I am really new at this. I just bought a used Giant La Free from which the battery pack had been stolen. I'd like to get one of the newer technology batteries, but I don't even know why there are 3 spades at the bottom of the battery bay for a dc system. I suspect it has something to do with monitoring the charge.
I'd like to modify this so I can help it get farther and faster. The chainwheel in the front is really small. I'm a cyclist and I'm perfectly happy pedaling myself at 20 mph. I'm hoping that I can use the effort of pedaling at about 15 mph to go maybe 30 for as long as possible, but I will have to do some modifications to even get a larger chainwheel to fit.
Any ideas, thoughts, experiences with a La Free would be helpful and much appreciated.
Hurm... http://www.batee.com/projectsanddesigns/offgrid/ebike/lafree/index.shtml
It seems the LaFree is no longer sold by Giant. Anyway the above has some discussion of the battery. They don't have a good explanation of why there's three connections on the battery connector, but do explain which are the + and - and that's the important part.
It's clear the battery is meant to be 2x 12v 12ah batteries. These are readily available. I would recommend looking on eBay for a battery seller PingBattery.. http://stores.ebay.com/PingBattery_W0QQssPageNameZstrkQ3amefsxQ3asstQQtZkm ... I have a 24v10ah pack from him and it's almost exactly the size of one 12v12ah SLA battery. I see on eBay right now he has a 24v20ah pack listed and these should be repackagable so it will fit into a battery tray meant to hold 2x 12v 12ah batteries. This battery will give lots more amp-hours hence lots more range, at less weight.
You're expecting to do 15mph worth of pedaling and have the motor oomph that up to 30mph? Hm, I've never seen it work out that way. In fact I don't think it can work that. Speed is based on wheel radius and RPM, where the number of revolutions of the wheel and the radius of the wheel directly determine how far the wheel rolls in a given unit of time, hence the speed. If your legs make the wheels go at a given RPM (a given speed) and the motor can also make the wheels go at a given RPM .. well, the two RPM's do not add up. I have seen some electric bicycles with a very large chainring which I assume is meant to help the rider maintain high speeds.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
I understand basic physics. What I don't understand is how the pedal assist system works. There is a sensor and magnet wheel on the rear wheel. the drive system does not drive the wheel, it drives the chain wheel. So if a speed sensor can be over-ridden, the motor shouldn't care how fast the road wheels are turning, but only how fast the chainwheel is turning. Or so it seems theoretically to me. Therefore a larger chainwheel that is more in line with the drive on a regular bike, should allow a pedal assist to go farther and faster with more effort supplied by the human. Am I wrong?
The new Giant has a larger chainwheel and an advertised range of 70 miles in economy mode, whatever that is. I think I saw something about a regen system also. And it is running li-ion batteries. But it still probably has the mandated speed restriction. And it costs $2200 which is more than $2000 more than I paid for my project bike and I'm not interested in laying out a ton of money for something that is just going to be fun.
I'd just like to see what the real potential is for this thing with the combination of an electric drive and a strong human.
Okay.. wasn't sure. It's a matter of physics as you say that c turns on the chainring becomes w turns on the rear wheel, and that the gear ratio is what determines the result. Well, that and Torque (or HP depending on how you wish to describe it).
I was just trying to understand this over the weekend and have a beginners grasp. The book I'm reading is Build your own Electric Vehicle and it goes into the physics showing how to calculate the desired gear ratio, but the stumper I have at the moment understanding the equations is the value for Torque.
Speed_of_vehicle = (RPM_motor * 60) / (gear_ratio * revolutions_per_mile)
gear_ratio = rpm_motor / rpm_wheel
wheel_rpm = (mph * revolutions_per_mile) / 60
Reading a little in the book I see .. if you have a desired mph, then with a given wheel size that gives you a wheel_rpm. Then based on your gear_ratio the wheel_rpm gives you a motor_rpm so if you have a motor with a given motor_rpm then you need a gear_ratio which gives you the wheel_rpm required for your desired speed.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
My heart's not set on a certain speed, though I guess I gave that impression. My goal really is to find out what this thing can really do. The thing I really like about this system that sets it apart from so many others, is that the motor drives the chainring as opposed to directly driving a wheel. So as I gear up through the derailleur/transmission I can maintain a lower rpm on the motor. I have a lot of bike parts and I can see how a regular bike crank will fit on the spindle, but the chainline is going to be outside the design limits and it might be hard to keep a chain on. With the size of the oem chainring it's clear that this was designed for people that don't like to pedal.
I think I'll be doing my own experimenting from the mechanics end. Where I'm really going to need help is from the electronics end. If I step up to say a 36v 20AH battery, will I lose the use of the oem monitoring system? If I leave this hooked up will it just burn out? How do I overide the rear wheel rpm sensor? How fragile are the motors and controllers on these things? How bad an idea is it to up the voltage by 50%?
I can experiment with bench testing this with batteries that I already have, but I would like to know what that 3rd spade is for?
I don't know what the specifics of the OEM monitoring system are. But given it was designed for a 24v battery .. e.g. if there is a battery "full" gauge it's going to read incorrect if the battery is 36v when it expected 24v.
On my Charger bicycle I totally ripped out the OEM controller and replaced it with a different one. But that's partly because I uh accidently destroyed the OEM controller. It's not terribly hard to replace the OEM controller with other ones. Well it's easy if the motor is a brushed motor, if it is a brushless then things do become hard because the connection to the motor is more complex. A brushed motor has two connectors (pos and neg) but a brushless motor has more, and since I've never played with a brushless motor it'll have to be for someone else to discuss how to work with it.
