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Eva's Electric Land Dinghies

Right from the beginning of the project we were exploring ideas for an electric land dingy to go on the sailboat. Initially we were looking at photographs and dimensions of electric scooters advertised for sale on the internet, trying to see how we could fit one into a space in the corner of the enclosed head compartment on Eva. There were some possibilities, but most of the scooter seemed just a bit too large and heavy to be practical for the purpose we had in mind.

The Razor E300
External Batteries
The Electric Bicycle
Scooter Upgrades
24V ebike

The Razor E300

When we set out through the Golden Gate in the fall of 2006 bound for Southern California and Mexico beyond we still had not done anything about getting a land dingy for Eva. When we arrived in Santa Barbara we were faced with the prospect of having no means of transportation with the nearest grocery store some two miles west and up a hill at the Mesa Shopping center. Most visiting yachtsman rented a car or called a taxi cab to go shopping, but we were thinking along the lines of higher levels of independence. Walking to the grocery store and carrying a backpack of grocers back down to the boat just was not the kind of fun that we had envisioned sailboat cruising to be, so when we saw the Razor E300 electric scooter at the Pep Boys autoparts store near downtown for only $200 we jumped on it.

The Razor E300 was somewhat more compact in overall dimensions than other 300 and 500W electric scooters we had been considering and with only two 7Ahr 12V AGM lead acid batteries for power it was also considerably lighter than the 12Ahr 36V models. The 7Ahr 24V drive train was quite weak, but it would pull up to 11mph and could even haul up a gradual hill.

The big problem with the Razor E300 was an extremely limited range. On flat ground it would go a total of 4 miles, and at that it was slowing down quite a bit the last mile back. This was however good enough to haul groceries from the grocery store 1.7 miles up the hill to the West of the Santa Barbara harbor as long as I pushed the scooter partway up the steepest hill. We found that a case of beer made an excellent seat on the scooter, and with a backpack and some polyethylene grocery bags hanging off of the handle bars quite a load could be hauled.

External Batteries

Almost immediately I began to think about an auxiliary battery pack for the little scooter, as those two 7Ahr AGM batteries were just not much storage. In Oxnard I found two more 7Ahr AGM batteries at a nearby Radio Shack store, but I pushed the scooter four miles all the way out to Highway 1 where a battery dealer was located. I purchased two 18Ahr 12V AGM lead acid batteries for what I thought was a rather steep $110 total with tax. With the batteries in a backpack I rode the scooter back to Channel Islands Harbor and bought a 6A 12V ProMariner brand regulated charger from the Chandlery for the low price of $35.

To mount the substantially larger batteries on the scooter I built an oak battery box out of 1/4" planks from the local Ace hardware store. I cut the planks by hand with a hacksaw blade, and screwed the box together with small #4 stainless screws and Gorilla brand foaming one part polyurethane water proof wood glue.

To charge the batteries I connected them together in parallel with a set of jumpers I made up out of AWG14 wire and alligator clips. To power the 24V scooter I used the same set of jumpers to connect the batteries in series, but the connection to the scooter was made with permanently mounted wiring and shielded blade connectors.

The advantage of the large external batteries and the small internal batteries in the scooter was that the weight of the vehicle could be divided for stowing onboard and carrying ashore. The scooter weighed about 37 pounds, and the batteries came in at about 30 pounds, so the total was quite high at nearly 70 pounds.

With the 18Ahr external pack and the 7Ahr internal batteries paralleled the E300 now had a total of 25Ahr of 24V power and both performance and range were dramatically improved. The substantial extra weight made initial acceleration from a stop a bit slower as the pulse width modulate motor controller limited current at slower speeds. Once up to about 8mph though when the D.C. brush type motor connected directly to the batteries power and acceleration was considerably greater than it had been with just the internal batteries. Top speed increased to 13mph and much more substantial hills could be climbed at close to full speed. The most dramatic difference of course was in the increased range, the new 25Ahr vehicle was capable of going 20miles on one charge.

The reason that the external battery pack so dramatically increased range was due to the Pukert effect of lead acid batteries. The 7Ahr batteries being drained at 10A lasted only twenty minutes where the 25Ahr combined battery capacity being drained at 12A was able to go for an hour and a half.

These general purpose AGM lead acid batteries were quite robust, and even though they were often discharged all the way down to where the voltage dropped off and the scooter slowed considerably they continued to take a charge and deliver full power and nearly full capacity year after year.

Eventually after two years of use and probably a hundred or so cycles the internal batteries in the scooter gave out and had to be replaced. It was obvious that the internal batteries being wired closer to the motor had been run harder, and it was not surprising that they gave out somewhat prematurely. The external batteries continued to work essentially as new even though they were also pressed into service powering a Minn Kota Enduro 30 dingy motor and racked up many more cycles.

