Willjones017 said:
Sorry I was not a little more clear with what I am planing, but I'm planning on building a small aerodynamic-ish trike with a range of maybe 10-15 miles used when the weather is nice to use to go to school, otherwise it's the bus :-(. So from what you are saying a duel (or maybe triple) 9c oil cooled set-up is not worth pursuing? 20ah of 40c lipo would be about thousand which is little more than expected but doable, what if I used low C lipo for cruising then bring in the lead acid to go fast 8) ? (I hope I'm not sounding like a total cheap skate but like any student money's tight) thanks for all answers I'm a total noob for all this so any comments are well appreciated.
LFP said it best, you're better off with one high quality motor than several disposable ones. With a small motor at some point you reach saturation point where more power in doesn't result in more power out, only heat. Your requirements are well beyond this point of diminishing returns for almost all 'bicycle' type hub motors. Hub monster is a different beast and the limits still really haven't been pushed, certainly not to the point of saturation.
Lead acid has no place on a high performance electric vehicle, or in fact any electric vehicle at this point. Big factor in acceleration performance is total system weight, lead acid is going to throw that in the bin pretty quickly. Your train of thought regarding two types of batteries is a good one, you can potentially run two varieties of lipo in parallel to cover your power peaks while delivering the required range for less $$ than a homogeneous pack, but it's more complexity and makes it a little harder to predict exactly what load each battery will see.
Regarding controllers - you're perhaps going to struggle with building something that will reliably deliver 24kw input for not a lot of money, cheap trapezoid 'infineon' type controllers at ~12kw each are a little bit hand grenade. You can luck out and find a combo that works for an extended period of time but it might take you a few tries to get there... personally I would be purchasing 2x Sabvoton sine wave 72v 150a controllers as seen
here
These should deliver 150a battery @ ~80v (12kw) pretty reliably based on other experiences on these boards. They also have proper throttle control which with this level of power is pretty essential. They have proper phase current control which will allow for programmable torque at low speeds without being massively excessive like with the 'dumber' controllers (which leads to failures). They have some field weakening/timing advance functionality that allows you to increase top speed beyond the standard KV of the motor, allowing you to push through to target speed despite having a very small rolling diameter wheel.
You will need some fabrication experience or access to somebody who can fabricate to come up with a frame that can accommodate the hubmonster in rear wheel, the substantial amount of battery somewhere it won't be impacted if you bail and correct geometry to handle and stop safely. You will need to think about charging and allow for that in the total budget. If you're planning on reaching 60mph you need to be able to stop reliably, so decent brakes.
I really hope you build this, I have been thinking about it for quite a while myself - but I do have to ask.. do you really need ~20+kw/60mph to get to school? I commute 11 miles each way every day with <5kw, i'm beating all traffic off the line and up to 35 mph cruise - I usually don't see a car more than once as I pass at the next light. My *average* speed over the journey is only a bit less than the speed limit, so there's no way I could go any quicker without blatant and excessive speeding. My bike was built to take 12kw input reliably, however in practice I just don't need it.
