Battery Low Start Engine W/Chime Listening To Radio Key/ACC

[diyer2]

I know I seen something posted about this. It happened to me. 

So I decided to monitor the voltage while listening to the radio with the key in the ACC position.

 

My wife sees a chiropractor on a regular basis due to being rear ended and getting whiplash.

I used to go in with her but started sitting in the truck and listening to the radio or I Pod.

 

I had a surface mount digital voltage meter on hand. A usb charger for our cell phones that stopped working that had a cigarette lighter plug with a foot of wire attached.

I soldered the charger wires to the voltage gauge with shrink tube. Made a voltage monitor that plugs into the cigarette lighter.

 

The drive to the chiropractor's office is 35 minutes so the truck is warmed up and the battery is fully charged. Battery is 2 years old and holds a good charge.

Key in ACC position with radio on it takes about 20 minutes for the battery voltage to drop to 12 volts, the chime sounds and the display on the dash - Battery Low Start Engine.

The same voltage and time frame every time when the alert happens.

 

With a good battery there is plenty of voltage to start the truck still as I have ignored the alert and sat for 45 minutes once when the doc's office was slow.

The computer sets of the alert at 12 volts.

 

 

 

 

[sporty061200r]

Actually, you are wrong your battery is not “fine “ at 12v it’s discharged to about 50% of it’s power that’s why your chime comes on , it’s trying to tell you to start you vehicle before it gets so low it will not crank over,

 

 

Sent from my iPhone using Tapatalk

 

[Spurshot]

Sounds like your battery has one foot in the recycle grave or you have a large load on that battery..  

 

50% charge is generous for 12v per this site 

http://batteryuniversity.com/learn/article/how_to_measure_state_of_charge

[diyer2]

I was trying to shed some light on how the system works when the low battery alert comes on. 

Thanks for the reply's.

Copied from the battery university site:

Measuring state-of-charge by voltage is simple, but it can be inaccurate because cell materials and temperature affect the voltage. The most blatant error of the voltage-based SoC occurs when disturbing a battery with a charge or discharge. The resulting agitation distorts the voltage and it no longer represents a correct SoC reference. To get accurate readings, the battery needs to rest in the open circuit state for at least four hours; battery manufacturers recommend 24 hours for lead acid. This makes the voltage-based SoC method impractical for a battery in active duty.

IMO

The best accuracy for a lead acid battery voltage test is a battery that rest's for 24 hours with no drain on it. Temperature compensated with a hydrometer. Like the one below, which I have. Over $60. It compensates for temperature.

 

I have had a solar powered off grid home for 20 years. I'm no stranger to lead acid, wet cell batteries.