Power drain while idle (Vampire Load)

[dsm363]

We don't have a ranger here.

Yes, they did tell me to jump the car. I asked more than once and in more than one way so as to ascertain that they DID want me to jump the car, because I was reluctant to do so (I don’t jump my ICE… I use AAA for that). I was subsequently told where and how to jump the car.

That's unfortunate they gave you incorrect information and that a Ranger isn't there yet to address these kinds of things. Hope it is fixed soon.

Just curious how you got to 50 miles of range before leaving it for 4 days. I think people could learn from this which is why I ask. Did you not get a chance to fully charge the day before (were you out of town or is it a car you don't drive every day)? Also, when the car was delivered, what instructions did they give you about the importance of keeping the car plugged in when possible? With many new owners, I was hoping they'd be more firm about the importance of plugging in and not letting your range drop to zero. Thanks.

 

[strider]

Just curious how you got to 50 miles of range before leaving it for 4 days. I think people could learn from this which is why I ask. Did you not get a chance to fully charge the day before (were you out of town or is it a car you don't drive every day)? Also, when the car was delivered, what instructions did they give you about the importance of keeping the car plugged in when possible? With many new owners, I was hoping they'd be more firm about the importance of plugging in and not letting your range drop to zero. Thanks.

Well, he said it was plugged in but a family member unplugged it to use a vacuum and failed to plug it back in. I would assume from that it was charging off 120V and so hadn't built much charge when it was unplugged.

I also assume he's not yet on 4.0 so vampire load is still an issue (or he left the key too close to the car).

This 12V thing is not new, even to ICE's. The 2005 Corvette had DBS (dead battery syndrome). You had to park the car in reverse (6-speed manual) to get the computers to shut down. Otherwise they would stay running and kill the 12V battery. They fixed this in the 2006 model year but it let to a lot of people having to crawl into their car from the trunk (that's the only mechanically opened door), pop the hood, and jump the car. It also seems to be a theme w/ hybrids and EVs - the Prius was notorious for killing its 12V battery.

I'm pondering attaching leads for a Battery Tender and run it into the frunk so if something like this happens to me I can just plug it in without having to tear off the front of the car (because you know this will happen on a weekday morning when my wife needs to get the kid to school and herself to work).

 

[dsm363]

Could this be an area EVs or Tesla could improve on (12V battery issue) or is it something more fundamental or too expensive? I have no idea how these systems work or what challenges they would have to overcome to make this system more reliable. I'm sure it's causing them enough headaches that if they could have eliminated any problems, they would have already with the 12V battery.

 

[ElSupreme]

Could this be an area EVs or Tesla could improve on (12V battery issue) or is it something more fundamental or too expensive? I have no idea how these systems work or what challenges they would have to overcome to make this system more reliable. I'm sure it's causing them enough headaches that if they could have eliminated any problems, they would have already with the 12V battery.

This is my speculation:

I don't think there is a problem with the 12V systems, and them distributing power. I mean there are plenty of ICE vehicles out there that don't have any problems, and a 12V DC system is really easy to design. I do think there is a problem keeping that 12V battery charged, and maintained at a healthy state of charge. I don't know why this hard but it seems to be.

Here are some possible problems:

1. Electric vehicles require a lot of monitoring when they are off. This consumes a lot of battery power when the car is off. And this is a known way to kill batteries.
2. 'Waking up' the traction pack consumes power so EV manufacturers try to do it as little as possible, causing deeper cycling on the 12V battery. Pb Acid batteries do not do well being 'deep cycled' (that is below 50%-60% state of charge) and it can dramatically reduce cycle life (by and order of magnitude or so)
3. DC->DC stepdown is not easy and not cheap so these systems may not be sized correctly in general. And not recharge the battery if there is still a load on the battery.
4. It may also be a general undersizing of the Pb Acid battery, it gets overworked and gives up on life early.
5. There may not be a communication link between the traction pack and the 12V battery state of charge. And there may be 'holes' in the programming that allow the 12V battery to discharge without it being looked at enough to charge it at the correct times.

I think it is a combo of 1, 2, and 4. I think 3 might be another factor.

I think this will surely be improved, but most likely by more integration with the traction pack in a PEM (Power Electronices Module). Where you might have a 12V Li-Ion battery pack that is more closely monitored and charged (if not much higher capacity) and babied such that you don't encounter a battery failure.

