Is trickle charging the 12v battery necessary?

[nayr14]

Not hate. Just more involved than needed. The various aftermarket monitoring solutions cause needless drain on both HV and 12V batteries. Tesla has done everything but officially advise against the use of these. Expect that to change in the coming months as they look to block the use of these.

+1 on not installing monitoring software that constantly pings your Tesla. My 2013 S never slept until I uninstalled the tool I had which constantly pinged the car API. Now our Tesla no longer suffers from insomnia. And we save 3 kWh a day. I did install an OBDII device which passively monitors from FleetCarma

ScanMyTesla is passive and reads the CAN bus. It a extremely, extremely small draw compared to the other various systems that are constantly running 24/7. It reads what the car is sending across the CAN bus, and it only reads when you have the app open and connect to the BT dongle.

The beauty of SMT is that the community has decoded the signal addresses, allowing those interested to learn more about their cars. Battery temperature, motor power, preconditioning, HV battery voltage, HV usable capacity (the REAL measure of degradation), motor temperature, coolant pump rate, etc. The list goes on and on - I've learned a lot about how my car works with that app, 110% worth it if you're interested in the inner workings. If you have any concerns, unplug the OBD2 dongle...

For tracking, I do use TeslaMate which is an opensource tracking software which uses the API. I run that on a RaspberryPi and it doesn't drain the battery. You can read more on their GitHub page if you're interested.

 

[smatthew]

ScanMyTesla is passive and reads the CAN bus. It a extremely, extremely small draw compared to the other various systems that are constantly running 24/7. It reads what the car is sending across the CAN bus, and it only reads when you have the app open and connect to the BT dongle.

The beauty of SMT is that the community has decoded the signal addresses, allowing those interested to learn more about their cars. Battery temperature, motor power, preconditioning, HV battery voltage, HV usable capacity (the REAL measure of degradation), motor temperature, coolant pump rate, etc. The list goes on and on - I've learned a lot about how my car works with that app, 110% worth it if you're interested in the inner workings. If you have any concerns, unplug the OBD2 dongle...

For tracking, I do use TeslaMate which is an opensource tracking software which uses the API. I run that on a RaspberryPi and it doesn't drain the battery. You can read more on their GitHub page if you're interested.

Do you have any concerns that Tesla might try to block SMT? Or do you think that's more of an issue for API based stuff?

 

[dmurphy]

This is the first statement I have seen on this subject that doesn’t sound like folklore and actually has a citation. Where did you obtain this Theory of operations document?

Nothing to add except that @smatthew is spot on. It's not folklore, it's documented, and why I've been such a big proponent of the "Set it to 90% and forget it" camp. That's not a recommendation based on voodoo and apocryphal stories; it's rooted in documentation from the manufacturer.

 

[nayr14]

Do you have any concerns that Tesla might try to block SMT? Or do you think that's more of an issue for API based stuff?

It's not possible for them to tell your viewing it. The OBD2 dongle is 100% passive, they can't detect it's connected.

The API monitoring that 3rd party software utilizes could be locked down if Tesla wanted, but they haven't made any move to do so.

 

[GigaGrunt]

It's not possible for them to tell your viewing it. The OBD2 dongle is 100% passive, they can't detect it's connected.

The API monitoring that 3rd party software utilizes could be locked down if Tesla wanted, but they haven't made any move to do so.

Can detect when 12V is being used via OBD2 port. Also, API can be closed. 90%...set and forget.

 

[rrolsbe]

Just a friendly reminder - lithium battery packs can become imbalanced. No, it's not a weight thing. Remember, you car has 96 "bricks" of 46 cells. When charging, the car stops when the first brick of cells hit the 4.2v cutoff. If one brick has a higher voltage than others, the car can use bleed resistors to very slowly bring everything into equilibrium. That means instead of only one brick reaching 4.2v, most of them do - and you have more available battery capacity!
BUT, this only happens when the battery SOC is >~85% (actually, the lowest brick voltage needs to be over 4.0v) and the car is in standby (i.e. sleeping). So I'm keeping my Tesla charged to 90%, as recommended in the battery service manual.
The cars aims to keep the delta-v - the difference in voltage between the lowest and highest brick to less to 5mv. The car can correct 1mv of imbalance every 24 hours.
BTW - this information is from the Tesla Model 3 Theory of Operations document.

Since the cooling pumps do not run while the car is sleeping, I guess cooling is not required during the re-balance? Also, after the re-balance the available range displayed could be higher than it was when you parked the car?

 

[smatthew]

Since the cooling pumps do not run while the car is sleeping, I guess cooling is not required during the re-balance? Also, after the re-balance the available range displayed could be higher than it was when you parked the car?

No, cooling wouldn't be required during rebalancing. It's putting a tiny tiny load on the brick it wants to bring down.
I believe that in order for the car to show a higher range, you would have to complete a new charge cycle. The car might be aware of a change in range, but it doesn't show it. I.E. rebalancing wouldn't change available miles (which we can see) until the next charge, but the car should show a difference in capacity via a tool like ScanMyTesla. But that might also take a charge cycle to process. I don't have access to ScanMyTesla yet to see what is going on internally. The theory of operation docs are thorough, but not that thorough.

