Nick first posted about his Electra Townie conversion way back in December of 2010. I was immediately impressed with several features. The battery enclosure in the frames’ triangle looked very professional, but when opened…it revealed that the technique he used would be easy for the average garage builder to copy. This central battery enclosure really knocked me out!
If you like this shape of frame and rider posture for a future project, you may also want to compare the Giant Suede and Trek Pure.
“I pre-drilled the holes with a bit that’s slightly smaller than the self-tapping screws I used to hold the side covers on with. I have checked several times for stress cracks and couldn’t find any (The main tube walls are almost 1/8″ thick). The 10-Ga aluminum side covers add a lot of shear strength. I think the frame is now way stronger than it was stock.”
“…To be honest, when [the weight of] all of the batteries were on the rear rack, it scared the shit out of me at only 30-MPH…”
Here’s Nicks battery enclosure method revealed: wooden strips are screwed onto the frame, and that provides a flat face that allowed for an easy attachment of the aluminum side-plates.
After mocking up the aluminum sideplates, Nick removed them and covered them with a $20 faux carbon-fiber sticker, simply because…it looks awesome!
This angle shows how narrow the central battery enclosure is. the V3 Cycle Analyst, motor temp read-out, and left-side mirror show that Nick is a serious commuter.
“…I really like the longer Townie frame and it handles super at 40+ MPH with the White Brothers fork and 24″ rear wheel. The combo of the fork with the Thudbuster and Brooks saddle plus 30-psi 2.5-inch Hookworm tire makes for a plush ride…The 26-inch with 2.3 Big Apple on the front also handles well. The bike is very stable at speed. I can take my hands off the bars at 40-MPH without worry…The long wheel base makes all the difference…the total wheelbase is 47-inches…The bike weighs 85-pounds with a full tank of Volts…”
“…As to the Thudbuster [suspension seat post], I’ll never own another hard tail without one. I have tried both models. The long travel (LT) does a good job. It has more travel than the ST. Both come with a variety of elastomers so you can adjust the hardness to whatever you want. I ended up with the ST model because I wanted more seat post length exposed, so I could mount a rack to hold the aux batteries. That is also why I bought the sprung seat. The combo of the LT-Thudbuster with the weakest elastomer along with the Brooks saddle turned out to be perfect for me…”
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Motor
“…I bought one of methods HT3525 Crystalyte motors but it smoked the windings within 1.5 miles (factory defect). But I must say that before it went poof It impressed me with its mid-range power. It went over 35-MPH and hadn’t hit top speed right before it cooked itself. It had way more torque than the BMC [geared hub] with the same volts & amps. Right now I am waiting to get one of the new sensored HT3525 Crystalytes as soon as somebody gets one in that I can buy…
…I guess I wouldn’t have changed anything if I hadn’t let a friend ride it with the amp limit switch off. He cooked the little BMC 600-S motor by pushing 3-kW through it while climbing a 4-mile hill…I did the amp limiting mod on my Cycle Analyst and mostly run it at 1500W…I have a switch on my throttle that bypasses the pot to allow [the BMC to use] 3-kW on flat land…
…Lyen’s 12-FET controller is now set at 60A battery current, and 135A phase, for driving the HT3525. It is working fine as is the Magura throttle. I wired the controller to a key switch that locks the motor when switched on. This is a nice feature that all Lyen’s controllers are capable of doing. The temp gauge in the motor never shows more than 80C and that is with bursts of 5500W…”
Here’s Nicks latest motor, the Crystalyte HT3525, with the ventilation holes right next to the hot stator-coils. I would recommend that anyone copying this should spray the insides with anti-corrosion spray and add a temp sensor while the motor is open.
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Battery
Back in 2010, LiPo was the only high-current batteries that were readily availble. We have recently collected some info on NON-LiPo batteries that provide high current, and that info can be found here.
“…Now, I’m hitting 42-MPH on 24S (24 X 4.10V per cell = 98.4V), and…nothing is getting too hot. The temp gauge in the motor never shows more than 80C (176F), and that is with bursts of 5500W (55A). I did drill my side covers [to vent excess heat]. If you nail the throttle at 10-MPH…it will lift the front wheel! …” (electricbike.com recommends 93C /200F as the practical heat limit for motors)
Here are the original nine 6S bricks to provide 74V / 15-Ah. Later Nick squeezed three more into the rear cargo rack for a total of 24S / 100V
Nick has a fast bulk-charger for putting 100V into the entire pack, but sometimes he does a slow balance-charge on each cell-string. Here’s his balance-charge set-up when he was running 18S (74V), configured as three 6S strings, which required three 6S RC chargers. Later he added a fourth charger when he went to 24S (100V)
Each LiPo brick has a low-amp JST-XH socket which allows each individual LiPo cell to be checked for its voltage, and also you can use it to slow-charge each individual cell to 4.1V. These sockets have one wire for the positive of all the 6 cells in a 6S brick, and one negative wire for each cell, so a 6S pack has a 7-pin balancing socket. Nick paralleled three common 5000-mAh bricks onto each string, and since he used three strings to get 18S / 74V (in the beginning), he looked for a single socket and plug that had at least 21 pins.
He found an appropriate waterproof Mil-Spec “Amphenol-style” connector (with a bulkhead flange to make attachment easy), and this made balance charging a little easier. Later, when he added another string of batteries to get a 24S pack, he had to add a fourth 6S charger, but he still had enough unused pins to continue using this connector. When not in use, it’s covered by a water-proof cap.
Back near the seat-post, he installed a key-switch that shorts the motor-phases through the Lyen controller so the rear wheel will not roll when it’s removed. That’s much better than it just not allowing power, because the bike could still have been pedaled away.
Here’s the 36-pin connector he uses for balance-charging, the power-ON switch, and back by the seat-post he placed the key-switch next to the Lyen 12-FET controller.
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Brakes
“…I ended up TIG-welding one of the extra brackets that came with the Avid BB7. Easy to set up, just clamp the caliper with bracket on the rotor (using the brake lever wrapped with a rubber band) right where you want it to be. Then tack it on. Remove the caliper and weld it up in steps so as to try not to get it too hot [to avoid warping]. I didn’t heat treat it afterwards, but it has held up fine for over a year now…”
This is the early version of the eTownie with the smaller BMC geared hub. The Avid BB7 brakes are very popular for E-bike commuters. They are not quite as powerful or sensitive as hydraulic brakes, but these are quite good, and much more affordable.
Here, Nick fabricated a simple custom bracket to hold a common micro-switch against the rear brake actuation arm, which energizes the very bright LED brake light from ebikes.ca.
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“…I really like the bike, but I also enjoy building stuff. So in the future I will be adding a Schlumpf drive [2-speed crankset] and 18″ motorcycle rims and tires, and probably a Crown motor with an 18-FET Lyen controller…”
If you want to see more discussion and details about this E-bike (along with more pics), you can see the build thread here.
Nick lives in Lompoc, California. It’s roughly about halfway between Los Angeles and San Francisco, and the beach is just an E-bike ride away whenever the mood strikes him.
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Written by Ron/Spinningmagnets, February 2014
