Author Topic: Smart Pie Vector  (Read 9005 times)

Offline Thuktun

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Smart Pie Vector
« on: June 12, 2015, 10:45:22 AM »
I've been riding around with it for a few weeks now, time for a review.

I had wanted a motor on my bike for a while, and had been looking at the 902 but it was out of stock when I was ready to order so I got a Smart Pie Vector. I wasn't looking for a really powerful motor, I just wanted something to level out the hills and negate the headwinds. 40km/hr with gusts to 60 is regular here.

I ordered the rear wheel kit for a 700c wheel. I got a 36v throttle and a thumb throttle. The bike is a cheapo $200 Nakamura. I had a really nice mountain bike but was hit by a car on it a couple of years ago, I have taken just about everything useful that would fit off of it and put it on the Nakamura, handlebars, shifters, derailleurs, pedals...

The first couple of rides I did with what I had, 6 6v12Ah SLAs. It ran but seemed to have issues under heavy load. I then bought 3 12v10Ah SLAs. Much much much better. They can deliver 30A, much more then the 18 the SP needs. At 36v the SP did exactly what I expected it to, it rode at a respectable 25km/hr on it's own and did fine on hills and against the wind with me pedaling. Acceleration was a bit slow, and going up a hill from a dead stop was a no go without human power, but it was a good ride.

But like everyone does at some point I imagine, I got curious. I wired up 2 of the 6v SLAs to get 48v. Oh my, what a difference. Two days later I replaced them with another 12v 10Ah. Acceleration is still a bit slow, but much better then at 36v. Going up a hill without pedaling can be done if it isn't steep. I still have the controller set to factory defaults so if I open it up on level ground it will do 40km/hr. If you are wondering if the Smart Pie is powerful enough for you, it probably is.

The motor is completely silent, you'd never know it was there and unless I point it out to people, they don't even see it.

A few words about running on SLAs. Everywhere you look people say don't do it, they are too heavy. I pedaled from Toronto to Newfoundland with far more weight on my bike then it has now with only my legs for power. It isn't unmanageable, you just have to use your head. Avoid big bumps like rolling off curbs, going up them isn't so bad if you are going slow. Make sure the battery is well mounted. I have an ordinary bike rack only rated for 40lbs. I replaced the flimsy steel steel strips that connect the rack to the frame under the seat with pieces of aluminum tubing and I attached what used to be the handle of a luggage cart to the back of the rack and the fender mounting holes down by the wheel hub. The rack is rock solid now. The battery sits on a foam pad and is held down with bungees and nylon straps as backup. It vibrates but I don't feel it because the rack doesn't.  Same for minor bumps, it has just enough give to absorb the shock. The only time the weight is noticeable is when walking the bike or going up and down the steps at my front door, but I can lift it, unlike when I had my panniers on my trip. I do plan to switch to lithium power at some point, but being a diy type of guy I'll be making my own.

I charge them at work and at home, they are always in use, charging or full. At work I charge them in parallel at 12v 2A, so .5C. I work long days, they are done before my day is half over. At home I also charge in parallel but at usually higher rates. I usually leave the charger on auto and it charges between 1 and 2C. At the discharge rates and amounts I'm using with the charge rates and habits I am using these batteries should last their maximum cycles, much longer then I will need them for.

On the diy note, I made my own lights. The front light is made from a 1200 lumen flashlight. It flickers at a high rate using a simple circuit I threw together using the reverse breakdown voltage of a transistor as the trigger. There's a small box stuck up under the frame holding the circuit and a voltage regulator which steps down the power to the taillight which has a 555 timer based flash circuit built into it. I'm partial to bells over horns on bikes because they are instantly identifiable so I set about making a bicycle bell electric. In the end I went with an old school door/fire bell design made from a bike bell and an actuator I took out of an old photocopier. I save everything for making stuff out of, that's where the bits for the rack came from, my junk pile. The bell rings simply by breaking the circuit each time the magnet pulls it over. Took some experimenting with springs so it doesn't ding with every bump but it's good now. I mounted a digital voltmeter to the handlebars as a"fuel" gauge. Works perfectly.

