Every Honda made in the last several years with auto idle stop, for example, measures the internal resistance of the battery each time the vehicle is turned on and constantly monitors voltage. This is done so the auto idle stop feature can be disabled if the battery may not be strong enough to restart the engine. If the battery is judged to be degraded, the auto idle stop feature will be disabled and a warning message will appear.
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Update on replacing OEM 12v lead-acid battery with lithium?
- Thread starter Pianewman
- Start date
Ostrichsak
Well-Known Member
Of everything I said.. that's the part you chose to focus on? People are weird about trying to discredit others on this forum. So one manufacturer has a similar feature that Tesla has had for a decade now. Cool. Still doesn't negate the more important aspects of my post.
MountainRatMat
Member
You read my location over on the left column?
I would disagree with this for the astute observer but for the average car owner you are correct. Every ICE I have had you could hear the starter struggling as the battery degrades ESPECIALLY as the weather starts to turn. I spend a lot of time in the mountains and when it starts to get cold is when you notice this happening. I would always drive down to the auto parts store, have them test my battery, and if it failed get it replaced. In most ICE cars there is no warning system, on new ICE cars they are starting to be more ubiquitous.
In my case my lead acid Tesla battery gave me no warning.
I'm mixed on this response, it's a very different application. In a Tesla you need the 12V to be operational at all times. On an ICE you really just need the 12V to provide very limited power when the car is off. Then huge amounts of Cold Cranking Amps to start the car. Then the alternator takes over when the car is running to constantly recharge the 12V. Lead Acid batteries are a good fit for ICE application. The Tesla theoretically charges the 12V lead acid battery when the contactors to the high voltage battery are connected but in reality it just degrades the lead acid batteries faster. Hence why all new Teslas now have LiIon 12V batteries.
While I agree with you that Ohmmu is crap, I would argue the Tesla LiIon 12V bettery is a excellent and fits the application much better than lead acid. It isn't the technology of the Ohmmu that is so bad it is the application of the technology that they failed at. Just look for a tear down video of the Ohmmu on YouTube, it is grade school science fair quality in there.
MountainRatMat
Member
You are correct but that is really semantics, it runs the low voltage systems in the car and not the high voltage like the main battery.
If one is really worried, I’d just suggest a new 12v OEM battery every 24 months. Maybe a birthday present or to celebrate July 4th. Would still take a while to pass the cost of an aftermarket Li battery. The OEM is really inexpensive for an 3 or Y, and it’s fully supported.
Usually you get weird behavior from warning lights that actually have nothing to do with the battery, usually the ABS system, sometimes traction control when the 12V battery of an ICE car is getting weak. This is also how you know your 12V battery is getting weak on a Chevy Bolt...
Since even an ICE car has multiple computer systems now a days, some of them are more sensitive to voltage problems than the main ECU, when those computer systems start getting low voltage stuff goes haywire before the power is actually depleted enough to not crank over the engine and start it.
Keith
Last edited:
CapsEngineer
Member
Saw that on my Edge where the sync system would start rebooting, or in their terms "Performing system maintenance" more than normal. Because it was "more than normal" I didn't realize that's what it was doing. After I replaced the 12V, I thought it was the reason, but I still can't be sure.
I have gained tons of knowledge from your posts……so I am interested in how you use a 9v battery to open the frunk……
Shown using a small A23 12V battery (my previous wireless doorbell button used this type battery) but also works with a common 9V battery. (Note: For security of the frunk, frunk bin contents this procedure will only activate the frunk release when the Tesla vehicle's 12V battery has failed.)
