51 Volt Power Pack

The heart of our WattCycle conversion is the 51v battery pack, likely the most expensive part of the conversion.  There were so many directions we could have gone when selecting a power solution, flooded lead acid, AGM, lithium, battery configuration, charging system, and the list goes on.  I wanted to use a system that met my demands for power throughout the day, giving me a range of 15-20 miles if needed.  I also needed a system that I could charge with a solar panel anywhere I went, WITHOUT plugging into the grid (I will cover the charging system in the next blog post).  I also had to seriously consider weight, durability and price.  I could have gone with the battery pack sold by the motor manufacture, easy but very pricey at $800-1500, depending on the amp hour rating.  All of these variables created hours of research, with the hope that it pays off.


The hub motor requires 36 - 51 volts for correct operation, the higher of the voltages will reduce my amperage consumption.  We went with a 51 volt battery pack because of readily available charging systems in that voltage and the flexibility for configuring a battery circuit.  Our next choice was either eating the expense of lithium batteries or purchasing sealed AGM (Absorbed Glass Mat).  Lithium packs are extremely expensive however have great advantages when installing them in a system such as what we were assembling, we bit the bullet and ordered lithium.

These lithium phosphate modules are rated at 12.8 volts and will give us 6.4 amp hours of current.  When wired up in series we should have 51.2 volts being supplied to our controller and eventually the motor.  The amount of Amp hours has been a big concern when developing this power system.  When you increase amp hours you also increase the duration of operation as well as the price you are going to pay for the power pack.  For our system, 6.4 amp hours falls on the low side of the scale, however the solar charging system that we are installing should (in theory) overcome this shortcoming.

Power Hub and Controller

Power Hub

I had many concerns when thinking about replacing the rear hub and gearing that was set up by Christiania.  I will admit, they did a great job in selecting the 7-speed Shimano hub.  The shifting was easy and smooth, the rear coaster brake was simple yet very handy.  When adding power to our bike, the rear hub replacement was the most convenient and cost effective solution, yet replacing the Shimano hub would mean we will lose two great features that were designed into the bike.

I had researched numerous power hubs for front or rear and thought about making a front wheel drive system of my own design.  What I finally selected was a 2000 watt, 36-55 volt, brushless/gearless motor made by Crystalyte, due to its ease of installation and proven technology.

Because this motor is brushless and gearless the reliability and lifespan should pay off, however a geared version of this motor is available.  Other advantages of the gearless motor is the speed it can produce and quiet operation but the disadvantage is the weight and  lower torque than the geared version.

As for sprokets, I am replacing the stock 19 tooth gear with a 15 tooth freewheel sprocket and hoping that one speed will be sufficient for riding around town.  If I find that a single speed system does not give me enough range, I can always add multiple speed cluster and deraileur system.

At the time of this post, the hub and rim are being assembled to make the 24" wheel that I need. We are excited to see the arrival shortly.

Motor Controller

The motor controller we selected has a range of 36 - 64 volts and can handle up to 3000 watts of power.  This controller from Crystalyte boasts reliability and smooth power delivery while also selling at a fairly reasonable price.  The controller will be tuned by the manufacturer to work properly with the power hub.

I opted for a thumb throttle due to the handle bar configuration on the WattCycle, however a half turn twist grip is also available.

A Need for Speed

Being an electrical service business, plans for introducing electrical devices to our work bike were easy to understand.  From the beginning we planned on adding batteries and inverter to help make remote service work easier, lighting to make the ride around town safer and solar panels to keep it all powered up.  Workload and excessive heat were not factored into our transportation choices.  During the first summer with the Christiania, both business and climate had become unusually hot.  It was obvious that I needed to make some changes to increase speed and reduce the effort spent to get from my home, clients boats, shop and the local suppliers during the hot summer months.

I had been studying everything possible on the latest technology the automotive manufacturers were introducing in hybrid and electric automobiles.  I have had the dream of introducing similar designs in sailing vessels by replacing the fossil fuel engines with electric and hybrid propulsion.  This same technology, on a much smaller scale, could easily be installed in our work trike and help me perform my job efficiently.  This blog is all about the metamorphosis from cargo tricycle to hybrid cargo trike, the WattCycle.

Our initial plan:

• Replace rear hub with a 2000 watt, 48 volt power hub
• Install a motor control system with thumb throttle
• Install a 48 volt battery system to power the rear hub
• Install an independent 12v battery system as a charging buffer
• Install a 12 volt, 65 watt solar panel on cargo lid
• Install a 120 volt power inverter for service load and 48 volt battery charger
• Install headlights and marker lights for safety at night

In the near future, I will describe each item, concerns and reasons we selected each component.

Follow us as we install and test our modifications.

The Beginning of a Vision

Watts Up Marine is a mobile marine service company that specializes in electrical, refrigeration and air conditioning in the Kemah, Texas area.  We have always had the desire to be more conscience of our world and the impact that we have during our lives.  Our long term vision was to create a company that offers products and services that change the direction of marine living.  Most of our service business is generated within a few miles of our home and shop.  I often spend an entire day working on numerous boats in one marina, a prime reason to make a transportation change.

We were fortunate to have met the owner, Jae of Houndstooth Road, an Atlanta based importer of classical European bicycles and stylish accessories.  Jae suggested a Christiania Box Cycle as an answer to our ecological desires and due to the proximity to all of the local marinas, a service/cargo bike made a lot more sense than a gas guzzling truck or van.  The Christiania had everything that we needed, comfortable seat and riding position, 7 speed rear hub with coaster brake, front disk brakes and most important, a large cargo box.

A cargo bike is almost unheard of here in the Southern Texas area and finding such a gem locally was impossible.  We immediately ordered one and had it shipped to a local bike shop for assembly.

Our new bike arrived one day in July 2010, while I was sailing from Tampa, Florida to Galveston, Texas.  Winds for this trip west were unusually unfavorable, either nonexistent or directly from the west.  The excitement to ride it for the first time seemed to summon favoring winds, as each time I was on the helm the winds increased to that of a squall and pushed us toward Galveston.  The day after arriving into port, I picked up our Christiania and took it home for the first time.  From the first ride, it caught attention, most would stop and look or ask questions.

Our dogs immediately took to the bike, they jump into the cargo box upon the ring of the bell.  Going to the local farmers market was a treat.  After adding a waterproof cargo lid to the box, I put the bike into immediate use and found that it was easy to get around my territory.  It was a huge step for Watts Up Marine to move toward a cleaner way of doing business.