Well, I thought I would throw out some information as to why you might want to slow things down.

**Vehicle Losses**

I will talk about parts of the system where power is lost and talk about how this can be related to charging current.

The chargers are lossy. They are converting the input voltage into DC and regulating the current that flows into the vehicle. Most DC/DC supplies are most efficient somewhere in the middle of their operating range, I don't think any are most efficient at the upper limit. There are several reasons why this is the case, one simple reason is resistive power loss. The charger circuitry has a fixed resistance in it's circuit that the current must pass. Using the equation to convert current and resistance to power, power=I^2xR you see that as the current increases the power is increased exponentially. Other factors that influence efficiency are losses in the magnetics used by the switching supply, the inductors and chokes. As the loads increase on the circuit, so do the losses.

The battery cells also loose power. The battery stores and releases energy through a chemical process but the battery cell also has a certain resistance internally (also called impedance). This loss can simply be thought of as a fixed resistance and using the power equation P=I^2xR you can determine the power loss due to current and resistance. As battery cells get older their impedance typically increases, so the internal cell resistance will rise over time.

Energy wasted is turned into heat. Maybe you need heat because you live someplace cold, maybe you don't. Let's say you don't need to warm up the battery pack, or worse yet you are parked over hot asphalt. The heat is going to need to be moved away from the critical components, the battery cells, the charger and dissipated to the air. Tesla does this first with a fluid, so a pump is involved, then a radiator and a fan. It takes power to run pumps and fans. If you charge slowly the heat may be able to naturally move through convection and dissipate without extra help. I don't know when active cooling kicks in, wish I could unlock that Tesla diagnostics screen, but you have probably heard fans and pumps running while you observe the Tesla beast sleeping. It isn't purring because it likes your garage.....

**Home Losses**

When you are charging, the car is part of a bigger system. A system that starts at some generation plant, includes power lines, transformers, your homes electrical, the car. It is big and complex and awesome. Let's focus on the part we care about, the part we directly pay for, and that is the numbers measured by our electric utility meter.

The meter at my house is digital, it shows the voltage, power and kWhr totals on it's display. If I draw enough current to cause a voltage drop between my meter and my car, then that is a sure sign of power loss. That loss is caused again by the fixed resistance in the wire, circuit breakers, and fuses in the network. Multiply the voltage drop by the current and you get the power loss. Another problem that voltage drop can causes is higher current draw. We know the equation for power is voltage times current, we know that a twin charging vehicle is rated for up to 20kW. If the car limited it's charge by power we could have a problem since voltage sag would require an increase in current to keep the total power equal. Lucky for us the fine electrical engineers gave us control over the current limit instead. Current is what trips our breakers and melts our wires, so current is what we need to limit. By the way, a quick calculation shows that since the current limit is 80A, you would actually need 250Vrms to reach 20kW, doable in Europe perhaps. A voltage drop in our home is something we end up paying for, beyond our meter we don't

**BUT**it does reduce the total power being delivered to the car.

To throw out a few numbers:

80A at 240V = 19.2kW

80A at 220V = 17.6kW

80A at 200V = 16.0kW

If your car shows 240V before charging, and 220V during charging then you are loosing 1.6kW continuously due to resistive losses.

**Summary**

You loose power in your house wiring. You loose power in the chargers. You loose power in the battery cells. You consume power to cool the chargers and the batteries. All of these losses are directly related to the current. If you lower the current you lower your losses.

I would like to see Tesla offer a software option where charging current is minimized based on a deadline. Lets say I leave for work every day at 8AM, I only care that my vehicle is fully charged the second I unplug the charging cable. I schedule a fixed starting time when my rates are lowest, lets say midnight. I set the upper current limit. The vehicle dials back the charging to the minimum required to fully charge by 8AM.

Secondary advantage is lowering your average SOC (State of Charge). The lower the charge level kept in your battery the better for it's life time. This method would optimize the SOC.

The information above is free. Take it, or leave it I don't care.