DIY stage 8: Continuous improvements...

[daniel.weck]

DIY stage 8: Continuous improvement...

Table of Contents:

http://www.pedelecs.co.uk/forum/electric-bicycles/4682-diy-stage-1-received-bafang-tongxin-kits-photos.html#post59183

http://www.pedelecs.co.uk/forum/electric-bicycles/4734-diy-stage-2-received-li-ping-lifepo4-battery-photos.html#post59988

http://www.pedelecs.co.uk/forum/electric-bicycles/4737-diy-stage-3-motor-testing-fork-photos.html#post60039

http://www.pedelecs.co.uk/forum/electric-bicycles/4747-diy-stage-4-16-wheel-lacing-building-photos.html#post60153

http://www.pedelecs.co.uk/forum/electric-bicycles/4769-diy-stage-5-prepping-fitting-electricals-photos.html#post60345

http://www.pedelecs.co.uk/forum/electric-bicycles/4778-diy-stage-6-fork-hub-torque-protection-photos.html#post60504

http://www.pedelecs.co.uk/forum/electric-bicycles/4786-diy-stage-7-first-ride.html#post60641

http://www.pedelecs.co.uk/forum/electric-bicycles/4825-diy-stage-8-continuous-improvements.html#post60991

http://www.pedelecs.co.uk/forum/electric-bicycles/6956-diy-stage-9-a123-nano-battery-pack-photos.html#post88165

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So, I've been gradually changing the battery + controller layout: my first major turnaround was to move the kit from the front (Brompton touring bag) to the rear (rack-bag). See "stage 7" to read why.

My latest refinement is to separate the battery from the controller, by moving the controller out of the rack-bag to a new location on the bike, using a quality water-proof frame bag. By doing this, the folding of the Brompton is much quicker as I only have to disconnect a big connector to the battery, undo the bungee cords to remove the rear bag, and fold as normal. The mini frame bag is non-obstrusive, in fact it fits nicely below my saddle (which stands higher due to an extended seat post).

This "Chivalry" frame bag is great, albeit more expensive than cheap triangle bags (20 GBP). I needed something waterproof (material, seems, *and* zip), and I wanted something semi-rigid (floppy material looks awful and makes it hard to arrange wires correctly inside the bag).

See how the main battery cable is routed to the rear:

 

[daniel.weck]

Isn't that pretty ?

 

[flecc]

That does look good Daniel, very compact and practical too.
.

 

[daniel.weck]

I've just temporarily installed a digital thermometer to pick-up the temperature of the controller, and accessorilly of the surrounding atmosphere (it's a two-pane display with one built-in sensor and a remote one).

That's a *really* ugly install (I am a bit ashamed to be honest ), but I need to monitor the effect of the semi-rigid insulated frame bag on the controller. I would not like to burn the mofsets due to negligence on my part.

There's a fair amount of hill-climbing involved in most of my cycling trips, so I should quickly be able to establish whether there is an overheating risk or not.

I would really like to have a power meter in order to check the Ah draw under heavy load. The battery is still in its infancy, so the BMS needs to stabilize the cells for a few more recharge cycles. Fully-charged, my voltmeter currently shows 45.5V and I tend to recharge after every local trip (<10 miles, but with a few hills). I will attempt deeper discharge once I feel that the battery has "matured" enough (as per Ping's instructions).

Any advice welcome !

 

[AndyOfTheSouth]

The ancient practice of electrical bicycling has generated many traditional sayings over the years, such as

‘Motor whine helps wood pidgeon take off on time’

And

‘Red sky in the morning, battery warning; red sky at night, you got home all right’

But none be so potent as

‘When a man finds himself taking the temperature of his controller, it is nature’s way of telling him to move on to the next project’


(Extracted from The Lore of the Pedelec)

 

[daniel.weck]

‘When a man finds himself taking the temperature of his controller, it is nature’s way of telling him to move on to the next project’

LOL Say what ?

I topped 36.1 Celsius degrees for a short 10mn ride with medium hills and descents. Interestingly, the temperature goes up as I cycle downhill...is it the heat build-up inside the frame bag due to the climb just before...oh, and this was in pedelec mode, not throttle (I don't know if it makes any difference).

EDIT: with the bike unused for several hours (well, just a quick unloaded spin to check the front wheel truing), but with the battery connected, the temperature inside the frame bag remained 10 Celsius degrees above the outside temp in my corridor. So, the controller-generated heat was a constant 30 degrees despite being inactive. Interesting. I have now disconnected the battery to see if the temperature finally drops. My assumption is that there might be a small current draw even though the motor is not running...but I could be wrong (the 30 degrees might have been generated by my unloaded test 30mn before I checked the temperature).

