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KMossman 10th February 2013 01:03 AM

electronic bikes
 
Wonder if we might discuss 'e-bikes'

Perhaps:

1 - modding the controller

2 - battery replacement

3 - charger replacement

4 - accessories

5 - brands


I have an e-bike - live in China - have some electronics background.

weltersys 10th February 2013 07:25 PM

1 Attachment(s)
Quote:

Originally Posted by KMossman (Post 3363340)
Wonder if we might discuss 'e-bikes'

Perhaps:
1 - modding the controller
2 - battery replacement
3 - charger replacement
4 - accessories
5 - brands
I have an e-bike - live in China - have some electronics background.

1) Generally the controller will be sized for the load and available power, adding heat sink area can allow more amperage to be used.
2) If you are presently using lead acid based batteries, going to LifP04 will be a huge upgrade. Very expensive, but considering the amount of charges they take, a better value than lead acid.
3) Lifpo4 are very sensitive to undercharge and overcharge, battery management systems should be employed to protect from over or undercharge conditions.
A charger specific to the battery type is required.
4) Accessories I plan to add are storage panniers.
5) I made my own:
Manufactured by Art Welter, Welter Systems Inc.
Motor: 24 Volt D.C. .8 horsepower American Lincoln Corporation
34 Amps, 1700 RPM, 50 Deg. Cent. Rating, Frame:56 5328D, Cat# 80059, Serial # 1063
Suspension and front wheel: 1977 Peugeot "motor driven cycle" number 768440
Front frame: Mountain bike
Rear wheel : Honda ATV
Rest of frame: 1/2 X1/16 square steel tube
Chain idler: Tracker skateboard truck with center channel machined, Peugeot chain guide
Gears: 13 tooth on motor, 60 tooth on rear wheel (55.5 inch circumference)
Curtis PMC 275 Amp Motor controller, model 1204-001
Batteries (Test runs): 4 PowerStar PS12-22W (12 volt AGM, 1 AH at 16.3 amp)
Batteries (Permanent): 2 GBS LFMP40Ah 8-packs (16 x 3.3 volts)
Bike lights run on 6 AA 1.5 volt batteries
Weight: 185 pounds, 70 front, 115 rear, AGM batteries 72 , motor 56
Weight: 163 pounds, 55 front, 108 rear, LiFePO4 batteries 52
Wheelbase: 49 inches
Length: 70 inches

Bike parts had previously been used on an electric trike built from 11/23/01 to 2/3/02, which took about 135 hours procuring materials, designing and building the frame.
The trike, weighing in at 550 pounds had to be geared for 5 mph going up the steep mountain hills to avoid burning the motor, the gear ratio only allowed a top speed of 15 MPH.
After it proved to be a road hazard, the electrical system was replaced with a pedal system for parade use.
After 10 years of parades hauling Santa playing a keyboard through loudspeakers, the trike was de-commissioned, frame cut out, and body put on top of a hill overlooking Madrid as a sculptural piece.

The electric bike was built from 11/10/12 to 12/1/12
It took 79.25 hours to design and get it operational, then another 32.5 to get it running smoothly.

Initially only two batteries in series were tried, but range was only 2.92 miles at around 12.5 MPH before the battery voltage sagged to the "limp mode", under 16 volts.
With 4 batteries, the speed was 15-25 MPH for 4.2 miles, voltage dropped to 47.8 (40% charge) recovering to 48.8v in an hour, more than 60% charge.

Climbing the hill to Wild Dog Road, a distance of 1.5 miles, voltage dropped from 50.6 to 48 @15 amps, then the amperage increased as the voltage dropped, by the top of the hill on the dirt road, the voltage had dropped to 19 @ 40 amps and speed was down to around 8 MPH.
Voltage recovered to 44 volts in a few minutes, but would sag again under load.

With the lack of hill climbing ability making the bike's range unusable in this mountainous region, decided to purchase two eight cell GBS 40 amp hour Lithium Ion Iron Phosphate (LiFePO4) batteries, costing $890 from EVolve Electrics, requiring a new charger and low voltage disconnect (LVD) costing an additional $188.
The batteries arrived in good condition, all cells between 3.29v and 3v on one pack, and even at 3.3 on the other, 26.3 and 26.4 pack voltage, 52.7 total, about 75% charged.

The battery research, covers, installation, charging, installing a speedometer and slow moving vehicle reflectors took another 38.5 hours from 12/7 to 12/20/12.

With the LiFePO4 pack put on 10.9 miles, up to Wild Dog Road, and down to Cerrillos and back. Cold ride, temperature around 32 degrees.
Popped the 60 amp breaker a few times, but at 19-20 MPH pulling about 40-45 amps uphill.
On the few flat parts of the road, it appears to draw just under 20 amps at about 21 MPH, par for the motor specifications and the gear ratio.
Down hill hit over 47 MPH, the CatEyeMate speedometer only goes to 47 :^).

Starting voltage was 52.8, immediately after the ride was 51.7, after about 1/2 hour voltage rose to 52. Next day brought up the level on three cells that were lower than the rest, started out with 52.3v, drove an additional 12.3 miles, for a total of 23.2 miles in 25 degree weather. Unfortunately, three cells had not been brought up quite enough to equal the others, and they dropped in voltage well below the others. Pack voltage dropped to a low of 34 climbing the hill back from Cerrillos, backing down on speed /amperage kept it around 40V, after the ride it was 44.1v, and rose to 46.37 in the next 75 minutes.

The chain was replaced with a heavy-duty BMX chain after another failure, then the front gear broke, so another cassette was fabricated using a 13 tooth front gear, taking another 9 hours between 12/22-31/12 including making an adapter to plug the charger in to the batteries, bringing the total hours of build time to 159.25.

