Just Another Electra Lux Fat 7D Build

HoraceLai

10 mW
Joined
Aug 25, 2013
Messages
22
I wanted a relaxed fat tire e-bike for various purposes: hauling the kids, going on all kinds of surfaces, commuting in a relaxed way, hauling cargo. After much Googling I found the Electra Lux Fat 7D, which has been converted many times before due to the possibility of it being able to fit the BBSHD inside the frame with some slight modifications. So I ordered one (March 2019) along with a BBSHD kit with a battery (I think July 2019). This ended up being a much longer project that I initially thought due to family (getting a 2nd child), and technical issues (described later).

The bike came with several scratches from the shipping. The company I ordered from was nice enough to refund some money back for it. At this point I was still waiting for the ebike kit so I started playing with the bike around the area, added a rack, and a child seat in the front.
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I needed some fenders and found some cheap ones in a general hardware chain store nearby. I mounted the front ones quite easily but the rear ones will require some fabrication which I ended up doing half a year later.
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At this point, all the ebike components had already arrived, but I was procrastinating and just in general out of energy at the end of the day, every day. By the time I finished denting the downtube, it was already January 2020.
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And by the time I finished denting both tubes enough to fit the motor, it was already April 2020!
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And then came the biggest setback of the project. I connected everything together and the bike just wouldn’t power on. The display shows nothing. I kept pressing the on button. Once in a while, the display would light up for a fraction of a second before it goes blank again. I talked to the kit + battery supplier (greenbikekit.com). They were quite to respond to give me some tips on what to measure, etc. When fully charged, the battery barely managed to output 50V. This is a nominal 52V pack, and the charger supplied charges up to 56.6V. So something is wrong here. Took apart the battery casing and measured the voltage of each parallel group. Two of the 14 groups had 0V, and that was the problem. GreenBikeKit got back to me explaining that the issue is that the BMS failed, and did not charge those two groups. They would send me a charger, new BMS, spare wires and connectors. I would have to cut the wires that go into those two parallel groups, charger those groups with the charger, and then wire everything up again with the new BMS. It really was a huge effort since I went into this project expecting the kit to be plug and play. I also replied back to Anna from GreenBikeKit explaining that I am worried that even after the recharging is done, the cells are most likely damaged and would have a huge loss of capacity. She told me not to worry and just try.

The battery when I first took it apart. Notice that the supplier cut corners on the series connection between parallel groups
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Charging the parallel groups
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Soldered back the connectors to the BMS
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Soldered new BMS onto the pack
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I should add that in the meantime, the bike also had some new stuff added to it. A rear seat (Hamax Caress) and rear fenders.
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I have also tried riding the bike with the battery pack, with the battery strapped to the front rack. The bike rode very well, fast (for me, I don’t go above 45kph), and powerful. It was super comfortable for such speeds. I lathed an aluminum rod with threads on both sides to mount the chain guard back on.
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Then I 3d printed some mounts to mount the battery on the down tube. I have no idea how well they will hold. It was printed in PLA, and I have printed spares for both mounts. I will reprint them in PETG later on when I have a better storage solution for these filaments. So far they have lasted for 20 days, and I don’t see any visual signs of damage yet. However, I have probably ridden only 40 km so far with these mounts on. I check on them after every ride.
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Here comes another bad news. The range of the battery sucks. I manage around 25km before the power shuts off. The battery measured at 51.6V at that time. That doesn’t sound very low. Opened up the battery again and measured the parallel groups. Unsurprisingly, all groups measured at 3.75V except for the ones that I had to recharge, which were at 3.59V and 3.12V. The BMS most likely cut out the discharge because of the low voltage on that 3.12V group. Talked to GreenBikeKit and asked for a refund on the battery. I settled on getting 200USD back. It is still a big loss (time & money), but I have to move on. I will source a new battery from em4ev as I heard good things about them.

This is all the progress I have made thus far. I will end here with a photo from last week, when I took the kids to the beach on a windy day and saw lots of kite surfers.
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