Whos riding high ? .... voltage

[Jestronix]

So in chasing power and speed I enjoy a high voltage setup. Less bulky wiring less amps through connectors etc.

Where do u draw the line ? I run 130v full charge, I have run 160v but all in the line of chasing kw with a wide power band on a mxus 5T. Safety is a concern, higher voltage = higher chance of conductivity through skin yeh ? Lower volts are safer irrelevant of amps , higher amps means nothing if conductivity is low.

This brings me to controllers , I want 10kw on an ebike, so 100v @ 100 amps and my controller is still a nice size. I want to go safe so I go 50v @ 200 amps, but now my controller is massive ! And my wires are huge. I take it controllers are massive due to needing bigger traces ? Caps would be same size ?

Where is the safe level ? Most ebikes are @ 48v tops , there must be some safety reason for this, I'd say above and it jumps skin easily.

Mmmmm I need to find a small 200 amp controller to be safe ..... but where ?

 

[wesnewell]

I've been running 24s lipo for years at 100.8V charged. One controller is limited to 40A on a 1000W motor and the other is probably ~60A (modded) on a MXUS 3000 4T. I went to higher voltage for several reasons.
More wattage with same wire sizes and amperage.
More range at same ah.
More speed and power for take off when I needed it.
See my videos if you want to grab the ends of your high voltage battery.

 

[MadRhino]

Higher voltage rated mosfets do have higher resistance than the 4110 that I like to use. That is why I limit my builds to 24s RC lipo. I can feed more power, yet risking less controller heat than going higher voltage. This is letting me use an 18 fet controller that is slick and convenient to mount on the frame in full air flow, and a faster motor of course.

I would consider higher voltage and a much bigger controller, if I was building a bigger bike for long range trips with a passenger. For my daily needs, I am still into optimizing power to weight ratio, so each new bike I try to build with a little more power and a little less weight.

 

[Drunkskunk]

48V is considered "safe" mostly because this is the limit where most people are just able to feel voltage when they contact both poles of a voltage source. the average person can handle live 48v wires with little risk of death. At my work, we consider 80v DC safe, and take no special precautions when handling the equipment. It's not comfortable to grab the ends of an 80V power feed, but it's never caused a death in my company's history, going back 100 years. The key is your skin. it's an insulator that keeps you safe from the effects of voltage.

Without your skin, a 1.5v watch battery will kill you. get shocked through the skin and across the heart, and you're done. "Safe" voltage is a myth. The big risk in a high powered system is burn through. If you get a hot enough arc that eats through your skin, it really isn't going to matter if you're running a 170v, or a 48v, or even a 12v system.

But how do you define "Safe"? pushing 10Kw through a bicycle designed for human power, (around 200w), is not remotely "safe". Fun? Hell yes! Safe? No. 10Kw on a bicycle can kill you fast and easy in a whole bunch of gruesome, painful, disfiguring ways. having your heart stopped by the battery is the least horrible way to get murdered by your bike.

 

[wesnewell]

Grabbing both ends of 24s lipo battery.
https://www.youtube.com/watch?v=-a0Tga0F3Js&t=10s
couldn't embed this for some reason.

 

[liveforphysics]

I have done some higher voltage builds it works but it's more BS to manage in exchange for no noticeable benefit (unless you can notice having an ounce or two less copper).

Controller availability and motor kV options are what determine the voltage that makes sense beyond picking a high or low voltage number you like.

If architecting a system from scratch, I always shoot for the lowest voltage that gets the job done with the parts available.

 

[Jestronix]

Grabbing both ends of 24s lipo battery.
https://www.youtube.com/watch?v=-a0Tga0F3Js&t=10s
couldn't embed this for some reason.

while building my 32s pack I got a number of 130v shocks with no problem, she tingles but thats about it. its not nice, but didnt seem to hurt. but.... try that with wet hands ! or on ya balls in the rain

 

[Jestronix]

I have done some higher voltage builds it works but it's more BS to manage in exchange for no noticeable benefit (unless you can notice having an ounce or two less copper).

Controller availability and motor kV options are what determine the voltage that makes sense beyond picking a high or low voltage number you like.

If architecting a system from scratch, I always shoot for the lowest voltage that gets the job done with the parts available.

this makes me think the first company to make a long thin flat controller will be on a winner, imagine a controller running under the front bar , 50cm long by say 2cm high and 5cm wide. large cooling area, high amps, less boxy and more slim line.

 

[rogervize]

High voltage is good..
The technical challenges are in the design of the motor.
Higher insulating ability... but thinner wire.
The motor needs to be designed specifically to the voltage and RPMs as these are closely related.
Probably not many are currently available for smaller EVs .. and the sweet spot at present seems to be about 85V.
My Stealth uses this to achieve 5Kw. Ample power for a light weight EV.
However this means the 5Kw motor was designed for high rpms.
Max efficiency is high up the rpms and internal heating is an issue at low rpms with max throttle.
However I believe the 5400 series Crystallite 5Kw motor is a good compromise when all things considered.

 

[Voltron]

Hmmm... did somebody say long, thin, under the downtube controller?

 

[MadRhino]

Hmmm... did somebody say long, thin, under the downtube controller?

Nice !

How much power is it able to survive ?

 

[Voltron]

Not a lot I would imagine... thats the stock Stromer controller. But it shows if you want it, it can be made...

Here's one from an Izip E3 Metro.. also pretty low power.

