I was looking at Tesla specs and found:
Two batteries available: 60KWh and 85kWh
Supercharger charge rate: 120KW
Looking at this, we can see that the 60KWh pack is charged at 2C and the 85kWh pack at 1.4C.
The batteries used are standard 18650 batteries right (NCR18650B for the 85kWh pack?)
Question: How can they charge these batteries that fast without damaging them? On the NCR18650B datasheet is stated that the standard charge is 0.5C. And we all say here on BLF that you really shouldn’t charge these batteries at more than 1C. Am I damaging my 18650s by charging them at 2C with a hobby charger?
I do not think NCR18650B are standard batteries for high drain requirements. On the Tesla forums you will see some talk about NCR18650BD, 10A 3C rated cells.
The great advantage of high drain cells or ultra high drain cells is higher charging currents. Which is a real advantage.
I have seen a guy posting on CPF about his 1C charging of the NCR18650B realing to cells failure after dozen of charges, he said he did something like 30 cycles. It would be good that I find that post so I can link it here rather than me posting from memory on this particular case.
Thanks! Yes, please post the link if you find it.
However I couldn’t find any datasheet for the NCR18650BD that would confirm that a 2C charge rate is ok.
Do they really use standard low-drain ICR chemistry cells in apps like that? I think they tend more towards LiFePO4s that can handle massive charge/discharge rates.
They run 9S69P according to this, so I don’t think they’d have trouble getting the necessary Amps. The interesting thing is the 8 year lifespan on the battery pack, what ideal charge rate and termination voltage allows them to last so long?
Half charge in 20 minutes is 1.5 charges in an hour, which is 1.5C.
Panasonic doesn’t state the max charge condition but I have seen it in other datasheets from samsung and lg rated as 1.5C or 2C. This were standard icr 4.35V types…
You have to think of the fact that the standard charging is only to 80% on a tesla(you have to select it manually if you want full capacity)of the battery if I am informed correct. So that will increase cycle count a lot.
Also battery pack gets cooled, this should benefit also in the cycle count.
http://www.teslamotors.com/supercharger
I based my calculations on the 120kW written under the graph. I assumed that it is also using 120kW for the 60kWh battery version. Maybe that they are not using the full 120kW for the 60kWh version…
Anyway, I will look in Samsung cells to see where they state a 2C charge rate.
I have seen various unofficial ratings saying 30A rated for Sony VTC5.
In the official specs I see 10A discharge with discharg graphs showing 20A, so that means the 30A rating is an unofficial rating just because someone tested the cells to work fine at 25A? Or how are these numbers throw around by these rebranders?
I believe you can’t fully charge with the supercharger, only up to 80% or something like that, so i assume it does the constant current but not the constant voltage portion.
Most electric cars limit the battery cycling to 20% discharge and 80% charge. Doing so increase the battery life over an order of magnitude… for some cells maybe even 100 times more cycles than doing full discharge/charge cycles.
BTW, I have seen a video of Luke doing a 100C (230 amp) charge on a A123 LiFePO4 cell…
