What determines SC rate

What determines SC rate

Supercharging rate to be fastest needs to be low SOC and warm battery but I recently had different experience:

After driving 2 hours SOC 128 miles remaining

Plug in get 145 kW almost immediately

2 days later back to same SC stall
After Driving 2 hrs ; SOC 25 miles remaining
Plug in and get only 64 kW, it slowly climbs to 120 kW with 120 miles range , then starts tapering,

So what’s up?

murphyS90D | May 23, 2019

Was the paired stall in use? 1A/1B, 2A/2B, etc. If the paired stall is in use you share the available power. As the first to connect starts to taper down the second to connect will start to increase.

GHammer | May 23, 2019

On one of the new battery chemistries, with a very low state of charge, the charge rate starts slow and then ramps up. My 85's start high even at a very low SOC while my 3 will start slow and then ramp up as you saw.

s.grot | May 23, 2019

I was not sharing the pair with anyone

If it was a slow start; why did it never get to 145 kW later in the charge cycle

Sonofman | May 24, 2019

It all depends on heat management. The first time the battery was in the perfect SOC and temp to receive 145kw where the second time it was too low so it started slower and then couldn't hit the max due to heat etc.

That's my rough guess knowing they manage everything very well for peak performance with longevity as well.

Bighorn | May 24, 2019

Sometimes it’s the charger and not the car that determines what’s possible

Tropopause | May 24, 2019

I noticed the Supercharger handles get a bit hot which could cause throttling back. The V3 should alleviate this occurrence.

s.grot | May 25, 2019

I was very surprised by the 145 kw at about 50% SOC, but I have frequently seen the low initial charging rate at low SOC. When I got there the second time I moved to 3 different stalls all gave the initial 60 kW.

Could be that at low SOC they don’t want to charge too fast for some reason. And then after 10 mins at 60 + kW the battery gets too hot to take 145 kW.

s.grot | May 25, 2019

I’ve also seen on high rates of discharge the battery will quickly overheat and limit the discharge. That’s one thing Tesla’s do not do well; high power output for long periods of time | May 25, 2019

@s.grot - Lots of variables, including the charger itself can overheat and throttle the power, although this seems rare. One reason for limiting charging is the battery isn't warm enough. As I understand it, the ideal charging temp is when the cells are in the 90F range. Tesla wants to heat the battery before applying max power. I've seen this on many occasions, and not just at low SOC. Then again, I've also seen an occasional stall that just doesn't seem to have enough power. Maybe one out of 30 that I've used?

Related to hard/track driving (not charging) - which model/variant do you have? Seems they solved it in the Model 3. Also the S/X 100 pack has a redesigned cooling system, but I don't know if this improved the high-acceleration driving time over prior S/X packs.