The Electric Bicycle

After crossing the Pacific in Late November and early December we landed at Hilo on the Big Island of Hawaii for the start of the very wet rainy season. The port at Radio Bay is about three miles from downtown Hilo and also about three miles from the shopping center south out Highway 11 so the electric scoter was a very popular item. We also walked into Hilo sometimes and there was some limited bus service as well but the electric scooter was by far the fastest, easiest and most fun way to get into town. The problem was that there were two of us and only one scooter. We took turns ridding into town, but time was of the essence on the few sunny afternoons between day after day of torrential downpours. It was at this point that a second electric vehicle became a priority. It was my father that demanded an electric bicycle, as he was always concerned about having to push the dead scooter back if he miscalculated the range. The reality was that the range was plenty far for going into town, and he never had to push back. He was however probably a bit jealous of the way that I would take nearly 20 mile cruises all around the area and get back just as the battery voltage was dropping off. Sometimes I did have to push the scooter a short distance back, but the use of a hand held chart plotter allowed me to keep close track of how far I had gone and how far it was to get back.

After a few months of pouring over the specs for various ebikes advertised for sale we decided that just what we wanted was not offered for sale. The 20" ebikes were just too big to fit into the space available next to the E300 scooter in the "garage". What I finally decided to buy was a DownTube brand 16" folding bike from a company in Pennsylvania and an ebike kit ordered direct from the manufacturer in Guangdong Provence, China.

What I had learned in reading sales literature and reports from users of ebikes was that the Lithium Ferro Phosphate chemistry was by far the best way to go for powering electric vehicles. Most cheap Chinese ebikes came with the LiFePO4 chemistry batteries simply because they were so much cheaper than the competing 3.7V lithium ion battery chemistries. The LiFePO4 chemistry was however also said to be much more robust, able to handle high charge and discharge rates as well as well tolerating somewhat less than ideal management over many thousands of deep cycles. The other things I learned about ebikes was that there was a Federal definition of an ebike as having less than a 750W motor and providing no electric drive power over 20mph. The California motor vehicle code had a more specific definition of an electric bike as being any two, three or four wheeled vehicle with a functional peddling system with no electric drive power over 20mph and an electric motor of less than 1000W. Both the Federal and California definitions of an ebike specified that use permissions and restrictions would be identical to a regular peddle bike.

The Goldenmotor brand "Mini" geared brushless D.C. hub motor was rated at 250W when run on either 24V or 36V but was said to also be able to handle 48V with some risk of damage to the planetary reduction gears. The Mini motor was also said to have a freewheel mechanism so that the bike could be peddled without having to spin over the "cogging torque" of the permanent magnet motor.

The kit that I ordered from Golden motor was a Mini motor in a 16" complete cast front wheel that was geared for the 20mph limit on 36V. The power for the kit was a 10Ahr 38V LiFePO4 battery pack in an aluminum case with integrated management circuitry weighing a rather hefty 12 pounds. The kit also included the motor controller with cruise control and regenerative braking capability, thumb and twist throttles, a switch cluster for controlling the cruise control, brake leavers with switches for the regenerative braking, a mounting plate for the battery and a peddle sensor for compliance with E.U. requirements for no electric drive power without the peddles moving. The cost of this kit was $750 including fast two day air shipping to Los Angeles and slower five day UPS surface shipping out to Honolulu.

The DownTube Mini arrived first, and we rode it around a bit on Oahu as we waited for the ebike kit to arrive. The little 16" folding bike worked pretty well, and the eight speed Sturmy archer rear hub shifted easily and held up to full power peddling in any gear. The eight speed Sturmy archer rear hub transmission worked better than the old three speed hubs from the past, but it still provided a noticeable amount of drag that was somewhat of a drag to peddle. Still though having such a wide spread of gears on such a tiny little bike was both fun and useful. The handling of the Mini was quirky but it did work even up to rather high speeds. Weighing only about 22 pounds the aluminum frame DownTube Mini was also about the lightest folder around, which was pretty impressive for it's diminutive $500 price.

When the ebike kit arrived I slapped it on the DownTube Mini and we took it ashore for a test ride the next day. The first thing that really blew both of us away was the heavy acceleration of the miniscule electric vehicle. From a standstill the motor would make quite a bit of groaning unpleasant noises but still torqued fairly well. Once up to about 10mph though the motor smoothed out and started to make unexpectedly high levels of power so that acceleration up to 17mph was really very rapid. With some peddling to go along with the electric motor the new bike we dubbed "Electra" was really pretty fast and could go up big hills with ease. It was no motorcycle, but compared to a bicycle it was very fast and fun to ride. Out on flat straight roads serious cyclists could easily dust the ebike, but with some hills, bumps and sharp turns the ebike had both an acceleration and endurance advantage.

