Hi Fellow Stangers,

After a recent drama with dying battery, I became seriously paranoid about the numbers on battery meter. I am constantly checking the fluctuations ever since mine gone wrong, more so after getting the replacement at the dealership last Saturday. The truth is, I became very well aware how import the battery is. Some might argue " Hey, it's just a battery nothing biggy."

Anyways. Seeing quite a few fellow Stangers with troubling batteries lately made me super curious what everyone is getting.

Mine was instantly reading 14.4(!) with brand new replaced (Sat), started going down to 14.2-13.9 (Sun), and finally 13.7 (Today).

What does (or should) your battery meter read?

 

Anywhere around 14V is normal. I've always had alternator/battery issues, so I monitor it constantly. Mine fluctuates between 13.4V and 14.2V, but is typically right around 13.8-14V most of the time.

If I remember correctly (at least for the 05-09 bodies) 14 is fine. 13 is fine. If it's in the 12V range, you should be concerned unless you know why it's low and are expecting it. If it's in the 11V range, you're dying and the car is about to start shutting off electronics to stay alive. Anything under that, and even the gauges will shut off and it's likely gonna die if you let the rpms drop.

Hope this helps...

 

Mine always reads 13.7-13.8v in the cluster with the engine on. But my passport conected above the radio always reads around 14.4v.

 

With the car off it should read ~13V assuming the lights are off, the radio is off etc.

When the car is running you should see an increase to between 14 and 15 due to the fact the battery is being actively charged by the alternator. At this point you're really measuring the alternator voltage not the battery voltage per se.

 

The voltage gage in your instrument cluster is really not a “battery meter”, it’s a voltage meter showing the charging system voltage. With the engine running it should be reading around 13.5 to 14.4 (Max) volts. It’s worth noting that when your engine is running, all of the cars power requirements are being met by the alternator and the battery is being charged. The battery is simply an electrical accumulator that supplies power to the cars “Grid” when the engine is off, or when the engine is running and surge situation occurs with a current draw so large the alternator cannot accommodate it, such as a fan kicking in or the AC compressor clutch engaging. Manufacturers are considering increasing the system voltage because the current 12v system is fast becoming inadequate to deal with the increasing electrical demand in cars today, as we are seeing!

Your actual battery voltage should be 2.12 to 2.17 volts per cell when fully charged for a total battery voltage of about 12.75 to 13.00 volts. Slightly higher is often observed when the battery voltage is checked immediately after a charging cycle. As the battery discharges the voltage will drop slightly. A good battery that is completely discharged would be around 11.9 volts.


If the battery voltage is down around 10.5 volts you have a shorted cell. You can measure individual cell health with a DVM by placing one probe into the acid and the other probe on the negative terminal. Depending on the state of charge it should read anywhere from 2.17 volts (Fully charged cell) to 1.98 volts (Completely discharged cell). If the cell voltage is well below that, it’s shorted and the battery is toast. Be sure to clean your meter probes in baking soda and water and dry when done.

If you want to nerd out on battery info, here is more reading for you:
http://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html

John