I can certainly believe that's occurring. However, at the same time your alternator is putting out the 14.3V, your car is utilizing electricity. Your running lights, spark plugs, radio, and other items that draw electricity.

If you have ever driven a car when the fan belt breaks (and I've had this done.....but on cars built in the late 60's) the car will continue to run, until the battery can no longer provide spark to the plugs....or if it's the same belt that turns the water pump (back in the day) the car will overheat. And I can tell you from personal experience, the 12V battery will not last very long with no alternator charge going to it.

On a golf cart if the battery tender doesn't shut down at or near peak charging, overcharging will occur and battery will be damaged. Then again, on a golf cart (electric cart) the only thing drawing amps is usually the motor. Sometimes headlights or an optional radio. So, what I'm saying is I would think some sort of BMS (Battery Management System) is on gasoline cars with alternators. So when the battery charge hits its max, no current will flow to the battery. And I can't think of an instance where a running gas engine car doesn't need current to run.

 

Just more unnecessary gadgets for a $75-K car.

 

Yeah....hassle is the right word.

The EV batteries on the hybrid Lexus have batteries that are rated from 240V to 288V. It puzzles me that even when an EV car is sitting in an airport for a month, that the system would not "tap" those high voltage batteries to keep that little 12V fully charged. That entire notion escapes me and I'm no engineer.

 

It would make sense that turning on the lights would cause the car to up the charge to the 12V battery. That 12V battery is where the energy is coming from to run the lights. Add to that all the other systems the 12V is being ask to do, the car would have to up the charge to it.

But, if you measure the 12V battery when you begin, and run the car say 20 miles one way with just the DRL's and check the 12V "at rest" voltage, it would seem to me it should be somewhere around 12.1V. Then if you run that same 20 miles back with your headlights on, when you get back that 12V battery should show the same 12.1 or close to that when it's "at rest". I'm speaking that the 12V battery is a newer one and in good health. A battery in bad health is another issue.

 

I find it necessary to prevent a dead battery. The price of the vehicle is irrelevant. I would find it just as annoying on a $20k vehicle.

 

We are simply TRYING to keep our 12V batteries in 'good health'. If that means running with the headlights on when the SOC (or voltage) drops to a certain level, that isn't too exhausting....

Now, if we had a reliable in-car warning that would tell us when that value is reached....

The ANCEL app warnings seem to be geared towards traditional ICE electrical systems.

 

There is a constant current draw any time the vehicle is on, but that doesn't really matter. Voltage at the battery is voltage at the battery. An automobile battery has parasitic loads that draw it down when the vehicle is sitting, and a large load upon starting that draws it down. It usually doesn't spend enough time running and charging to fully charge it after starting.

Now if you were to keep a constant 14.x volts on it for a long enough period of time, it would eventually damage the battery, but that's not what happens in an automobile. The proof is in the fact that automobiles have been using charging systems that supply 14.x volts constantly for decades. Even on long trips, somehow the batteries survive. It's not ideal, but it's way better than the current Lexus/Toyota charging algorithm.

Ironically, it would be a simple matter for Lexus/Toyota, in my opinion, to make the algorithm into a true multistage charging system that would be better than any other automobile charging system I'm aware of, but for some reason, they don't do that.

I have no doubt that disconnecting the 12v battery sensor would solve most people's problems with the 12v battery. The only thing that keeps me from recommending it at this point is the unknown effect on the charging system components. I have no doubt that the battery would stay in a healthier state of charge, and remain in a healthier condition for far longer, with the sensor disconnected.

 

A hybrid traction battery is not meant to stay fully charged. Its supposed to vary between some floor to provide engine starting, say 20% as a guess, and 100%, but due to the nature of battery charging, it will rarely get fully charged.

It sounds like your traction battery and system is functioning exactly as it should and exactly as every hybrid vehicle I've ever driven worked.

I don't know what to make of the earlier "always charged" condition, but that is simply not how hybrids are supposed to function.

 

When I read the above section of your post, it appears you're saying that if systems constantly provided 14.x long enough, it would damage the battery. Then you say that the systems do provide a constant 14.x and on long trips, the battery doesn't get destroyed.

So, I'm not sure what you're saying.

