Car knows when it is time to replace battery?

[bbhero]

No..


It is how some cars are programmed to run today.... Only when you are off the gas pedal does the amperage flow to the battery... This is due to the fact that with a regular charging system the car loses 0.1 mpg of fuel mileage if it is sending amperage to the battery with the driver using the gas pedal... So by reversing this typical set up and only having the alternator send amperage when you are off the gas pedal it helps "save" just a bit of gas. This new fangled process is why batteries in those vehicles are almost always undercharged.

 

[wrcsixeight]

A vehicle voltage regulator alters the field current to alternator.

Ithe alternator makes as much amperage as required to satisfy voltage regulator.

A battery will accept as much amperage as it wants at the voltage reaching battery terminals. The higher the voltage. The more amps the battery will accept.

A fully charged battery cannot accept much amperage even at hugh voltage.
A depleted battery can. And higher voltage can double and triple the amperage the depleted battery accepts.

So a voltage regulator on some modern vehicles might deliberately keep battery discharged. So that it can accept high amperage when it will not affect mpg.

This strategy trades battery life for a tiny improvement in mpg.

A 140 amp alternator will only produce 140 amps when cold. Spinning fast and when the voltage regulator is 'fully fielding' the alternator. The cabling from Alternator to loads and battery must also be sized to handle 140 amps.

Proper
Battery charging is all about voltage regulation.

 

[barryh]

The smart alternator on my car definitely undercharges the battery. I charge it every weekend to bring it back to full charge but even after one trip it's back down again. Not by much though as it only takes approx. 2 Ah to bring it back to full.

 

[Vikas]

WRC, I had misunderstood you. You are correct.

By the way Honda has been doing somewhat similar (or is is dissimilar?) by their ELD aka electronic load detector system since late 90's. The alternator "floats" the battery when you take the foot of the accelerator and there is no other load on the alternator. That logic gets overwritten if there is enough load on the alternator.

There is some bug in my Honda Odyssey aftermarket alternator and I end up driving it with headlight on to avoid getting the randomly flashing battery light.

 

[charbaby]

Vikas,
Out of curiosity what is the OE group size of the TLs battery?
Group 51R, Group 35 or Group 24F?

 

[Vikas]

24F aka pretty much 90% of the cars on the road today; come to think of it, I think for last 30 years every car I owned had that same size battery!

 

[charbaby]

My cars seem to be coming with Group 35(Altima) or smaller such as Group 51R(Civic). Our Lexus had a 24F.
Many new Honda's are also coming with smaller batteries including some Accords however, I'm not sure which Group size they are nor which engine get which battery. I'd like to install a Group 35 in the '15 Civic but, I'm not even sure if there enough room. It's really tight in there.

 

[y_p_w]

Originally Posted by Char Baby
My cars seem to be coming with Group 35(Altima) or smaller such as Group 51R(Civic). Our Lexus had a 24F.
Many new Honda's are also coming with smaller batteries including some Accords however, I'm not sure which Group size they are nor which engine get which battery. I'd like to install a Group 35 in the '15 Civic but, I'm not even sure if there enough room. It's really tight in there.

Smaller batteries are adequate to start almost any car. I used a Group 51R to jump start much larger cars. But it's stuff like running the radio or map lights.

Sure there's "room" for a Group 35, but not with the OEM frame and clamps.

 

[nomas]

Jesus [censored] , it's a nearly 7 year old battery . Just change the [censored] thing ! All of this advice to check the voltage 12 times a day under different conditions is nonsense . Your time and peace of mind is worth a lot .