Bike Converters

It seems that the battery capacity has decreased

2010-07-01T23:06:00.004+02:00

After several weeks not using the E-Bike, we have discovered an (aparent) important lost of capacity in the battery.

The logical hypothesis is that the cells are unpaired.
This means than the 16 serial battery needed to give the nominal 48 volts have diferrent electric charge.
Then when we discharge (using the bike) the battery:
a) When the cell less charged arrives to the minimum admited voltage. The BMS (battery management system) cuts the power. But there are still cells with near 50% of residual charge.
b) When we recharge the battery, the cell with more charge arrives to the maximum admited voltage. The BMS cuts the power. But there are still cells charged near of the 50% of its capacity.

But this 'never-end loop' has a solution:
The battery charger during the charging process gives a current of 2.6A but it really doesn't cut totally when the most charged cell reaches the max cell voltage. Then it just gives a standby current near 0.085A.
This means that this standby current doesn't overheat the already loaded cells, but let the not full charged cells arrive to be loaded. This process will pair again the cells.

What is the problem:
This is a slow process for a 20AH battery. If our battery has some cell charged at 50% of the other, this means that we will need to recharge 10AH with a source of 0.085A.
In other word we'll need 117hours (near 5 days) to finish the process.
By now we have recovered 2.5A, we will need to be patient.

Lesson learned: If you don't use the E-Bike for a long time, connect the charger at least 24h every 2 weeks ;)

BMS example:
http://www.conhismotor.com/ProductShow.asp?id=132

Some pictures of our first prototype

2009-12-06T02:24:00.003+01:00

Until we get the necessary torque arms for the new bike with front wheel motor (the wheel jumps off the fork every time we accelerate) here you have some pictures:

From the Volttour me eting (http://www.volttour.net)

And from the Mussara and Albiol trips:

First tests with the 500W motor

2009-11-02T22:23:00.004+01:00

From our friend XaviTa:

Saturday night (everyone has a different sense of party) I mounted the electrical kit in my wife's bicycle and I gave a tour... 3am till 3'30am...
Sunday morning I decided to go breakfast's 'Croissants' shopping to Cànoves, 5 km from home... no pedaling at all... came back at around 50km/h!!!
When arriving home something made me a kind of 'Castanyada flight'... scratches on knee, hands... that's what R&D is, isn't it?

I'm really glad to say it's heaven!!!!!!
The only thing is the battery weight... 9.5kg on shoulders... the motor, 48V 500W, needs 15A...

I don't really know how the front wheel went out of the frame... dangerous!!!
Fuse wire solder melted, needs to be rewired assuring good contact.
Battery wire was pretty hot (good for in-jacket heating?).
Pay attention to front traction wheel in slippery track.
Internal motor friction is quite high... investigate.

Spare 20A fuses or change for DC magnetothermal protection.
Concentrate wires in a single connector. (maybe iron frame could do negative path, to 'save' one or more wires)
Mount back solid rack for batteries, too heavy in a backpack.
Mount regenerative controller.
Buy confortable seat with suspension as 50km could become long!
Use full suspension bicycle as motor/battery weight reduces quite a lot comfort.

Ideal: 48V, 1kW motor, 15A 4kg or less batteries, boost converter (from 24V to 48V) with current limitter (battery protection).

Other: Mount traction on a back trailer instead of bicycle.

500W Kit received

2009-10-27T13:38:00.007+01:00

We have just received the 48V500W kit. This time, it took about 25 days, from China to Spain.

Battery 48V, 15Ah, LiFePO4, 9.5Kg, 31cm x 15cm x 15cm. Charge at arrival 52.7V.

Battery bag. Much better quality than previous one, but still too small (Battery doesn't fit inside), so it's useless.

Regenerative Controller

EValbum.com

2009-10-24T12:32:00.001+02:00

We have added our bike in EV Photo Album (great page where you can find details of over 2600 electric vehicles):
http://www.evalbum.com/2954

Performance of the first kit

2009-10-15T23:05:00.002+02:00

After several months using the bike, we can sum up the main features:

Maximum Speed: about 50km/h (downhill, I've seen 58km/h ;)
Range: from 50km (at full speed without pedalling) to 75km (pedalling)
Charge time (with 3A charger): 7 hours

We have ordered 3 new kits

2009-10-15T22:58:00.004+02:00

After the great experience with the 1000W motor with 48V20Ah battery and regenerative controller, we have ordered:

Another 1000W motor for the front wheel (yes, we will try with 2 motors in the same bike ;)
A 250W kit with 36V 10Ah battery (LiFePO4), we want to see how a street legal version performs.
A 500W kit with 48V 15Ah battery (LiFePO4), we want to try this battery with the 1000W motor, too.