Cheers, Dan

 

[daniel.weck]

Pedelec

Ok, so I've just installed the pedelec option. I had to grind the plastic magnet disc a little for it to fit within the available space, and the fitting of the sensor wasn't straight-forward. As you can see, silver duct-tape is one of my favorite tools

The fitting is pretty solid though, and easily reversible if pedelec gets in my way more than it helps me.

Using this kind of pedelec, there's an immediate contradiction with the throttle-only mode: to climb up hills, I must increase the pedal cadence, otherwise the motor comes to a halt. The sensor detects the crank's rotational speed (not the torque), and I assume that the controller tries to be clever by correlating this value with the signal coming from the motor, in order to adjust the power output. Because of the lack of information (current gearing, actual ride speed), this mechanism is sub-optimal and the power delivery is jerky on edge-cases, i.e. it is fine most of the time, but not at the beginning of an ascent, or mid-climb when stopping/slowing due to an unexpected event. During such edge-case, I resort to the throttle in order to guarantee that the motor assistance kicks-in when I need it.

By contrast, the Panasonic/Yamaha pedelec control algorithm is probably more efficient due to the location of the motor (on the crank itself), and I hear that there are torque sensors as well as speed detectors.

So, with pedelec, I get rewarded by extra motor assistance when I pedal fast. In pure-throttle mode, I can keep the cadence low and manually adjust the power output to suit my needs. Which one do I prefer...I'm not sure yet.

My Sturmey Archer 3-speed hub requires a little flick of the pedal (quick jerk backwards) for changing gears down or up. It's not "smooth" and instant. Now, to keep the cadence up (and therefore request power assistance in pedelec mode) I must drop gears...unfortunately the small pedal kick I apply to change gear sometimes confuses the controller, which suddenly cuts power ! The controller takes one second (estimated) to "recover", before it starts feeding power again. Very annoying, especially when going up-hill. In this case, I much prefer overriding the pedelec sensor with some manual throttle control.

I enjoy not having to leave my thumb on the throttle in most cases (flat and moderate hills), but it looks like the sub-optimal pedelec system is more disturbing than helpful during serious hill-climb. I shall see as I pile-up more miles.

Cheers, Dan

 

[AndyOfTheSouth]

Dan - I must declare an interest. I am eager to see your analysis of the performance of the Bafang in a 26" wheel and that of the Tongxin in any!

 

[daniel.weck]

Dan - I must declare an interest. I am eager to see your analysis of the performance of the Bafang in a 26" wheel and that of the Tongxin in any!

Lacing the Bafang in a large wheel is a very tempting proposition, as this would make a pretty fast full-size e-bike indeed !

As for the Tongxin, I have no time to work on it for my Brompton until sometime in November/December.

Oh well, more time for cycling then !!

 

[daniel.weck]

Update about controller temperature

With the bike unused for several hours (well, just a quick unloaded spin to check the front wheel truing), but with the battery connected, the temperature inside the frame bag remained 10 Celsius degrees above the outside temp in my corridor. So, the controller-generated heat was a constant 30 degrees despite being inactive. Interesting. I have now disconnected the battery to see if the temperature finally drops. My assumption is that there might be a small current draw even though the motor is not running...but I could be wrong (the 30 degrees might have been generated by my unloaded test 30mn before I checked the temperature).

At any rate, this frame bag is a really good insulator ! The "electrics" smell inside it was pretty normal, nothing that I would worry about.

 

[daniel.weck]

With the bike unused for several hours (well, just a quick unloaded spin to check the front wheel truing), but with the battery connected, the temperature inside the frame bag remained 10 Celsius degrees above the outside temp in my corridor. So, the controller-generated heat was a constant 30 degrees despite being inactive. Interesting. I have now disconnected the battery to see if the temperature finally drops. My assumption is that there might be a small current draw even though the motor is not running...but I could be wrong (the 30 degrees might have been generated by my unloaded test 30mn before I checked the temperature).

At any rate, this frame bag is a really good insulator ! The "electrics" smell inside it was pretty normal, nothing that I would worry about.

I can now confirm that when the battery is plugged-in, the temperature of the controller inside the frame bag remains at approximately 30 Celsius degrees. It's only mildly hot to the touch, so it doesn't matter, but it means that some current is drawn from the battery. From now on, I will make sure to unplug the battery before going to bed

 

[didi28]

I measured at 40V 56mA standby current of the 3-switch-controller with all cables plugged in. This is about 2W. Enough to warm the controller in a good insulated bag.

 

[daniel.weck]

I measured at 40V 56mA standby current of the 3-switch-controller with all cables plugged in. This is about 2W. Enough to warm the controller in a good insulated bag.

Interesting. Thanks !

 

[daniel.weck]

I've plotted some riding statistics (using Mac OS X TrailRunner software) based on tracking data from my GPS receiver (Holux GPSlim 236) hooked-up via bluetooth to my Nokia N810 (Linux) running Maemo-Mapper.

