High Power Wall Charger - Actual DC Volts/Amps Going To Battery?

[RaySuave]

The high power wall charger is rated at 240v 80amps AC. After the AC to DC conversion by the twin on-board chargers, does anyone know what the actual DC voltage/amperage output of the on-board chargers is that is feeding into the battery?

I am also looking for information regarding the series/parallel configuration of the battery.

If not, can someone point me in the right direction for this information?

 

[shokunin]

The car display will show you your AC input from the HPWC in volts and amps giving you +KwH into the pack. It does not show the DC voltage (unless you're on supercharger) . On a 85Kw pack there over 7000 individual battery cells and their configuration is part of Tesla's IP. I'm sure some are in series and some groups are paralleled, but how many cells per section is not publicly known.

Is there a reason to know what the DC voltage and amperage is after the twin chargers?

 

[RaySuave]

Thanks for your reply. The reason I would like to know is for some research Im doing regarding directly charging with DC instead of using AC.

For the super chargers, Ive read that they pump 440V DC at 90kw into the car. So is it safe to say that the amperage would be about 205A right?

 

[TurboFroggy]

Figure the chargers are 95% efficient and 20KW in would equal about 19,000 watts into the pack. If the pack is 380-400 volts or so then 19,000 watts / 380 volts = 50 amps. This would only be the case if it was 20KW in or 250 volts * 80 amps = 20,000 watts. A more reasonable rate would be 230 volts * 80 amps = 18,400 watts. 18,400 / 380 volts = 48 amps.

 

[FlasherZ]

Thanks for your reply. The reason I would like to know is for some research Im doing regarding directly charging with DC instead of using AC.

For the super chargers, Ive read that they pump 440V DC at 90kw into the car. So is it safe to say that the amperage would be about 205A right?

For SC's the display shows 360V @ 275A.

Some of Tesla's safety documentation says "400V".

One of the service managers was once able to rattle off very specific information on the battery structure, to include cells, sheets, modules, etc., but I never committed anything to memory but 7,104 cells in the 85 kWh battery pack.

 

[GSP]

The battery controller will tell the charger what voltage and current to provide. This is true for both on-board and off-board chargers (AC or DC input to the vehicle). The battery most likely is charger at constant current until a set voltage is reached, with the battery SOC determining the voltage required to achieve that current. After reaching the set voltage (at about 80% SOC) the battery is most likely charged at constant voltage until the target SOC is reached.

GSP

 

[RaySuave]

Thanks for the replies, with the efficiencies and display information, I have a much better idea of what kind of power the on-board chargers are supplying. Hopefully one day I will own one a Tesla. If I find more info on the chargers elsewhere, I will post it.

 

[jkirkebo]

For SC's the display shows 360V @ 275A.

Some of Tesla's safety documentation says "400V".

One of the service managers was once able to rattle off very specific information on the battery structure, to include cells, sheets, modules, etc., but I never committed anything to memory but 7,104 cells in the 85 kWh battery pack.

That seems consistent. Most EVs have 96 cells in series, it seems the Model S has the same number due to the voltage. 7104/96=exactly 74.

But 74 is only dividable by 2, so my guess is the battery is either made up of 96 bricks in series which each has 74 cells in parallell, or 192 bricks of 37 cells in parallell connected 2p96s. My main guess is for the latter. Thus you must replace 1/192th of the battery if one brick goes bad.

The 60kWh battery must have different sized bricks because it has more than 70% of the voltage of the 85kWh batteri (seems to be
around 85-90%). My guess is around 86 bricks of 58 or 2*29 cells in parallell.

 

[RaySuave]

It looks like the charger efficiency is around 80%, based on a few posts I have found like these where people have equipment to measure how much AC input wattage is needed for a full charge.

sergiyz | DECEMBER 12, 201292% maximum efficiency per the specs page.
From my experience by comparing kWh spent vs what Chargepoint reports as used during a charging session, it's about 80% or less.
Not sure how much it depends on charging current (Chargepoint is 30A) and weather conditions (if the battery is hot, tesla is running a cooling pump during charging).
It would be interesting to gather more data.

Hans (Amsterdam) | FEBRUARY 23, 2013EPA data Tesla model S 85 kWh:
range 265 miles
combined fuel economy 38 kWh / 100 miles (from the grid)
effective battery capacity (range charge): 95% x 85 kWh = 80,75 kWh
total kWh from the grid: 265 x 38/100 = 100,7 kWh
charging efficiency: 80,75 / 100,7 = 80,2 %
Charging efficiency will be a little better since the Vampire Load will account for some losses during charging.

SOURCE: http://www.teslamotors.com/forum/forums/charging-efficiency-0