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[NEW2elec]

Former Top Gear presenter James May did a video recently about his Tesla's 12 volt battery being discharged and not being able to access his car. It's not unique to Tesla or even EVs since I know some Zero owners have had their newer 12v aux batteries die. Even with no 12v aux battery I have had my DC-DC converter start it's death process. Losing all your lights and dash functions are quite unsettling in the day time and can be catastrophic at night.

I've tried to think of solutions to this problem. First is simple redundancy. Dual converters with some type of relay switch to use the second unit if the first goes out (giving the rider a warning or error code when activated). The units aren't that big but i know on motorcycles every inch of space counts. It's the same problem with dual 12v batteries only more so as they will self discharge over time leaving you with a dead backup as well.

So perhaps a separate 12v BMS that can monitor the aux battery health and tell the EV's main computer to close the main contactor so the main battery can recharge the aux battery through the DC-DC converter. Mr May said even though his Tesla was plugged in, once the main battery was fully charged it shuts down leaving the 12v aux battery on it's own.

I posted this on another forum but since I believe it to be a serious safety concern, I put it here as well to get as much input as possible.

[DonTom]

Former Top Gear presenter James May did a video recently about his Tesla's 12 volt battery being discharged and not being able to access his car.

Easy solution. Carry another 12V battery in the Frunk and a nine volt battery in your pocket.


My 2018 Tesla has the original 12V battery. But for now, I carry a spare lithium 12V battery and a nine volt battery in my pocket. But the nine volt battery can be taped to the wires in the front of the car behind that cover for those who don't want to carry it in their pocket. I always take my FOB and leave a nine volt battery next to it that I also take with me.


BTW, the nine volt battery will only open the Frunk when the 12V battery is too weak to open the Frunk. That way, what is in our  Frunks cannot get ripped off by somebody walking around with a nine volt battery.


Any Tesla owner should know to make sure they have access to a nine volt battery when they are outside the car. If you do not want to keep a large spare battery in the Frunk, a little lith motorcycle battery should work until you can get the 12V battery replaced. That should work for an electric motorcycle as well.


You should be able to replace the 12V battery with no tools, other than what is needed to remove the battery cables. I forgot what size it is, but I keep all the necessary stuff in my front in case the Frunk battery craps out when I am outside the car.


BTW, we usually get an error message on the screen to replace the 12V battery before it craps out. But sometimes the battery  fails with no advance warning. Best to be ready for it to happen.


But if one does get the warning, replace the battery as soon as you get the car home--without leaving the car before getting home.


-Don-  Reno, NV

[Richard230]

Zero should have a BMS that will warn you when your 12V battery is low on juice.  On my BMW I have a push button start system that uses a key fob to activate it (when pushed) when you are close to the bike. The bike's computer can tell when the battery in the key fob is getting low on power and it is time to be replaced. I gives you a wrench symbol on the dash about 3 months before the CR2032 battery in the fob calls it quits. Plenty of time to replace the battery. I would think that something similar could be designed and implemented to let the rider know the the 12V battery needs to be replaced or otherwise serviced. 

[MrMogensen]

...

BTW, the nine volt battery will only open the Frunk when the 12V battery is too weak to open the Frunk. That way, what is in our  Frunks cannot get ripped off by somebody walking around with a nine volt battery.
...

Good tip about 9V battery. I'll at least be sure to have one at home in the house. At work I can easily get one. That covers about 90% of all destinations.
Have a 2019 Model 3... Wondering if I would be screwed since I have installed the Hansshow Auto Frunk?
I am on the look out for a lithium 12V that doesn't cost a fortune to ship to Denmark and simply replace the existing. I don't think the original is of exceptionally good quality - even though it bothers me a bit to swap something out that isn't near death. I have to measure it's power sometime soon...

[NEW2elec]

Well I used Mr May's video to show it's a common problem that has been with Tesla in particular for a while.  The first model S had the black oval "grill" that could be removed giving you (somewhat easy) access to the 12V battery.  May's is of course new and buried it under plastic panels and gives owners access through the wheel well for a Frunk release.  He set up a longer trickle charge plug cable for when it's in storage while he's away.

To me that's having a fix for the problem but doesn't avoid the problem.

What I'm thinking and it looks like Richard agrees is that a 12V BMS is needed along with protocol firmware that can close the main contactor to use the main battery to recharge the 12V aux.  Why they haven't done this already, I don't know.
Of course a 12V doesn't last forever and a notification that it's coming to it's end of lie is always nice.

It's the motorcycles and their very small 12V aux batteries and even the gen 2 Zeros that only use DC-DC converter that can leave you in a bad spot.  The constant internet connection looking for OTA updates has caused a few postings of dead aux batteries already.  It comes mostly after a period of storage or little use.  For those again a 12V BMS with priority of it's SOC to the main battery's (to a certain level maybe 35% SOC) should avoid the issue.

As for a failing DC-DC converter, that kills all your lights and dash function.  That is very dangerous if it ever happens when ridding at night.  Having two units that swap over when one fails is the only solution I can think of for that one.

