Pimp my ride


This article is divided into two parts: the first half is about my experiences with the “bakfiets” and some improvents of it. The second half is about the technical details of converting a normal bakfiets to an electric assisted one.

The “bakfiets”

In the Netherlands we all ride our bicylces. This goes for me aswell ofcourse. And since I’ve become a father, I started looking at bigger bikes. This way I can take my little daughter and some other stuff along with me on the bike. I could have gotten a so called “mamma-bike” (which is a bit longer than the normal ones, so you won’t kick your kid off the seat at the stearing wheel). But I always liked the idea of the so called “bakfietsen”. This translates to cargo bikes, but somehow this name feels odd to me, because the main “cargo” in my bike is my daughter. So it will be bakfiets from now on!

Anyway, I wasn’t sure if this kind of bike was right for me, so I bought a second hand bakfiets (a Babboe Big). It wasn’t in the best shape, but that was okay. The price was suitable for the state the bike was in, so all was fine. And, in case I wouldn’t like it, I could simply sell it once again.

When I bought the bike it looked like this:

I did some trips with the bike and so far I still liked it. As said, the bike wasn’t in the best shape ever. One of the first things I wanted to fix was the weather hood. It had a cut in the front window. Because of this the rain could easily get inside and make everything wet.
I first checked what a replacement hood would cost. An original one was around 140 euro. A bit too much for me still, because I wasn’t fully sure if I would keep the bike. So I decided to check a webshop which sells tent fabric and other materials. I ordered some window material, double sided tape and some water resistant sewing thread. This cost me around 30 euros and was more then enough to replace about three windows if I wanted.

When the materials arrived I had a new task: discover how on earth a sewing machine works and how to do this myself. As we all know, YouTube is your friend for these kinds of things, so I started watching some video’s. Actually I watched some before I did the order, and learned that I really needed water resistant sewing thread and some border material for around the window (which you put in place with quite thin double sided tape). Otherwise it would be leaking for sure and could easily get damaged.
After watching some video’s I had an idea how to do this all and started to work on the front window. Below you can see the result half way:

I’ve cut out the window in the same shape as the old one, but made it just a bit bigger. I found the old one quite tight and thought that could be the reason for the cut. So initially I started with some sheets of paper and made the final shape I wanted. Then I placed it on the tent window material and cut out my new shape. I sewed the lining around the window and put it together again with the hood. From now on I’ve got a waterproof hood on the bike!

Since my bike is still a cargo bike, I was wondering how much stuff you can put into the basket. We recently bought a new table and chairs, so the old ones needed to go to the dump (because the second hand store didn’t even wanted them…). I could have taken the car for this job, but why do things the easy way right? And so with some creative placement, it all fits just fine. This test was a success for the bike too!

When spring started to arrive, I decided that I really liked the bike. It was practical for my daughter and all the stuff we wanted to take along. You could also fill it up with groceries or other large items. There still were two downsides for me: one was that the bike weighs around 60kg and with some load and myself on it, it takes quite some energy to ride it around. For short trips to the city, this is fine. But now the weather is improving, I really would like to go on longer (>5km) trips as well! So I wanted to put an electric motor on the bike. In the Netherlands this is allowed, as long as the motor isn’t bigger than 250 Watts and you need to peddle to keep it activated. Also it shouldn’t add support above 25km/h.
The second thing I would like to change were the wooden panels. Some of them were starting to turn grey. Also the color of the wood was something I’ve never liked, but this is how they make this kind of bakfiets.

So two new tasks for me again! I first started with painting the panels, because if this fails I don’t have to invest in an electric motor kit yet. Below you can see the progress of taking the bike apart.

When I’ve finished removing all the panels, the steering dampers became visible. You could normally reach them from below, but that requires you to put the bike upside down. Since I now could take them out very easy, I decided to take a closer look. I’ve noticed when riding the bike that the steering wouldn’t always return in the middle.

After pressing the damper in and releasing it, it became quickly clear that only one of the dampers still worked as supposed. The malfunctioning damper did went in, but never wanted to come out again. So these needed to be replaced. Luckily Babboe has quite some spare parts for sale. So I ordered a set of replacement dampers.