How to open the Tesla frunk when the 12V battery has failed
golfpilot
Member
Been running EVs for over a decade now. The early Tesla drivetrain I had (Rav4) gave no warning until the car wouldn't start and if if went completely dead you risked bricking the car. My Model 3 has gone through 2 oem batteries. Both failing at 24 month on the number. Neither time did I have any warning. The car had to be jumped and/or I had to drive to the SC in another car to get a new battery. The 3rd time I went with the Ohmmu with dream of not getting stuck somewhere again. It has been a year and it hasn't failed yet. The BIG issue with the Ohmmu is lack of Tesla support. Tesla added a desulfation mode and it wrecks havoc with the Ohmmu, especially in the cold. The good news is that you get a notification and I am able to get it reset in about 30 seconds using software. The bad news is that it happens every so often. Updating the firmware on the battery is somewhat difficult and their is 0 hint that Tesla will support a 3rd party battery or allow a service toggle for desulfation.
If I could do it again I would have just replaced the 12v a third time and put a reminder in my phone 23 months out to replace the battery again. But in the meantime, it isn't a big enough hassle to warrant getting rid of it.
If I could do it again I would have just replaced the 12v a third time and put a reminder in my phone 23 months out to replace the battery again. But in the meantime, it isn't a big enough hassle to warrant getting rid of it.
No - the "BIG issue" is the risk of fire or damage to the vehicle.
Ok, thanks for this thread, I now know not to use the lithium battery.
Can someone weigh in on replacement 12V batteries for 2018 M3: OEM or 3rd party "group 51r" ok? and let me know which replacement 12V lead acid battery is a good replacement when the main one dies? or is the same exact oem battery still the right choice after 5 years? (answer in the other thread if possible)
Can someone weigh in on replacement 12V batteries for 2018 M3: OEM or 3rd party "group 51r" ok? and let me know which replacement 12V lead acid battery is a good replacement when the main one dies? or is the same exact oem battery still the right choice after 5 years? (answer in the other thread if possible)
The OEM from Tesla is the best deal.
If you live near an O'Reilly's Auto Parts store they sell a 12V AGM battery in Group 51R that will fit the Model 3, Model Y with the + and - battery posts in the orientation to fit the Tesla 12V battery connectors. Someone on TMC installed one in their Model 3. I did not see a follow up post.
The Tesla OE 12V battery in the 2018 Model 3 is a maintenance free flooded lead acid design. Absorbent Glass Matt (AGM) batteries are also maintenance free. AGM type batteries are highly resistant to damage from vibration, won't freeze at temperatures that could freeze a flooded lead-acid battery. The charging protocol and float voltage of a 12V AGM battery are not the same as for the flooded lead-acid battery. Not sure how an AGM 12V would hold up when installed in the Tesla.
The Tesla OE 12V battery in the 2018 Model 3 is a maintenance free flooded lead acid design. Absorbent Glass Matt (AGM) batteries are also maintenance free. AGM type batteries are highly resistant to damage from vibration, won't freeze at temperatures that could freeze a flooded lead-acid battery. The charging protocol and float voltage of a 12V AGM battery are not the same as for the flooded lead-acid battery. Not sure how an AGM 12V would hold up when installed in the Tesla.
Definitely different for AGM. There is a risk of overcharging the AGM battery (depending on temperature) if the float voltage is too high. Also, AGM batteries require a higher initial charging voltage before the charging voltage is reduced. Tesla has revised the 12V battery charging parameters multiple times. I don't know what Tesla uses for the current iteration of the 12V lead-acid charging voltage.jcanoe: So, the AGM Group 51R will FIT, but you're unsure if it functions properly in a Tesla?
The question is: does a 12V AGM battery have a different charging protocol and float voltage compared to a flooded lead acid 12V?
Maybe you'd like to start a new thread, posing the question?
This might be much ado about nothing. Years ago I installed an Optima 12V (AGM) replacement battery in my GM vehicle (designed for 12V lead-acid) and the Optima battery outlasted the OE lead-acid battery by 3:1.
The Tesla OE 12V lead-acid replacement battery is very reasonably priced. I just performed a conductance test on the original Hankook AtlasBX 12V lead-acid battery in my 2020 LRMY and the 12V tested good at 3.5 years. I may yet be proven wrong but I anticipate that the factory 12V in my 2020 LRMY will last beyond 4 years (the Tesla new vehicle warranty period).
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