Battery Vehicle Society

hihi finally got round to posting on here.
I got wound up by who killed electric car, trouble is I'm a bit out of my depth and would really appreciate more advice and opinions.
I have 400kg quadracycle and 8kw 48v Lynch motor
my requirements are:-
20mile range
50mph
Must have regen
I intend to use lead acids, at least initially
Thinking of 4QD-200-48 controller
I dont really want to use cvt if it can be helped
need to sort out drive to transmission which will need round 9,000rpm for that top speed.
Will the Lynch move the vehicle at this ratio(3 to 1 step up)thing start?
If not a 2 speed gearbox seems a sensible way to go. Any ideas on that front.
Feel free to call me an idiot if anything I have suggested is of the wall.
But please give constructive advice as well. Thanks

Cedric Lynch gives a useful "rule of thumb" way of estimating whether direct drive will work OK for his motors. He suggests multiplying the weight of the vehicle (400kg) by the maximum speed in km/h (80) and if the result is less than 30,000 you're OK.

In you case, the answer is 32,000, which is marginally over this magic number, so top speed might have to be reduced by a mph or two or a few kg removed from the max weight, although as it's a rule of thumb my guess is what you suggest will work fine.

Gear the motor to get your design maximum road speed at the loaded motor rpm/volt figure (I don't have this to hand for the Lynch motor you're using). You should still have enough torque to pull away - hill starts being the challenge.

Jeremy

The 4QD controller you mentioned is only 210 amp max, you'd really need at lest the '300' model.

I've not seen many people use them for roadgoing vehicles above bicycle size.

Cedric himself would probably recommend a Brusa controller, but they're a lot more expensive.

We used to use small 4QD controllers on our greenpower car & they were pretty good. They were a simple 'buck' regulator in voltage mode with synchronous switching & we measured 99% efficient(!). Anyway, reason for post - we did DIY controllers in the end using a current mode switcher, resulting in throttle position directly controlling amps in the motor & although the controller was less efficient (94% boooo ) it was a much better way of driving the motor. Is this an option for commercial DC drives? - effectively gives torque control.

The Brusa Permenenant Magnet DC controllers worked this way. I just took a glance at the Brusa website (www.brusa.biz) and they're not listed there any more.

The manual is still avalable though.

http://www.brusa.biz/assets/downloads/m ... xx_D11.pdf

hi thanks for comments, so no negatives about 4qd?
cheers

Jeremy wrote:Cedric Lynch gives a useful "rule of thumb" way of estimating whether direct drive will work OK for his motors. He suggests multiplying the weight of the vehicle (400kg) by the maximum speed in km/h (80) and if the result is less than 30,000 you're OK.

In you case, the answer is 32,000, which is marginally over this magic number, so top speed might have to be reduced by a mph or two or a few kg removed from the max weight, although as it's a rule of thumb my guess is what you suggest will work fine.

Gear the motor to get your design maximum road speed at the loaded motor rpm/volt figure (I don't have this to hand for the Lynch motor you're using). You should still have enough torque to pull away - hill starts being the challenge.

Jeremy

Be careful, that rule of thumb assumes 60 volts! At 48 volts you need to reduce the 30,000 figure to 24,000. So you will need to look at more voltage or a gearbox.