Installing the Regenerative Controller

2009-10-05T00:18:00.002+02:00

The only documentation that came with the regenerative controller was a sheet of paper written in Chinese, so we requested some info in English to the seller. This is what we received: http://dl.getdropbox.com/u/367893/Regenerative%20Braking%20Controllers.doc

There are several differences between the connectors of the Standard Controller and this one:

no input for the Pedelec Sensor (not a problem as we don't use it).
no input for the On-Off switch (button in the throttle). Instead, there are two orange wires (connector 2 in the document) for the same function.
there are 2 additional connectors (number 10) to supply an external alarm device (we haven't tried it yet).
there are 2 blue wires (number 3) needed when installing the controller for the first time.
there are 2 white wires (number 5) to activate the Cruise Control function.

First, we have connected all the wires excepting for number 5 (Cruise Control). The motor should turn in one direction (forward or backwards) and each time the throttle is pushed, the wheel should turn in the opposite direction. In our case, this was not happening. It was always running forward, but with some noise, low torque and the controller and wires were very hot. After connecting and disconnecting everything several times, we saw the expected behaviour. Then, we disconnected the blue wires (just after the motor was going forward), to keep the configuration.

Regeneration starts only when the brake levers are pressed. The braking caused by the motor is quite powerful, but not excessive. Actually, the original brakes of the bike were not powerful enough due to the increase in weight and speed, and the regenerative braking is a great help. In fact, most of the time, we don't even use the brake pads. We just push a brake lever slightly, so that the regeneration kicks in and stops the bike quite quickly.

The Cruise Control function is great. If the throttle is fixed for 8 seconds, then it can be released and the power is maintained until the brakes are used. The only problem is to keep the thumb throttle completely still for 8 seconds. Any vibration or slight movement is detected.

To sum up, the Regenerative Controller is highly recommended: it helps braking, and recharges the battery noticeably (we are now taking some measurements).

LogBook and Gauge tuning

2009-10-04T23:57:00.004+02:00

Here we have a report to show how the bike is working.
We've made a basic correlation to have an idea of the residual energy.
We've also tried to check the energy loaded to validate the estimation.

This is the link to the document: EBike.logbook

We also detected that the gauge was not adjusted for our battery.
It seems that our battery produces 90% of the energy between 54V to 51.5Volts.

But the green and orange LEDs were ON even when the battery was discharged (below 51V). The gauge was probably designed to detect voltages from 43V to 49V, not for a LiFePO4 battery pack.

We've slightly modified the circuit:
1st) A 5.1 zener diode has been added to make the green LED switch off at 53.2V
-> Now it indiacates that there is more than 66% of energy left.
2nd) For the orange LED it has been a bit more complex.
A TL431 chip turns on the LED when the voltage in reference pin is over 2.5V.
Originally this pin had a voltage divider with 3 resistors: 100K + 5600 + 590 (ohms). The comparison voltage was fixed too low. We have shortcircuited the 590 ohms resistor, and now the comparison voltage has increased to 52.3V.
-> Now it indicates that there is more than 33% of energy left.

The references are approximate, and visible when you release the throttle.

New connector for the Regenerative Controller

2009-10-04T23:37:00.004+02:00

We have a second regenerative controller.
This one has been tuned up: the original bike wiring has been concentrated into a DB37 connector to simplify the connections.

Now we have only a connector to the battery and a second connector to the bike.

This is the pin-out that we have adopted:

Standard Controller

2009-10-04T23:29:00.003+02:00

David, this is the picture of the standard controller.
If you need more info, let us know.

Some wires have overheated

2009-08-14T19:55:00.004+02:00

After riding the bike for 15-20 minutes (at full power most of the time), I've noticed some heat under my ass. I've stopped and seen that some wires were very hot, and that the fuse cover was melting. The fuse cover was close to the battery pack, so the tape around the battery pack has been sligthly damaged, too...