 

[Jestronix]

I wonder if there is a market for a high power version ? I'd buy one height wise it's just the caps that would cause an issue

 

[Mündawg]

I like what you did there with the title of the thread!

Not currently riding high... Voltage. But i've only had my ebike for 7 weeks. I already want more speed and power. So something at or above 52V is a must on my next build. I would LOVE a 100V setup. But that won't be for another year or so by the time i can save up enough money.

 

[Jestronix]

I like what you did there with the title of the thread!

Not currently riding high... Voltage. But i've only had my ebike for 7 weeks. I already want more speed and power. So something at or above 52V is a must on my next build. I would LOVE a 100V setup. But that won't be for another year or so by the time i can save up enough money.

Yeh it bites I think it was about two months and I went from 3kw starter bike through to 14kw ! 160v @ 100 amps, crazy power on a bike id say @14 kw And you'll say that's too much and drop back to 8kw, which I rekon is the sweet spot for off road. 8kw above this on my mxus and most kw was wasted as heat. And errr let's say two or three hard pulls @ 14kw and ur motor is toasty.

 

[Ykick]

I always loved the crusty old factory electricians who said: “difference between 250V or 600V fuse?” “about 2 inches”.

One reason I stick close to 50VDC is that it’s much more NEC (national electrical code) friendly. You probably gotta charge someplace on electrical grid and once you go over 100V, it’s a much different animal with regards to safety code.

https://en.wikipedia.org/wiki/National_Electrical_Code#High_and_low_voltage_rule_classification

And when you go over 50VDC you’ll probably need/want anti-spark circuitry.

Granted, I’m not a hot rodder or competitive type so my criteria is much different than many around here but 50V range equipment is plentiful, affordable and more than enough for electric "bicycles".

Even motorcycles and EV's don't "need" high voltage but I get the allure of those systems and any reasonably savvy technical type should be able to handle it safely.

But as LFP correctly points out, there’s very little “practical” advantage in regards to electrical efficiency comparing properly designed systems.

 

[liveforphysics]

All of my clients today range from 500W of motor output per Volt of battery pack to 2000W of motor output per Volt of battery.

50V is more than plenty to make the most nasty powerful deathbike beating machine, even 20V could do it fine if you had the right controller.

When a vehicle crosses above the 100v MOSFET range (20s-ish), they are making a decision that meaningfully impacts controller power density and hence system efficiency etc.

 

[wesnewell]

All of my clients today range from 500W of motor output per Volt of battery pack to 2000W of motor output per Volt of battery.

That's 500A - 2000A per volt. 100KW at 50V. What's the catch here.

 

[Mündawg]

All of my clients today range from 500W of motor output per Volt of battery pack to 2000W of motor output per Volt of battery.

That's 500A - 2000A per volt. 100KW at 50V. What's the catch here.

Ridiculously high current i would guess

 

[liveforphysics]

All of my clients today range from 500W of motor output per Volt of battery pack to 2000W of motor output per Volt of battery.

That's 500A - 2000A per volt. 100KW at 50V. What's the catch here.

You already stated the catch. You have a couple feet of thick wire feeding the controller(S). It's not so bad, more OEMs hopefully will also try voltages not based around legacy industrial VFDs where HV is required to get power long distances. When you only need to get power a few feet, and you're in the sub ~20kW range, a pack around 40-50v is a pretty sweet place to be running the excellent OptiMOS5 generation of 60vdc MOSFETs.

Contrary to popular EV belief, current is the friend of performance EVs and watt sipping EVs alike. It largely hinges on what controller(s) you've got available, but you may find it almost never makes sense to exceed ~20s until you're into the multi-MW range or for some reason your battery pack must be located some significant distance from where the power actually gets used.

 

[Samd]

I'm running 72v200a and 72v600a - albeit at 90volts. I don't like to go over 100v due to possible induced fields in the frame.
The 72v200a is a pretty tight package.

 

[Jestronix]

I'm running 72v200a and 72v600a - albeit at 90volts. I don't like to go over 100v due to possible induced fields in the frame.
The 72v200a is a pretty tight package.

Tell me more those are some serious amps, how big are those controllers ?

I'm actually dropping my pack to 24s in the 100v range sensibility prevales . 600amps I take it is on a motorbike?

Back emf in the frame to worrying levels ?

 

[Punx0r]

I like the argument for low-voltage systems, but the power-density of IGBTs does look very attractive (and it clearly must do to many OEM's). Can FETs really compete? Or is it more a case of offseting the disadvantages to the controller with the greater advantages of reduced battery & BMS complexity & hazard?

 

[parajared]

Golf carts are made to haul 4 fat dudes and all their golf bags and those things are usually only 24 or 36 volts. Wattage is what matters, whether your motor gets that wattage through amperage (fatty wires and high kv) or voltage (small wires and low kv) it doesn't seem to matter much from the wh/mi or wh/km perspective.

Viable reasons to go higher voltage:
-you want more wattage but don't want to use bigger wires
-you want a higher top speed but don't want to buy a higher kv motor and a high amp rated esc

When you bog the motor your esc heats up (I don't know exactly what the reason is for this). So if you are running your "high" voltage setup for a top speed of say 60 mph you are going to run very inefficient (if you define efficient as wh/mi) if you coast along at 12mph.

 

[liveforphysics]

It's watts per number of cells. Has no cell C-rate implications to be low voltage or high voltage.

If you have say 100 cells and you need 10kW, it doesn't matter to the cells if you connect them all in parallel it's 100W per cell, if you connect them all in series it's 100W per cell.