Do you know that you must keep your battery charged?

[qwk]

I give up....

You can lead a horse to water....

[dpeilow]

Send me a PM and I will e-mail you a PDF copy of the 2.5 manual.

The 2.5 manual is on here. I bounced the thread yesterday.

[eledille]

This is an unprotected cell. They have virtually 0 self discharge. Any Li-ion battery will have a protection circuit on them. It prevents thermal runaway. These are passive circuits attached to the cells when the battery is manufactured. This is what chews power passively, and should not be removable/bypassed.

I'm almost completely certain that this is wrong.

They have overcurrent and overheating protection devices, but those do not consume any power at all. What consumes power is balancing, active monitoring, fans, heater elements, possibly AC and whatever else is in there. All those are installed by and controlled by Tesla, and this stuff is what sets the Tesla battery pack apart from all the rest.

Some of these systems can be turned off, some can't. As richkae said, you don't want a fire, a dead battery is actually not as bad as that.

[Lloyd]

The 2.5 manual is on here. I bounced the thread yesterday.

I know I just thought it would help if I sent him a copy directly!

[JRP3]

Generally I think you are correct. During charging is the real issue with thermal runaway. But if cells get mismatched voltages you can also have current flowing between them they 'charge' each other. Which could start thermal runaway (gets more likely at 0 charge). Current heats up the electronics, which raises internal resistance and voltage drop in bad cell. More current runs through higher resistance ... fire.

The only cells that will share current between them are cells in parallel, and because they are in parallel they self balance and very little current flows. Cells in series, or blocks of parallel cells in series, do not share current between them, even if they are out of balance. Also, Tesla balances cells during each charge, they will not go severely out of balance in one discharge cycle, or just sitting around doing nothing.

[nleggatt]

Ok, I have to admit I was unaware that the car could be bricked. I did know that I should have it plugged in when possible, that part is obvious. The question becomes at what point does the car "brick"

For instance, if I drive up to my cabin and hit traffic and for some reason run out of charge on the highway in the middle of the mountains... (yes, the car beeped and told me I was running low, but I kept driving cause, well, hopefully I'll make it... ) is the cat at "0 SOC" when it stops driving? Is it now a brick?

How long does it take to be a brick? What if it takes an hour and half for me to flag someone down (there's no cell reception) and then for a tow truck to get to me? Will I be out $40k?

What if I leave my car plugged in at a friends house when we go camping and I dont realize that his plug is not providing the power the car needs... 3-4-5 days? Will the car be dead?

Just a thought, which would be cool! The car realizes its dying... dials BCCA Auto and in a SIRI voice "Help, I'm an electric car and I need a charge because my owner is away and I'm dying.... my GPS is... 123.123) lol. That would be great. Or even if you could set a list of numbers it could call and you could record your own message... now there's an app idea.

I think the car needs a "0 distance gauge" and then another 10% that is standby allocated and if you hit 5% it starts screaming at everyone and everything.

If we are talking, run it dry and park for 2 weeks, thats different.

[eledille]

When just sitting, not charging or driving, any drains could be disconnected once a certain lower level is reached. Cells don't need protection when not in use, especially if that "protection" is going to kill the cells.

The cells do need protection when not being used, but only from accelerated aging, not from catastrophic failure.

richkae mentioned fires due to thermal runaway, and I initially I agreed, but the cells must get extremely hot for that to happen. Even direct sunlight onto a cell phone on a black dashboard in a closed car usually does not start a fire. By looking at temperature for the past few days the firmware can decide whether thermal runaway is a possibility. If not, then the fans should be stopped, sacrificing cell life to avoid a dead battery.

[Lloyd]

I received this from my customer advocate today. The improved references to the newer batteries may make some feel better:

We are definitely aware of the article in reference, I apologize for its upsetting content.



In response, it is important to point out that all electric vehicles should be plugged in and charging when not in use for maximum performance. All batteries are subject to damage if the charge is kept at zero for long periods of time (in cars or consumer products). However, Tesla employs numerous counter-measures to avoid such issues. Tesla batteries can remain unplugged for weeks (even months), without reaching zero state of charge. Owners of Roadster 2.0 and all subsequent Tesla products can request that their vehicle alert Tesla if SOC falls to a low level. All Tesla vehicles emit various visual and audible warnings if the battery pack falls below 5 percent SOC. Tesla provides extensive maintenance recommendations as part of the customer experience.



Beyond our official response to the article you referenced, I can provide some further context that is specific to Model S and Model X. Future Tesla vehicles will use different battery cells than Roadster - ones that are developed specifically for our use. Model S and Model X will also have advanced and revised battery management systems. In combination, this allows the car to sit for longer periods of time without power being available. Despite this, the basic fact still remains that leaving any lithium based battery empty and unplugged for long periods of time will cause permanent damage. This is spelled out clearly in our Owner’s Manual for Roadster, and will be for future Tesla vehicles. Warranty documents and other pertinent information for Model S and X will be released shortly before deliveries commence.



Please let me know if I can be of further assistance.

[JRP3]

The cells do need protection when not being used, but only from accelerated aging, not from catastrophic failure.

richkae mentioned fires due to thermal runaway, and I initially I agreed, but the cells must get extremely hot for that to happen. Even direct sunlight onto a cell phone on a black dashboard in a closed car usually does not start a fire. By looking at temperature for the past few days the firmware can decide whether thermal runaway is a possibility. If not, then the fans should be stopped, sacrificing cell life to avoid a dead battery.

Exactly. The only protection needed for cells is cooling to keep accelerated aging to a minimum. However even that should be disabled if SOC drops low enough since continued cooling will drain the cells too low and lead to potential bricking. An unused cell in a hot environment should not go into thermal runaway.

[JRP3]

For instance, if I drive up to my cabin and hit traffic and for some reason run out of charge on the highway in the middle of the mountains... (yes, the car beeped and told me I was running low, but I kept driving cause, well, hopefully I'll make it... ) is the cat at "0 SOC" when it stops driving? Is it now a brick?

No. If you then let it sit for weeks without charging it, then it could turn into a brick. When driving the car stops moving before the cell is actually empty, to protect the cell.