"Small battery" fully discharges in a month or so if the vehicle is not operated?

[howardnj]

If I don't start my Lexus for three weeks the battery is almost dead.

How old is your Lexus Battery? If your battery is not sealed and has vent caps, a $10 battery hydrometer that measures the specific gravity can show up a cell not accepting a full charge. If that is the case it is best to replace the battery. If the battery is more than five years old it should also be replaced.

 

[RowdyMY]

How old is your Lexus Battery? If your battery is not sealed and has vent caps, a $10 battery hydrometer that measures the specific gravity can show up a cell not accepting a full charge. If that is the case it is best to replace the battery. If the battery is more than five years old it should also be replaced.

My 2010 Infiniti G37x had quite a bit of parasitic draw. I am mil so often left it sitting for months on end. If my wife forgot to drive it for me the battery was toast. Replaced it 4x with dead cells in the 8 years I owned it. Drove it to ~130k.

The batteries I used were high-quality too. I always sprang for the Optima red-tops, as they lasted longer in my personal experience. I had a trickle charger/battery MX charger that I could use sometimes, but didn't always have that luxury depending on the situation. Letting lead acid batteries discharge to low states just wreaks havoc on them.

...This coming from the guy that had a 12v system fail with a bad cell + a PCS fail in the first 2 weeks of ownership

That said, from what I can tell in the 30k of Tesla ownership across our M3/MY, the BMS should maintain the 12v battery just fine when not plugged in. Our 2020 M3 (delivery in Oct/Nov of 19) is still on it's first battery and we have definitely left it unplugged for pretty significant periods of time. I understand thats a sample size of 1 but it isn't something that has been a nag in the back of my mind.

 

[Calliope]

I left my BEV in an underground garage for 6 weeks (Leaf, not a Tesla) and it started right up when I returned......However, I left the lights on in my Leaf (on another occasion) and drained the 12V battery - locked myself out of the car. Of course, all I had to do was give the battery a boost, and I could get in. I keep a car booster in my frunk in case the 12V gets drained and needs a boost, though it's probably never going to happen in my Tesla.
(Yes, the Leaf had an "auto" light feature that would turn off the headlights when the car was parked, but the control was in a location where I often managed to switch it from "auto" to "on". Once I figured out what I was doing, I knew better.)

 

[rosinhound]

On a different note, I wonder how an ICE vehicle would perform if "not operated for weeks"

(although I know that's not what you were getting at)

Just fine - I had a ford pickup in my driveway for 7 months sitting - started right up

It’s the gasoline going stale thats a worry

 

[EVer Hopeful]

I had a Ford van and it used to take me about the same amount of time to get it to start

 

[norcalbowler94]

How old is your Lexus Battery? If your battery is not sealed and has vent caps, a $10 battery hydrometer that measures the specific gravity can show up a cell not accepting a full charge. If that is the case it is best to replace the battery. If the battery is more than five years old it should also be replaced.

Good suggestion.

It probably two years old and it's sealed. I have a small battery I can jump it with if needed. I just start it once a week and run it for five minutes. Lately, I'll been driving it short distances as park at work car. It's not really dead at three weeks but there is less cranking power.

I think the car has a security system that is doing something even when the door isn't locked. I've had Lexus for almost 23 years.

I went on the web and it seems the battery drain is normal. My old 2014 X3 was about the same. It would let me know the battery had low state of charge. I just drove it around and it was fine. I would let it sit because I was driving the Lexus.

 

[drtimhill]

So while driving with the tow truck driver to get my flat tire repaired (4 flats in 16 months, all rear tires, that's another story) I got to hear interesting/crazy stories about why Teslas need to be towed. He said a biggie is the "small battery" going dead making the vehicle inoperable because the computer is dead. He said if the vehicle is plugged in but not operated for weeks, this small battery does not get recharged and can fully discharge. So the big battery for the motor is fine but the small battery is not, and he gets called out to tow the vehicle to the nearest Tesla service center to recharge the small battery and reprogram the vehicle doors, etc. He said it happens in the mountains where he works, when the weather is cold and people leave their vehicles sitting for weeks without using them, even though again they are plugged in. Anybody know if this is true or fiction?? If true I'll need to think about this next time I take a long trip away from home.

The "small" battery is automatically recharged from the "big" battery by the car as needed. It's quite possible that some of these cars he mentioned had a low charge on the main battery and/or were left for a very long time, thus draining the big battery as well. Of course, its also possible he is just talking out of his ....

 

[norcalbowler94]

It seems I've been doing battery management wrong this whole time. From what I read the alternator isn't putting back in as much as it takes out to crank an engine over successfully. This is when I am just starting the car and letting it idle. I'll need to get a smart charger to keep it charged properly.

 

[Rocky_H]

It seems I've been doing battery management wrong this whole time. From what I read the alternator isn't putting back in as much as it takes out to crank an engine over successfully.

You're expressing that as a yes or no situation, but it isn't. It's a relative speed of energy input and output, and there's a crossover point.
Cranking the engine will take energy out of the battery very fast. The alternator will be putting it back in, but slower. So there will be some amount of time where it gets back in as much energy as it initially lost from starting the engine. I don't know how much time that is, but it's likely not within just 1 or 2 minutes. Also, that's not just a fixed rate from the alternator. Its speed of energy regeneration is tied to how fast it spins, from the engine RPMs. So that's why it's frequently recommended to drive a car around some, rather than just letting it sit running at idle, if the goal is to recharge the battery some.

