Controller efficiciency differences for speed 2 vs 3?

[__mike]

Hi guys,

My Setup is as follows:
Leaf 35mm 5t / em3ev Infineon 9fet 4011 / 16s lipo / 26" wheel/cav3

Am happy with this setup for now but the speed is around 15km/hr more than I use/need. Good to have it there 'if' I need it but am curious if there is any benefit in removing. I don't want to change out my pack (8s2p2s) and I know I can restrict speed with the cav3.

If I change the default speed setting with the controller back to 75% I'll be at ~48km/hr which is plenty. The pulses (??) that control the speed will be less , amps\input voltage remains the same, my throttle control range should still be 100% of this 75% speed / pulse range. My Max speed capability will be less which will the be closer to my average riding speed. So effectively my controller will be operating the motor closer to its maximum speed and will run cooler? If I'm full throttle at this speed on flat Tarmac / neutral wind I'll be drawing say an estimate 1500watts instead of 2000watts/still accelerating. I know I can use partial throttle for the same result but it's just easier to hold full throttle over rough ground. Does this make any sense / truth? Or no benefit leave it alone ?

I know riding around on a lot of partial throttle gets the controller quite warm which got me thinking...... Maybe too much

Mike

 

[motomech]

It probably would have been better if your system would max out @ 110% your desired top speed, which would be 10 to 20% more than your avg. cruise speed.
The efficiency would be better, but enough to be measurable, perhaps not.
Dogman is fond of saying that what kind of jacket you are wearing or what you had for lunch has more effect on range than the magnitude of less than optimum system you are talking about.
It also sounds like you are fetting to much about component heat. "Warm" doesn't really mean anything. Quantify with a thermosensor or at the very least tell us the what's-a-ma-jig is too hot to touch and then it's time to talk about "over-heating"
If everything thing else in your system is ok, I wouldn't change it, with the possible exception of reducing the Lipo down to 14S. You have some Volts you could give up and my experience is, it is much easier to balance charge(and even bulk charge) 14S as opposed to 16S.
How do you charge your Lipo now?

 

[__mike]

Hi motomech,

Next pack will be back to 12s or possibly 14s. I charge as a bulk 8s 13200mah pack. 2 plugs I disconnect to charge as 8s and reconnect in series

Mike

 

[teklektik]

If I change the default speed setting with the controller back to 75% I'll be at ~48km/hr which is plenty. The pulses (??) that control the speed will be less , amps\input voltage remains the same, my throttle control range should still be 100% of this 75% speed / pulse range. My Max speed capability will be less which will the be closer to my average riding speed.

So effectively my controller will be operating the motor closer to its maximum speed and will run cooler?

No.
The controller 'speed' settings limit the max PWM % - they are electrically equivalent to PWM throttle stops but the actual throttle rotation is re-scaled so WOT is a lower PWM % instead of going to block commutation (no PWM) at 100%. This lower PWM % lowers the 'speed' by reducing the WOT max RMS phase voltage (speed = Kv x phaseVoltage). If you do what you propose, holding the throttle WOT at 100% of 75% PWM will be no different than holding the throttle at 75% with 'speed=100%'. In either case the controller will be at exactly the same PWM % and so will not benefit from the efficiency improvement of being in block commutation at 100% PWM (where there are reduced switching losses). There will be no efficiency changes at all - anyplace. So - this will do what you want throttle-wise, but without the efficiency advantage you postulate.

Since you have a V3, I assume you are using Current Throttle. I would recommend that you use a 2 or 3 position CA switch to make the bike more manageable at low speeds. Since you are effectively limiting the controller to the MaxCurrent setting, the available acceleration will be reduced if you go WOT in a reduced-current setting. To keep the same acceleration potential in reduced current settings, you can set the switch up for speed limiting and directly go after the max speed issue. In either case, the switch gives you the option of 'boost mode' for those times when you want it. The main difference over using the controller switch is that the CA knows what is going on and can do a better job of control than when you limit controller throttle effect behind its back...

Although CA 3-position switches are electrically different than controller 3-speed switches, a simple CA 2-preset switch requires just a switch and so is easy to try if you want to go with a simple boost option (see the Guide).

• FWIW - I ride with a V3 with 3-pos switch and an over-volted pack because it was lighter/smaller to increase the V than the Ah to bump up the Wh a bit. Since The bike was originally configured to usually run at 80% throttle, it was always in PWM anyway so the battery upgrade introduced no material efficiency changes -- and the boost mode is very handy - particularly with CA temperature rollback to avoid 'WooHoo!' mishaps...

 

[__mike]

Thanks teklektic exactly what I was after

With regards to the CA I'm using 'pass thru' throttle mode. Is this the Controller at work here? I have all the Ramps turned up as I prefer a more sensitive throttle. I found Current throttle mode too laggy. I have the em3ev 3 position speed switch setup so I have 3 selectable current settings on the fly which Comes in handy. I need to reduce block time here once my replacement program cable arrives as the power will spike given enough throttle most noticeably in speed 1 / 50% of my current limit (35a).

I'll leave things as they are for now

Mike

 

[teklektik]

Thanks teklektic exactly what I was after

With regards to the CA I'm using 'pass thru' throttle mode. Is this the Controller at work here? I have all the Ramps turned up as I prefer a more sensitive throttle. I found Current throttle mode too laggy.

Ya - with PassThru you're basically looking at the controller response with the CA ramping layered over it - this is the most responsive setup. Turning up the Up/Down rates as you have done takes any CA delays out of the picture.

 

[__mike]

Thanks