High Vampire Drain

[Droschke]

I had my 12 volt battery changed at SC three years ago (the odometer difference between then and now is only ~4500 miles).

My typical vampire drain used to be about 2-3 miles a day. I now notice to be 6-8 miles a day, with the car not driven and parked in the garage. I don’t use any 3rd-party data gathering app. MY Energy saving=ON, and Always connected=OFF.

Can it be that the 12v battery is weakening and it’s being charged with much higher frequency?

 

[ucmndd]

Definitely could be. The older cars seem to have a 3-ish year replacement cycle for the 12v - largely a time function, not mileage.

 

[cpa]

I replaced the original 12V after a little more than two years.

The replacement pooped out last fall after another 5-plus years.

I don't think lead-acid battery technology has changed a whole lot since WWII (but feel free to discredit my assumption.) I do think manufacturing of those batteries has improved over the decades. But, there are always going to be those batteries that fail after 30 months while others last 72 months or longer.

Anyway, that is my story, and I am sticking to it.

 

[Droschke]

Not aware of any technical reason for Tesla not using the lithium batteries as replacement for our cars. But, I do know that the lead-acid batteries in our cars go through lots of charging cycles, compared to the ICE cars, to keep up with all the electronics, especially when the car is not being even driven.

 

[ATPMSD]

Can it be that the 12v battery is weakening and it’s being charged with much higher frequency?

Very likely. You get a battery replacement warning when the battery cannot be charged to a sufficient level. A battery replacement warning is likely around the corner; three years seems to be a common time for replacement.

 

[turen009]

Does the 12V system power the headlights and power steering system?

 

[ATPMSD]

Does the 12V system power the headlights and power steering system?

You have two sources of power, 12VDC and 350VDC (at least that is the HV battery in my car). Here is list I found:

Main battery powers:
HVAC,
Heater
Drive Units

12V powers the rest:
Lights
Audio
Screens
wipers
Powered brakes (without power, you can still mechanically brake but harder)
Powered steering (without power, you can still mechanically steer but harder)
Battery Management System (no 12V means no way to charge the main battery)
Small motors/solenoids/electronic latches: for seats, windows, doors...
Accessories...

 

[ucmndd]

You have two sources of power, 12VDC and 600VDC (at least that is the HV battery in my car).

350-400VDC, not 600.

 

[ucmndd]

Does the 12V system power the headlights and power steering system?

Generally yes, but when the car is on and the contactors are closed that energy is coming from the HV battery through the DC-DC converter, not via the actual 12v battery (which powers the car's low voltage system when the HV contactors are open).

 

[ATPMSD]

350-400VDC, not 600.

Yeah, I just fixed that It is 350 in mine.

 

[Rocky_H]

Not aware of any technical reason for Tesla not using the lithium batteries as replacement for our cars.

There is a very straightforward technical reason. They can't be used in cold climates. If you try to charge a lithium ion battery when it is below about freezing point, it causes terrible damage to the battery and will destroy it in short order if that is done several times. These 12V batteries get drained and refilled somewhat often and don't have a heating system, so in Winter, they would get destroyed quickly. So that's not feasible.

I have an electric motorcycle that doesn't have a 12V battery but does have the main lithium ion battery. It doesn't have heating for the main pack, but does have that temperature monitoring. When it's below freezing, and you plug it in, it will just not charge to prevent destroying the battery. It has to stay in the garage long enough to warm up from ambient air until it can start charging in a non-damaging way.

 

[Droschke]

There is a very straightforward technical reason. They can't be used in cold climates. If you try to charge a lithium ion battery when it is below about freezing point, it causes terrible damage to the battery and will destroy it in short order if that is done several times. These 12V batteries get drained and refilled somewhat often and don't have a heating system, so in Winter, they would get destroyed quickly. So that's not feasible.

I have an electric motorcycle that doesn't have a 12V battery but does have the main lithium ion battery. It doesn't have heating for the main pack, but does have that temperature monitoring. When it's below freezing, and you plug it in, it will just not charge to prevent destroying the battery. It has to stay in the garage long enough to warm up from ambient air until it can start charging in a non-damaging way.

Ah, OK. It makes sense. Thanks for the explanation.

 

[Droschke]

Do we have an understanding of what a normal and/or abnormal vampire drain is? What's acceptable and what's not?

Any consensus out there?

 

[mswlogo]

Since you are not “starting” your car, the number of miles makes very little difference on the condition of your 12 V battery.

The car is constantly draining and charging the 12v from the HV battery.

In fact 12v might be in better shape if you drove it more.

 

[Droschke]

Since you are not “starting” your car, the number of miles makes very little difference on the condition of your 12 V battery.

The car is constantly draining and charging the 12v from the HV battery.

In fact 12v might be in better shape if you drove it more.

As an energy source, does the HV battery substitute the 12V battery as the car is in motion? In other words, is the 12V not used (hence not charged or discharged constantly) when the car is driven since all the necessary energy comes from the HV battery?

 

[ucmndd]

As an energy source, does the HV battery substitute the 12V battery as the car is in motion? In other words, is the 12V not used (hence not charged or discharged constantly) when the car is driven since all the necessary energy comes from the HV battery?

Yes, as I said above, when the car is “on” and the HV contactors are closed, 12v power comes from the DC-DC converter, not the 12v battery.

This is analogous to the alternator in an ICE vehicle.

 

[ATPMSD]

Do we have an understanding of what a normal and/or abnormal vampire drain is? What's acceptable and what's not?

Any consensus out there?

With Sentry, summons and cabin overheat protection off it is about 0.5-1 kWh / day
With Sentry on it is about 5-6 kWh / day.

 

[Droschke]

Yes, as I said above, when the car is “on” and the HV contactors are closed, 12v power comes from the DC-DC converter, not the 12v battery.

This is analogous to the alternator in an ICE vehicle.

Yes, you in fact had mentioned that earlier. A memory lapse on my part

Thanks.

 

[mswlogo]

As an energy source, does the HV battery substitute the 12V battery as the car is in motion? In other words, is the 12V not used (hence not charged or discharged constantly) when the car is driven since all the necessary energy comes from the HV battery?

I don’t know for a fact. But there is a DC-DC converter that periodically charges the 12V battery when parked. And some computers and radios are always running off 12V. When the car is running I think that DC-DC tops of 12V and runs all 12V devices. That’s my understanding. And welcome any corrections.

I also I know when it’s plugged in, it draws nothing unless it’s actively charging. It doesn’t “trickle” HV or 12V.

 

[Droschke]

I had my 12 volt battery changed at SC three years ago (the odometer difference between then and now is only ~4500 miles).

My typical vampire drain used to be about 2-3 miles a day. I now notice to be 6-8 miles a day, with the car not driven and parked in the garage. I don’t use any 3rd-party data gathering app. MY Energy saving=ON, and Always connected=OFF.

Can it be that the 12v battery is weakening and it’s being charged with much higher frequency?

Update:

I have been doing some measurements since I started this thread.

- The measurements are taken for 24 hours intervals each; and only when the car is parked in the garage, plugged in, and not driven
- The average miles loss = 5.1 miles
- The average percentage loss = 2.13%

Is the drain high, low, average?