Tesla shares 48V architecture with other automakers

I know the older Honda CT110 postie bikes came in 6v in the old days. That was a kick start.

Yes. Post 2021 teslas have nine cameras scattered all over the body. For AV, Tesla would like to get much higher resolution and frame rates out of them.

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The equation for power delivered by an ideal system is P = IV, or power (P) = current (I) * voltage (V). Power is measured in watts, and that is generally the overall number that matters, in terms of what you can run off of your system at the same time.

So to increase the wattage (power) of your system you can either increase the voltage or the current.

- Increasing the voltage of a system increases the amount of resistance it can "break through". In "danger to human" terms, our skin is generally not a great conductor, so voltages lower than 50V usually won't enter the body (read: vital organs) at all. Voltages above 50V will start to enter the body depending on conditions, which is when electricity becomes much more dangerous.

- However even if the voltage is high enough to enter the body, if the current (I) isn't very high it still won't be dangerous. Current is measured in Amperes (A), and the usual number at which a current inside the body becomes dangerous is above 30mA. 30mA can cause respiratory failure if it passes through the lungs, current as low as 100mA can cause cardiac arrest if it passes through the heart. In a car's electrical system, the currents we're operating with are definitely going to be over the 30mA threshold we just established, so we want to keep the voltage under 50V instead.

Anyway back to cars and ignoring danger to humans for a second. Resistance is the main thing you want to overcome when it comes to the efficiency of such a system. The equation for power loss is P = I^2 * R, or "power dissipated (as heat) is proportional to the square of the current times the resistance". So if you increase the current of your system (in order to deliver more watts) you will also increase the amount of power you lose as heat. You can decrease the loss by decreasing the Resistance.

The equation for resistance through a material is: R = ρ * (L/A), or Resistance = resistivity (an innate property of the material) * Length / Area. In other words, the longer your wire is the more current you will lose to resistance. But if you increase the cross-sectional area of your wire (A) by making the wires thicker, you decrease the resistance.

So in short: if you have a high current (amperage) system, you use thicker wires in order to ameliorate resistive heat loss. But you can alternatively just decrease the amperage to reduce your resistive heat loss, which means thinner (and therefore much lighter) wires. But then you need to increase the voltage of your system in order to offset the power you're losing by decreasing the current. If you increase the voltage by 4x, from 12V to to 48V, this keeps it under the human danger zone (of 50-60V) and means your wires can be up to 16x thinner, taking up less space and less weight. Having it be a nice multiple of the previous system (4x) should make upgrading the relevant circuits a little more straightforward as well.

If you design 100v computers, monitor, headlights, seat adjustment motors, window/windshield motors, pumps, etc. you could cut these 48v wires in half again but if you end up stepping everything down anyway it loses its utility.

The safety rules about voltage and the human body are often poorly overstated, as is the addage that 'its the amps that kill you, not the volts.' in reality it takes a whole lot of both [0].

As further research, here[1] is styropyro touching 2 contacts which have more current than the largest bolts of lightning (enough to almost instantly vaporize a crowbar) with his bare hands, but because it is 12V it is not able to pass through him.

[0] https://youtu.be/BGD-oSwJv3E

[1] https://youtu.be/ywaTX-nLm6Y

If they’re both flat I agree, I’m curious what you do.