COVID Infects Tesla 12V batteries

[LastGas]

The first 12V battery in my Model S lasted nearly 4 years, but its warranty replacement barely lasted 2. What's up with that?

I asked the Tesla Mobile Service technician why the battery only lasted 2 years. He said it he had seen a lot of 12V battery failures and suggested it was because of COVID. He said that cars weren't being driven as much and because they weren't being driven, the battery was cycling up and down, and degrading.

I think he was mostly right. The problem isn't that the cars aren't being driven, but that the cars aren't being charged. If you don't drive much, there is little reason to plug the car in at night, and indeed the 12V battery does drain and is recharged from the main battery -- over and over.

Early Tesla cars came with a card in the glovebox that said: "A plugged in Tesla is a happy Tesla." When the car is plugged in, the electronics are powered from the AC source and the battery doesn't cycle. If you want your 12V battery to last longer, keep the car plugged in when you can. And of course, don't set the charge limit higher than you need.

 

[Watts_Up]

You should instal a 12V Bluethooth monitor, you will see that the 12V battery get recharged
by the DC/DC in-board charger as soon the voltage drop under 12.5V.
Typically, the in-board charger runs for about 2 hours every 2 days, when the car is sleeping for a long time.

>> He said that cars weren't being driven as much and because they weren't being driven,
>> the battery was cycling up and down, and degrading.

I don't see why not driving can affect the 12V battery, since the 12V battery get automatically charged.

A phone or any battery device, if used or not used, get its battery discharge and need to be recharged.

IMO. your "new" 12V should have lasted more than 2 years, are you sure it was a "new" battery?

 

[LastGas]

IMO. your "new" 12V should have lasted more than 2 years, are you sure it was a "new" battery?

All I know is that Tesla Mobile Service provided and installed the battery. I presume it was new.

 

[LastGas]

I don't see why not driving can affect the 12V battery, since the 12V battery get automatically charged.

The point there is if you don't drive the car, you might not plug in the car. And if you don't plug in the car, the electronics run off the 12 V battery rather than the AC. When the car is plugged in, the 12V battery doesn't get used and it doesn't need any charging cycles. At least that's what I've read.

 

[Darmie]

They are making a good point but requires more testing. I see the point that if the vehicle is not being charged and or if in a deeper sleep, the 12V battery could potentially be further discharged. If Bjorn wasn't driving around in other EV's, he would make a good candidate to do this testing.

 

[Winglessflight]

Here is an excellent article explaining the 12-volt degradation...

12 Volt Battery Compendium – TeslaTap

teslatap.com

 

[theothertom]

Here is an excellent article explaining the 12-volt degradation...

12 Volt Battery Compendium – TeslaTap

teslatap.com

I was just going to post that.
From the article:
"Paradoxically, if you put a few miles on the car, it may last as little as 1-2 years. The difference is how many discharge/charge cycles the battery goes through and how deeply the battery is discharged"

 

[ATPMSD]

The point there is if you don't drive the car, you might not plug in the car. And if you don't plug in the car, the electronics run off the 12 V battery rather than the AC. When the car is plugged in, the 12V battery doesn't get used and it doesn't need any charging cycles. At least that's what I've read.

Incorrect, plugging in the car does NOT power the 12v system! When parked the car runs off the 12v system, when the battery management system detects the 12v battery is low it closes the high-voltage (HV) relay and the DC-DC converter then powers the 12v system to charge the car, once the battery is charged the HV system disconnects. Plugging in the car only charges the main battery when it drops below the set point and does not impact the 12v battery.

When driving the car, the HV relay is closed and the DC-DC converter supplies the 12v system.

 

[Darmie]

Incorrect, plugging in the car does NOT power the 12v system! When parked the car runs off the 12v system, when the battery management system detects the 12v battery is low it closes the high-voltage (HV) relay and the DC-DC converter then powers the 12v system to charge the car, once the battery is charged the HV system disconnects. Plugging in the car only charges the main battery when it drops below the set point and does not impact the 12v battery.

