I recently bought a battery and charging system monitor. So I tested my Tundra battery (about 4 yrs old) and its readings are 11.92 not running and 14.18 running. Then tested my 2007 Yaris battery (original) and its readings are 11.88 not running and 14.22 running.
Each vehicle starts up quickly with no problems. But the readings for each when not running are low.
When I had to replace my Tundra battery last time there was absolutely no warning - as in difficulty starting - it just didn’t start.
Should I avoid a problem and replace these batteries now?
Or should I wait? And if so, what reading would indicate it is absolutely time to replace a battery.
The only sure fire way I know of monitoring battery life is with an ammeter, not a volt meter. After starting a vehicle with a new battery, the ammeter will start high and then go down to about 1 amp charge as the battery is replenished. As the battery ages, the “charge” after replenishment will begin to rise. At a steady 6 amps, the battery is getting near the end. If you see a good deal on a battery, it would be wise to buy. When it rises to about 10 amps after replenishment, the battery may not work the next time you go to start.
There is a wide range of battery life even between two identical batteries. The vehicle, climate etc. can cause one battery to go in 3-4 years where the nest one on the shelf might last 8 years.
Those readings, if accurate, are definitely low. But I would have the battery load-tested. Many places will do this for free. This is the best determination of how healthy your battery is.
I recently bought a battery and charging system monitor. So I tested my Tundra battery (about 4 yrs old) and its readings are 11.92 not running and 14.18 running. Then tested my 2007 Yaris battery (original) and its readings are 11.88 not running and 14.22 running.
What’s YOUR explanation for the difference? Given that the readings are all similar, is it possible that this is normal?
Each vehicle starts up quickly with no problems. But the readings for each when not running are low.
Low compared to what they should be, or what you expected? Have you calibrated the device with a new battery?
When in doubt, swap 'em out.
“Low compared to what they should be, or what you expected? Have you calibrated the device with a new battery?”
The ‘not running’ readings are good’ but the ‘running’ readings are low according to the levels that the literature that came with the voltage tester said they should be.
It says that the reading should be 12.6 or higher.
OK, maybe my math is a bit screwy…
are you saying 14.18 and 14.22 are LOWER than 12.6??
They all sound about right to me. Maybe the standing (not running) voltage is a tad low, but nothing serious. My 4Runner and VW are in that area. Running voltages are a tad higher, too, but not much.
Are you testing with everything turned off (lights, A/C, fans, radio, etc)?
Last time I checked 14 was higher than 12.
The readings in the 11’s are just a tad below 12V which seems ok to me especially if the batteries are “cold” when you took the readings. The 14V readings show the charging system is OK. Don’t see any reason to buy new batteries now.
The consensus is there is nothing unusual in your measurements. I agree. It is good that you are curious about the readings, but this is a problem with digital instruments. You are applying too much precision to your measurements. The differences are only several hundredths of a volt and can be due to a lot of things; the temperature of the cells, differences in the construction of the batteries, how long the battery has been sitting, how old the battery is, how good the connection is between the meter and the terminal, and on and on. If the batteries aren?t sealed you could buy a hydrometer and measure the specific gravity of the electrolyte. It is also possible your battery monitor isn?t completely accurate. Relax, be curious.
To chaissos - Thanks for pointing that out. I said the opposite of what I meant. The ‘running’ readings are good, but the ‘not running’ readings are low.
And thanks to others for your thoughts. I did take the ‘not running’ reading before driving the car. First, per the instructions, I turned on the headlights for 10 seconds, then turned them off and took the reading.
As MTraveler mentioned, the first thing I wondered was if the monitor was accurate.
Anyway, I think I’ll just keep monitoring and wait to replace the batteries.
thanks again…
Okay, I’ll bite. What does turning on the headlights for 10 seconds do?
“Okay, I’ll bite. What does turning on the headlights for 10 seconds do?”
According to the instructions that came with the monitor, it removes the “surface charge.”
Thank you, I just looked it up. Apparently that’s real.
These voltage readings seem fairly normal, but voltage is not the greatest concern about the condition of the battery. Amperage is. What kind of battery and charging system monitor are you using? The best kind I have found (that I can afford, anyway) is the simple silver box with a switch and a couple clamps on it. The humble 100 amp load tester. I have found these to be very accurate at assessing the condition of a battery. You can pick one up at any big box department store like Walmart or Meijer for $20-30. Just don’t burn yourself on it. A healthy battery will make it hot.
A fully charged 12 volt car battery should provide a reading of 12.6 volts. There are 6 cells in the battery and each should provide 2.1 volts.
The voltages running are fine and will vary based on load. The more load applied (lighting, wipers, A/C, etc.) the lower the voltage will be.
If the battery has removeable caps a VOM can be used to test between cells to determine if one of them is getting weak.
You could also disable the engine so it will not start (fuel pump relay out, etc.) and crank the engine over while watching the voltage reading. After 10 seconds or so of cranking if the voltage reading is down to 10 volts or lower then you have either a battery that is not fully charged or one that is getting weak. It really should maintain 10.2 volts at a minimum after the extended cranking.
How accurate is this “monitor”?
Compare it against a decent digital volt meter.
Was the battery disconnected for the not-running reading?
An unloaded battery should be at least 12.5V.