 

[norcalbowler94]

You're expressing that as a yes or no situation, but it isn't. It's a relative speed of energy input and output, and there's a crossover point.
Cranking the engine will take energy out of the battery very fast. The alternator will be putting it back in, but slower. So there will be some amount of time where it gets back in as much energy as it initially lost from starting the engine. I don't know how much time that is, but it's likely not within just 1 or 2 minutes. Also, that's not just a fixed rate from the alternator. Its speed of energy regeneration is tied to how fast it spins, from the engine RPMs. So that's why it's frequently recommended to drive a car around some, rather than just letting it sit running at idle, if the goal is to recharge the battery some.

That's why it's wrong. I just it idle until it's somewhat warm and the alternator isn't spinning fast enough to charge up the battery. I'll just used a smart charger, so I won't need to drive unless it's necessary.

 

[Pianewman]

norcalbowler94: With a short (5 minutes) idle period and engine shut-off, the startup procedure has produced a LOT of water in the exhaust, which is puddling in the exhaust, not getting evaporated by a full warm-up DRIVE (15-20 min?)

 

[norcalbowler94]

norcalbowler94: With a short (5 minutes) idle period and engine shut-off, the startup procedure has produced a LOT of water in the exhaust, which is puddling in the exhaust, not getting evaporated by a full warm-up DRIVE (15-20 min?)

The idle time varies. I may idle longer and leave the door or a window open to let the exhaust escape. There is a chance there is water in the exhaust. I don't really know. What I am certain of is if it's not started in three or four weeks it may not start very easily. I don't recall when the battery was new if the time was the same or extended. I'll probably start driving it a couple of times a week. If the cars weren't parked in tandem I would probably drive it to work more.

 

[jcanoe]

norcalbowler94: With a short (5 minutes) idle period and engine shut-off, the startup procedure has produced a LOT of water in the exhaust, which is puddling in the exhaust, not getting evaporated by a full warm-up DRIVE (15-20 min?)

Connecting a 12V battery tender would be a better alternative to starting and running an ICE vehicle for short periods. Starting, idling an ICE vehicle wastes fuel, creates the highest level of exhaust pollution when the engine is cold. As @Pianewman noted the moisture in the the exhaust stream when the engine is cold can collect in the exhaust system where it can corrode and damage the exhaust system components. This also true of the engine oil. Not fully warming up the engine by driving for at least 10 or 20 minutes can leave water in the engine oil which will degrade the oil and can damage the engine components.

 

[Pianewman]

Connecting a 12V battery tender would be a better alternative to starting and running an ICE vehicle for short periods. Starting, idling an ICE vehicle wastes fuel, creates the highest level of exhaust pollution when the engine is cold. As @Pianewman noted the moisture in the the exhaust stream when the engine is cold can collect in the exhaust system where it can corrode and damage the exhaust system components. This also true of the engine oil. Not fully warming up the engine by driving for at least 10 or 20 minutes can leave water in the engine oil which will degrade the oil and can damage the engine components.

jcanoe is being gentle here. It DOES collect in the exhaust. Large amounts. The corrosion it causes is on the inside, where it can't be seen. This is why folks are caught off-guard when an exhaust system rusts through, because they can't SEE it. Ditto for the seriousness of water in crankcase oil which doesn't get burned off unless the engine gets fully warm.

It's nice that we don't have to discuss these issues with our EVs

 

[brkaus]

The other option for long term storage is to disconnect the 12v.

 

[jcanoe]

jcanoe is being gentle here. It DOES collect in the exhaust. Large amounts. The corrosion it causes is on the inside, where it can't be seen. This is why folks are caught off-guard when an exhaust system rusts through, because they can't SEE it. Ditto for the seriousness of water in crankcase oil which doesn't get burned off unless the engine gets fully warm.

It's nice that we don't have to discuss these issues with our EVs

It is worth noting that for many years exhaust systems have been manufactured using stainless steel components. While not rust proof stainless steel resists rust and corrosion much better than conventional steels. If you think about it; when was the last time that you had a leaky exhaust pipe that corroded all the way through the pipe?

The Federal Emissions Warranty is an extended warranty covering certain major emissions-related parts on your vehicle. This Emissions Warranty applies to vehicles less than 2 years old and has less than 24,000 miles (up to 8 years/80,000 miles for specified major components). The included engine exhaust components include the exhaust manifold, exhaust pipe (up to the converter), catalytic converter.

The Federal Emissions Warranty is Often Overlooked When Your Vehicle Needs Emissions Fixes

 

[CapsEngineer]

It is worth noting that for many years exhaust systems have been manufactured using stainless steel components. While not rust proof stainless steel resists rust and corrosion much better than conventional steels. If you think about it; when was the last time that you had a leaky exhaust pipe that corroded all the way through the pipe?

Yep. The last time I remember replacing this was when I was on my third lifetime muffler from Sears on a 74 Dart.

Muffler replacements were free. The rest of the exhaust replacement was not. And it had to be replaced because of rust.