However, here's a video explanation of cars charging batteries at idle, and at speed. It may clarify matters for some.

https://www.google.com/search?q=do+g...l0B8ThiAQ,st:4

I understand what you're saying. However, as I stated, when you turn on the headlights the demand on the 12V battery increases, thus causing the car's system to "toss" more current at the battery to keep it charged. If you don't have the headlights on, you don't need the battery to be charged at a higher voltage.

I'm saying I don't think turning on headlights will resolve or accomplish anything.

I think it's also a matter of where you live. Here in SW PA I travers many hills\mountains. Locally my car goes down "downhills" that are a mile or longer. In fact, when that occurs the "Energy Flow" on the display shows the EV batteries are fully charges, and then the car begins to engage the gas engine, turn it without letting it consume fuel, just to dissipate the energy the car is generating from the down hill run. I can hear the vehicle do this when that occurs.

My EV battery levels rarely drop below two bars.

 

I'm saying it never stays above 14.x volts long enough to damage the battery, even on long trips.

No, more current does not get sent to the battery because the headlights are on. More current goes to the headlights. The charging system simply maintains the voltage. The current goes to whatever loads are present. The battery is one of those loads, but the battery current is based on voltage and overall internal resistance of the battery, which varies based on a number of factors, not whatever loads the charging system is supplying.

You are correct in that the headlights on don't help the battery, because the voltage doesn't go up whether the headlights or on or not.

[

 

While 14VDC won't damage a 12V battery, MORE than that will, for sure.



I'm a member of the Old Duffer Mechanic's Club,and I remember malfunctioning voltage regulators damaging batteries, literally 'cooking' them!. <---that was when they were separate from the alternator/generators

Back when I had a car with only a 28-ampere generator with a 20 - minute traffic jam to get out of our industrial park, I used to turn OFF the headlights to 'save' the battery on dark winter commutes.

 

I think we are saying the same thing. When the headlights are on, it prompts the system to send more power to the "battery". So, the charging will show a higher voltage. But the battery isn't getting all that "extra" voltage that is being output. That "extra" voltage is being directed or used because other systems are demanding the voltage.

There's no doubt that Lexus has a 12V battery "management issue". I mean if a 1966 Chevy Malibu can get charging a 12V battery right, then so should anyone in the auto business. I don't know if it's a "battery type" that's the issue or what. But it seems like a problem that should not be all that difficult to identify.

I have a marine battery in my pickup that is hooked up to a winch. I charge it once a month with an ordinary battery charger and I check the water levels two to three times a year. A Marine battery provides a steady long discharge cycle as opposed to an ICE battery that needs the initial boost to turn over the motor.

I have no idea if a marine type battery would be effective in my Lexus...as the 12V battery in the Lexus doesn't need that initial big boost of power. But a long steady discharge of power seems to me to be the more likely "need".

Then again, I'm no engineer. I've fooled with FLA and Lithium batteries for over a decade with my golf cart. I have a repurposed Nissan Leaf 14 cell battery pack with a JK BMS that I've been running for 8 years now with zero issues. Prior to that there were 8 Trojan FLA's that I ran for 7 years. I have some understanding of battery charge and discharge cycles. If Lexus can't figure this out maybe they need to steal an Engineer from Duracell. It can't be that difficult.

 

The headlights being on or off does not effect the voltage. The voltage does not increase when the headlights are on. The voltage does not decrease when they are off.

The only action a driver takes that increases the voltage is putting the vehicle in park while the hybrid system is on.

 

Why wouldn’t the Daytime Running Lights be sufficient for this?

 

Headlights: Some vehicles discontinue energy saving mode when headlights are on to achieve full brightness from incandescent light bulbs, lights are brighter at 13.5 + volts. There is no benefit in increasing charging system voltage with LED headlights on these vehicles.

Back then we had to add water to the battery during each oil change, I don't consider that to be good battery management. The charging system in my old Dodge will adjust charging system voltage according to battery temperature to prevent overcharging/overheating the battery.

These extreme energy saving measures are done to comply with EPA Corporate Average Fuel Economy standards. CAFE standards have been increased by 3.5% each year for light truck/SUV, the current standard for light trucks is 30 to 40 mpg depending on vehicle size.