I haven't reprogrammed the controller for a maximum 32km/hr because around here there are at least a dozen gas powered bicycles zipping around town. The police aren't bothering them, they probably won't even notice that my bike is powered anyway so I don't expect to be hassled. I rarely go the 40km/hr anyway, but I like having the option. There is a hill on my morning commute that I speed up before I hit.

Overall I'm very pleased with my decision to buy a motor. I think an SP would be more effective with a smaller wheel due to the increased torque, but it's more than good enough for my purposes. I don't pedal at all on my morning commute except half a stroke when moving from a dead stop, I'm too tired in the mornings lol. Going home I pedal along for most of the ride just for the exercise, I don't need to, the motor moves my 180lbs and the battery just fine.

Offline Thuktun

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Re: Smart Pie Vector
« Reply #1 on: June 12, 2015, 10:59:44 AM »
A few pics. You see the mods to the rack and the bell on the fork.

Offline Thuktun

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Re: Smart Pie Vector
« Reply #2 on: June 12, 2015, 11:07:27 AM »
More rack pics, the flimsy steel I removed. I used those crimp type hose clamps on the back because it was what I had with the plan to replace them with the screw type ASAP but I'm going to leave them as a safety valve of sorts. They should open up if under enough force rather then something else giving somewhere else. Maybe lol, depends on which direction the force goes.

Offline Thuktun

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Re: Smart Pie Vector
« Reply #3 on: June 12, 2015, 11:13:01 AM »
Left out the battery box. It's made of foam board and vinyl tape. I got several rolls of that yellow and black stuff really cheap, that's the only reason I used it. It has a 30A fuse in there but not switches yet, I have to manually plug in it. There are 2 leads on the positive line, one has a resistor to limit current when connecting to the motor. I have switches on order, you can't buy squat here locally if you go to a job every day. I'm going to make a new box once they arrive.

Offline Bikemad

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Re: Smart Pie Vector
« Reply #4 on: June 12, 2015, 11:49:09 AM »
It's good to see you've sorted the controller and have the bike back in action again.

At work I charge them in parallel at 12v 2A, so .5C. I work long days, they are done before my day is half over.

I'm puzzled as to where you get the ".5C" figure from, as three 10Ah batteries in parallel is 30Ah (and four in parallel would be 40Ah) so a 2A charger would effectively be charging three batteries at 0.067C which would take almost 15 hours to completely recharge if fully depleted (or four batteries at 0.05C would take 20 hours.)

I'm amazed it recharges fully before your "day is half over" considering that "it's mostly uphill", you have to contend with "a 40km/hr headwind pretty much every day" and you "don't pedal at all on my morning commute except half a stroke when moving from a dead stop".

I can only presume that you don't have to travel too far to go to work or you must work exceptionally long days. ;)

Alan
 

Offline Thuktun

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Re: Smart Pie Vector
« Reply #5 on: June 12, 2015, 02:59:22 PM »
Isn't 40Ah at 2A .5C? If 10Ah at 1A is 1C it should be.

I don't have a long ride, about 6kms, and I work at least 11 hours every day, so both. :)

Offline Bikemad

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Re: Smart Pie Vector
« Reply #6 on: June 12, 2015, 04:18:59 PM »
Isn't 40Ah at 2A .5C? If 10Ah at 1A is 1C it should be.

If 10Ah at 1A was 1C then it would be, but 10Ah at 1A is only 0.1C (1A/10Ah = 0.1C, 10Ah at 10A would be 1C)

The "C" is used to represent the battery's charging and discharging capability, so if a 10Ah battery has a charge rating of 0.5C , it can safely be charged at up to 5 Amps (0.5 x 10A). My 5Ah LiPo packs have a maximum continuous discharge of 20C and a peak discharge of 30C, which means they can output up to 100 Amps continuously (20C x 5Ah) and a peak current of 150 Amps (30C x 5 Ah) but only for 20 seconds bursts. The maximum recommended charge current for these packs is 5C (25 Amps).

Quote from: batteryuniversity.com/
Smaller batteries are rated at a 1C discharge rate. Due to sluggish behavior, lead acid is rated at 0.2C (5h) and 0.05C (20h).

