[adammunich]

6.3V is the standard voltage of a farm tractor battery --these vacuum tube heaters were designed to use them.

12.6V is two farm tractor batteries (one car battery), which is why our computer industry uses 12V for motherboards (12 volts - 0.6V reverse protection diode).

Early computer power supplies used voltage regulators that were designed for car radios, originally.

[madaxe_again]

That’s because you get ~2.1v out of a single charged lead acid cell, and an old tractor battery contains three. Your car battery has six.

So the real answer to “why” is because of the electrochemistry of lead.

Kinda similar to how a lot of our world is structured around the dimensions of two horses side by side.

[foobarbecue]

Also the electrochemistry of sulfuric acid (the other half-cell)

[psychphysic]

It'd be very hitchhiker-esque if OP got the answer because 3x(1.69 - -0.36) ~ 6.3

[bluGill]

Farm tractors and cars switched from 6 volt to 12 volt at about the same time, and for the same reasons. However the old 6 volt farm tractors are still around and used for framing, while 6 volt cars are rare collectors items (even though there were more of them).

[gary_0]

Some people in the auto industry want to double the voltage again (for efficiency and to reduce the weight/complexity requirements for all the wiring, especially in EVs) but the 12 volt standard is pretty entrenched.

(Note that I'm talking about the voltage used for everything outside of the internal engine/li-ion electrical systems, which already use higher voltages as needed.)

[namdnay]

I think bikes are 6V, as well as stuff like quads, jet skis etc

[tiedieconderoga]

But don't 12V lead-acid batteries have a wide voltage range between charged (~14.5V) and discharged (~10V)? I don't think they would provide exactly 12.6V very often, or for very long.

[humanpotato]

They are not 14.5V charged. They need about 14V to charge.

https://footprinthero.com/wp-content/uploads/2022/05/Lead-Ac...

[ddalex]

But is the SBR the width of two horses asses ?

[CoastalCoder]

Horses don't "have" asses. They're both individual contributors.

[ChrisRR]

Are you sure about that? Many computers used ±12V in the 80s/90s when LDOs weren't common at all

[rrobukef]

I think the cause and effect was switched. 12V was used because of 12.6V is two batteries, LDO's are used nowadays because 6V, 12V was standard.

[ShadowBanThis01]

Cool info, thanks!