Use the CA simulator when possible. Very accurate and much better than subjective or anecdotal evidence.
Battery 1 : 91x NCR18650B 13S 7P 48,1V 23Ah 47Amp max (48V * 45A = 2.160W theoretical max output)
Battery 3 : 120x NCR18650B 20S 6P 74,0V 20Ah 40Amp max (74V * 40A = 2.960W theoretical max output)
Your Xlyte 4065 is not in the simulator but the alternate wind 4080 model is so we can just adjust the simulator to convert its model of a 4080 into a 4065 using Kv adjustment. Looking at the specs (http://www.crystalyte.com/The%20Crown.htm
) for these two motors, we use the unloaded data to determine the Kv of each then figure out the ratio to get an adjustment factor:
With the motor model set up in the simulator, we just need to pick a battery and controller that match the battery proposals. Here's a couple comparison runs with the highest voltage battery as System A and the lowest voltage as System B. The battery and controller were configured as:
- The batteries are filled in using a 'Custom Battery' choice with a per-cell nominal voltage of 3.75V/cell, then working out the pack voltage from the series string.
- Controllers have two limits: 'rated' (battery) current and 'phase' (motor) current. While a controller is limiting battery current, it can deliver more phase amps at lower voltage to the motor than it draws from the battery - so we need two current limits. The controllers are filled in using a 'Custom Controller' choice and limited to the battery max current to protect the battery. The Phase current is set to 2.5X the controller limit as a common Infineon-style setup. (Otherwise, choose limits as appropriate...)
The bike is set up using ho-hum generic MTB settings - your weight and posture may vary.
The top speed results on the flat without pedaling are:
Here some of the interesting settings and results are highlighted (I used a very slightly different 4080->4065 correction factor when I took the snaps - not worth doing new pics).
(1) Not surprisingly the high voltage battery smokes the low voltage one with a top speed about 10mph faster. A rule of thumb says you can comfortably cruise at 80% of top speed since the motor won't be spun out and will still have some throttle response left - so about 20mph and 28mph for these two cases. Interestingly, the 48V bike is predicted to hit 25mph as the motor manufacturer claimed....
(2) Next, the higher voltage/higher capacity pack appears to have a shorter range, but that is running at WOT in this image and so the higher speed creates more drag and eats power for the highV bike. If you were to re-run the simulation with partial throttle on the highV bike (about 63%) so its speed matched the top speed of the lowV bike (and so had the same drag), you would see the high capacity pack had a proportionately longer range.
Here you need to look at available Whr of the batteries. So:
- 72V pack --> 20Ah * 72V = 1440 whrs
- 48V pack --> 23Ah * 48V = 1104 Whrs
So at the same speed the 72V pack is going to have very roughly 1440/1104 * 100 = 130% the range of the 48V pack.
(3) Finally, you need to scrub the cursors along the X-axis to get different accelerations assuming you are slamming it WOT off the line. Here's a sample of what the accelerations would be as you blew by 10mph.
Again, no surprises - although the controller matched with the lower voltage battery (System B) has a higher max phase current limit, neither controller curve shows the controllers are running into their max phase current limits (red output power curves have only one point of inflection instead of two) so the max phase current settings in the controllers really don't matter in this case - just the controller rated (battery) current limits. But we know that the controller with the higher input power is going to have the higher output power (red curve) and thus the higher phase amps at any given speed. Since phase amps translate into torque (blue lines), the higher voltage (and higher phase amp) bike out-accelerates the low voltage bike by over 30% and will similarly climb hills better.
- EDIT - There is a tiny bit of phase amp limiting going on with the higher voltage battery under 5mph. Although the added inflection point is barely noticeable in the red power curve, we see it pretty plainly in the blue torque curve as the flat horizontal fixed torque due to phase amps being held to a limit in the 0-5mph range (torque is directly proportional to phase amps). In this example this is due to the controller 100A phase limit not the controller 40A rated limit.
So - your proposed higher voltage, higher capacity pack will have a higher top speed, greater range, and will out-accelerate the low-voltage pack.
As you can see, the controller is playing a critical role when the controller is limiting (the bike is under load accelerating or climbing hills) and where it can provide more phase amps according to the power limit (the red power curves to the left of the inflection point). The part of the curves to the right of the inflection point are where the controller is no longer limiting; there we see the raw motor characteristics play against the battery directly with essentially no effect by the controller. Translation - available battery power and controller limits are primary factors in motor performance for acceleration/hill climbing.
You can mess around with this setup here to see what happens on hills (speed, how long it will take overheat, etc):
http://www.ebikes.ca/tools/simulator.ht ... &throt=100
Anyhow, just a quickie look at your proposals....