an uber account ready

[nazali]

so there are 2 things then, involved in short commutes and winter driving

1> short trips bad, due to engine condensation, so need to do a good run every week or so
2> (from above) this is NOT going to charge the battery, leaving it on idle will do ? IDK or if the funky BMW stuff will do it's stuff

I need a walk in garage

[TheWatchGuy]

Originally Posted by nazali

so there are 2 things then, involved in short commutes and winter driving

1> short trips bad, due to engine condensation, so need to do a good run every week or so
2> (from above) this is NOT going to charge the battery, leaving it on idle will do ? IDK or if the funky BMW stuff will do it's stuff

I need a walk in garage

it will if your battery is low.

Think of it this way.

The alternator is a faucet and the battery is a glass. If the glass is full, the faucet wont fill it any more so it turns off (stops charging the battery). If you drink from the glass, after you drink a certain amount, the faucet will turn back on and fill the glass back up.

[RM7]

Originally Posted by nazali

Someone pls school me on Alternators.

So different people say different things and want to just understand on tis subject

Alternators:

I thought, that alternators charge the battery and also deliver v, DC for the electrical system. A friend of mine point blank said "you cannot charge a battery by driving a car" (as in, if the battery is low)

so I'm confused, as, we drive our cars and unless there is a problem, we don't always plug the car in ? Unless the demand is high (like short trips in winter) or a short in the electrical.

The message does come up saying "battery discharged or low while stopped, start engine" or similar putting on the Ctek overnight did the trick, but a 100km round trip didn't fix it.

So pls skool me yall !

So here's how it works, when the car is in operation, both the battery and the alternator are an integral part. They both ground to the frame of the car. All the components ground to the frame of the car. The car is kind of running on the alternator, the alternator is charging the battery, except when the amp draw would exceed what the alternator can provide. At some point, the battery becomes fully charged. In situations where the amp draw exceeds what the alternator can provide, the battery acts as ballast to the system, momentarily being able to supply a few more amps for the spike, again they are both grounded to the frame of the car. If you can get the car running, you can theoretically remove the battery and drive the car on just the alternator, except for if you have an event where you need all those amps at once, like you are driving at night with the A/C on and decide to move a few switches that increase the load for a little bit. A possibility is collapsing the entire electrical system, then everything shuts down and goes "dark". That's what the battery is doing while you are driving around, providing ballast for the system.

Cars are coming with ever-increasing alternator amps, to help alleviate this and to power all the increased electronics that are coming on cars, but they are also moving to systems where the alternator does not continuously charge the battery, only during braking situations or for timed intervals, as this increases efficiency. I have noticed this may make it a little harder to charge a battery on these cars. I had a situation where the dealer had let the battery discharge and I had to go find some pretty big hills to drive down to get the charge back up so I wasn't getting a warning. After that, no issues.

Automotive alternators use a rectifier unit to change 3 phase AC to DC.

You can charge a battery, if the battery is low. You cannot charge a bad battery that won't hold a charge.

[nazali]

Originally Posted by TheWatchGuy

it will if your battery is low.

Think of it this way.

The alternator is a faucet and the battery is a glass. If the glass is full, the faucet wont fill it any more so it turns off (stops charging the battery). If you drink from the glass, after you drink a certain amount, the faucet will turn back on and fill the glass back up.

^^^ that right there is total awesomeness ! fantastic explanation...

SO... for the dumb at heart, why after my 100km drive did the car say "battery discharge while stopped" and only went after a night on the ctek

oh wait, maybe I have answered my question, the alternator on newer BMW's only charge the battery on overrun, not on good old cruising ?

[HighlandPete]

Intelligent alternator control IGR.

The basics, and why going "for a run" does not fully charge the battery. Driving profile can lead to a battery gradually losing a decent SoC.

Even a new battery requires attention over a relatively short time, if the driving parameters are suspect.

[RM7]

I don't know if it's the same for cars, but typically idle is pretty terrible at charging in an airplane. I'd like to think modern cars will up the RPM if the demand increases, but on airplanes you have direct control over the propeller RPM. Usually less than 1000 results in a discharge to the battery, as it takes over that number to actually charge the battery. Sitting around idling at 600rpm can wipe out your battery relatively fast. Driving the car relatively hard is usually one of the better things to charge, given the braking and higher RPMs.

With your BMW efficiency dynamics, it does not charge much of the time, I believe there is more information on this in the manual.

[HighlandPete]

Originally Posted by nazali

^^^ that right there is total awesomeness ! fantastic explanation...

SO... for the dumb at heart, why after my 100km drive did the car say "battery discharge while stopped" and only went after a night on the ctek

oh wait, maybe I have answered my question, the alternator on newer BMW's only charge the battery on overrun, not on good old cruising ?

Partly depends on the electrical demands, while you drive that distance. The over-run phases are key to maximising the charge.

I've experimented with an older battery, 30 miles does not improve the voltage, (or SoC) of a partially discharged battery. The 'start' and energy used in the trip, blunts the charging, particularly if there isn't much over-run. My typical trip is near constant speed driving, so not a good way to try and charge the battery.

Same apples to a new battery, the 30 miles is not enough in itself to keep the battery in top condition, (if there are several days between use), when the locked/alarmed consumption slowly depletes the battery anyway. I'd get away with it, if I used the car most days, but definitely not if only once or twice a week.

[nazali]

damn I'm too old skool, going to have to re thunk this

damn you BMW your too got dang smart, you win again !