Next step was painting the panels. I’ve chosen “Wijzonol dekkend halfglans” paint for this job. This paint was suitable for usage outside and could be applied on previously treated wood. I went for semi-gloss paint because high-gloss would show damage and scratches quite easily. I’ve painted the panels twice at every side. I put them horizontally when painting, and afterwards straight up against the wall to avoid dust falling on them. The second layer of painting I did with all panels standing up. It appeared that even just painting with the panels on the ground there was some dust present. Doing it this way really improved that.

I let the panels dry for almost two weeks (because the weather was terrible anyway). After that I started to add car wax to the panels, because they are easily accessible now. This made the panels less sticky and way more shiny!

Conversion to electrically assisted

With the newly painted panels, the bakfiets was looking good! So I decided it was a go for the conversion to electrical. I found out that this kind of bike really required a rear wheel motor. It was possible to drive the two front wheels, but it required some complicated tech to keep them both in sync. This was not the way forward. Another option was a mid-drive kit. This is a motor which drives the chain near the peddles. There were three downsides to this: the motor would cause excessive wear on the chain and gearing. The motor would be even lower than the frame now is. This would result in problems when going over a bump. And last, this kind of kit is the most expensive one of them all.

So a rear wheel build it should be. I read that it drives quite nice and wouldn’t be an issue in the winter with a spinning front wheel when there is snow on the roads.

I did quite some research on conversion kits. There were several cheap ones from China. Most of them didn’t support the pedal sensor, which is required to be a road legal e-bike. So this was a no-go. I did found some other ones which suited my needs very well. The brand I chose in the end was Bafang (8FUN), since I read a lot of good reviews about these kind of motors.

There were still two things that needed attention: the bike had a 8 speed hub gear (Shimano Nexus SG-8R20) with a roller brake. Most kits didn’t seem to have rollerbrakes support and all kits required a derailleur gear instead. After quite some research, I found out that a few bike shops were fitting a roller brake mount adapter. This got bolted onto the disk brake screw holes. So that fixed my braking issue.
The next problem was a bit more difficult. Most hub gears are way smaller than derailleur gears. So I read that I needed to widen the back wheel mounts. On this site it all gets explained. There is quite some force needed for this to happen, so there is a risk of damaging the bike. In case of steel frames, this should be less of an issue. You don’t want to try this with carbon or aluminum ones though!
Widening of the frame went quite well in the end. It did require me to stand on the wooden beam (see photo below) with my full weight and even then jump a bit to get things in action.
Another thing that needed some attention when converting from hub gears to derailleurs is the actual mounting of the derailleur arm. Standard derailleur bikes have mount points for the derailleur arm welded on the frame. My bakfiets doesn’t, since it was never built for it. To fix this problem, I’ve found a Shimano Tourney RD-TY300, which can be placed on the rear axis and kept in place by the frame. This way, you don’t need any existing mounting points.

Here you can see my attempt of fixing the rear mounts:

For everything to work, you also need a new chain (because hub gear chains are different from derailleur gear chains), a new crankset, a new 7 speed pion on the rear wheel, matching shifters on the steer (I chose a Shimano Revo SL-RS45 7SP) and a removal tool for the crankset.

After some hard work, I put it all together! Here are some photo’s of the finished build (the white spots on the wooden panels is some car polish I didn’t have polished out well enough when I made the photo):

The last part every e-bike needs is a battery. I did quite some research on this as well and found out most fully built e-bike batteries are quite expensive. Especially compared to lead acid batteries or SLA’s for short. SLA batteries have two downsides: they are heavy and they are large. Another option is to build a battery yourself from 18650 Li-Ion cells. I considered both options and really wanted to build a battery myself from the 18650 cells. I decided to not do this yet, because it would require even more research and time on how to do this. Since I really wanted to ride my bike, I ordered three 12 volt 12 ampere lead acid batteries. These are deep cycle batteries, so they are suitable for getting drained quite well. Be aware that starting batteries are very different (they are build for a short, big power spike and then recharging again).
In the photo below you can see how I connected the three batteries and added a fuse. The PVC pipe holds my controller and all the connected cables. I’ve put them in this pipe, just to be sure they can’t get wet.

