teslanv
1 MW
This was my very first ebike build, after becoming interested in the technology last fall.
I was looking for a set-up that could handle the numerous hills I have on my 20-mile round-trip commute from my Home in Bellevue, WA to the jobsite where I work on Mercer Island.
After some research and some excellent feedback from forum members like dogman and spinningmagnets, I decided that I wanted the versatility of a Mid-drive that could take advantage of my bicycle's rear gears.
I also am experimenting with recycled laptop cells and building my own battery, but after some persuasive arguments from dogman in particular, I caved and went with HK LiPo's - And I am glad I did. They have an excellent power to weight ratio and are very reasonably priced. - Be aware that LiPo's can be more dangerous (i.e. - fire) than other battery types, so following safety precautions like monitored charging, fireproof enclosures/bags and careful electrical connections is a must.
The Battery:
Here is the HK LiPo pack I assembled.
The Cost of this 12S - 10AH pack is $165 SHIPPED from the US Warehouse. (not including the custom wiring harnesses or charger)
And here is the web link for the packs I purchased:
http://www.hobbyking.com/hobbyking/store/__15521__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack.html - If you are in the US, make sure you select the US Warehouse, otherwise you'll pay a boatload to have it shipped from China.
My Pack is (6) of these 4S packs run 2 parallel and 3 in Series for a total of 12S (44.4V nominal/50.4V Max) and 10AH
Charge & Connection Harness:
I tried buying a harness kit from iceman http://lipoconnectionsolutions.com/ but he had quite a backlog at the time, so I built my own harness. His videos and photos are quite helpful, and I had no trouble assembling the harness. Parts sourcing was from hobbyking - mostly the 4mm Bullet connectors and Silicone wiring. - The 4mm Bullets are quite easy to solder - much easier than soldering a Deans (T) connector, which I used on some of the other connections.
I made 3 sets of parallel harnesses that join two LiPo packs, plus one extra connector on each harness for a third parallel pack for future upgrades. (I taped off the extra connector on each parallel harness so it won't accidentally get connected until I am ready).
Then I made a 3S Serial Harness. The Serial harness is routed through a small hole in the triangle pack and stays in there at all times. (I can't charge it at 12S anyways, since my charger will only charge up to 6S Packs.)
When I am ready to charge my pack, I remove the serial harness and set my pack in a fire-proof enclosure (repurposed Brinkman BBQ/Smoker) Then I just have to connect the three parallel leads from the pack to a parallel charge cable which is connected to my charger and plug in the 6P Balance cable harness if I want to balance the pack.
The connections to the charger are ALL parallel, so the charger only sees one big-ass 4S, 30AH battery pack.
This set-up makes it nearly impossible for me to connect the pack wrong - (The main cause of KFF - Look it up if you want to see pics).
The Charger:
For charging, I started out with an Imax B6 Charger. It's only rated for 50W, so it took a LONG time to fully charge the 12S-10A Pack. (I charge it in 4S x 6P) The pack has 444 WH of capacity, so it took almost 9 hours to fully charge at 50Watts. I have since upgraded to a 200W iCharger 106B+ as shown here: https://www.hobbyking.com/hobbyking/store/__6792__iCharger_106B_plus_250W_6s_Balance_Charger.html - 5 times the power. Except that my power supply (an Old Asus Desktop PS) could not handle the 250W for some reason - it made a terrible screeching noise.. So I bought a 700W Dell Server Power Supply off ebay and converted it to power the HK Charger. - Again iceman sells these pre-built for RC Chargers and has good photos of how to convert them.
The Frame:
I had originally planned to install a kit on my '98 Giant Rinkon. - I spent a Saturday afternoon making my 20-mile round trip commute on this bike, just to assess the difficulty without electricity. - I am 5'10" and 190 lbs - Not particularly in shape, but not obese, either. - The ride kicked my ass. With no suspension and V-Brakes, I knew there had to be better options so I started scanning my local craigslist for a Hardtail with disc brakes, and I found this Iron horse Maverick SE 5.5 (well-used) for $100 http://www.performancebike.com/revi...-5-5-Mountain-Bike-Performance-Exclusive.html
The Rear Cogs and chain were pretty worn, and I knew the Mid Drive would be working those components pretty hard so I replaced them with an SRAM PG850 11T-32T 8-speed Cassette and PC 850 Chain, as well as replaced the derailleur/shifter cable. The suspension forks are nothing special, but the headset is standard, so I can change those out when my budget allows. - The Giant Rinkon had a non-standard headset, so not many options there to upgrade.
