Battery voltage - how low is too low?

Hi Everyone, my truck has an original battery in it, exactly 3 years old. I had the alternator tested at Napa yesterday and it’s putting out somewhere around 13.5 volts. Cold crank amps are at 600. The battery charges while the truck is running but when I shut it off and wait a few hours sinks to 11.5 volts, sometimes lower. We are going on a big road trip in hot weather soon…should I replace the battery?

Thank You

 

Absolutely yes

 

Lower than 12.5 is not good.

 

Yep. 12.5 would be a normal reading after a few hours .....unless you have a serious parasitic drain.

 

Most EFI systems will not even run correctly or send enough voltage to the fuel injectors to fire if the battery voltage during key-on/crank is around 10 volts. So it sounds like you have a bad cell, that is turning your battery into a resistor as opposed to a capacitor. Definitely replace it.

 

Take it to a diagnostic place. This isn't a battery issue. Batteries die for a lot of reasons, but generally not just sitting there
unless you have an electronic dead short. It could be a dead cell, have the battery tested. Have you installed anything lately or changed anything? Double check connections
especially any and all grounds.
But primarily have your alternator load tested and looked at. I suspect you may have a diode issue on your alternator, and
that will be an ugly road side failure on a road trip. So get it looked at ASAP.

 

I’ve been chasing a parasitic draw for awhile on my truck. Doesn’t go dead in hours like you mentioned, so maybe there is an issue with your alternator as Cruiserpilot mentions.

I think I’ve isolated mine down to a front camera I had in my bumper.

 

Thanks everyone! I think I may have jumped the gun. I have one of those VeePeak OBD II Bluetooth diagnostic plugs I got with our Genuine Cooling Systems kit trans cooler kit. I got the OBD fusion app off of the App Store as well as the Toyota extension. This gave me a number of dashboards to look at on my phone. One of them called “Battery” which registered 11.4 volts. I just double checked this with a volt meter at the battery terminals and they actually read 12.5 volts! I wonder why the VeePeak reads so much lower voltage. I now think the battery is probably fine! Strange. Anyhow thanks for all the great battery and alternator info, I learned a lot!

 

Grrrrr....f'n computers! That's why when I want to go on a long road trip I take my mechanically direct injected JDM diesel
that will still run without an alternator! Take a portable power booster on your trip, ya know, just in case...

 

3 year old factory battery = time for a new battery

 

Yup, replace.

One good reading isn't necessarily proof positive you're in the clear. You need to monitor over a week or two to look at the readings to see if there's an irregularity, and if so, that battery can still be defective.

 

13.5 running voltage is 100% normal. It’s a voltage regulated system, so you’re never going to see anything at or over 14 volts aside from a brief few minutes on a cold start. 3-4 years is the norm these days for battery life. It’s not going to hurt to get a new one. If anything, it’ll give you peace of mind, which is priceless haha