I was using Pedelec (no throttle other than to kick-start from standing still).

Going down-hill:

Coming back using a different route:

I've tried a number of other mapping tools from this thread (it's fun !):

http://www.pedelecs.co.uk/forum/electric-bicycles/4623-online-cycle-mapping.html#post58596

The GPS innacuracies in the source GPX data are problematic but can be eliminated using a smoothing function in the software tool (my registered max speed is 104km/h otherwise !!). GPS-Babel does a good job at that too: GPSBabel 1.3.6: Chapter 4. Data Filters

I would still prefer to use a proper bike computer to cross-check the speed information deducted from GPS tracking.

Cheers, Dan

 

[daniel.weck]

I realized why the GPS data was messed-up in my previous tracking test: the receiver was in my pocket next to the device that connects via Bluetooth. There was obviously some interferences leading to crazy 100k/h spikes and bizarre off-road coordinates !

So, here's an update about a short hilly trip with a fully-loaded Brompton (I mean, *really* heavy, with shopping items front and rear):

Nearly 50 km/h going downhill, pedal cadence borderline out-of-control

EDIT: On my stock Brompton M6R+, 40km/h in the highest gear is achievable at 100rpm (50T chainring, 13T rear sprocket, 3-speed SRAM gear hub, 170mm crank, 16" 1-3/8 349mm wheel). At 120rpm, 48km/h is achievable (that's how fast I had to pedal in my downhill test, and it felt pretty uncomfortable indeed) --> Sheldon Brown's Bicycle Gear Calculator

The above elevation data is obtained from the GPS (not super reliable), so here's the curve after adjusting the altitude data based on ordnance maps:

 

[daniel.weck]

More interestingly, here is the ride uphill (respectable 15 km/h):

...and after fixing the elevation data:

 

[daniel.weck]

Oh, one thing to note: I was using pedelec mode (crank speed-sensor only, no torque sensing) and I am now starting to enjoy it. It's harder work than throttle-only because of having to find the right cadence (the choice of gear is important), but it's nice to just ride with the hand comfortably sitting on the handlebar or bar-ends. At any rate, it's a fantastic ride, and it really does flattens the hills

 

[jerrysimon]

Interesting Dan.

When you get to the supermarket do you take your Brompton in with you ? I am wondering (when) I get my Brompton if I can sling it in a trolley do my shopping and then get it out at the end to save the hassle/worry of locking it up outside.

Regards

Jerry

 

[daniel.weck]

Interesting Dan.

When I came back, my wife was asking me if I intend to produce GPS stats+diagrams everytime I go for a ride rolleyes: with rolling eyes in despair). I lied: I said no ... LOL, it'll get even worse when I order a Cycle Analyst for christmas: then I will add a current draw / consumption curve to the graphs

The truth is: I have a cold / sore throat at the moment, and I wouldn't even contemplate cycling up this hill if it was not for the fun of riding with the e-assistance. And now I just do it with a smile on my face and 10kg of shopping in the bags ! It's awesome !

When you get to the supermarket do you take your Brompton in with you ? I am wondering (when) I get my Brompton if I can sling it in a trolley do my shopping and then get it out at the end to save the hassle/worry of locking it up outside.

I take the rear-bag off the rack (battery) and put it in the trolley, along with the helmet and a bag of accessories (GPS devices, front/rear LED lights, riding glasses, yellow jacket, gloves etc.)

The front touring bag also goes in the trolley, fully-opened so I can load as I shop (to make sure I can actually carry everything once I leave the shop). I have 2 side pockets on the rack-luggage as well, so I can afford to overflow (which I did indeed).

The Brompton remains unfolded and is attached to the dedicated cycling area, with a cable-lock to secure the front wheel, and my trusty Abus Granit X-Plus 54 to secure the frame+rear wheel. The parking area is right in front of the main entrance, and it's a medium-size Tesco supermarket. I'm not worried about thieves to be honest.

I'm getting the hang of it now, undoing and fastening things is getting quicker by the day ! Setting-up the GPS tracking devices is what takes most of the time (Bluetooth, reset, etc.).

Cheers, Dan

 

[jerrysimon]

Thanks for the reply Dan.

Whats the view/thoughts on these

Garmin eTrex H Handheld GPS Navigator: Amazon.co.uk: Electronics & Photo

Or this

Garmin eTrex Venture HC Handheld GPS Navigator: Amazon.co.uk: Electronics & Photo

Or these even

Sat Nav GPS Digital Photo Frames, Portable DVD Players, In Dash DVD, In Dash GPS, Dual Sim Mobile Phones

Bet you can't wait for Santa to come lol

Regards

Jerry