On 1/11/13 the weather finally got slightly above freezing, the batteries were all individually topped off to 57.5 volts (3.59 each cell) and a 32.6 mile run was made at speeds of 17-25 mph. After checking battery voltage and finding it at around 51.2, (which I thought would be about a 50% charge), decided to ride fast, and did another 6.4 miles at 25-28 MPH, but then the voltage dropped rather instantly to the LVD point of around 40 volts, recovering to 43.58 volts, a total of 39 miles run in cold conditions. Perhaps a warm day on flat land could get mileage to the mid 40s.

So, unfortunately the bike won't make a round trip from Madrid to Santa Fe and back (50+miles) without opportunity charging there.
I'll be looking for outdoor AC outlets rather than adding more batteries ;).

KMossman 10th February 2013 09:46 PM

Quote:

Originally Posted by weltersys (Post 3364454)
So, unfortunately the bike won't make a round trip from Madrid to Santa Fe and back (50+miles) without opportunity charging there.
I'll be looking for outdoor AC outlets rather than adding more batteries ;).

TOTALLY fascinating read!

Thank you very much for sharing your experience in writing and photos!

sreten 10th February 2013 09:59 PM

Hi,

Are we talking about electrically assisted pedal
bicycles or electrically powered motorcycles ?

I'd guess the point of modding the controller
is the removal of the speed limiter for road
legal e-bicycles, but that is not difficult I
understand as off road models are not
limited in the speed they can assist.

rgds, sreten.

UK - a legal electric bicycle is supposed to
provide no assistance above 15mph, 24kph.

KMossman 10th February 2013 10:06 PM

Quote:

Originally Posted by weltersys (Post 3364454)

1) Generally the controller will be sized for the load and available power, adding heat sink area can allow more amperage to be used.

2) If you are presently using lead acid based batteries, going to LifP04 will be a huge upgrade. Very expensive, but considering the amount of charges they take, a better value than lead acid.

1 - anyone done any mods to the controller itself? Or replaced the controller?
The ones here seem to 'fade' at moderate speed - lots of kick at accelerating from a full stop, but rapidly lose dv/dt - if that makes any sense.

2 - I am quite surprised that Li type batteries.........work. I had assumed they would not be good at handling the initial current rush (when accelerating from a full stop). Do they react any differently?

KMossman 10th February 2013 10:14 PM

Quote:

Originally Posted by sreten (Post 3364656)
Hi,

a - Are we talking about electrically assisted pedal
bicycles or electrically powered motorcycles ?

b - I'd guess the point of modding the controller is the removal of the speed limiter for road legal e-bicycles,

c - UK - a legal electric bicycle is supposed to provide no assistance above 15mph, 24kph.

Here in China no-one really differentiates between the two; the lines are blurred: I would presume the key difference would be power and speed and stability[at higher speed]. Would the e-motorcycle would be, in Western terms, a 'proper' vehicle - not different, except in propulsion, than a regular motorcycle?

b - to me, yes

c - no-one in China really cares, though I would not be surprised to learn of such a statutory definition.

sreten 10th February 2013 10:53 PM

Quote:

Originally Posted by KMossman (Post 3364665)
1 - anyone done any mods to the controller itself? Or replaced the controller?
The ones here seem to 'fade' at moderate speed - lots of kick at accelerating
from a full stop, but rapidly lose dv/dt - if that makes any sense.

Hi,

I'm no expert but that would make sense for bottom of the market
wheel motors for export. As the RPM's build the motors back emf
builds up reducing the motors power output. Effectively they self
limit to the sort of legislation I referred to. If that is the case then
no basic mods to the controller will help, its inherent in the design.

AIUI the best electric bicycles are crank driven, with a full gearset
(hub gearing usually) to get round that that very basic limitation.

rgds, sreten.

KMossman 11th February 2013 12:02 AM

Quote:

Originally Posted by sreten (Post 3364715)
Hi,

I'm no expert ......... As the RPM's build the motors back emf
builds up reducing the motors power output.

AIUI the best electric bicycles are crank driven, with a full gearset
(hub gearing usually) to get round that that very basic limitation.
rgds, sreten.

I am VERY FAR from an expert.............Information about Hub Motors seems to be a very reference.

VERY few crank-driven e-bikes in China............wonder why! Can you say price?

KMossman 11th February 2013 12:10 AM

So the only [practical] way to increase [the top-end] speed is to change the motor?

weltersys 11th February 2013 10:24 PM

Quote:

Originally Posted by KMossman (Post 3364793)
So the only [practical] way to increase [the top-end] speed is to change the motor?

You can increase the voltage- doubling the voltage will generally double the RPM. However, just like speakers, too much average power will burn the motor windings.

My old motor was designed for industrial use, scrubbing floors all day, using 24 volts. Going to 48 volts doubles it's top speed and is no problem for short time periods, but if I tried to maintain that speed the motor would eventually burn out, and of course I could be busted for exceeding the moped 25 mph limit. I'd have to license and carry insurance as a motorcycle, while mopeds are street legal here without.

In response to your previous questions, LiFePO4 can provide as much as 10C (ten times the rated amp hour rating) for short bursts, making them great for "off the line" performance.

Your reference to controllers: "The ones here seem to 'fade' at moderate speed - lots of kick at accelerating from a full stop but rapidly lose dv/dt" could be a voltage control time constant kicking in to protect the motor (and controller) from burning up, or Peukert's law, the lead acid batteries recover voltage when the load is removed, but voltage drops again after a while when demand is close to the AH rating.

The "puke out" syndrome was exactly why I paid the big bucks for better batteries, LiFePO4 are almost immune to Peukert's law.

Art


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