 

[Lloyd]

Speculating: It appears that the Model S needs some other redundancy for the 12 V Battery. Perhaps a 2nd one to allow you to keep operating when the primary has failed? Maybe it could be handled with the traction battery step down with proper software, or a larger or better quality 12 V primary.

 

[mknox]

I'm pondering attaching leads for a Battery Tender and run it into the frunk so if something like this happens to me I can just plug it in without having to tear off the front of the car (because you know this will happen on a weekday morning when my wife needs to get the kid to school and herself to work).

I was wondering in another thread if one of those portable 12v emergency batteries would work. The ones you keep in the trunk and plug in to the cigarette lighter for a few minutes to "boost" the battery. Model S does have a 12v port in the center console.

- - - Updated - - -

Just curious how you got to 50 miles of range before leaving it for 4 days. I think people could learn from this which is why I ask.

50 miles would be a full charge on a Chevy Volt, and I haven't heard of them losing that much over night.

Tesla claims that you're supposed to be able to leave the car parked for extended periods (i.e. the airport) unplugged. If I leave for the airport with a full charge, use 40% to get there, and assume I'll have somewhere near 60% to get back home a week later, I think I might be in trouble.

 

[dsm363]

50 miles would be a full charge on a Chevy Volt, and I haven't heard of them losing that much over night.

Tesla claims that you're supposed to be able to leave the car parked for extended periods (i.e. the airport) unplugged. If I leave for the airport with a full charge, use 40% to get there, and assume I'll have somewhere near 60% to get back home a week later, I think I might be in trouble.

I assume he has pre 4.0 software update or has 'put displays to sleep' off. 8 miles a day wouldn't get him from 50 to 0 so maybe it was a problem with the 12V system. If you are going leave the car unplugged for a long time and normally leave the displays power on 24/7 then that's one thing you can do to conserve power dropping it down to 2 miles of range a day.

My main question was if he did a standard charge the night before and drove 200 miles down to 50 then didn't plug in for 4 days (I know he was unplugged accidentally and didn't realize it for 4 days).

 

[JRP3]

Electric vehicles require a lot of monitoring when they are off. This consumes a lot of battery power when the car is off.

They shouldn't. A simple temp sensor should allow systems to shut down when temps are in range, and only fire up when temps are out of range. Voltage monitoring does not take much power either. Other EV's don't seem to have these problems, which tells me Tesla has a design flaw. As has been mentioned, the Volt has a 50 mile range pack and will not drain to zero when parked for 4 days. It also has a temperature controlled pack.
Last I checked the DC/DC converter Tesla uses has two channels that convert pack power to 12V, one is to power most of the 12V accessories and the other is to keep the 12V battery charged. I am guessing that the problem is when the traction pack drops to a low SOC, it shuts down everything, including the DC/DC converters, but there must still be a drain on the 12V battery, which is no longer being recharged. So there are two problems going on, vampire loads are way too high if 50 miles of range are gone in 4 days, and when the traction pack is shut down at low SOC the 12V battery needs to disconnect from all loads, which would allow it to still have power to switch a relay and turn on the DC/DC converter and power up the system. Remember, a lithium battery on it's own can sit with almost no self discharge for long periods of time. A system that "manages" and "monitors" the pack by draining the cells to a low SOC is not a good design.

 

[TXjak]

They shouldn't. A simple temp sensor should allow systems to shut down when temps are in range, and only fire up when temps are out of range. Voltage monitoring does not take much power either. Other EV's don't seem to have these problems, which tells me Tesla has a design flaw. As has been mentioned, the Volt has a 50 mile range pack and will not drain to zero when parked for 4 days. It also has a temperature controlled pack.
Last I checked the DC/DC converter Tesla uses has two channels that convert pack power to 12V, one is to power most of the 12V accessories and the other is to keep the 12V battery charged. I am guessing that the problem is when the traction pack drops to a low SOC, it shuts down everything, including the DC/DC converters, but there must still be a drain on the 12V battery, which is no longer being recharged. So there are two problems going on, vampire loads are way too high if 50 miles of range are gone in 4 days, and when the traction pack is shut down at low SOC the 12V battery needs to disconnect from all loads, which would allow it to still have power to switch a relay and turn on the DC/DC converter and power up the system. Remember, a lithium battery on it's own can sit with almost no self discharge for long periods of time. A system that "manages" and "monitors" the pack by draining the cells to a low SOC is not a good design.

