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insaneoctane
Well-Known Member
So, are you expected to occasionally charge it manually? That's what I would do every year or 6 months to try and avoid replacing it all the time????
stopcrazypp
Well-Known Member
My understanding is that it is this: when the car is off, the contactors disconnect the high voltage traction battery. The small 12V battery however provides power for alarms, unlocking doors, etc (same as ICE car). The difference is that it also provides power for all the features you have in the app. This leads to a considerable amount of vampire drain.
Occasionally the contactors connect the HV battery again to charge up the 12V battery using the DC-DC converter. Given the vampire drain, this puts a considerable amount of cycles on the 12V battery (more than most typical ICE cars), and that is why they have such a short life (the small size of the 12V is another factor).
Another factor is that Tesla doesn't appear to float charge the 12V battery when the car is plugged in and it is finished charging. So it's still putting on extra cycles on the battery even in that case.
Syonyk's Project Blog: Tesla Model S 12V Battery Analysis
As for the comment about it not getting charged, that is false. It is charged by the DC-DC converter, same as a traditional ICE car's 12V is charged by the alternator.
The way to fix it is to reduce vampire drain (no one has any idea if there is improvement over Model S yet, I hope it does). In Model S there is an "Energy Saving" mode you can set to lower vampire drain, hopefully the same mode is present in the Model 3.
The other way is to leave the 12V battery on a battery tender (similar to an ICE car). But that is obviously inconvenient, especially for daily use (might be possible for longer periods not using the car). The newer Model S don't have easy access to the battery posts to connect such a battery tender, and I imagine the Model 3 is similar.
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insaneoctane
Well-Known Member
Ok. So, if your 12V battery died and you couldn't do the usual things (unlock doors, etc) if you "jump" the system, will the high voltage battery be reconnected and everything is fine until you turn the car off again? If so, what "size" jump do you need? You definately wouldn't need an ICE-style starter capable one, right?
Here's a small one, as an example, that might do the job to get you out of a pinch?
https://www.amazon.com/dp/B004LX3AXQ?th=1
Here's a small one, as an example, that might do the job to get you out of a pinch?
https://www.amazon.com/dp/B004LX3AXQ?th=1
stopcrazypp
Well-Known Member
Correct, You definitely don't need a ICE starter capable one. The jump only needs to be strong enough to power up computers again and the contactor to connect the HV battery.
The one you linked though seems to be a charger only though and at 1.1A has fairly low power.
However, portable jump starters are around the same price (just a quick search on amazon, probably there are cheaper ones with less features and power):
Amazon.com: Customer reviews: BEATIT TECH 600A Peak 14000mAh 12-Volt Portable Car Jump starter Booster Battery Charger Power Bank Vehicle Emergency Kit, Compass & Built-in Flashlight
voip-ninja
Give me some sugar baby
It's been said a lot of thought was put into a world of autonomous driving and (with news of the camera on the rear-view mirror) autonomous Tesla ride-sharing. I imagine the door opens electrically because the designers thought ahead to the Tesla Ride Sharing program. Someone hails a car, the car pulls up, and if the door only opened with a mechanical latch, the car couldn't open the door for a passenger. Once you have a method which relies on electricity vs. mechanical effort, you need a a backup in case the electrical method fails.
It is odd that they have such trouble with the 12V. The worst battery I ever had still lasted 3 years before it went out. Most were around 5.
JeffK
Well-Known Member
Dynastar
Member
One handy thing Nissan did with the Leaf is the tiny solar panel on the hatch, which is only used to charge the 12v battery. Basically it's a built-in battery tender. I assume the Leaf has a lower vampire drain too, but the 12v battery seems to last a long time.
JeffK
Well-Known Member
I only park in garages at home and at work... that feature would be kind of useless for me.
stopcrazypp
Well-Known Member
The other fact is that the one in Tesla and also many hybrids/EVs tend to be tiny (less than half capacity), so for the same demand, there are more cycles on it.
SageBrush
REJECT Fascism
I have a competitor model.
My hybrid had been sitting for a couple months and had a dead 12v.
"No problem," said I, and pulled out my dandy (never used before) battery gizmo.
Nada.
Thankfully I was at home so all it took was an hour to recharge the gizmo.
JeffK
Well-Known Member
yeah, have to make sure it's topped up every once in awhile.
I'm guilty of the same thing with my spare tire... I go to use it and it's flat, Doh! Luckily I had a portable air compressor.
Why is Tesla I guess then? I'd like to understand the technical reasons why they don't have a better option to produce 12V somehow.
Well this is disappointing. One of the ways I was justifying the extra cost of this car was the reduced maintence costs. No oil changes, no filters, break pads (or at least much less frequent) etc. Now it sounds like I need to factor in a yearly battery change which will cost more than a years worth of oil changes.
My battery replacements were all covered under warranty (except my last one, because my warranty has now expired). And we don't know that the Model 3 will have this problem.
Had my 12V replaced once in 4 years. Got a warning message that 12v was in need of replacement, and to schedule appointment to replace it. Tesla said that after the message pops up you have about 1 week before the 12v battery dies (the car monitors the 12v's state of health), so it isn't like it just happens out of the blue.
SageBrush
REJECT Fascism
I REAAALLLY hope the 12v is an owner DIY item on the Model 3. I just cannot imagine driving 6 hours to the nearest service center to have it replaced, or even to drag a ranger out to my place for the service.
I do plan to let the poor 12v rest as much as possible, and to minimize vampire drains. Beyond that though, it is up to Tesla to improve the 12v longevity it currently enjoys.
I do plan to let the poor 12v rest as much as possible, and to minimize vampire drains. Beyond that though, it is up to Tesla to improve the 12v longevity it currently enjoys.
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