The Ah rating of most lead acid batteries is based on a 20 hour discharge (0.05C) so a fully charged 10Ah lead acid battery should theoretically discharge at the rate of 0.5 Amp (0.05C) continuously for 20 hours.

Unlike a 10Ah lithium battery (which will typically deliver 10 Amps continuously for ~1 hour) most 10Ah lead acid batteries will not deliver their stated capacity of 10 Amps for anywhere near an hour, in reality you'd be lucky to get ~35 minutes from a lead acid battery when discharging it continuously at a rate of 1C, which only allows around 5.8Ah capacity to be realised instead of the expected 10Ah.

The size and weight is not the only reason why people prefer Lithium over lead acid.

Once you have become used to the power, size and weight advantages of lithium, it would be very difficult to go back to lead acid again. A bit like swapping from a young thoroughbred race horse back to an old retired shire horse.
 
Alan
 

Offline Thuktun

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Re: Smart Pie Vector
« Reply #7 on: June 13, 2015, 07:24:06 PM »
Hey they get me from a to B with minimum hassle and cost. Good enough for me. :)

Offline Thuktun

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Re: Smart Pie Vector
« Reply #8 on: June 13, 2015, 07:56:00 PM »
The data sheet for these batteries says they can be charged at up to 3C. So you are saying I can charge them at 30A of current safely? My understanding of C rating is it's 1/10 of capacity. That's how I've seen it explained everywhere else. Guess they are wrong or I'm reading it incorrectly.

Offline Bikemad

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Re: Smart Pie Vector
« Reply #9 on: June 13, 2015, 09:35:20 PM »
3C sounds much too high for the charging rate of a lead acid battery. Are you sure it isn't ".3C" or "C/3" or perhaps a discharge rate of 3C?

Quote from: http://web.mit.edu/evt/summary_battery_specifications.pdf
A C-rate is a measure of the rate at which a battery is discharged relative to its maximum capacity. A 1C rate means that the discharge current will discharge the entire battery in 1 hour. For a battery with a capacity of 100 Amp-hrs, this equates to a discharge current of 100 Amps. A 5C rate for this battery would be 500 Amps, and a C/2 rate would be 50 Amps.

If you look closely at the attached picture of a typical 12V 10Ah lead acid battery, you will see that the maximum charge rate is 3 Amps (0.3C).
You should also notice the 10Ah/20hr rating of this battery which means the 10Ah rating is actually derived from a 20 hour discharge test at C/20 or 0.05C.

The ā€œCā€ rating refers to the total capacity of the battery in terms of Ampere-hour (Ah) and is a rating of how quickly energy can be discharged from a battery, and is often used to indicate the rate at which the battery can be recharged as well.
Typically, the discharge "C" rating (the one commonly shown on the battery) will be much higher than the recharge "C" rating.

I hope that after reading this that some of it will make more sense to you.



Alan
 
« Last Edit: July 02, 2017, 10:26:05 PM by Bikemad »

Offline Ron

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Re: Smart Pie Vector
« Reply #10 on: June 14, 2015, 04:05:15 PM »
I would like to know how all the weight of  the lead acid batteries effects the handling of the bike?  I built a box that fits in the bike triangle to house my 44v 15AH lipo pack.  The pack weighs in at almost 5kgs.  It sure would have been easier to throw them on a rear rack but I had read that the bike would handle better with the battery weight further forward.  I must admit I don't notice any adverse handling from having the battery packs in the middle of the bike.

Offline Hastings

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Re: Smart Pie Vector
« Reply #11 on: June 15, 2015, 07:54:02 AM »
I have a total built weight of 9 kg to the rear including metal box. I can ride but have low pressure on the front wheel as well as numerous breakages of the support rack in ALU. I used Stainless an spot welds that cracked over time . giving the bike a slithering movement on cornering that was preferable to when it was fixed... For my next built (delayed by divorce...) I am planning on a split battery inside the  frame triangle

Offline Ron

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Re: Smart Pie Vector
« Reply #12 on: June 15, 2015, 04:28:04 PM »
Hi Hastings, Thanks for the feedback.  Sounds like putting the batteries forward and as low as possible is the answer then.


@Thuktun, hope you got your battery charging straightened out.