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When Did You Need to Replace Your 12V Battery?
- Thread starter PianoAl
- Start date
What about 'never'? This poll seems much like "When did you stop beating your wife?"
Black306
Active Member
This is not a question of 'if,' it's a question of 'when.' If you haven't changed your 12v battery yet, just wait.
I am totally at a loss at how you could even ask this, if they get charged "at all". If they didn't get recharged at all, they wouldn't last more than a few days, much less years. Of course they get recharged. The car monitors the level of the 12V battery, and when it gets low, it uses a DC to DC electrical circuit in the car to use some energy from the really big main battery pack to refill the 12V. Even when the car is off, that 12V is being used for some minor electronics and is still being monitored, and the car will occasionally top up the 12V battery from the main as needed.
I guess I was expecting the more frequent question of "How do they get recharged?"
I'm sure TJ was asking
"Do Teslas charge the 12v battery at all when driving or only when charging?"
The answer being "any time they get low."
Living in Phoenix, premature death of 12v batteries is common in ICE vehicles. Given the workout ours get running virtually everything in the car, I replaced mine at 1 year (prior to the start of hot weather here) with an Ohmmu. Expensive? Yes. Worth the peace of mind from finding HAL bricked in a mall parking lot in August (and the OAT is 110f)? Absolutely.
Our 2018 Model 3 with a VIN less than 17k is still on the original 12V battery. Its 4th anniversary of delivery is coming up at the end of the month. However, the car is garaged all the time at home and my wife's office in the mild climate of Silicon Valley. I thought about proactively replacing it based on other people's horror stories, but it just keeps chugging along.
I did mine proactively once I reached 50k miles and it was out of warranty. That occurred almost exactly at 2.5 years. A service reps told me that the most common time for them to fail on the M3 to right at 3 years.
FWIW, mobile service will do it for only around $30 more than the cost of the battery. My bill came to $121total! Plus they fixed a couple other small issues for FREE. That's not much for peace of mind and not getting stranded somewhere.
Ambient temperature is the biggest variable. Pheonix - 1 year sounds reasonable. That would be silly in Maine.
That lesson was driven home with the Leafs - sure different battery tech but chemistry is still temperature dependent.
There is a battery life expectancy map somewhere - made for ICE cars but fully relevant for Tesla's 12V.
That lesson was driven home with the Leafs - sure different battery tech but chemistry is still temperature dependent.
There is a battery life expectancy map somewhere - made for ICE cars but fully relevant for Tesla's 12V.
smatthew
Active Member
Then we need an option for "I changed mine at X" years despite having no errors yetThis is not a question of 'if,' it's a question of 'when.' If you haven't changed your 12v battery yet, just wait.
Black306
Active Member
No, cause that would dirty the data. The OP is looking for when batteries fail, or nearly fail by presenting an error message, so that he can preemptively replace the battery before it’s needed. Data for when a battery was changed by choice is not what he is lookin for.
Jeremy3292
Active Member
I'm not there yet but this is for sure my plan as well. I drive ~20k miles a year so I'll be at 2.5 years like you were also.
smatthew
Active Member
Except that it shows "Oh, my battery lasted X years and was still fine." They're all valid data points.
Black306
Active Member
Where does it say "Oh, my battery lasted X years and was still fine?"
Are you referring to when a false message pops up? ie Message shows but the battery is still good.
Last edited:
Thanks all. I plan to proactively replace the 12V some time this year. I'll use the dough I saved on oil changes.
Iain
Member
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