It's not clear to me that the main battery was drained. How many miles did the car show after the 12v battery was replaced?

 

[Jkam]

It's not clear to me that the main battery was drained. How many miles did the car show after the 12v battery was replaced?

I agree. From what I've gathered it seems to me the problem could be entirely explained by the 12V battery being faulty. Of course I'm no expert.

 

[William3]

I thought Elon bragged about the (fully charged) Model S being able to sit unplugged for a whole year, and a Model S (run down to zero miles remaining) being able to sit unplugged for a whole month. What gives?

 

[jerry33]

I don't think there is a problem with the 12V systems, and them distributing power. I mean there are plenty of ICE vehicles out there that don't have any problems, and a 12V DC system is really easy to design. I do think there is a problem keeping that 12V battery charged, and maintained at a healthy state of charge. I don't know why this hard but it seems to be.

Every car that has a big battery has problems with the small 12V auxiliary battery (more problems if the owner isn't aware of it). The big problem in my opinion is that the 12V battery is just too [expletive deleted] small. If a standard sized car AGM battery was installed, the issues would either go away or be minimized.

 

[dsm363]

I thought Elon bragged about the (fully charged) Model S being able to sit unplugged for a whole year, and a Model S (run down to zero miles remaining) being able to sit unplugged for a whole month. What gives?

I believe that's before the battery is trashed. It still might require a Ranger coming out if it sat too long to help wake the battery up but it should go into a dormant state to try and save the battery pack I believe.

 

[JRP3]

Every car that has a big battery has problems with the small 12V auxiliary battery (more problems if the owner isn't aware of it). The big problem in my opinion is that the 12V battery is just too [expletive deleted] small. If a standard sized car AGM battery was installed, the issues would either go away or be minimized.

I should point out that my EV has no problem with the 12V battery. I use an Enersys Odyssey 19 ah AGM battery, PWC/motorcycle size, charged up by the DC/DC. Of course I don't have all the systems the S has, but I also don't have it isolated from the 12V accessory systems. I also have manual switches that disconnects the main pack and the 12V battery for long term storage without any bricking worries.

 

[TXjak]

I think it's just a SMOP.

(Small Matter of Programming)

 

[strider]

I thought Elon bragged about the (fully charged) Model S being able to sit unplugged for a whole year, and a Model S (run down to zero miles remaining) being able to sit unplugged for a whole month. What gives?

dsm363 is correct. The change in battery mgmt from Roadster to Model S is that Model S won't destroy it's traction pack trying to keep itself conditioned. At some point it will switch to a hibernation state that will require a Ranger or shop visit to wake it up. In the OP's case the traction pack is fine - just the 12V battery is toast.

 

[ddruz]

Mike K - Are you running software version 4.0? You seem to have a huge vampire load. If you are losing that much range with 4.0 that's perplexing.

 

[MikeK]

Mike K - Are you running software version 4.0? You seem to have a huge vampire load. If you are losing that much range with 4.0 that's perplexing.

Yes, 4.0, I should have mentioned.

As I said, it was parked outside in the cold, so I speculate that it had to use energy from the pack to keep the pack temperature within acceptable limits. I had almost no regen available for most of my trip to work because of the low temperature.

 

[jerry33]

I should point out that my EV has no problem with the 12V battery. I use an Enersys Odyssey 19 ah AGM battery, PWC/motorcycle size, charged up by the DC/DC. Of course I don't have all the systems the S has, but I also don't have it isolated from the 12V accessory systems. I also have manual switches that disconnects the main pack and the 12V battery for long term storage without any bricking worries.

Yes, you have a large enough battery (and it's a high quality battery) to do the job. Prius, Tesla, and Leaf don't.

 

[swegman]

I have a 2005 Prius and have never had a problem with the 12 volt battery. Nor have my friends have problems with the 12 volt battery in their Pri's. I did just replace the battery, but not because it was bad. I gave the car to my 17 year old son, and figured after 7 years, it would not hurt to replace it.