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I did some searching but couldn't find any definitive answers on what the "safe ranges" are for the 12v battery on a Gen 1 Volt.

My 2012 is a late production (manufactured June 2012), so the battery is a tad over 6 years old. I'm the second owner of the car, so it's possible (but extremely unlikely) that the battery isn't the original one, but erring on the side of caution I'll assume it is.

I got one of those USB voltage meter doodads, plugged into the dash cigarette lighter plug. When driving, the voltages initially vary wildly from just above 12V to over 15V, but seem to settle in at 14.8V or so. Once I turn off the car, before opening the door, it decreases gradually and seems to settle at 12.6V after several minutes.

1. Am I testing properly?

2. What numbers should I be looking for as a red flag to consider battery replacement?

Thanks.
 

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I did some searching but couldn't find any definitive answers on what the "safe ranges" are for the 12v battery on a Gen 1 Volt.

My 2012 is a late production (manufactured June 2012), so the battery is a tad over 6 years old. I'm the second owner of the car, so it's possible (but extremely unlikely) that the battery isn't the original one, but erring on the side of caution I'll assume it is.

I got one of those USB voltage meter doodads, plugged into the dash cigarette lighter plug. When driving, the voltages initially vary wildly from just above 12V to over 15V, but seem to settle in at 14.8V or so. Once I turn off the car, before opening the door, it decreases gradually and seems to settle at 12.6V after several minutes.

1. Am I testing properly?

2. What numbers should I be looking for as a red flag to consider battery replacement?

Thanks.
Your battery appears to be in good condition. AGM batteries show slightly different voltages than conventional 12V batteries. 12.6V is >80% SOC. 12.05V is ~ 50% SOC. I would be concerned if the voltage after powering off the Volt dropped to 12.0V or lower. There is a chart of AGM battery voltages (when the battery is under load) here.
 

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When I pulled the rear deck and measured I was at 12.3V, according to chart that's 70% (5 years old). Never had any problems to date. Haven't got my doodad in the mail yet to keep a closer eye on it. The car has been in optimal conditions ambient temperature wise.
 

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What you are measuring while driving is not the battery, but the APU. You are only measuring the battery when the car is off. And then it is just the instantaneous voltage, but without any kind of deliberate load testing. And that is also immediately after being charged, so it still has surface charge on it. Your ability to test the battery like that is very limited. For instance, you could tell if the battery were completely discharged, but not if it is just getting weak, which is what you are trying to decide.

A much better way to test a battery is with a proper battery load tester as you can have done at an auto parts store typically for free. But even that in my experience is not very good at identifying batteries that are marginal.

So really it comes down to how old the battery is, what conditions it has lived under, and how lucky do you feel? I changed mine at 5.5 years even though the car was still starting and running fine. However, I did find that one quirky problem with the GPS went away after the battery change, so I think I hit the timing right.

I don't think the OEM batteries have a date code sticker on them (mine did not), but a replacement battery should, so you can use that to help determine if it has been replaced, and if so, how old it really is.
 

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Those voltages you are reading are within spec for the battery and the APU. One of the better, more reliable sites about batteries and charging is here: http://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

Most quality AGM's and lead acid batteries should last you about 8 years before the capacity will start to decline rapidly. At 10 years old most of them will not have much more than 15-30% of stated capacity.

Some folks here have stated that at even 6 years of age capacity has declined significantly but you probably would need a proper load test to determine by how much. Sometimes one just gets unlucky with a battery that fails prematurely.

If you are really into batteries and testing I suggest a proper load tester such as this one:

http://www.westmountainradio.com/cba.php
 

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the 15 volts is still being applied to the battery so is a factor.
Depending on what the car is doing other voltage is possible. (the service manual page posted some time ago has more info)

for watching for the LONG slow death of a 12 volt battery not used to crank a ICE car power port will help.
road side people never seem to have a voltmeter.

you can monitor battery during 'Service Mode' if you want longer than the 10 mins before opening the door
 

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It has been 6 years. Get a new battery, it is not worth the risk.
 

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why wait 6 years when

"Near annual replacement of 12V battery is typical according to Tesla Service Tech :) "

but the topic is more about -- is the battery ok NOW and getting some heads up on premature battery problems.
The Spyder thinks it is. But I think not. For AGM, I'd NEVER EVER want to see it below 12v, and if it couldn't show 12.5 or above after sitting in circuit for a couple of hours, then just opening the hatch and metering between the terminals as-is, it goes into the "gonna need to replace that soon" category, and 12.4 is "replace now please". Plain old flooded batteries use lower voltage thresholds and treating an AGM like a flooded lead acid is a great way to wreck one on Tesla-like schedules.

I've seen this sooooo often on house batteries on boats and RVs. Someone gets a bank of AGM because they're swayed by the better self-discharge and longevity, but they don't adjust or replace their charging system and alternator regulation, and the wreck the whole bank in a season by chronically undercharging and draining them too far.
 

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You can do one of three steps:

1. Ignore the condition and keep running until the 12 VDC battery fails.
2. Carry a jumpstart cable set or a portable Li-Ion 12 VDC jumpstart pack.
3. Prevent the risk, spend money, and buy a replacement.

I am doing #2. My 2009 Equinox had a battery replaced last year (2017). The original AC Delco failed but I started it and went to AAP (once known as Western Auto) for the replacement. BTW, the DIC shows the voltage as I drive, so I know if the alternator fails.
 
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