Battery and alt help

So I might have a issue. 06 tacoma battery 3 years old. After 2 day not driving it . Start up but drive and stop at a light it will drop from 14.3 To 13.3 at the light. Then steady 14.3 when moving. After a day it will be fine. Is it cause haven't driven in a while?

 

You're over-monitoring the vehicle. Charging system voltages can fluctuate according to engine speed and electrical load

If the battery/charging system warning light isn't on and the truck starts every time you're fine.

 

Anything over 13v is good to go.

 

All of those numbers are above the charged resting voltage of a flooded or AGM battery.


I agree. Death by overanalysis.

 

Just making sure it ok

 

Understandable. I didn't really get into batteries until I started taking the camper off grid. Let's just say that a battery in use is going to show a voltage that's not indicative of it's charge. Meaning, a battery that's draining is going to show an apparent voltage that's lower than it's charge state, and one that's charging is going to show an apparent voltage that's in between battery and charger. Or in other words, a voltmeter when the engine is running and the radio is playing is a useless measurement. It means nothing.

A brand new fully charged battery that's at rest should be between 12.75 and 13 volts, depending on type. This will decrease as the battery ages. The only accurate way for the average home tinkerer to determine battery health is to get a resting voltage (truck off for 30 minutes) at the terminals with a multimeter, and then get a second volt read while a volunteer starts the engine.

At rest and fully charged, a serviceable battery should not be below 12.0 volts. Some people say 11.9, but I like to replace mine before it leaves me stranded. When someone starts the car, that voltage should not drop below 10.5 volts at any point.

 

Hard to say to cause im running 2 agm group 31 batteries