Lohus

Stock battery on IS250.
Measuring voltage remotely with GSM pager installed in the car.

Now it shows 11.3volts, will the engine start?

On my practice, with 12.5v (fully charged battery after a few hours ride) and 11.7v (about an hour of listening music with engine stopped) engine started the same (very fast).

Gville350

iTrader: (10)

Yeah, you'll be fine.

Lohus

Well, you were wrong

awd_pwnz

iTrader: (3)

No such thing as minimum voltage. Whole car running on 12v system. So anything lower than normal operating voltage, car will not start or if it does it'll run funny. Ignition cutting out, alternator working harder..yada yada..

APynckel

This is not correct. Once the car starts, the engine runs directly from the alt, providing it's working properly and outputting the correct voltage, the engine will run fine. The battery is completely taken out of the system except to run peripheral systems, and then the alternator charges the battery to compensate.

dackp143

iTrader: (3)

Good explanation and here is some more info... it's pretty much like this:

Good battery: 13-15 volts

Low battery: Car will still start and once cranked the alternator will charge the battery assuming the battery is still good enough to take the charge.

Dead battery: Car won't crank, makes ticking noise.

Dead alternator (but GOOD battery): The car will still start. After 10 minutes of driving your head lights will turn off, your dash instrument cluster will stop working, and finally the car will turn off.

Dead alternator (but DEAD battery): Car will not start and will make NO ticking noises.

Though do remember that the you can pull the alternator out and drive the car a good 20-30 minutes before it will completely shut off. You can also drive the car with NO battery as long are you take the old battery out and use another car to jump off the battery-less car (don't recommend this though).

I work at a dealership, we see this stuff EVERY single day.

darkdream

I have listened for hours and started my car up fine. Do you have a power hungry aftermarket sound system?

Infra

iTrader: (1)

You are asking a meaningless question.

What's important is the minimum amperage your battery can supply, or put another way, the minimum amount of current needed.

A starter will crank at least as low as 7.5 volts.

Unless you have some high watt aftermarket amps, your battery should not be dead after an hour of music - if it is, you probably have a faulty battery. (If your car is still under warranty, have your dealership test it)

chi123

iTrader: (12)

Wow, 13-15? I bought a new battery from Autozone like two months ago and it was 12.7 volts new.

SPS

You are correct. The chemical reaction in the battery makes 12.7 volts. When the car is running, the alternator makes 14 volts. Thus, when the engine is running, power tends to flow INTO the battery, keeping it charged. That is why a previous poster said the battery is only used for starting and does nothing when the engine is running.

Lohus

When my battery is charged (just after the engine is turned off) I've got not higher than 13.0 volts. When the engine is running, I've got 14 volts.

Is my battery is not fully charged because of 13 volts?