Who needs more than 250W?

[jb]

Higher volts mean less losses due to resistance, which is why the grid runs at incredibly high voltages.
Also it reduces amps needed which takes the strain off components.

Italian motorbikes were known for bursting into flames because they used high amp low voltage rectifiers.

The down side is the you need better insulation to prevent it escaping and there is an increase in the likely hood of a shock.

[PH]

I'm trying to get my head round this, if there are advantages of 48V, why have the major players chosen 36? Economy? Weight? Something I'm missing? When I see 48v systems advertised they are often higher powered systems that don't comply with the regulations, or are easily modified not to. For those intended to be used as regulated, is there an element of not needing more than 36v? Is 48V sometimes used to compensate for less sophisticated systems?
I've recently started riding a bike with a Bosch Performance Line CX motor, 95kg rider, up to 20kg cargo, plus 24kg of bike, it'll climb any hill I point it at, comfortably at around 18kph and the full 25kph with still less effort than I'd climb unaided (At under 10kph) It certainly doesn't feel like it needs any more of anything.

[offroader]

However it's worth noting that these days 36V is often fitted to lower spec bikes so if you're comparing a 36V Happy Shopper setup to a 48V Bosch system there is likely to be a performance difference

I thought the systems of all the major players, Bosch, Shimano, Yamaha, were 36V?

You're quite right.
I must admit I've not needed to closely follow the market for a couple of years and just assumed that since most manufacturers have recently released new kits they would have made the switch.

Why haven't they switched

Difficult to say for sure but at a guess....
There's a lot of capital and R&D invested into 36v technology - custom motors, controllers and tooling in particular but also control software and general motor behavioural knowledge

At this time it looks like the market wants flashy bells and whistles (Look, there's an app for that!!! Bluetooth!!!!! GPS!!!!!!!!) rather than improvement in the fundamental technology and it's far easier to service that with software upgrades to legacy hardware

Plus there is an element of good enough. While there are gains to be made from higher voltage they are in real terms small unless you go really high.

I see one company who I know has a 48v system that is still promoting their 36v setup with more shiney trinkets.
C'est la vie

[hemo]

Woosh are now adopting 48v kits and Wisper have introduced a 40v/11s system on their new range.

The extra voltage will provide more torque for the same current used, a gain of approx.33% at 48v. Acceleration will also be quicker as can top speed if one can change the speed limit.

The main reason for 48v is to keep pace with mid motor players who are now quoting 100- 120nm torque for some of their drives, a few years ago they all use to be about 40/50 nm but have doubled the power in the last few years.

An 18a /36v system would output an average 648 w temporary in comparison a 48v system would only need to provide current of 13.5a for 648w, less current is easier on the controller electronics so runs cooler. If one was to stick with 18a/48v then one would have 864w available average, a 33% odd gain.