 

[nayr14]

Can detect when 12V is being used via OBD2 port. Also, API can be closed. 90%...set and forget.

There isn't an OBD2 port. You're adding a connector to the rear of the center console (or wherever there is 12v and CAN high/low) which allows access. Tesla couldn't detect this, and frankly I doubt they care.

Geotab HRN-CT20T1

 

[rrolsbe]

No, cooling wouldn't be required during rebalancing. It's putting a tiny tiny load on the brick it wants to bring down.
I believe that in order for the car to show a higher range, you would have to complete a new charge cycle. The car might be aware of a change in range, but it doesn't show it. I.E. rebalancing wouldn't change available miles (which we can see) until the next charge, but the car should show a difference in capacity via a tool like ScanMyTesla. But that might also take a charge cycle to process. I don't have access to ScanMyTesla yet to see what is going on internally. The theory of operation docs are thorough, but not that thorough.

I have SMT and no data is available while the car is sleeping even though the OBDII dongle has 12V power while the car is sleeping.

 

[Bubbatech]

Nothing to add except that @smatthew is spot on. It's not folklore, it's documented, and why I've been such a big proponent of the "Set it to 90% and forget it" camp. That's not a recommendation based on voodoo and apocryphal stories; it's rooted in documentation from the manufacturer.

Can you point me to this documentation? I can’t find it.

 

[dmurphy]

Can you point me to this documentation? I can’t find it.

I wish I could ... it’s not published publicly, unfortunately.

 

[Bubbatech]

I wish I could ... it’s not published publicly, unfortunately.

That’s unfortunate. Without it, the information Remains unsubstantiated. If it truly exists, one wonders Tesla’s motivation is in keeping it secret.

 

[dmurphy]

That’s unfortunate. Without it, the information Remains unsubstantiated. If it truly exists, one wonders Tesla’s motivation is in keeping it secret.

I know you don’t know me, but I absolutely assure you it’s accurate and substantiated. Because it’s behind a wall doesn’t mean it doesn’t exist.

 

[Zoomit]

Here a reddit link to the Theory of Operations text that refers to brick balancing:

Discussion on detailed info from scan my Tesla and OBDII adapter : teslamotors

 

[smatthew]

I know you don’t know me, but I absolutely assure you it’s accurate and substantiated. Because it’s behind a wall doesn’t mean it doesn’t exist.

Exactly. Sorry, I'd love to post excepts of it, but I don't want Tesla's legal team to send me takedown orders. If you want to see it, find a copy on the internet, or pay Tesla $100 for 24 hours access. Welcome | Tesla Service

 

[Bubbatech]

I know you don’t know me, but I absolutely assure you it’s accurate and substantiated. Because it’s behind a wall doesn’t mean it doesn’t exist.

Sorry about that. I am a professional scientist, so I tend to question everything until I can see the primary information. It’s what I do.

I have now seen an excerpt (thank you!). As I was told, it strongly supports “set it at 90% and forget about it”. The calculated capacity of the battery is tied to the brick with the lowest voltage, so I think balance Is the key to the variation observed in calculated range. Also: I have long doubted the significance of the statement that lithium ion batteries last longest at 50%. While the base statement is true, one wonders how much of a practical difference that makes with modern battery chemistry, especially those supplied in our cars. The critical question is: what Is the difference in the rate of degradation at an SOC 60% versus %90? There is also a time element here as well because it is a rate. The time would be a function of the nominal lifespan of the pack. Tesla has stated that a pack should last somewhere around 500,000 miles. If we assume an average of 12000 Miles per year (without factoring in the effect of aging) that’s about 40 years, if it is 250,000 miles, it’s half that. So a 10% difference in the rate of degradation over that time scale is, from a practical point of view, negligible. Conclusion: I’m leaving the charge limit at 90% and plugging it in whenever it’s in the garage.

 

[lUtriaNt]

as a data point in terms of battery drain, sleep etc., ive not driven my car since friday may 1. it was at 45%. i do not have charging in my garage and do not use any 3rd party apps to monitor data on the car.

i have checked the car on the tesla app once or twice over the last week and today it still shows 45%. temps in the garage have been in the low to mid 70s. sentry is off when home.

 

[scgator1]

My apartment has no charging. Does the HV battery charge the 12v battery even when the car is not plugged in?

 

[smatthew]

My apartment has no charging. Does the HV battery charge the 12v battery even when the car is not plugged in?

Yes

 

[jerry33]

My apartment has no charging. Does the HV battery charge the 12v battery even when the car is not plugged in?

The car will wake up every so often and check various things, including the health of the 12V battery whether plugged in or not. There's no need to do anything but set to 90% and forget. It's best if you can keep it plugged in (even if it's just a 120V outlet).