Motors tend to be very forgiving about being overvolted. It's possible to overvolt too far and burn up the motor.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Upon closer inspection and with some new information I can see that I was way off on my assessment of the primary drive. The reason the chainwheel is so small is that there is an internal transmission between it and the crank, so 1 revolution of the crank turns the 21 tooth chainwheel 3 times - equal to a 63 tooth direct drive. It looks like a 30 tooth chainwheel might fit which would give me a 90 tooth effective primary drive which should up my human input into the system considerably.
This is going to be fun!!
I have two of these Giant LaFree's.
The first one I added a Ping 24V 20Ah LiFe battery to. Top speed is 22 MPH (I can easily maintain this speed) with assist, as you get closer to 22 MPH the assist backs off and you are left doing all the work over 22 MPH. The battery pack and charger were $350.00 from Ping. I had to add a 26 gauge wire to the shunt to keep the pack from cutting out. The longest ride I had been on with this pack was 28 miles (the SLA are good for like 15 miles), mostly flat with couple of small hills and one quarter mile long steep hill. I still had juice left after the ride. The gears make for awesome climbing power, took the bike off road and was able to climb hills at a few MPH's which would normally just cause me to spin the back tire or pop a wheelie.
The second LaFree is a woman's bike that I cut the front half off of and adapted a full suspension bike to. I tried out different voltages on this bike. 24, 36 and 48 of SLA batteries. 24V was to give me a baseline with SLA, it was a little weaker then the LiFe at 24V on my other bike. 36V was a nice upgrade in power, top speed was just over 25 MPH with assist. At 48V there was another jump in power, top speed was about 32 MPH with assist. 48V made the motor get warm after a couple of full power runs, makes me think I would have to adapt a fan to make it reliable. Right now I'm thinking I will just go with a 36V 20AH LiFe from Ping. That should put me up around 27 to 28 MPH with pedaling. This seems like it would be a good speed for most of the city streets I ride on. Can not really get going that much faster as the stop sign spacing keeps my speed down.
The bikes have a pretty sophisticated computer on them. There is the throttle, torque sensor on the crank, brake cut off switches, wheel movement sensor, diagnosis ability, low battery power conservation, beginning battery voltage reset.
I really like the bike a lot, I'm betting it's one of the best built bikes out there and driving through the gears allows the rider to keep the motor in it's peak torque range for acceleration and hill climbing.
Deron.
Also on the bike I ran at the higher voltages, I removed all the stock electronics. I just used a heavy duty push button and started pedaling and pushed the button. All of the electronics are for safety, battery longevity and a little more control. You can get away without using them. The LiFe batteries have their own management system. I use full throttle all the time so a controller to me is just going to waste valuable battery power. I might add cut off switches on the brakes, a thermal overload on the motor, a keyed cut off and a fuse.
Deron.
Well I won a bid on a 36v 20ah ping lifepo4 so I'm looking for a 36v controller. Will I need a 36v throttle also or will the stock 24v throttle work OK? What controllers do people like and recommend? I don't think I'll be burning around at full throttle all the time, but I don't know yet. My idea is to input as much human power as is needed to achieve max efficiency. I've pedaled this around as a bicycle and I still think the gearing is low compared to my roadbike at 53x12, but I'll wait till I get the battery installed and working before I start working on further mods. There's not a lot of great biking in the high mountains of Colorado in the winter, so I should have plenty of time.
Terry
The motor uses 24 volts, the computer runs on 12 volts. Thats why there's three spades coming into the bottom of the battery box. One ground or common, one 12v take off, and one 24 v.
The standard battery pack is 2x12v batteries in series to make 24 volts so it's easy to take 12v off of one battery. Using more voltage would kill the computer so users who've modified LaFree's that way have bypassed the brains.
Have a Lafree sport, center terminal is labeled Common, it is a serial communications link to the controller from a TI BQ2013a battery gauge. The IC is on the small circuit board on the bottom of the battery pack. Mine has a problem, with batteries fully charged, controller doesn't like what it gets back from the gauge and goes into error, 2 beeps, 5 led's flash once a second. If let bike sit for while, turn it on, works fine, data controller to/from gauge once a second. Have found out Lafree had at least 3 revisions of this small board. Anyone have one? Or has fixed this problem?
We also the same problem with our lafree. It doesn't seem to be in the battery pack, because when we change battery backs with another lafree the problem is only in the one bike. Must be in the computer. Any help on solving this problem?
I have a LaFree Sport and I am also having the identical problem as above. When I turn on the key, the bike beeps two times and the 5 LED’s start flashing every second. I administered the on-board five point self diagnostic check of the electronic features and all items passed.
I have called Giant, NYCE Wheels, and Electric Bikes Northwest and they told me to replace the batteries, which I did and the problem still persist. There is even a Yahoo UK blog under "lafreeowner" which recently posed the same question.
The bike was purchased new in 2001 and I have had many enjoyable times riding it, never having a problem. Such a wonderful bike, it would be a shame to have it sit and gather dust.
Your help is greatly appreciated...
I have had my Giant La Free for at least 8 years, and it had the same problem described above. The problem on mine was fixed by an electrician at work - it was all caused by the middle spade connection being too loose (battery pack - bike). He cleaned up the connector and used a small tool to bend the metal inside the connector on the battery pack to make a tighter connection. That fixed the problem for about 4 months or so, then it came back. I re-tightened the connection and it worked again (current status). If this problem comes back, I'm going to put in a separate wire and bypass that connection altogether.
Also, I had a question for anyone who has converted to Lithium battery pack - can you describe the wiring needed to accommodate the new pack? Or, do you just bypass the bike's wiring altogether and just connect the new battery pack directly to the motor?
Thanks.
Mike