Questions after 1 Month

[CertLive]

I honestly don't know, as Tesla don't publish any details about their 2170 cells. All we can go on is the sort of performance that other big brand 2170 cells makers are publishing, and then guess that the Tesla cells will most probably be a bit better.

In the case of the Samsung cell data linked to earlier, then they don't quote a max charge C rate, but it's reasonable to assume that it is probably around the same as the max discharge C rate, at least for short periods (say 70% SoC or so), so perhaps over 10C. 175 kW with a 54 kW battery pack is only 3.24 C, which isn't that high. Maximum discharge rate for the SR+ is 250 kW, which is of 4.63C, again not really very high.

As mentioned earlier in this thread, I doubt that the cell max C rate is the limitation on supercharging speeds, it's most probably related to the battery management system and specifically concerns over cell groups getting out of balance as a consequence of several rapid charges in succession. I would guess that Tesla are deliberately being a bit conservative, both because they don't want to see battery failures, and because they are still gathering data about how the battery pack and management system perform in the field. It may be that they change things in future in the light of the data they are collecting from the cars sold so far. It seems that they have done this in the past, which tends to support the view that they start off with conservative settings and then maybe change them in the light of experience.

An interesting insight Thank You!

 

[UrbanSplash]

Yes, these are placed on the wheels at manufacture to ensure the car is driven respectfully slowly. When peeled off they allow the car to attain maximum speed. Technology - its marvellous!

Good job I removed them then!

 

[J0hn.r]

Anecdotally, I can say I'm pretty sure it uses the mains (at least in part) to heat the car when plugged in.

My reasoning is fairly simple. I have a smart meter for Octopus Go. If I watch the instant consumption, it jumps from around 200W to around 7kW when I turn on the heat, and drops back to 200W soon after stopping it. So, it's definitely drawing the max power available from the mains to heat the car, but may also use the battery if it's using more than 7kW.

You can see this in the car too. Plugged in, switch off charging, turn on heater. Then look at the Charging screen. You can see it draws somewhere between 7-10A, then, if you switch off heating, that goes to 0-1 A. Turning on charging, it takes the maximum of 30A (7KW)

 

[MrBadger]

Out of curiosity, if you turn down charge rate limit to 16A, when turning on heater as above, will you get 30A (7kW) or 16A (~3kW)? I know it honours the charge point setting (in our case 10A, stupid/dangerous if it didn't) but would be interested if, in this case, it honours the in car setting. If it didn't, that could be an issue running a UMC 16A commando off a 13A flying lead - UMC will offer 16A which is too high for the 13A plug.

 

[mick4545]

Jeremy, you say earlier in the thread that 75% SOC is optimal for long-term storage. I was under the impression that 50% was best, am I wrong.

I don't commute and my car is permanently set to 50% at home. I only charge above that prior to setting off. I estimate the charge I need then charge half of that above 50%. If I think I'll need 40% I'll charge to 70% and aim to arrive back at 30% then top up to 50%. Anything wrong with that.

Always plugged in unless thunder storms or torrential rain is forecast.

 

[Glan gluaisne]

Jeremy, you say earlier in the thread that 75% SOC is optimal for long-term storage. I was under the impression that 50% was best, am I wrong.

I don't commute and my car is permanently set to 50% at home. I only charge above that prior to setting off. I estimate the charge I need then charge half of that above 50%. If I think I'll need 40% I'll charge to 70% and aim to arrive back at 30% then top up to 50%. Anything wrong with that.

Always plugged in unless thunder storms or torrential rain is forecast.

I doubt it makes much difference, TBH, but 75% SoC has been used for a long time as the general rule of thumb for long term storage of lithium cells. The main thing is to ensure that the cells aren't near max SoC, and that they have enough energy to remain within the mid range SoC for the likely period of storage, without losing too much energy from vampire drain or self-discharge.

 

[mick4545]

Thanks.