Battery voltage too low?

R

RichardZ

Joined
Aug 10, 2019
Messages
47
Location
Downeast, USA
Hi, I have a 2015 Toyota 4Runner still on its OE Panasonic battery. The vehicle starts fine, but I noticed the resting voltage at 12.2 - 12.3V. This seems low to me. I thought a fully charged battery should be in the 12.6-12.7 range ? I measure the battery after sitting overnight with two different volt meters.

Should I start shopping for a new battery. Again, it currently starts and runs fine.
Thanks!
 
A resting voltage of 12.2 - 12.3V would mean a worn battery, most times you won't notice it unless you have some really cold weather. If you get it load tested it will most likely be borderline or fail.
 
RichardZ said:
I noticed the resting voltage at 12.2 - 12.3V. This seems low to me. I thought a fully charged battery should be in the 12.6-12.7 range ? I measure the battery after sitting overnight with two different volt meters.
Click to expand...
12.2-12.3 vs. 12.6-12.7? That's pretty minimal and could even be from the resistance in the voltmeter cables.
 
12.2 volts is about 60% state of charge for a good battery. It would likely take 6 hours of driving to get it near 100% charged. I'd suggest you put a charger on it overnight and then let it sit for a day or so. If it's back down where it was, you're probably going to be battery shopping soon. I like to throw the charger on a car whenever I'm working on it. Seems to help batteries live longer.

Just as an aside, the last (and only time) I replaced a Panasonic it was 10 years old.
 
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The battery is toast. At 5 years old, you have gotten your money's worth out of it. Replace it now before it leaves you stranded or it takes out your starter (this has happened to me on a Toyota).
 
I don't think you guys get the state of charge charts. That's a fully charged battery at rest with no load on it at 70 degrees. Adjust for temperature and load. When it's connected to the car, it has a load on it. Last time I took a battery out and fully charged it, I had 12.7 volts no load. Once connected to the car, about 12.4-12.5 volts. Do the load test to see where you really stand. And you could put it on a charger too. Lots of times the new charging system won't fully charge up the battery just because that saves on gas and gets the manufacturer better CAFE numbers and they don't care if your battery fails early because it never gets fully charged. I have an AGM battery that's almost 13 years old and another one that's about 9.
 
RichardZ said:
Hi, I have a 2015 Toyota 4Runner still on its OE Panasonic battery. The vehicle starts fine, but I noticed the resting voltage at 12.2 - 12.3V. ...
Click to expand...

12.3V could be fine if the battery was very cold. What was the battery temp when you measured voltage. ?

Connect it to an external charger overnight, and then get a load test done.
 
Wolf359 said:
I don't think you guys get the state of charge charts. That's a fully charged battery at rest with no load on it at 70 degrees. Adjust for temperature and load. When it's connected to the car, it has a load on it. Last time I took a battery out and fully charged it, I had 12.7 volts no load. Once connected to the car, about 12.4-12.5 volts. Do the load test to see where you really stand. And you could put it on a charger too. Lots of times the new charging system won't fully charge up the battery just because that saves on gas and gets the manufacturer better CAFE numbers and they don't care if your battery fails early because it never gets fully charged. I have an AGM battery that's almost 13 years old and another one that's about 9.
Click to expand...
A normal car only has a parasitic draw of about 50 milliamps. That's not enough to pull the voltage down on a healthy, fully charged battery to 12.4 volts. Even a worn battery will show higher than 12.6 volts right after being fully charged. They call this the surface charge. After sitting for a while, the voltage goes back down to it's normal full charged state.

I got a new Interstate battery a couple weeks ago and charged it up before installing it. The initial voltage after taking it off the charger was 13.2 volts. After I installed it and started the car and turned it off, (thus removing the surface charge) it read 12.7v.
 
A fresh battery fully charged should be around 12.65V at 77F.
Temperature is the important factor here.
Voltage drops about 0.1V per 10 degrees F. This is why colder days are the concern for starting a vehicle.

If it was at 77F, then you're at about 60% capacity. Which really is fine, but may want to monitor.
You should start to worry when battery capacity is less than 50%.

I'd put a charger on it, if that improves it great. Even if it doesn't improve you still have life on this battery.
It should pass a load test.

Bottom line I don't think your at a point where you should even be concerned.
 
atikovi said:
12.2-12.3 vs. 12.6-12.7? That's pretty minimal and could even be from the resistance in the voltmeter cables.
Click to expand...

No it couldn't as voltmeters have very high internal resistance... a few tenths of an ohm in the tester cables makes no difference as there's almost no current flow anyway.
 
Thanks for all the info. I’ve got the battery on a charger. I’ll see if that brings the resting voltage up.

I’m measuring at approx 40-50 degrees F.
 
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