The Blog

Tuesday, February 16, 2010

Our Electric Bicycle Challenges

Building the electric bicycles for our cross country trip has turned out to be more of a challenge than we had anticipated. No surprise there, since most projects tend to be much easier to build in our imaginations than in the physical world. After deciding to go with the recumbent bike and choosing the mid-drive system over the hub motor, we figured it was just a matter of getting the right components and mounting them on the bike. With the considerable skills of Charlie Cunningham, mounting the components was accomplished.

The drive system we are using comes with a plate that holds the motor and a sprocket that connects the motor with the bicycle pedals via 3 chains. It’s a little complex and requires very accurate alignment in order to function optimally. This is where Charlie’s skills will hopefully result in optimal drive train efficiency. While Charlie had his brazing torch out, we added supports under the seat to support the battery packs. Of course, the drive chain also passes under the seat, so extreme care had to be taken to make sure that everything fit. With all of the pieces in place, we figured we were set to go. But then, two other challenges needed to be confronted. Recumbent bicycles are designed as road bikes so they come with narrow, rather light wheels and tires. This is not a problem until the added weight and higher speeds of the electric drive system are added. It became very clear that we would have to “beef up” the rear wheel. Thankfully, the downhill mountain bike industry has led to the development of very strong wheels, so we now have dramatically stronger wheels than we had before. Since the frames we are using do not have shocks, we also added big “balloon” tires to protect both the rims from impact and to protect our spines from road shock. The big tires add some rolling resistance but the comfort and durability we gain are worth it.

While we were getting ready to build up the wheels, the issue of brakes came up. It was obvious from the experience we had gained that the braking power that came with the bicycles was not enough once we added the electric motor and batteries. So we once again took advantage of Charlie’s skills and mounted brackets for big disc brakes on the frames. Finally, we have some of the strongest hydraulic disc brakes available on the bicycles and our stopping power gives us the confidence we need to protect our safety.

But the story is only half told. So far, I have described the mechanical challenges which were relatively easy to solve once we figured out what needed doing.

The electronic challenges have proven to be more elusive. The three main components on an electric bicycle are the motor, the controller and the batteries. The motor has proven to be reliable although I think we will bring an extra one with us! The controllers have been extremely challenging. We keep burning them up. I’m not sure how many we have “fried” but we are hopefully getting close to finding a controller that will work for us. (My understanding is that the controller manages the power delivered from the batteries to the motor and helps manages the power delivered to the batteries during charging. Neither of these tasks are electronically difficult but for the young electric bicycle market, it has been challenging getting a good controller for a price that keeps the final product within reach of the consumer.) We plan to bring a few extra controllers and we are setting up the bikes so that all components can be switched out easily.

Now to the batteries.

Again, the challenge is a lightweight battery that delivers power, range, and durability in a pack that is affordable. For our ride, the affordability issue is almost irrelevant. Most electric bicycles have a range of 20 to 30 miles where we want 80 to 100 mile range. We need a lot of battery power so we are investing a small fortune just in the battery packs.

On the whole, I am quite hopeful that within the next year or two, motors, controllers, and battery packs will all improve dramatically. I don’t think that prices will drop as dramatically, but for the type of use that most people will want electric bicycles for, there should be very good quality complete electric bicycles available for around $2,500.

That may still seem like a lot but if it is able to replace someone’s need for a car, it is a great deal. Side benefits include, no registration, no gas, almost no electricity, exercise, fun and maybe most importantly, switching from a car to an electric bicycle is the kind of meaningful contribution to a sustainable future that we Americans need to be making.

1 comment:

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