Lead acid battery charger (or alternator) switching to trickle with (2025 Update)

See my other post. I agree with you, that's how every car I've worked on has been wired. AFAIK, the voltage regulator just keeps ~13.5 to 14v on the system, which has the alternator, battery and car loads all tied together.

Unless there's some clever circuitry monitoring each battery wire individually and subtracting the currents, the alternator can't tell the difference between a battery taking 12 amps, and a battery taking 2 amps plus lights taking 10 amps. The second one requires switching to trickle charge, the first doesn't.

There is no trickle charge. Apparently car batteries are fine at ~14V while the car is running, they don't overcharge and nothing bad happens.

That doesn't explain why I observed my own car switching from 14.4 to 13.8, after someone told me they do that.

I would agree. I probably broke my battery by having it at about 14.5V 24/7 for months. I had incorrectly assumed all car battery chargers (although this one was very old) would not overcharge. AFAIK that charger was just a transformer and diodes, made to give out about the right voltage, probably made just for a single overnight charge. It's strange as the battery was only taking about half an amp when full, although I guess that's 7 watts of heat being constantly dissipated inside it.

Not really true with anything but the most primative regulator like you might see on an old outboard. Voltage is regulated somewhere between 13.x and 14.x, not just reflecting what the alternator can do against the load. Rod is right, they look at current from the alternator There is nothing they can do about the load so they don't give a s*it about the lights. The regulator just watches alternator current and cranks up the voltage to keep it up. When current drops off it is either because there is less load or because the battery is taking less of a charge. That is when the voltage ramps down. If current gets really low, like the battery is charged and there is not much load they hit the bottom of the range ... essentially a trickle charger that is also running the radio and heater fan.

As for a smart charger, usually the voltage is all they need to know. When the voltage drop across the battery starts to rise. it indicates the battery is charging and at a certain point they either turn off or turn to trickle. Different batteries have different "fully charged" voltage levels so they usually have a switch for different types . (deep cycle, AGM etc)

Lithium batteries are a whole other thing and have smarter chargers matched to the battery. Mix them up and your pants might really be on fire.

Er that's what he just said, it can't. The car must have more than one meter, on every wire coming from the battery, so it knows what's being consumed and what's used for charging.

I believe mine has three. Alternator, starter, everything else. The alternator itself can't know where it's current goes once it reaches the battery terminal. Does it go to the lights or into the battery itself?

Take this situation: You start your car with the battery 3/4s full. The alternator provides a high voltage and charges it quickly. It's dark and cold, you have demisters, lights, etc on. How does the alternator know when the battery is full? As current will continue to be taken from it to power all those loads.

I guess charging a car battery with a charger plugged into the house won't work if you have a load in the car like lights (or in my case a faulty alarm). The charger will think the battery is still drawing a fair current and isn't full, when in fact it's the load eating it up.

Lithium are actually very easy to charge. For a single cell, just provide 4.2V, with the current limited to what it could handle (or what the charger can handle). A lithium cell will take virtually zero current when full if you give it 4.2V. It in fact will stay at 4.2V when you disconnect it from the charger. I have a charger here for 18650 torch cells - I think it's just a 4.2V 1A current limited voltage regulated supply. Up to an amp, up to 4.2V.

Yes, they do that but it isn't *switching* per se. They drop to the lower voltage as the battery becomes charged. Turning a load on, like the headlights, will cause a more sudden increase in voltage since you have increased the current requirements. The battery is a *load* on the system and so is anything you turn on.

Some better home chargers measure voltage, and temperature, and apply some kind of program. My Chevy seems to cut off charge completely at times, depending on some sort of program. That's scary cause looks like alternator is bad.

Greg

Because then there is an ammeter, dummy. I have yet to see a car that has a sensor in the cable path to the battery. And obviously it's not needed because lead acid car batteries worked for most of a century BEFORE there was any computer to monitor or control anything and the batteries worked fine, lasted just as long.

That is just a connection to the computer dummy and cars had batteries for most of a century BEFORE OBD2.

BS as proven by all the cars I've worked on over the years. Battery, alternator, car loads all tied to one common point. And the VOLTAGE regulator simply monitors that common point for VOLTAGE.