When driving the car, the HV relay is closed and the DC-DC converter supplies the 12v system.

This is good to know. How does the Sentry mode play into all of this? I was aware that the HV contactors were closed when sentry was on. I drive the Y daily but if I didn't, I think it may be worth the investment in a cheap tender.

 

[android04]

This is good to know. How does the Sentry mode play into all of this? I was aware that the HV contactors were closed when sentry was on. I drive the Y daily but if I didn't, I think it may be worth the investment in a cheap tender.

Keeping Sentry Mode on basically just keeps your 12v battery at 100% charge the whole time the car is awake, because everything is powered by the high voltage battery the whole time.

 

[Resist]

I think that mobile service technician suggesting 12 volt battery failures were because of Covid, could be because of the manufacture workforce issues due to Covid causing workers to be a bit more sloppy causing defective batteries. But I wish Tesla would come up with a way to eliminate the 12 volt battery altogether.

 

[Brando]

I think that mobile service technician suggesting 12 volt battery failures were because of Covid, could be because of the manufacture workforce issues due to Covid causing workers to be a bit more sloppy causing defective batteries. But I wish Tesla would come up with a way to eliminate the 12 volt battery altogether.

I'd suggest going to ethernet Power over Ethernet - Wikipedia
safe power levels, smaller wiring, networking (vs single wire) (saves weight both size % number of wires)

 

[ATPMSD]

I believe early Teslas did not have a 12v battery, only the DC-DC transformer. Unfortunately, a lot of owners came out to find cars with dead HV batteries, which is a very bad thing. Hence the 12v battery was added.

 

[father_of_6]

The battery vaccines will save us!!

 

[Brando]

I believe early Teslas did not have a 12v battery, only the DC-DC transformer. Unfortunately, a lot of owners came out to find cars with dead HV batteries, which is a very bad thing. Hence the 12v battery was added.

Tesla has always had 12v lead acid car battery until this new Likthium battery replaced the lead acid one.

12 volt batteries & parts for over 100 years.

 

[Resist]

Does anyone know if the OEM lead acid 12 volt battery can be replaced with the new Tesla lithium Ion battery. I'm not interested in an aftermarket one. Or do you think down the road as all the current lead acid batteries start to die that Tesla will be replacing them with the new battery, if you have them replace it?

 

[ATPMSD]

Tesla has always had 12v lead acid car battery until this new Likthium battery replaced the lead acid one.

And @Resist

“The earliest Tesla roadsters didn’t include a 12v battery but used a portion of the main lithium-ion pack to supply 12v for accessories and lights. This was not ideal, and in 2010 Tesla switched to a separate 12V battery in the Roadster 2.0. All Tesla vehicles since that time also include a separate 12v battery.”

12 Volt Battery Compendium – TeslaTap

teslatap.com

 

[father_of_6]

And @Resist

“The earliest Tesla roadsters didn’t include a 12v battery but used a portion of the main lithium-ion pack to supply 12v for accessories and lights. This was not ideal, and in 2010 Tesla switched to a separate 12V battery in the Roadster 2.0. All Tesla vehicles since that time also include a separate 12v battery.”

12 Volt Battery Compendium – TeslaTap

teslatap.com

I thought I read that Tesla was working on powering everything with the traction battery. Hmm... oh well.

 

[Resist]

And @Resist

“The earliest Tesla roadsters didn’t include a 12v battery but used a portion of the main lithium-ion pack to supply 12v for accessories and lights. This was not ideal, and in 2010 Tesla switched to a separate 12V battery in the Roadster 2.0. All Tesla vehicles since that time also include a separate 12v battery.”

12 Volt Battery Compendium – TeslaTap

teslatap.com

Interesting but you'd think they could have found a way to effectively ditch the 12 volt battery.

 

[father_of_6]

Interesting but you'd think they could have found a way to effectively ditch the 12 volt battery.

Yeah. One less problem for service to deal with.