GM 3kw motor/controller Lipo pack questions

[stonezone]

I have a couple of questions about what battery pack to build for my new motor/controller before I fill out all the loan paperwork.

Have this Motor/controller combo sitting in the box and i'm itching to start my build.

Golden Motor HPM3000B -- High Power BLDC Motor
Voltage:72V
1. Voltages: 72Vdc
2. Rated power: 2-3KW
3. Peak power: 6KW
4. Speed: 3000-5000rpm
5. Rated torque: 10 Nm
6. Peak torque: 25 Nm

GM Sine Wave Controller Model: VEC200
Voltage: 72V
Rated continuous current:80A
Maximum phase current: 200A

I'm looking to maximize the power on this motor/controller combo and don't want to skimp on batteries. If I want range i can just tune it with my CA, or go light on the throttle. I definitely don’t want my batteries to be the bottle neck I’d prefer to spend a little extra and make sure my batteries are not going to be the bottleneck. Here are my options:

Option 1 -- If i go big 20s4p:
http://www.hobbyking.com/hobbyking/store/__16500__ZIPPY_Flightmax_5000mAh_5S1P_45C.html)
16 x $65 = $1040

Option 2 -- Slightly less large option but still legit:
http://www.hobbyking.com/hobbyking/store/__16501__ZIPPY_Flightmax_5000mAh_6S1P_45C.html
18s4p
12 x $75 = $900

Questions:

1) What would the difference between 18s and 20s be in terms of performance and power?

2) Am I over-building my pack? what’s the lowest C-rating in 4p before I’d loose performance?

3) Any other suggestions?

Thanks Team!

SZ

 

[dogman dan]

Since it's not for a race, I think 40c or above should be fine, for a bike with low sag under load. You'll have 80 amps at 2c. Should be plenty, but do know that above 5c you might start seeing some sag. But with 40c stuff or above, you'd have 10c at just 25% of the rate they claim.

Bear in mind, a motor that big, unless you weigh 300 pounds, you are going to launch so fast you won't spend a lot of time pulling more than 80 amps.

I always say, cut the stated c rate in half, but with HK stuff, cut it by 75%. in 20 ah size, you could use 20c stuff. But like I just advised another guy in another thread, you might want to carry less than 20 ah at times, so starting with 10 ah of better c rate cells is a good idea. Then based on the performance you see with the first 10 ah, you might add 10 ah more of cheaper cells.

Make all your wires and connections big, so you don't cause sag with a wires bottleneck.

Most of us find a bit better capacity from the larger turnigy packs. The zippies do take up less space though.