Charging this kind of batteries is another thing. You do need to find a charger compatible for 36 volt batteries. I found out that specialized battery shops do sell them. Even though the quality isn’t always great. I’ve first ordered a 36v Powercharger (yes, that’s the brand name) EPA100-36. The first time I connected it, it blew up. That was a bad start, but I contacted the supplier and they sent me another one. Also this one directly blew up and I got a bit disappointed on these kind of chargers. I even got to wonder if I did anything wrong. So I charged all three batteries separately with my motorbike charger (12v). That went without any problem and I got to ride my electric bakfiets for the first time! That was a really nice experience. I hardly needed to add force to the peddles and I reached 25km/h very easilly!
But charging the batteries this way, takes a lot of time. I searched for another type of charger, because I was quite sure the charger was of bad quality. This got confirmed even more when I opened one of the chargers. The soldering was done very badly, and there were some small parts of solder loose in the box. I don’t expect this to be caused by the explosion of the charger.
In the end I found another charger: a brandless (possibly DLON) DL120W 36Volt 2.5A. This one did the charging without any problems! I do need to say that when connecting the batteries to the charger or the bike, you can get some sparks. This is normal, and nothing to worry about. But it’s good to know if you connect the batteries for the first time!

Since I learnt how to use the sewing machine and found out that getting the batteries out of the bike is quite a hassle. I decided to attach the batteries together in a sort of pack. I’ve used strapping material for this. It appeared that this material is very strong, as long as you sew it well together. I made a square and then a cross in the center of it, as you can see below in the photo. I sewed the straps together too, so both bands are kept in place. This made it very easy for me to lift the 12kg’s of battery!

Until now I’ve used the bakfiets for 500 km’s in total. It appeared that I could drive for approximately XXX (to be determined) km’s on a fully charged battery. This is with the hood on (which really adds to the wind drag) and most of the time my daughter and some stuff in. I think these kinds of batteries aren’t the best choice. I don’t think I can use the full capacity of them, because of two reasons: The first is that you should discharge these batteries to a maximum of 50%. This is to keep them in good state and make the lifetime longer. The second problem these batteries have is quite a voltage drop when discharged heavily. This happens usually when you are standing still and need to get driving after XXX+ km’s. The problem that is caused here is that because of the voltage drop, the controller sees the batteries go under a set limit (which can’t be changed unfortunately on my controller) and shuts down the system. You can start up the system again and keep going if you are driving at a certain speed or with a lower assistance level.
Talking about the controller and assistance levels: I’ve chosen the KT-LCD1 display. This display enables you to choose from 5 assistance levels. For me this is more then enough. When riding along with my wife on a normal bike. I set the level to “2” to avoid going to fast or to have to peddle very hard. When alone I usually choose 3 or 4 depending on how fast I want to get somewhere. Level 5 is possible too, but you are going quite fast to 25 km/h and is not suitable for busy roads or roads with lots of bumps or turns.

Another thing which I started to dislike were the small bumps in the road. Usually caused by roots of a tree. These cause the bike to shake quite violently, which is unpleasant for my daughter. I was thinking on the possibility of adding shocks to the wheels, but that turned out very difficult. Then I noticed some special tires on the market: Schwalbe Big Apple’s. These so called baloon tires need only half the pressure of normal tires and they do provide some damping. I immediately purchased two for the front wheels to test them out. I’ve chosen the “plus” variant, which should have more puncture protection in them.

When disassembling the wheels I noticed that some spokes have broken. I also had a problem when using the front brakes that the bike would wiggle for a bit. Especially when braking not very hard. This could be a potential cause for this problem. The wheel seemed to also be not fully round and had a slight twist, so there was a problem there! I ordered a Tacx T3175 Exact, a spoke tool and bought some extra spokes from the local bike shop. Since spoking a wheel is difficult some people say, I did watched some YouTube video’s once again. It appeared to be quite simple, as long as you know what you need to do and take your time. I started replacing the broken spokes and after that aligning the wheel again. It took quite some time and did this procedure for both wheels, since they were off the bike now. I got both wheels very nicely round and without any odd wiggles.
The next ride was even more comfortable! I didn’t have much problems with these small bumps and the brakes worked as supposed.

All in all this was quite some work on the bike, but I think it was all worth it! The bike rides very smooth and easy. I expect quite some more kilometers to ride and I hope this post can be usefull to someone who wants to do the same.

And to conclude this article, a photo the bakfiets in “the wild”:

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