Aggressive Current Draw

[FreepZ]

After listening to Richard's interview with Brian, I created a wiki entry that describes the BMS behavior when the battery is low. (Read it here)

That raised a question in my mind about current draw.

Brian says that being aggressive on the throttle results in a lot of current draw, but what does "aggressive on the throttle" mean?

• Keeping the throttle wide open for long periods of time?
• Accelerating hard?

Earlier, Brian said that (in normal mode) the motor is most efficient at about 7k RPM.

So when I'm running low on energy, should I be trying to keep the motor close to 7k, or should I be going as slow as possible, even if that means the motor is under 3k?

[Brammofan]

Have I thanked you yet for contributing to the wiki?

If not, thank you!

[FreepZ]

Have I thanked you yet for contributing to the wiki?

You have, and you're most welcome.

Note that I'm doing this for my own reference too. I appreciate having the information that I want to know available on a well organized Wiki site. It saves me searching though millions of web pages to find something.

[protomech]

I would guess the motor efficiency in reasonable ranges varies by a few percentage points.

35 mph should use around 50% less Wh/mile than 70 mph.

Going slower - to probably 15 mph or so - will basically always trump small motor RPM effeciencies.

[Shinysideup]

Brian says that being aggressive on the throttle results in a lot of current draw, but what does "aggressive on the throttle" mean?

• Keeping the throttle wide open for long periods of time?
• Accelerating hard?

Those are pretty much the same thing: Anytime your right hand is WOT, you be accelerating hard!

I've experienced a very slight cutback when accelerating hard up a steep long hill when my SOC was around 20%. It was nothing startling, just felt like an ICE that was misfiring on one cylinder a bit. My response was probably exactly what the Brammo gurus intended: I just backed off on the throttle a bit and everything was fine.

My real life experience verifies Protomech's dictum: Going slower always trumps motor RPM differences. Recently I made a longish ride of about 30 freeway miles. On the way out I kept to about 55 mph in the right lane, never accelerated hard, and kept it in Normal mode. I arrived with 63% remaining on my battery.

Then I charged at a public charge station while I took care of my business and did my return trip, slightly different route, but at 30 miles I had 52% remaining. The difference: I rode back in the 75 to 80 mph range, in Sport mode and accelerated away from lights as briskly as I wanted. Not as big a difference as I expected.

Of course, if I could have kept my speed under 35 mph (can't on a freeway), the difference would have been more pronounced.

[ttxgpfan]

That's what I felt about the race bikes on the banking of Daytona.  Really thought there would be a more pronounced difference.

[FreepZ]

Thanks for the data, Shiny. The more we have, the better predictions we can make about real life range.

It seems like you're saying that there's not much difference between 55 mph and 75 mph. Still 63% vs 52% is significant. It's nice to know that you can have a little fun without completely sucking the battery dry in half the time.

[flar]

I know that on my big ride today I actually enjoyed spending a fair bit of time on a boulevard in stop light traffic, but part of that enjoyment was realizing how much easier it is to ride in such traffic with an e-bike.  Even with a clutch there is no clutch to worry about and every time you have to slow down for a light you can think "woohoo - free electrons!".

(I'm sure that will get old fast, but my clutch hand was definitely enjoying the difference...)

[protomech]

Electric bikes are marvelous at low speeds. I commuted once a week or so on the gas bike for three years, it was always a pain operating the clutch in stop and go through the gate.

Today I had on my lighter summer gloves (50 degrees am, 65 degrees afternoon!). With the summer gloves I can grab my badge from my zipped side pocket while slowing down for the gate, so that I take almost zero additional time vs a car to present the badge. No freaking way on the gas bike.

[flar]

And don't forget the motorcycle wave.  It's a lot easier to be friendly when there is never a reason to cover the clutch.

Speaking of waves, should we have a special "electric power" wave to spread the good word?

[protomech]

Yes. It's a square wave.

[flar]

Can members be banned for really really geeky puns?  We wouldn't want to tarnish the he-man reputation of the forum...just sayin...

[Brammofan]

Can members be banned for really really geeky puns? 

Yikes. I hope not.

Square wave. Ha. Wonder what that looks like.

[flar]

Can members be banned for really really geeky puns? 

Yikes. I hope not.

Square wave. Ha. Wonder what that looks like.

Drat.  I hate having to compete for the title...

[860]

Speaking of waves, should we have a special "electric power" wave to spread the good word?

The first rider should raise one hand with two fingers spread (signifying the prongs on an electric plug) and point them directly to the eye "sockets" of the approaching fellow emoto rider.  The second rider should quickly raise one hand between his eyes, with all fingers together pointed up, with the palm perpendicular to the face.  This is to signify crossing the divide between gas and electricity.

Give it a try and let me know what you think.

(going for first to get geek ban...       )