Battery Gauge

So I have dug around... found nothing on this topic.

So what is "normal" for your battery gauge to read? Mine has always been in the middle, should it be at the top, does that mean I have a half life? Brings on a slew of questions now, what is the sole purpose of that gauge? can I run accessories (engine obviously off) for X amount of time without killing my battery?

I only ask because my Taco didn't have this gauge so I am trying to learn me some stuff. Thanks guys

 

middle is good.

some cars have different (mainly higher) charging voltage. I am not sure what the Toyota specs are but the following are general guideline for Tundra:

• dead center is 14.0 Volts (lowest mark is 9.0 V ... then 11.5 , 14.0 , 16.5 , 19.0)
• when the car is running and charging, the voltage should typically be between 13.5-14.5 V (+- 0.2 volts) so middle (14V) is good.
• For reference, fully charged battery is 12.6 V (PERFECT battery and disconnected).
• you would typically read 12.1-12.3 V with accessory (acc) on (ignition not on, car not running). some people make a mistake of leaving the key on ignition on (see below) when they only need to use the accessories.
• next position is ignition on (after acc on, you are planning to start the engine but car still off) I have measured as low as 11.8-12.2V because you start to draw current for pumps, computer, display, GPS, etc.
• once you start the car, you may see the gauge a little above dead center (14.2 Volts) and then may drop below dead center (13.5 volts) once the car has warmed up and battery is charged. In some newer cars, as the air temp goes up, the charging voltage will go down to protect the battery.
• I would start getting concerned if reading outside the expected 13.5-14.5 (+-0.2 V) when the car is running.

as far as what it takes to discharge a battery to prevent a start, that's a loaded question and depends on the health and the age of the charging system and the battery ... I had left my Tacoma with a 5 years old battery in the airport for 5 days and had left the interior map lights on and it started fine. I wouldn't worry too much about charging cell phones or listening to music, etc. even for hours ... You'll know when u are abusing the battery!

 

Heck yeah, I appreciate the info. Yes I pulled the lazy card and probably could pull out the manual but pfft who does that when you have a kickin forum to visit.

 

yes, please read the manual in case the above info is not right on. I haven't read the manual to be honest with you and its on my to-do list
the above info was based on my experience with various cars and playing with the Tundar and my new voltmeter ...
my guess is that a light will come on to warn you about the low charging levels. not sure about the over-charge. maybe it does and maybe the manual talks about it!

 

Read the manual he says....

 

I appreciate the info regardless!

 

GREAT POST!

Follow up Q: Is the intent of this gauge really to monitor the alternator by indicating the battery charge?

 

The voltmeter intent is for monitoring the health of the entire charging system.
This can include the alternator, regulator, battery, belt, loose connections, short circuits, parasitic discharge or drain, etc.
For example a car can have a loose alternator belt/pulley but other than that the rest of the charging system is fine ...

I checked the manual and didn't see any details regarding the voltmeter and all I could find was:
"Charging system warning light ... Indicates a malfunction in the vehicle’s charging system"

as I suspected, the car manuals don't get into too much details for obvious reasons!
having said that, IMHO the voltmeter gauge should have a green zone (for expected voltage range) and maybe yellow zones for marginal charging range and 2 red zones for over/under charge. That's one complain about the Tundra gauges they lack any details. you look at them and say so what!