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I'm ignorant and curious: why 48V specifically? Why not 40V? Why not 50V? Is there some ideal ratio that makes DC-DC conversions more efficient or something? F

I'm ignorant and curious: why 48V specifically? Why not 40V? Why not 50V? Is there some ideal ratio that makes DC-DC conversions more efficient or something? For comparison, Makita (and I think some other power tool makers) have augmented their 12V lineup with a newer 40V platform for tools that need a bit more oomph. I guess there's no need for them to interoperate with other DC voltages, so maybe that explains the "messy" number? USB, on the other hand, recently grew support for a handful of pleasantly neat voltages: > Increased power levels from existing USB standards up to 240W. New 28V, 36V, and 48V fixed voltages enable up to 140W, 180W and 240W power levels, respectively. Does anybody know how these decisions are made?

owengee 3y ago
For batteries it tends to be multiple of the battery cell voltages. So 48v is probably so you could wire 4x12v batteries in series but that is a guess. With tool voltages this tends to be a multiple of the nominal battery voltage (rounded for marketing).
- stickfigure 3y ago
  To riff on this, a lead-acid cell is 2.2v. If you look at the 12v battery in your (typical) car, it has six cells. It's less obvious with modern sealed batteries, but super obvious with flooded lead acid batteries in golf carts. Lithium batteries do not have 2.2v cells; typical li-ion cells are 3.7v. So there's no particular reason why you should stack them to 48v, except that there's already some amount of industrial capacity for 48v components due to the preponderance of 48v golf carts. Of course, these systems don't work at exactly 12v or 48v or whatever; voltage on the bus fluctuates with state of charge (and state of charging).
  - 1970-01-01 3y ago
    This is it, there are many ways to get there. The 48-volt architecture is achievable with four 12-volt lead acid batteries in series, or thirteen lithium-ion cells in series at their nominal 3.7-volts, or fifteen LiFePo4 cells in series at their nominal 3.2 volts. You can ask for any of these to manufacture a 48-volt vehicle.

owengee 3y ago

For batteries it tends to be multiple of the battery cell voltages. So 48v is probably so you could wire 4x12v batteries in series but that is a guess. With tool voltages this tends to be a multiple of the nominal battery voltage (rounded for marketing).

stickfigure 3y ago
To riff on this, a lead-acid cell is 2.2v. If you look at the 12v battery in your (typical) car, it has six cells. It's less obvious with modern sealed batteries, but super obvious with flooded lead acid batteries in golf carts. Lithium batteries do not have 2.2v cells; typical li-ion cells are 3.7v. So there's no particular reason why you should stack them to 48v, except that there's already some amount of industrial capacity for 48v components due to the preponderance of 48v golf carts. Of course, these systems don't work at exactly 12v or 48v or whatever; voltage on the bus fluctuates with state of charge (and state of charging).
- 1970-01-01 3y ago
  This is it, there are many ways to get there. The 48-volt architecture is achievable with four 12-volt lead acid batteries in series, or thirteen lithium-ion cells in series at their nominal 3.7-volts, or fifteen LiFePo4 cells in series at their nominal 3.2 volts. You can ask for any of these to manufacture a 48-volt vehicle.