add kalkhoff draft article

content/blog/05_durban_display_en.md

@@ -0,0 +1,102 @@
+title: Kalkhoff durban G9 Ebike - Display mod
+date: 2019-08-25
+author: Philipp Schönberger
+tags: bicycle, ebike, display, bafang, durban g9, kalkhoff
+category: projects
+
+E-bike buying decision
+----------------------
+
+Last year in October I bought a Kalkhoff durban G9. It is a 28" bike with a mix between a
+load bicycle and a touring bicycle.
+
+[lightgallery
+    /images/blog/TN-GSD-G1-touring.jpg Tern GSD Source: https://www.ternbicycles.com
+    /images/blog/Kh17_PRO_DURBAN-g9.jpg Kalkhoff Durban G9 Source: https://www.derby-cycle.com
+lightgalleryend]
+
+It wasn't my first choice but for my usage it is enough and fulfilled all requirements.
+
+I wanted to have a normal size bicycle with a lot of storage space for groceries. Also the range does no have to be
+super huge with about 30-40km  but I shall be extendible if needed later for some tours or the battery capacity drops.
+
+Therefor I found the Tern GSD and the Kalkhoff durban G9 pretty appealing.
+The GSD costed about 4000€ and the Durban 1200€
+
+First I wanted to have a Tern GSD since it would more fit to me from point of driving and loadable storage.
+Also the lower mass centre and the fact that I would not have to steer against the front rack are the real benefits.
+
+However one big drawback would be the price. I could have bought nearly 3.5 times the Durban g9 for the same price as one GSD.
+
+An other con was that this is a Bosch bike. Bosch Ebikes have for each battery one CanOpen controller inside, which
+results in the fact that only Bosch batteries can be used. If you would connect a third party battery the motor drive would not support
+you even though it gets power.
+Also I got the information from a former working college that self replacing the 18650 cells is on some bosh batteries nearly impossible,
+since they lose the configuration if power gets lost and therefore do not work with the CanOpen bus.
+So instead of replacing just the 40 cells for 5€ each in case of good LG cells with 3500mAh (so 200€ total) you would have to buy the 700€
+official Bosch akku.
+
+So I boughth the Kalkhoff Durban g9 since it is much cheaper and the storage room would be enought for me at the current possion.
+I would however change to the Tern GSD if I would need a bigger storage room or need Kid seats.
+Then I could sell my Kalkhoff and buy a maybe used GSD much cheaper than the 4000€.
+
+
+Kalkhoff durban G9
+------------------
+The Kalkhoff has a rear hub motor SWX02 36V 250W from the Chinese company Bafang.
+The Kalkhoff is a "made in Germany" so I guess china is now part of Germany ;D.
+
+[lightgallery
+    /images/blog/bafang_motor.jpg Bafang motor
+lightgalleryend]
+
+
+However the con of this bike system is the missing display for battery values and choosing the support levels.
+With the official system only 3 steps of support are possible: 0%, 70% and 100%
+
+Also the battery indicator is hard read since the frame pipe is blocking the view and not that bright in sunlight.
+The change is done via one press on he button which is on the battery. This is not comfortable while riding.
+
+This I wanted to improve so I disassembled the controller and battery of the durban and did take a closer look.
+
+On the bottom connector plate there exists a bafang typical port for debugging and configuring. However this is he same interface as the
+Display is using to send over a serial bus the support level.
+After some research I found the pinout and connected my logic level analyser and I saw the protocol of the "display" which in this case coming from the battery.
+
+[lightgallery
+    /images/blog/connector_controller.jpg Ports at the bottom of the controller;
+    /images/blog/connector_pinout.jpg, Bafang port pinout;
+    /images/blog/kalkhoff_battery_bms.jpg, Kalkhoff durban g9 - battery managment system pcb;
+    /images/blog/kalkhoff_battery_cells.jpg, Kalkhoff durban g9 - battery cells;
+    /images/blog/kalkhoff_battery_connector.jpg, Kalkhoff durban g9 - battery connector;
+    /images/blog/kalkhoff_battery_side.jpg, Kalkhoff durban g9 - Cell placement 3P 10S;
+lightgalleryend]
+
+Therefor I ordered a display from aliexpress which should replace the "display" within the battery.
+There are several display options available. In order to save space on the handlebars I've chosen the "500C".
+
+[lightgallery
+    /images/blog/bafang_500c.jpg, Bafang 500c Source: Diatone 2018 GT M3 130mm Source: www.banggood.com;
+    /images/blog/bafang_500c_mounted.jpg, Bafang 500c mounted on Kalkhoff Durban G9
+lightgalleryend]
+
+For connecting the 500C the 2 serial wires have to be disconnected from the controller and only the new 500c is connected to the
+debug port of the controller at the bottom.
+However there was one problem. The battery is including a display which auto turns off in case it could not communicate with the
+controller. So after 10 min the battery turns off and the motor support is gone.
+
+To solve this issue the Rx cable for the battery has to be plugged in. With this the battery reads the feedback of the controller but
+can not transmit its own commands.
+The Rx cable you can see in the pics below with a XXX isolation.
+
+With this configuration you can choose the support level and limit by the 500c (yes also the limit :))
+
+With this the range of the battery can be optimiced so turn off support on easy tracks and add additional support for steep hills if fully loaded.
+I really wonder why Kalkhoff did no add this kind of display from the start. The only reason I could think of is to have a con or attractive selling points for
+the bosch ebikes.
+
+[lightgallery
+    /images/blog/kalkhoff_loaded.jpg - Kalkhoff durban g9 used for groceries and getting milk from an automat
+lightgalleryend]
+
+