Pretty quickly we also learned that the range of the ebike was quite impressive. With no peddling at all it would go 20 miles at 17mph, and with some light to moderate peddling it would go 40 miles at 19mph. As it turned out the Mini motor in the "casted" front wheel as Goldenmotor called it did not have the freewheel mechanism, but the regenerative braking did work well. It was just a one speed regenerative braking that would ramp up gradual for the first second or so after the switch was closed. The regenerative braking was limited to 10A, so the braking force actually appeared to taper off at higher speeds. The 10A 39V of regenerative braking was however enough to traverse pretty big hills without needing to use the friction brakes. As it turned out the regenerative braking was a really good feature that accomplished two separate things. First of all it meant that the 40 mile range could be attained either on flat ground or in moderately hilly areas with quite a bit of climbing and descending. The regenerative braking also turned out to be a very useful feature on the 16" Mini loaded down with a big heavy 220 pound rider and some 25 extra pounds of batteries and equipment. The smaller 12" diameter rims of a 16" bike have only 55% the heat dissipating capability of the 22" diameter rims of a full size 26" mountain bike. Loaded down with a rather heavy rider, a nearly 50 pound total bike weight and a 30 pound backpack full of groceries those little 16" rims could easily come up a bit inadequate on a big descent. The regenerative braking totally took care of this potential braking problem, and I never had any trouble with the brakes even in quite aggressive downhill ridding.

Scooter Upgrades

Knowing that the old Razor E300 scooter was going to seem weak and slow compared to the new ebike we had also ordered a new 26Ahr 26V LiFePO4 battery at the same time we ordered the bike and ebike kit. This new LiFePO4 battery was actually two individual 13Ahr 12.8V batteries in aluminum cases with integral control circuitry, and when tapped together into one unit weighed a miniscule eight pounds.

With just an eight pound external battery pack instead of the thirty pound external battery pack the scooter felt very light and nimble. The extra voltage of the 26V pack also bumped up the speed and performance of the scooter quite a bit. It was still slow to accelerate down at low speed where the motor controller limited the current delivery, but once up to 8MPH it took off and accelerated much harder up to a 15.5mph top speed. The range was also a bit longer at about 25 miles, which allowed the scooter to run with the ebike fairly well. The scooter was still slow compared to the 19mph ebike, and the 25mile range was still a lot shorter than the 40 mile maximum range of the ebike but these slight differences did not keep the two vehicles from being able to do approximately the same type of ridding.

I also replaced the internal 7Ahr AGM lead acid batteries with a 14Ahr 26V LiFePO4 battery which fit nicely in the same battery compartment. The biggest advantage of this upgrade was that it then had a nice long range without having to carry an external battery. It was also a bit faster with the batteries wired right to the motor controller without as much voltage drop in long skinny wires up to the external batteries. With the LiFePO4 external battery attached as well it could finally go as far as the electric bike as well, and that was quite useful sometimes. I eventually disconnected the controller on the brush type motor, and this yielded hugely increased acceleration and slightly higher top speeds but it also drained the batteries down quickly and I worried that so much current might damage the brushes or burn out the motor. The cheap little brush type permanent magnet motor however never failed under this abuse.

24V ebike

The motor controller that came with the Goldenmotor ebike kit had a voltage cutout for 36V lead acid batteries at 32.5V which was not really needed since the 10Ahr 38V LiFePO4 battery pack had it's own overdischarge protection enabled management system built in. In order to run the bike on 24V I also ordered a 24V version of the same motor controller which had a 21V low voltage cutout for use with 24V lead acid batteries. The 24V controller worked just the same with the Goldenmotor 38V battery, but I was then also able to run the bike on the 26V scooter battery. A few times I took both batteries out for an all day ride, but the reality was that just one battery was nearly always enough range.

The big advantage of the 26V battery was that it was more efficient in very hilly terrain. The lower voltage allowed the motor to produce the same amount of low speed torque with less current consumption, and the lower maximum speed meant that the range of the bike was much farther on the lower voltage battery. The low 14mph cruising speed with the 26V battery however felt too slow compared to the 18mph cruising speed with the stock 38V battery, and I only used the lower voltage battery to go on very steep climbs up mountains. Later I also used a small and extremely lightweight two pound 5Ahr 22V "airplane battery" as an emergency second battery on long rides. The 22V battery did not go very far before the 21V low voltage cutout kicked in, but it was still nice to have just a bit of extra range sometimes so as not to have to peddle back the last few miles of a long ride.

Over the years I did end up peddling back a few times, and the cogging torque of the motor made this a particularly unpleasant task. By staying in a low gear and going slowly the cogging torque was only a small problem and it certainly was possible to peddle the bike back after it went dead. Eventually after years of use and probably about two thousand miles the bike started to wear out and fail. Of course the torquey front motor was hard on tires, and I had to replace the front tire about four times where the rear tire lasted much longer. I only replaced the chain twice on the same original sprockets and the brake pads lasted the whole time. The worst wear problem though was with the Sturmy Archer hub transmission which began to drag more and more as the miles piled up. Eventually the transmission failed and was just stuck in high gear, and this made it essentially impossible to peddle the bike back if the battery went dead. The combination of increased drag in the hub transmission itself and the substantial cogging torque of the motor while traveling faster made it just horrible to peddle even on flat ground.

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