Tesla Service draining battery

That may be a better question for Service than the forum.
I can tell you that when we had a battery replacement a year nod a half ago, they simply asked us not to charge it above 50% the previous night.

I could see this vary by location/equipment, and change over time.

 

I've never known them to intentionally drain the battery pack. There are disconnects they employ for safety.

 

Interesting question on environmental sustainability. If they have to drain the battery power, I speculate it should not be too difficult for an inverter to feedback the battery power into the grid or consumed at the battery maintenance center at the proper voltage and frequency. IMO, It would be similar to a PowerWall.

 

From what I've heard they just run the heater for a while if they need to drain the pack.

 

Yes, to service the contactors and/or replace the battery they must bring the pack below a certain amount (I want to say 40% is what I recall).

 

As confirmation, this is correct. I brought my car in for service and they surprised me with a "we're going to replace your contactors today!" notification. Unfortunately, the vehicle was fully-charged, and they ran the heater on full blast for something like 12 hours straight to bring the charge down low enough to perform the replacement. :frown: They pulled mine from 90% to 40%. They were still doing it that way as of about 6 months ago.

I saw someone mention they now have a tool they use to drain the battery, but I've only seen it mentioned a few times. I'm not sure how widely it's used. Hopefully widely, because presumably our heaters don't appreciate being run on full for multiple hours in a row.

 

Their target is 30%.

 

Do we know why they need to discharge the pack to change the contactors? It's not like ~350V is really any safer than ~400V...

 

When I dropped my car off for contactor replacement, it had about 40% SOC on it. For some reason, they pulled it inside and plugged it in, charging it to 90% (I could see this on my mobile app from home). Probably some "default" protocol when someone drops their car off and leaves it overnight. When I got the car back, it had over 100 miles added to the odometer (I always record the value whenever I take any of my cars in for service), so I guess I know how they drained it before working on the pack!

 

heh that'll do it. that heater at full blast is a killer on range.

- - - Updated - - -

I heard they have one of these at each service center and they hook the battery pack up to it and all the staff members take turns getting shocked until the batteries are fully depleted and whoever holds on the longest gets the rest of the day off.

 

The P85+ required a battery removal after a flat bed to Fremont. They ran the heater to take it down to 25 miles remaining range before working on the car. Took a day just to get the battery down to that level. They had to service circuit board, and I would not want to do that with a 224 mile charge on a battery. 12volt Auxiliary battery was not being charged correctly due to some issues.

That was a few weeks ago, so seems to be current practice.

I must say, the car left me by the side of the road. After it realized we were safely off the pavement, she shutdown and asked me to contact service. It would not come out of "Park". But Tesla took care of everything; Uber ride home - my wife did not even notice Tesse was MIA; managed the flat bed tow - Car as picked up 2.5 hours later, Tesla Service called to let me know; Tesla managed the car remotely unlocking and monitoring its security from the 877 number service center; Fremont serviced the car; and flat bed delivery back to office the following Monday. The failure happened on a Wednesday evening drive home.

 

Still not sure I understand how a battery at 360 V is any safer than one at 400 V. Even at less than 30% the pack is capable of outputting very dangerous levels of power.

 

Maybe less likely to start a fire if shorted at low SOC? As you stated, the wattage available even at 30% is still substantial. Even a minor safety increase might be deemed worthwhile (hey, it's not Tesla's heaters they're running hard): "Tesla catches fire at Tesla Service Center" would not be a great headline for them.