That depends on how you define alternator. On many cars today, the voltage regulator is part of the alternator, when you buy a replacement it comes with it.

Exactly what I've said too.

The

Agree, except it;s obviously not a trickle. Todays cars have a lot of loads in them to be powered, which is why they use 100 amp alternators.

In the old days of coil ignition, a vehicle's alternator

Agree with you. Now maybe you can explain that to the folks that are talking about computers, OBD2, and the alternator monitoring current output.

Nonsense. Cars used voltage regulators for better part of a century and they are simple electronics which is well understood. And, AFAIK, that is STILL how it's done, all the FUD here notwithstanding. Some cars may have something more elaborate, but it's obviously not required to keep the battery correctly charged, which was the OPs question about charging.

Correct, within reason and the physical limits of the battery. A battery looks like an ideal voltage source connected in series with a low value resistor.

The voltage regulator actually senses VOLTAGE, which is why it;s called a voltage regulator. But I agree, I have yet to see a car where the computer is monitoring the current flow into the battery. And even if some very modern cars do, it doesn't change the fact that 99.9% of cars have worked fine with the same batteries and just a simple voltage regulator. And that seemed to be your question, what is required to keep a battery properly charged and how it works. Obviously no complicated computers, current monitoring, etc is required as evidenced by billions of cars.

You do realize who you are dealing with here, right? Here is some of the other BS he posted and then just continued to lie about, refuse to acknowledge it was all wrong:

How can one dope be wrong on so many things?

The 737 MCAS doesn't rely on just one AOA sensor (It does)

The FAA would never approve that design (They did)

The data from the FDR on Lion Air has not been released (It was in Oct/Nov)

Boeing doesn't know what caused the Lion Air Crash

The 737 can't be trimmed mechanically (It can)

It's impossible to have a design where it's both electrical or mechanical trim (BS because all 737s and most other planes have both)

The Cessna 150 can't stall (It can, stall speeds are listed by Cessna)

Denies that it's common for FAA to put out directives soon after a crash, requiring inspection of what they believe caused the problem in all similar planes in service. (Of course it's common)

The AOA sensors were a known problem with the 737 Max and were already being replaced at the time of Lion Air crash (total lie)

The FAA didn't ground the 737 Max, Boeing did. (Trump announced the FAA grounding we have it on video)

Pilots are required by law to read the manual in an emergency, before taking action. (speaks for itself)

You have a 50" CRT TV (posted lame pic of a much smaller TV, no tape measure, no model, nothing to verify it

Electric pole transformers can glow orange hot, it's not uncommon (Still waiting for the pics of some of those)

Former leaders have no say in the details of their state funeral (beyond stupid)

The tax rate on capital gains was 93% after WWII (It was more like ~45% max and in the 50s was reduced to just 25%)

No one was buying US manufactured goods just after WWII. (ie the US didn't have a huge advantage as a manufacturing economy with much of the rest of the world destroyed following WWII. Obviously more total lies and stupidity)

Investment isn't for capital gain.

Then you wont have any difficulty listing all those countrys buying US manufactured goods just after the war had ended. (implying that the US wasn't exporting manufactured goods after WWII, as much of the rest of the world was in rubble and rebuilding)

Digital Equipment Stock DEC, was never sold for a capital gain.

The 911 terrorists didn't need flight training, anyone can fly a 767, just use a PC simulator to learn.

you don’t even know that there even was a doctor involved with Obama's birth certificate. (it's signed by Dr. David Sinclair)

No doctor signs the birth certificate, f****it.

Hardly any presidents have one term. (Ford, Carter, Bush 41,

President Trump invited himself to visit the UK

NYC still dumps all it's trash in the ocean

There isn't enough glass from recycling to use it for concrete

The Autobahn, a highway, is an example of socialism.

The financial crisis in 2008/09 was not caused by bad loans.

We have no idea how many companies Trump has (it's 500+ from his disclosure)

Trump has one company.

Ipe wood doesn't come from rainforests.

Obama didn't impose any restrictions on Bill Clinton's speaking engagements and fees.

There is always more than one wire going to the positive terminal of a car battery.

What a total moron!

Well of course the battery is the *load* in his simple example. The power supply is the power source, the battery is the load and 4A is being delivered to the load.

See even an elementary school level explanation of electric circuits.

