Balancing and Topping Off?

[swogee]

I have been reading the threads to try to figure out what exactly balancing and topping off is, but I haven't found a specific description yet. I have only had my RAV4 EV for about a week or so so I am still learning about it. Any thoughts or ideas are welcome. (I am currently using a Toyota 120V charger until I complete the wiring for 14-50R circuit.)

Thanks in advance.

-Steve

 

[Dsinned]

Unfortunately, this is a closely guarded secret within the bowels of Tesla. I don't believe anybody really knows, least of all the people like us who own and drive the RAV4 EV. Something kind of "weird" happens after every charge, hours after so-called "completion". While still plugged in and undisturbed, the car resumes drawing a small amount of current from the EVSE for about 30 minutes to do "something"; presumably topping off and/or balancing the cells. This can be easily observed. However, exactly what is happening is not really understood, and why only in this seemingly quiescent period of time at the very end of a charging cycle.

The closest thing to perhaps someday better understanding our RAV4 EV's batteries is this new app hopefully coming out in a few months.

http://www.myrav4ev.com/forum/viewtopic.php?f=9&t=1164

 

[smkettner]

Balancing is a process where the vehicle matches the individual cell voltages so there is an equal charge in each cell. Fully automatic, nothing you can do to change the process.

Topping off would be giving the battery some additional charge if the vehicle determines the initial charge process has the battery slightly lower than the goal. Again controlled by the vehicle, just let it charge.

OK there are probably more complexities but that is the basic idea of it.