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Empty Supercharger Stations - Not getting max amps

Has anyone else been experiencing this? I'm not an electrical expert by far but do understand the battery technology and why the superchargers slow down the rate of charge as you approach a "full tank". But more than a few times now I've been at the Gilroy station early in the morning when it's completely empty and I only get 80-90A/255A. Voltage is still high close to 350V but the charge is metered down from the start.

Any ideas why? Each time I've started with only 15-25miles rated range left...

Does it stay low throughout the charge? Many notice it starts slow, then speeds up.

Same Q here. I've only used an SC one time, but they ramp the current up to peak then back down...it doesn't go straight to peak.

And what is your initial SOC when you start. When i was at Gilroy - in a few minutes rocketed to 200+ amps and then when it started to get towards the end of the charge, tailed off considerably. So to address the question - need to know if you were 20-30 miles off you top end or 100+.

I believe it is supposed to be low when the charge is extremely low to protect the battery, quickly ramp up to maximum until around over 50% charge, and then gradually drop off.

I haven't used a supercharger yet as there are none near me, but this is based on my understanding of how lithium-based batteries should be charged as well as other's reports on using the Supercharger.

what are your favorite charging stations..public? jestenab

I agree with Jat. Most likely due to several factors, all centered around getting you the most rate of charge as fast as it can, but not at the expense of battery life. A somewhat cold battery, a fully depleted battery, and possibly other factors raise the internal impedance of the battery. Changing at 200A in those situations can probably damage it so starts off slower and ramps up as the situation allows.

I've always started the charge between 15/35 rated miles left or in that range. And I sit in the car the whole time so I can confirm it never ramps up. Starts there and stays there. I've also tried parking at the next stall over etc with no difference...

Try ignoring the "rate" readout and doing your own arithmetic on total miles and time. There appears to be a bug in the "rate" readout.

There's also the battery to consider. I've read anecdotal reports that some of the 60 kwh batteries are getting lower rates of recharge at SCs than their 85 kwh brothers do. I also recall Elon talking about improvements in recharge rates at SCs and wonder if there's a glitch there that Tesla is working on.

@Vawlkus - 60s should charge slower -- basically you will get 50% of the maximum charge in about 30 minutes, as the rate each cell can take power is the same and it has fewer cells.

Yeah Jat, but the rates aren't the same across the board for the 60's the way they are with the 85's.

@jnoori,
Any calculated rates, per Brian's comment, and/or feedback from Tesla?

@jat@jaet.org - actually It's my understanding that there are the same number of cells for 85KW and 60KW models. They use a 3.1. Ah cells in the 85 KW and an older (i.e. lower cost) 2.2 Ah cells in the 60 KW. The 40 KW will have fewer of the 2.2 Ah cells.

Still I think your basic assessment is correct - you can only provide a maximum of 50% of the system's capacity in 30 minutes, which means less amperage for the 60KW. I've used the Superchargers about 5 times now, but I didn't record what the amperage was, so I can't confirm the lower amperage for the 60 KW that I have.

@Frank2:

I thought it was the 40Kw pack that had the different cell specs?

I've not been able to run down a confirmation source. JB Straubel, Tesla’s chief technology officer, said more than 7000 batteries are used in the 85 KW model (http://wheels.blogs.nytimes.com/2012/06/23/tesla-motors-launches-model-s...). It's been conjecture that the same number are used in the 60 KW, but assuming they are using the new technology Panasonic batteries at 3.1 Ah, and the 60 KW model uses the older 2.2 Ah, the same number of cells are used.

85 / 3.1 = 60 / 2.2

Of course Tesla could use fewer of the 3.1 Ah batteries and power the 60 KW models just fine. Since the weight is about the same, my guess is they switch the battery types and use the same number of cells.

Both batteries are of the same type.

Originally Posted by ddruz
Recapping the 85 kWh vs the 60 kWh car:
-Curb weight: 4647 lbs 85 kWh, 4464 lbs 60 kWh
-Battery cells: Both cars use Panasonic 3.1 ah 18650 Li-Ion cells, the 60 kWh cars use fewer.

source: http://www.teslamotorsclub.com/showthread.php/12879-60-kwh-vs-85-khw/page6

Sorry for the late reply to the questions. I always sit there with the calculator on my iphone playing with the readout/recharge calcs to see how they fit and track. I'll do a more detailed tracking next time I'm there and post the results. But for what it's worth I do have the superchargers installed on the car and I have gotten full charge rate there before. Just seems that more often than not I get limited charge rates when I'm there...


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