Not on any car I've owned or worked on. And more to the point, it's obviously not needed because cars have worked with the same lead-acid batteries and alternators with basic voltage regulators for most of the last century.

Even if there is an additional wire, explain to us how you monitor the current in the charging cable with that wire.

But the essence of his question is how cars switch to trickle charge and AFAIK, the answer is they don't. Again, the battery, alternator output and all the car loads are connected TOGETHER.

And that's all that's needed to keep the battery correctly charged and working. There was no "trickle charging".

Any other obfuscation you want to throw in? Alternators with voltage regulators have been used with lead-acid batteries in cars for the better part of the last century. And the principles with generators are the same.

we are discussing what the

Xeno and I have correctly described how the basic, widely used charging system has worked for decades with the same lead-acid batteries. We can point you to many auto websites which will explain it, how it simply uses an alternator and a simple voltage regulator. So here's an idea. You provide us some references that show the more elaborate method that you claim is actually what is used today in all cars. And why it's needed when the other system works. ????????

Get back to us when you have some credible cites that explain the new charging method that you claim all cars now use. And it's irrelevant anyway, because car batteries have been being charged with alternators and very simple voltage regulators for better part of the last century.

Are you as sure about car charging systems as you were about all this?

How can one dope be wrong on so many things?

The 737 MCAS doesn't rely on just one AOA sensor (It does)

The FAA would never approve that design (They did)

The data from the FDR on Lion Air has not been released (It was in Oct/Nov)

Boeing doesn't know what caused the Lion Air Crash

The 737 can't be trimmed mechanically (It can)

It's impossible to have a design where it's both electrical or mechanical trim (BS because all 737s and most other planes have both)

The Cessna 150 can't stall (It can, stall speeds are listed by Cessna)

Denies that it's common for FAA to put out directives soon after a crash, requiring inspection of what they believe caused the problem in all similar planes in service. (Of course it's common)

The AOA sensors were a known problem with the 737 Max and were already being replaced at the time of Lion Air crash (total lie)

The FAA didn't ground the 737 Max, Boeing did. (Trump announced the FAA grounding we have it on video)

Pilots are required by law to read the manual in an emergency, before taking action. (speaks for itself)

You have a 50" CRT TV (posted lame pic of a much smaller TV, no tape measure, no model, nothing to verify it

Electric pole transformers can glow orange hot, it's not uncommon (Still waiting for the pics of some of those)

Former leaders have no say in the details of their state funeral (beyond stupid)

The tax rate on capital gains was 93% after WWII (It was more like ~45% max and in the 50s was reduced to just 25%)

No one was buying US manufactured goods just after WWII. (ie the US didn't have a huge advantage as a manufacturing economy with much of the rest of the world destroyed following WWII. Obviously more total lies and stupidity)

Investment isn't for capital gain.

Then you wont have any difficulty listing all those countrys buying US manufactured goods just after the war had ended. (implying that the US wasn't exporting manufactured goods after WWII, as much of the rest of the world was in rubble and rebuilding)

Digital Equipment Stock DEC, was never sold for a capital gain.

The 911 terrorists didn't need flight training, anyone can fly a 767, just use a PC simulator to learn.

you don’t even know that there even was a doctor involved with Obama's birth certificate. (it's signed by Dr. David Sinclair)

No doctor signs the birth certificate, f****it.

Hardly any presidents have one term. (Ford, Carter, Bush 41,

President Trump invited himself to visit the UK

NYC still dumps all it's trash in the ocean

There isn't enough glass from recycling to use it for concrete

The Autobahn, a highway, is an example of socialism.

The financial crisis in 2008/09 was not caused by bad loans.

We have no idea how many companies Trump has (it's 500+ from his disclosure)

Trump has one company.

Ipe wood doesn't come from rainforests.

Obama didn't impose any restrictions on Bill Clinton's speaking engagements and fees.

There is always more than one wire going to the positive terminal of a car battery.

What a total moron!

He's probably as old as you.

He isnt.

I've met Bod and he's (I'm about to insult him most likely) very very old indeed. I'd have to guess 80 to 90. For some reason I've always assumed you're about 70.

That’s just the furious drunken grave dancing and flagrant drug abuse.

You're still wrong.