Still analyzing the root cause, but it seems that the wires (that actually came with this 20Ah battery) are too small and we should install bigger ones (more section). But the battery should come with proper wires, shouldn't it?

Pedelec sensor not recommended

2009-08-14T00:03:00.003+02:00

After some trials with the Pedelec sensor, I do not recommend it (at least the one I tried).

I found two main drawbacks:

- First of all, it's not a progressive system. I thought that the faster you pedaled the more power the motor would supply. But, it's not like this. If you move the pedals (no matter how slow), you have full power from the beginning (there is a 1 second delay). If you stop pedalling, the motor stops completely (with a 2 second delay). This is not a good thing when it comes to comfort and battery life.

- It takes about 2 seconds for the motor to stop once you have stopped pedaling. This is really dangerous with a 1KW motor. It has some delay (about 1 second) when starting pedaling, too, but this is not really a problem (you get use to it easily).

To sum up, I was really disappointed with the Pedelec system. It needs lots of improvements (we may develop our own Pedelec system in the future).

Installing the Pedelec sensor

2009-08-13T22:56:00.022+02:00

Thumb throttle works perfectly.

Now, we want to try the Electrical assisted pedaling using the Pedelec sensor.

It consists of a disk with 5 magnets and a sensor to detect the movement.

I was not able to remove the pedal until I used an extractor.

The sensor (with the plastic side looking outwards) is fixed with the shaft nut (which needs to be removed first).

Then the disk with the magnets is inserted in the axle. But, surprisingly, the sensor detects the direction of the movement, so the disk has to be inserted as in the picture below. Be careful with this, otherwise, the motor will start only if you pedal backwards (which is funny, by the way).

Finally a picture of the sensor and disk properly installed.

Some pictures

2009-08-04T23:10:00.008+02:00

Motor in rear wheel with only one gear.

Regenerative controller (the one with a label) versus regular controller.

Battery pack (48V 20Ah) with Battery Monitoring System (blue). Size is 31 x 14 x 18 (cm). Around 10 Kg.

Battery pack, regenerative controller and battery charger.

Charging the battery pack for the first time.

Interesting links

2009-07-31T09:30:00.002+02:00

http://www.electricbicycleworldtour.com/en/

http://www.ev-network.org

Battery pack received

2009-07-29T01:08:00.003+02:00

On Tuesday July 28th we have received the battery pack (48V) and the charger.

It has taken 15 days, but it was actually shipped 3 days after the kit, so shippments from Shanghai to Spain take around 10-12 days.

The material seems to be in perfect condition. The battery voltage is 53 Volts, so we decided not to charge it before using it.
The only drawback is that the battery pack does not fit in the bag that was provided with the kit. I guess the bag is thought for the 10 or 15Ah battery pack, not for ours (20Ah).

The wheel was already mounted, so we have connected all the wires and needed components (brake levers, thumb throttle, regular controller) and the battery pack, and have switched it on for the first time.
It works perfectly! And how powerful the motor is! It's virtually impossible to stop the wheel, even with the whole weight of our body.
You should have seen the EV grin in our faces... (EV stands for Electric Vehicle).

But a lot of things are still pending: looking for a proper way to hold the 11kg battery, trying out the pedelec sensor, trying out the regenerative controller, ...

We are having fun!

Disassembling the gear bearings

2009-07-29T00:43:00.003+02:00

Once we got the tool to unscrew the gears from the wheel (picture), we confirmed that the bearings were completely damaged.

We couldn't find a set of 5 gears (as the original one) to replace the damaged one. We've only found sets with 6, 7, 8 or even 9 gears, but they wouldn't fit because they are wider. So we have finally mounted 1 gear only.

It's quite strange to see a mountain bike with only one gear in the rear wheel, but this is what we have right now.

Next surprise: the gear we have mounted is wider than the chain. Did you know that bike gears are available in different widths? Neither did we. We are actually asking ourselves if we really got a bicycle gear... Anyways, the width of a gear is nothing that a miter radial saw cannot reduce...

After some hard work, finally the wheel fits in the bike (and the chain in the gear;)

Just waiting for the battery, now.

How a brushless motor works.

