Replying to myself, and I guess this is only an issue if you have third party apps and can see what your car is doing, but I lost my bottle after 50 hours asleep and woke the car with the app. After doing that (and nothing else) it stayed awake for 2 hours charging the 12v….
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[UK]2022.4
- Thread starter goRt
- Start date
Regulo
Member
Excuse my ignorance, but how would I know whether my car has "woken up" or not, if it's been in my garage for 3 days?
But surely Teslafi wakes the car up every time it requests a status update? I deliberately don't use any apps to request data from the car and avoid checking its status with the Tesla app (or use Sentry mode of course). Doing that results in a very low discharge rate for the traction battery, as I would expect.
However, I've only been running a Model 3 since last June and my understanding isn't as complete as for the other EVs I've been running for years.
Is there something special about Teslas in general and the Model 3 in particular that means they suffer from loss of 12V (and hence traction battery) charge when parked? 12V batteries shouldn't need topping up for weeks unless the car leaves on a significant (other than monitoring the locks, for example) load. Our ZOEs, for example, do an excellent job of removing almost all load from the 12V battery when parked up.
spooksman
Member
I think if you want to 'see' the state of the car you'd need to be using something like TeslaMate, TeslaFi or Tessie (for example). These use the streaming API, so don't wake the car.
However, I'm also a little confused, as I thought the 12v battery ran all the 'normal' systems in the car (central locking, lights, radio etc) much like an ICE car. ICE car batteries only get charged when they are being driven, and leaving an ICE car for a week or two without driving it is not an issue for the battery these days. Why does the Tesla need such frequent replenishment of the 12v battery - is there an inherent flaw?
I assume that as you unlock/drive/charge the Tesla it will be recharging the 12v battery in much the same way (although from the main battery pack).
I believe that Tesla are moving to lithium versions of the 12v (15v?) battery, is this why (other than then just being more efficient and lighter)?
Only asking as I'm pretty sure that a large majority of 'average' Tesla drivers would have no clue about whether the car is asleep tbh...
MrBadger
Badger out
No. It checks first if the car is awake and only then uses API requests that will wake, or keep the car awake.
So for a car that is asleep, it will remain asleep.
Don’t read too much into my concerns, I have an automatic boot and bonnet lifter so my car will have a little more vampiric drain than normal.
That said, Teslas do seem to use more 12v power than normal cars mainly because they’re always alive in some form to be in a position to be reached over LTE to be woken up properly, detect phone keys, etc.
Regarding when the car charges the 12v - like an ICE car it’s charging it whenever it’s awake, but it will also spontaneously wake itself up to charge it if it detects that it needs to, i.e. If it hasn’t been driven for a while.
Also as said above third party apps use the Streaming API so they don’t wake the car themselves by being used (unlike opening the app), so if you have these apps running constantly they can basically tell you how long it’s been asleep for.
Basically it’s not something you need to worry about, the car takes care of itself. It’s only something that’s an issue for me because I know my car has previously been waking up every 24 hours to charge the 12v, and now it doesn’t (but it should still need to as I’ve not changed anything)
Maybe a stupid question, but how do you know it was charging the 12v during that 2 hours?
Regulo
Member
I don't! I've left cars in the garage for weeks previously, without any problems, so I wonder what all the fuss is over whether the car is dozing or itching to move
I'm sure you're right but I don't think it's going to be a problem for a few days. I don't think LTE runs when asleep as it needs the wake-up SMS signal before that level of connectivity kicks in. SMS is a much lower power feature.
Basically from just having done quite a lot of research into it, and having TeslaMate working on the car since I got it. The car will recharge the 12v battery in hour blocks. In my case it tends to be 2 hours, but I’ve seen three and very occasionally 1.
When it was waking up every 24 hours for 2 hours each time I opened a service request because I was concerned. It used to do it every few days, and then every 48 hours, which then became every 24 hours, which suggested to me that the 12v battery was degrading. Tesla confirmed to me on the phone (with timestamps) that the periods that it was spontaneously waking up and staying awake for 2 hours was “supporting the 12v system”. They told me not to worry about it, that it takes care of itself, and that the car would tell me when the battery needed to be replaced.
I should add that I barely drive my car, maybe once every 2 weeks, sometimes once a month, depending on what’s going on, so I see this behaviour more acutely and predictably than someone who drives the car often (if I do that it throws the pattern out for a day or so, because the 12v is always being maintained when the car is awake, and I have Sentry on everywhere except home)
I wouldn't worry too much about the current draw of the LTE terminal. It's just sitting there waiting for an SMS from Tesla. An old Nokia phone could sit on standby waiting for incoming calls or SMS messages for over a week with a tiny battery. And no reason why listening for Bluetooth phones or fobs should consume any more than other cars with passive entry.
I do wonder whether Tesla are starting to turn some of their battery management expertise to the 12V battery, and tracking the state of charge and intelligently scheduling 12V charging for when it is needed rather than waking up and checking on a fixed schedule. Maybe the new Li-Ion 12V battery needs more intelligent charge management, and some of the benefits of that work are spilling over into cars with lead-acid batteries, too. Just speculation, though.
Cheers - great explanation, thanks. Usually I drive the car every day so maybe why I haven't been seeing this so obviously - last 5 days I have been stuck in the house so more visible.
The vehicle uses a 12v system to run the electrics but not from the 12v battery - there is a converter that produces a 12v supply from the main high voltage battery. Whenever the vehicle is awake it is powered from the high voltage battery which is also charging the 12v battery. The 12v battery is only powering the alarm, mobile communication and Bluetooth central locking when the vehicle is powered down.
That 12v battery is quite small, as it doesn’t need to be big to start an ICE, but that means it can discharge quite quickly, plus lead acid batteries don‘t like being discharged more than 50%, so the vehicle will wake up every couple of days to check the state and charge it back up if required.
Yes, it's not of a spec that's suitable for the heavy discharge involved with starting an ICE but actually at 45Ah it's quite a decent capacity and similar to many ordinary cars (ones that don't run an auto stop/start system).
