Swapping Oxydrive CST controller for Kunteng one. Will it work?

e_kid

Finding my (electric) wheels
Dec 1, 2017
13
1
36
UK
I'm currently injured and won't be able to cycle for a while, so I've been looking at buying a fairly powerful kit (using mainly throttle only), when I remembered that I have this old kit laying around (see attachment), and thought I'd have some christmas fun and turn it into something a bit more exciting.

It's a 250w Oxydrive CST kit that comes with a Bafang SWX02 (10) motor, and a 36v 11ah battery. The label on the controller reads 7A, 15A max.

From what I've read online, the motor is capable of handling much more power (exactly how much, I'm not sure), so I want to upgrade to a 20A max. controller to give +700w. From what I've read, the silent Kunteng (KT) sine wave controller seems the way to go.

Further on in the future I also plan on building a 48V battery pack to take it towards 1000w and increase the max speed.

However, there are a few issues that I need some help with:

- I'm not sure whether I can reuse my battery, as the controller is built into the component that the battery slides onto. Will there be compatibility issues, or can I somehow bypass the controller? If not, is there a rack without a built-in controller, that is compatible with my battery, or should I just get to building that 48V battery now and forget about the one I have? It would be nice to reuse as many parts as possible.

- Also, are there any glaring issues with what I've proposed? Is it destined to fail/blowup? Would I be better off getting a new motor as well? I have been looking at the Q128c. But again, it would be fun to reuse the parts that I already have.

Thanks for your time!
 

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Nealh

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Aug 7, 2014
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No issues what so ever, even if you go to 48v later. I have done it and the Bafang /8funs can take it in their stride with ease to about 22a, though we do have a new forum troll who will likely say you will crash and burn but don't worry about this as not so and just some scare mongering.
I did the same with an original 8fun cst code 10 which by the way is 270rpm load speed. You can use the battery but you will need a lcd3 to match with the Kt controller (buy a dual voltage 36/48v one) and the peripherals needed as you won't find julet ones at the mo , also the Daskit battery has 17a bms or that is on a label on my bms, so you may have to limit a 20a KT to 17a via the setting parameters which is easy peasy to do.
The cells used are Sam 22F pretty poor/ very mediocre cells and only rated 4.4a but are 5p config, the bus construction isn't configured for good current sharing so some energy will be lost to heating up the nickel esp for more then 15a.
The controller is mostly a solid state one bedded in liquid silicone so you will have to dig it out and remove it (my made horrible noises & went funny, the lvc was cutting in on fully charged batteries). You will still need the controller base unit if using the Das battery case , cut the supply wires at the controller board leaving them soldered to the 4 pin discharge connector inside. Solder splice & insulate new wires to these (utilising the rear controller base grommet and poke them thru) then simply feed them to the new KT controller.
I used an under cross bar bag for mine but you could also use a large size under seat bag. The dual voltage controllers some times get a bit hot confined so I added a couple of 5v fans to aid cooling, the KT S09S has a larger heat sink casing so may be better at heat distribution otherwise freeair will keep cool.
The Q128c is pretty good but the Bafang is much gooder imho.
 
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Nealh

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I had DAS 22 & 26F but in reality the cells are quite poor 2 years and capacity/range deteriorated so I withdrew them, the 26F I deconstructed and made some 6p3s booster soft packs up and now these are used in series with 36v PF hardcase and soft packs for 48v for better range for my days out when riding . I have a pair of 48v set ups like this and parallel them together utilising a frame hardcase battery and the rest in a rear top bag set up.
 

e_kid

Finding my (electric) wheels
Dec 1, 2017
13
1
36
UK
Hi Nealh. Thanks a lot, that's music to my ears.

I will most likely pull the trigger on the KT36v/48v 20A tomorrow, although I'm seeing if I can squeeze in an extra 2A from somewhere.

Although, that being said, does the 17A BMS on the Das battery mean that I am bottlenecked to 17A? And is the only way round this to replace it with a new one? If so, I wouldn't mind giving this a go, but probably won't be able to get round to it for a while until I have bought a spot welder, etc. And then I may as well upgrade the cells at the same time, as like you say, the range on it is absolutely terrible. I bought this kit second hand and from what I remember, always struggled to get 30km from it, even in eco mode.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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I can't remember but yes think 17a might be the limit, strangely with the original controller I was always able to go faster then with the 17/20a kt one.

I'm currently re- celling one of my DAS cases with Panasonic 10a cells as 10s 4p, the config/layout allows for a better more even current share though will be using the original BMS to see how it fairs.
I will be using normal z shape nickel with slits with additional 0.8m copper wire added/soldered to uprate the bus current carrying capability.


Edit;
The bms 17a is most likely the continuous rating but it will have a pulse/over current rating which is usually higher so should be ok for higher current up to 25/30a for about 30 secs.
 
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