[MrMogensen]

I think it was in a recent interview between Elon Musk and Sandy Munroe (I'm not sure)?...
They spoke about why 12V batteries was still being put in electric vehicles. Of course it had to do with all the stuff that still needed 12V. Probably all sorts of motors (windows, mirrors, cabin fan, interior (maybe also exterior) lights

Some day in near future most electric cars (hopefully also bikes) will ship without the 12V battery... Most likely Tesla that will start pushing this through.

[Crissa]

The newest cars have a lithium battery with a newer management.  Tesla has gotten better.

-Crissa

[DonTom]

The newest cars have a lithium battery with a newer management.  Tesla has gotten better.

-Crissa

I carry this as a spare in my 2018 Tesla M3 Frunk.


While my original L-A 12 V battery is still okay, I will probably change to the lith today and take the L-A out. In fact, I will do that right now as I am thinking about it.


-Don-  Auburn, CA

[MrMogensen]

The newest cars have a lithium battery with a newer management.  Tesla has gotten better.

-Crissa

Guessing my mid 2019 is not one of those... But I better go check before I cash out 

I carry this as a spare in my 2018 Tesla M3 Frunk.
[/quote]

The OHMMU is most likely great quality, but I can't find any EU dealer - import tax and shipping will be insane!

[DonTom]

The newest cars have a lithium battery with a newer management.  Tesla has gotten better.

-Crissa

A lot better! You have been keeping up with my Tesla  updates better than I have! I just replaced my 12V battery with my new lithium. I spent more time testing the unexpected results than the time it took to replace the battery.

There seems to be no need for the 12V battery these days. With it disconnected, I could still get in the car, even listen to the radio. Use the FOB. No need for the 9V battery either. There was a message on the screen that the 12V battery is disconnected. I have no idea how that is detected, because here are the facts:

Battery voltage unconnected to anything=13.20 volts (lith 12V batteries are a higher voltage than L-A)
Battery cable voltage not  connected to battery=13.20 volts
Tesla powered down, and car powered off under "security" , 13.20 volts on cable to battery NOT connected to battery.

Even tested with frunk down using leads, 13.20 volts.

13.2 Volts at all times, no matter how it is checked, with or without battery.

I will make the assumption that the 12V battery doesn't do much these days, if anything ay all. Seems a DC2DCC is really doing ALL the work these days, even with the car off and powered down.

I no longer see a need for the nine volt battery.

I will now post a message in the Tesla forum to find out about all this. If the DC2DCC is on at all times, why the battery?

-Don-  Auburn, CA

[Crissa]

The 12v battery can provide tiny amounts of power arbitrarily, so it's better for the radio/cellular controls.  The DC-DC conversion is very inefficient, and more difficult to kick on.

-Crissa

[Richard230]

Speaking of Tesla. The news media has been reporting for the last few days that Consumer Reports and NTSA are not happy about the car right now. They say that Tesla removed the radar detection from their latest (built) models and is only relying on a camera to detect surrounding vehicles and that change makes them unsafe when using the auto pilot mode. This news must mean that my issue of Consumer Reports will be arriving in the mail soon.

[DonTom]

Speaking of Tesla. The news media has been reporting for the last few days that Consumer Reports and NTSA are not happy about the car right now. They say that Tesla removed the radar detection from their latest (built) models and is only relying on a camera to detect surrounding vehicles and that change makes them unsafe when using the auto pilot mode. This news must mean that my issue of Consumer Reports will be arriving in the mail soon.

I wonder why they would remove the radar detection.  Perhaps in trying to get the costs down?  But I would assume Tesla did a lot of testing on their new design and decided the radar wasn't really  necessary.


Kinda like Energica saying the extra battery cooling wasn't really necessary after bragging about how great it was in 2020 on my model.


Or how Yamaha bragged about how great their YICS system was until they removed it completely three years later on all models. I removed the YICS  on my Yamaha Venture (plugged the four vacuum ports)  and then got better performance and much better MPG. They brag about how it uses no moving parts, but they don't mention how the chambers start to leak around a week after the warranty expires!


It's always the best thing out there until they decide otherwise.    Especially when they are the only company to have it. Until they decide it isn't necessary, of course, on some newer model that has some new whatever that nobody else has. 



-Don- Auburn, CA

[Crissa]

I wonder why they would remove the radar detection.

Their stated reason is that the additional range the radar sensors has is causing more spurious phantoms than it's discovering unsafe situations.

They would know, since they have the discovery data from millions of miles of driving.  Their visual identification of surfaces has advanced greatly.

The radar has trouble with seeing soft things (like the consumer reports inflatable trailer rear-end test) and when a target vehicle is traveling the same exact speed.  It also sees flashes and reflections which create phantom objects to the AI.

-Crissa

[Richard230]

I wonder why they would remove the radar detection.

Their stated reason is that the additional range the radar sensors has is causing more spurious phantoms than it's discovering unsafe situations.

They would know, since they have the discovery data from millions of miles of driving.  Their visual identification of surfaces has advanced greatly.

The radar has trouble with seeing soft things (like the consumer reports inflatable trailer rear-end test) and when a target vehicle is traveling the same exact speed.  It also sees flashes and reflections which create phantom objects to the AI.

-Crissa

That is interesting. The news media was speculating that it was due to trying to cut costs. There was not a peep regarding Tesla's explanation.