My 8 month old battery is reading 12.31 volt at rest. Alternator is new, and voltage goes above 13 volt when engine is running. Battery is a very reputable brand with a good warranty. 12.31 volt seems a bit low for a 8 months old battery, but I’m a bit concerned because the previous battery died in February during winter. It was a same brand of battery, and the store gave replacement under warranty. It’s now early October, and not yet winter. Should I just try charging it to full at this point and see how it goes? I certainly do not want to get stranded due to a dead battery. What do you think? Thanks.
Go back to the place you bought it from and let them check it . That is what warranties are for.
The store is one these big franchise warehouses like BJs, Samsclub, Costso. They just sell batteries. They don’t check batteries. I tried to checking the replacement battery they were giving me back in February with a multi-meter, but they prevented me. I’m a bit skeptical if they’ll honor the warranty for 2nd time.
How many days per week do you drive, and how far are those typical drives?
You might not be driving enough to keep the battery charged.
You might want to give the battery a full charge every couple months.
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Most large auto parts stores will do a free battery and alternator test, no matter if it came from them or not. Just don’t buy a new battery from them and try to take it back if you get another replacement from the other place as they won’t do it. According to the FLOODED 12V chart, you are at around 75%. Are you using a different style such as AGM? If so, you can see this is even worse.
There are also different grades of batteries. The cheapest often fail very early like this so go for the good one with the long warranty if you haven’t. You might also return the original if that is possible and just get one somewhere else. Of course you will have to know ahead of time they will take it back so you can drive to a parts store and buy one, then drive to the warehouse store and swap them out in the parking lot when you return the other one.
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Look on the battery for the date of manufacture.
A battery that sat on the shelf for a long time before being sold can show low battery voltage.
Tester
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The label on battery says 1/22. I got it in 2/22. From my observation, this warehouse doesn’t seem to stock batteries with labels older than 1 month. The battery price is competitive to non-warehouse stores, but it is a very well known reputable brand recommended by car repair shops I’ve been to.
And I’m not using different style or different grade. If 12.31 volt is about at least 60% full, that seems like that may be as realistic as it can get. No batteries, even the new ones, can be 100% full.
You will not know untill you ask .
The new battery’s I buy always read 12.6-7 volts.
Tester
Ok. according to that chart, 12,31 volt is just under 70%, Would that bad for a 8 month battery? Should I be concerned about it and considering charging it or getting it replaced at this point? New batteries being charged 100% seem a bit unrealistic in my limited observation and getting few mechanics’ opinions…
Getting stranded will cost more than getting a new battery, but it’s definitely troublesome that this reputable brand of battery seems to degrade fast on multiple occasions.
Again, you might not be driving enough to fully charge the battery.
If that is the case you might consider getting a battery charger.
If that is not the case, most auto parts stores will check both your battery and charging system for free.
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Ok, both options are good. I just spoke with a mechanic in my area, and he says the voltage readings on my battery seems fine because there are many factors affecting the voltage so I shouldn’t have to worry. So it’s further perplexing that mechanic’s opinions seem to differ from laymen opinion…
I would have to wait until a sunny weather to charge the battery on my driveway. It’s raining now. I have a trickle charger. So you connect the red clamp to positive terminal, and connect the black terminal to to an unpainted body chassis with the battery installed in the car? . Is it safer to disconnect the negative ground cable on the negative terminal? Car is 2006 Toyota Camry.
Just go for a nice 1 hour drive on secondary roads with some scenery and relax.
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You get perplexed just because someone has a different opinion than yours 
I leave the battery connected (don’t like having to reset things and waiting for the ECU to relearn things), and connect red to red, black to black.
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I have two vehicles, a 2007 Kia and a 2000 Tacoma both have permanently attached solar trickle chargers. I consistently read 12.3-12.4volts on them with my Fluke voltage meter. The only time I read 12.6volts is right after taking them off a battery charger or coming back from a long ride. I typically get 5-7 years out of my batteries. They’ve never failed to start my vehicles. I only replace them when I start to get a lowering specific gravity reading in one cell.
Ok. Thanks. That seems to be similar readings as mine, and I don’t even have permanent solar trickle charger attached.
The last time I checked my batteries about a month ago, the car that sits a lot was at 12.39 volts, and the car driven most days was at 12.64. I was not concerned.
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What year Camry is it? I know some newer Hondas and GMs play games with the charging system purposely undercharging the battery in some conditions to gain a miniscule amount of fuel economy. Maybe Toyota does the same.
If you only use vehicle for short trips the cumulative effect can end up being a perpetually undercharged battery.
Define at rest.
Does this mean absolutely everything off? Just pop the hood with all lights (including hood light,) doors shut, and accessories off? Are you checking voltage right at the battery itself? or 12v port or something on the dash?
if key on engine off- 12.3 is fine. If everything off and shut, take the car for a good long drive and recheck voltage again tomorrow morning and see what it is.
also check and make sure battery cables are clean and tight. 
Toyota Camry is year 2006 model. 12.31 volt is the reading from battery terminals with engine off and nothing on. I have my car key pulled out from the ignition.
BTW, I have not thought of car battery solar trickle charger. Solar trickle charger seem more conservative than charging from garage wall outlet. I guess you would have to get one with the lowest voltage to be safe. Would one under $30 from Amazon be ok? Maybe something like this (https://www.amazon.com/Sunway-Solar-Maintainer-Motorcycle-Powersports/dp/B06WP95W51?th=1)
I think you should still disconnect the solar trickle charger when the car is being driven…? Right? You would only connect it to the cigarette lighter port when the engine is off?