2009-07-27T20:44:00.003+02:00

This is a good document that explains how a brushless motor works and how to design a sensorless driver.
Despite our driver is a conventional driver, with several extra wires, this document gives a good description of the motors used in electric bikes.
http://spsis.com.ar/electronica/back_emf_tesis.pdf

Material received

2009-07-26T13:13:00.001+02:00

On Thursday July 23th, we have received the kit: rear wheel (26'') with electric motor and 5 gears, 2 controllers (regular and regenerative), thumb throttle, pedelec sensor, brake levers, and a bag to carry the battery and the controller).
It has taken 10 days. Not bad.
Everything seemed to be in perfect condition, but when we have started assembling the components, we have had two problems. One is a small issue, but the other one is a show-stopper:

The rear wheel, when mounted, was not exactly centered. It was slightly shifted to the left (the gears are on the right hand side), so it was not possible to mount the rear brake (the left pad was always in contact with the wheel). We have been able to solve this problem (at least partially) by smooting out the hole that holds the wheel axis.
The big problem is that there is something wrong with the gear bearings: the gears are stuck to the wheel. So, the only way to ride the bike is not to stop pedalling (not very nice in an electric bike, by the way). We need now an special tool to disassemble the gears... Damn!

Following the shippment

2009-07-14T23:48:00.003+02:00

Today, I got the confirmation that the kit (without the battery pack) has been shipped.
However, it seems I'll have to wait some more days to get the battery pack. This is their explanation: "because this month we have a lot of battery order,so the battery need waite some days send to you".

Material already ordered

2009-07-13T00:26:00.003+02:00

Finally, we have ordered the following material from an ebayer (daoji666):

1000W 48V Electric Bicycle kit with 26'' rear wheel (5 gears) and thumb throttle.
Pedelec sensor.
48V Regenerative braking controller.
48V 20AH LiFePO4 battery.
LiFePO4 48V battery charger.

About $800 including shippment (from China to Spain).

Can't wait...

Learning about batteries

2009-07-11T13:23:00.002+02:00

We have taken the decision to get the 48V 1000W motor, so now, we need a 48V battery pack.
There are several options, between 10Ah and 20Ah, and two main technologies:

LiMn2O4 (Lithium Ion Manganese Oxide): 3,7V cell. Recommended for up to 15Ah.
LiFePO4 (Lithium Iron Phosphate): More expensive. Recommended for more than 15Ah. Flat discharge curve. 3,2V cell.

We have decided to take the big one (LiFePO4 48V 20Ah), so that if we add a second motor (front wheel), we don't need a second battery pack.

Twist throttle or thumb throttle?

2009-07-08T00:13:00.011+02:00

This is another decision we have to take before ordering the kit.

My bicycle already has a twist gear shifter, so we'll need to choose the thumb throttle.

Wheel size

2009-07-07T23:06:00.007+02:00

First step is to check the size of the bicycle wheels to know which kit to order.
It's not as simple as it sounds. I've measured the diameter of the wheel (including tire): 64cm = 25,2''.
Kits are available for: 10", 16", 18", 20", 24", 26", 700C, 28". Mmmmm, not maching...
I take again the wheel, and on the tire I can read: 26 x 2.00 (54 - 559).
Well, it looks like it is a 26'', but now, I want to understand the meaning of all the numbers.
Thanks to http://www.sheldonbrown.com/tire-sizing.html I've learnt that:

26: diameter code of the wheel (including tire), in inches. In the past, 26'' wheels were 26'', but nowadays, there are many variants of 26'' rims and tires, and you can even find 26'' wheels that are less than 25'' in reality. I understand now why my 26'' wheel is actually 25,2''...

2.00: width code of the tire, in inches.

54: width of inflated tire, in centimeters.

559: ISO Bead Seat Diameter (see picture), in centimeters.

So, we know now, that we have to order the 26'' option.

Looking for components

2009-07-06T23:40:00.002+02:00

We will start with a powerfull electric bike conversion kit for the rear wheel.
There are lots of options in Internet and ebay:

The 48V 1000W model in Sanny's camp Ebay Store looks great.
daoji666 in ebay seems to be a bit cheaper.
Another option is goldenmotor.

Defining the project

2009-07-06T23:26:00.000+02:00

Roberto and I have decided to convert a bicycle to electric.
We will start with my bicycle (Decathlon Rockrider).
The main goal is to have fun while we learn about electric motors, controllers, batteries, ...
The project may finish with the development of a two-wheel-drive electric bicycle.