Battery Managment system

[Majerus]

So as everyone is aware by now there have been nemerous reports regarding the "Bricking" Roadster. One such example is the crap post that Autoblog Green has recently posted.

Tesla bricking update: can other electric vehicles suffer the same fate? Unlikely

I am interested as to why a threshold has not been set on the Roadster to keep this from happening. It seems like many other manufacturer have set this kind of threshold. If this is not implemented why not? What is the technical reason?

 

[ElSupreme]

This is probably not absolutely true. I believe that the Leaf and others may have more battery buffer at 0 charge. They may also be more willing to eat some battery costs, for marketing purposes since they are huge companies, and their batteries are half the size.

But this is pretty much being discussed here:
Do you know that you must keep your battery charged?

 

[tdelta1000]

Why would someone would want to "brick" their EV? It sound like negligence on the part of the owner for not properly maintaining their car.

 

[JRP3]

I am interested as to why a threshold has not been set on the Roadster to keep this from happening. It seems like many other manufacturer have set this kind of threshold. If this is not implemented why not? What is the technical reason?

Tesla is the only EV builder using LiCo cells. They have high energy density and low cost, but are the most volatile. They need more active management, which takes energy. The early Roadsters may have been over managed, meaning they kept actively managing the pack until it drained itself. The newer cells and packs may not have such aggressive management and may shut down the active management as the cells approach zero in order to prolong pack life while unplugged. Nissan uses more stable cell chemistry that has lower energy density but needs less active management. The LiFePO4 cells I used in my conversion are even more stable, I have no active management at all other than an occasional manual balance, and I can leave my car unplugged for a year or more with no worries of self discharge by flipping two switches that disconnect the pack and the dc/dc converter. I also don't have to worry about long periods of high temperatures here in NY, while OEM's have no control over where their vehicles are operated.

 

[strider]

Another thing to remember is that by default (Standard Mode) Tesla hides the top and bottom 10% of capacity from you so you have to manually (by entering Range mode) tell the car to use every last electron. Otherwise if the car shuts down at 10% it can survive for awhile before the pack is damaged.

 

[Robert.Boston]

And even then, you can never use "every last electron." The car will disable driving and optional systems before you kill the batteries.

 

[dsm363]

Maybe Tesla shouldn't allow access to the bottom 5% then as a safety manager. I'd hate to give up the range but sounds like a few people need that added protection. I guess they may already be doing something like that if the car can sit at zero miles for 30 days with the Model S.

 

[JRP3]

I don't think any EV builder allows full discharge to zero while driving. Even in Range Mode I'm sure there is some buffer left.

 

[stopcrazypp]

I don't think any EV builder allows full discharge to zero while driving. Even in Range Mode I'm sure there is some buffer left.

I remember a post by Martin Eberhard (I think) that said they deliberately set the "zero" point about 0.2V higher than typical just for battery longevity reasons.

 

[Majerus]

Looks like Telsa has responded to the battery issue.

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