The Kit:
I wanted a motor that could handle the numerous hills I have on my commute. The options finally came down to a MAC 12T Geared Hub or a mid-drive. The issue with the Geared hubs is the high-power requirements for the steep, long hills I have to contend with. - And I did not want to tax the battery to get up the last big hill on my way home - So it was down to the mid-drives.
I looked at the GNG Mid Drives, but after reading reviews about the cranks being of low quality, I decided against the GNG drives.
Spinningmagnets wrote a great article on Electricbike.com http://www.electricbike.com/bafang-bbso2-750w-mid-drive/ which convinced me to go with the Bafang BBS02 750W Unit.
I ultimately found it here http://lectriccycles.com/products/750-watt-mid-drive-conversion-kit from lcrewse. - Cheaper purchasing options from China do exist, but I believe in supporting the local (USA) economy and also value the added service and responsiveness of a US Supplier, and http://lectriccycles.com/ has been wonderful to work with. And the reality is that for $750 SHIPPED, It wasn't that much more than a cheaper Chinese motor or geared hub, once you factor in about $150 for shipping either of those from China.
I chose to order the Bafang with the speed limited to 31 MPH (50KPH) but lcrewse can also program it for unlimited speed. I also had the LVC set to 38V, since I was using a 12S (44.4V Nom) pack, but after some further research, I think that LVC is too low for a HK LiPo battery - 42v LVC is probably more appropriate for a 12S pack. - I added a wattsup meter to monitor the pack voltage.
Performance has been great, although we are still working through some minor details with regard to the PAS Settings. According to lcrewse, the 5-level PAS Settings should correspond to 20% increments in current between the levels, but a couple of us have experienced slightly different increments. I find the best PAS setting for me is on level 2 of 5, but since the number of PAS levels is user-selectable, I am going to try increasing to 9 levels to see if I can get a finer range of assist wattage. The lag of start and stop for the PAS is noticeable, as it is based on cadence and not torque. Bafang is reportedly working on a torque sensor option, but is having difficulties with it.
Up-shifting under power worries me, and I try not to do it. Using the PAS exclusively, this means having to pause your cadence briefly before you up-shift. Down-shifting seems to be less of an issue. - Of course this is all about the quality of your drive-train. A reliable IGH would be a sweet set-up with this mid-drive in my opinion.
The Details:
I bought the largest Triangle Bag I could find on Amazon. This one fit my bike nicely and also fits the battery pack comfortably. http://www.amazon.com/gp/product/B006JA8WEG/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
It is very streamlined and keeps the bike agile and well-balanced. The bike with the motor & battery weights in at 49.0 lbs., which I think it quite reasonable for an ebike.
I have plans to add a rear rack and mount up a 50-Cal Ammo Can for the battery enclosure. - This would allow me to fit up to 30AH of HK Lipos or to house my hybrid HK LiPo/laptop LiCo pack when I complete the Laptop Pack. - It's also very fire-proof as battery enclosures go. - But I would probably not ride like this unless I had a really long ride planned. The triangle bag I have now is a great solution for my planned 20-mile commute.
I also added a knock-off wattsup meter http://www.amazon.com/gp/product/B00C596UIA/ref=oh_details_o00_s01_i00?ie=UTF8&psc=1 since the Bafang Display does not provide detailed battery info - just a battery meter bar.
Overall Impressions:
I am so glad I went with the Bafang BBS02 750W Mid drive for my first ebike project. It was incredibly easy to install as a novice builder, as all the wiring connections are idiot-proof as well as water-proof, the controller is built into the drive unit and the display unit is quite useful and included in the purchase price. lcrewse is great to work with, and I highly recommend that you purchase from him, especially if you are in the US. And this bike is a blast to ride. - I find myself smiling uncontrollably every time I peg the throttle.
