Some advice for a ebike newb

Catchmydrift?

Finding my (electric) wheels
Mar 15, 2025
7
3
Hi, just joined the forum hoping for some advice from you knowledgeable chaps and chapeses

Ive converted 3 bikes over the last couple of years (two for my son, one for my mum), all 250w, one using the voilamart kit and two using the yose power kits. They're great fun, so I'm now looking to do the same for myself, but more of a custom job.

I purchased a cheap second hand MTB with disk brakes (160mm rotors) last weekend for £130, is basically new, so pretty pleased with it. Should be good enough for a "250w" build.

The advice I'm after is simply about the parts to use. I've had a browse on this forum over the last few days and have came across some good info.

I would like this to be a budget build, would love a battery from em3ev, but they are a bit more than I want to pay. But this looks more in my price range:


The above company seems to be recommended on here as good cheap batteries?
I'm wondering if there are any other UK companies in a similar price range anyone knows of?
(I'm looking for a 48v or 52v, but not sure if going for a 52v would cause problems sourcing a controller and LCD to suit?)

I keep hearing about KT controllers, do people mean KT Ketang such as these?:


As they seem to be out of stock everywhere, as presumably I would need one that is capable of 1000w peak power from the 250w motor to be safe, so for example, 15a x 48v = 720w. Would the controller have the option to adjust the amps that the motor can draw? So I can adjust the peak power? (This is a feature on the yose power LCD on my son's).

Do the throttles on the KT controllers have the ability to increase/decrease power based on the PAS setting you are in? And the option to use as just a normal throttle? (For off road use only obviously, as I'm aware we do live in a police state now)

Do the KT controllers have the ability to adjust the top speed, so it can be limited to 15.5mph, or allowed to go above when using off road? If so, what's the max? If they have a max?

There seem to be many controllers listed as "KT" controllers, are most of these knock offs, therefore I should only be looking for genuine KT Ketang ones?

(Edit- I guess actually, the above will relate to the LCD rather than the controller, was considering a UKC1 LCD display, would that be compatible with the KT controller?)

Then there's the motor! (I was thinking a motor that was ment to be 36v @ 15.5mph on a 48/52v battery, unless you just decide based on motor rpms?) I've seen many suggestions for a 250w, but a decent budget one that can handle as much torque as possible whilst still having a decently high rpm?, I know that's kinda like asking how long is a piece of string, but one that was capable of 30mph using a 48v battery and still have decent torque would be nice (again, off road only), and would the linked battery posted above be of large enough capacity to hold the voltage up enough to actually give decent performance? (As it's only 13ah). I presume so as the BMS can handle 40amps. (I'm guessing the power would drop off after not so long due to the low AH) Are these types of batteries capable of being discharged for example at 1.5 or even 2C?

Lots of questions I know, hence why I'm here asking!

Thanks very much guys

(Edit- again. After some more reading, I think I'm going to prefer the punchiness of a square wave controller, will need to be 30a for future proofing (assuming I can limit the amps with the LCD), I guess what I'm after is max torque/acceleration from a 250w motor. I tend to like running things to their limits, so may see how long the motor lasts at say 20 or so amps @ 48v for example - be nice if anyone has tried this personally?)
 
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Catchmydrift?

Finding my (electric) wheels
Mar 15, 2025
7
3
As the above post is waiting for approval, been doing some more reading, think I've decided to go with the UKC1 display and a YF controller as the KT controllers don't work with the UKC1 displays, and all the KT displays look a bit dated imo!. The controller below is also dual mode square/sine so can see what suits me best, is a 35amp (presumably 17amp continuous from the description) so should me more than enough.


Still interested in the battery posted above, would like a larger capacity, but they just look a bit chunky and heavy! So still not decided 100% yet.
(Actually the above battery only has a 30amp BMS , the 17ah one has the 40amp BMS, so may need that to be future proof.. - but I guess as I can limit the amps on the display, it wouldnt be pulling 30amps from the battery anyway, certainly not a "250"w motor surely?)

Not sure at all about motors though, rpms etc...
 
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Catchmydrift?

Finding my (electric) wheels
Mar 15, 2025
7
3
Probably best to ignore most of the first post as found out most of that over the last couple days, thanks. . Just making a decision on the motor, and battery now
 

matthewslack

Esteemed Pedelecer
Nov 26, 2021
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Hopefully amongst what you have learned is that 52V is illegal, an off road mode switch is illegal, 30mph is illegal, and the conditions in which those laws don't apply are extremely limited: private land with no public access and with the owners permission. Not forest tracks, bridleways, canal towpath etc.
 

Catchmydrift?

Finding my (electric) wheels
Mar 15, 2025
7
3
Hopefully amongst what you have learned is that 52V is illegal, an off road mode switch is illegal, 30mph is illegal, and the conditions in which those laws don't apply are extremely limited: private land with no public access and with the owners permission. Not forest tracks, bridleways, canal towpath etc.
Yes I'm aware of the laws, like I mentioned, we live in a police state. It's for my own private land. I'd like you to point out the law that states 52v is illegal though .... (Not that I've decided to go with 52v anyway, 48v should be fine). I also didn't mention anything about an off mode switch, as long as the top speed is limited electronically, which it will be. If something is "capable"of a certain speed, but is limited from doing so, that doesn't break the law.
 
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sjpt

Esteemed Pedelecer
Jun 8, 2018
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If something is "capable"of a certain speed, but is limited from doing so, that doesn't break the law.
That depends on how easy the delimiting is. If it can easily be delimited by a 'off-road' switch then it is not a legal EPAC.

Unfortunately there doesn't seem to be a precise definition of 'switch'. My interpretation is that if the delimiting can be performed while mounted then it is a switch. If it is more complex and can only be performed off the bike (eg firmware upgrade) then it is not a switch and the bike in speed limited state remains a valid EAPC.

I'd be interested if anyone can come up with a precise legal definition of a switch in this context; or alternative interpretations from the sources that do exist; or sources that show my interpretation is incorrect.
 
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Catchmydrift?

Finding my (electric) wheels
Mar 15, 2025
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And after all the reading I've done over the last few days, looks like it was a waste of time anyway (although I guess I've learned a thing or two), as a friend from work has just offered me his bike cheap as he's upgrading. I've not seen it, just a photo, is a "woosh" bike, looks nice, and it's even 100% legal. - sounds a bit boring I guess, but I'll have a go when he brings it in tomorrow.
 

matthewslack

Esteemed Pedelecer
Nov 26, 2021
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52V is more than 50V, which is a limit specified in a law that has much wider applicability that just ebikes.

There is a potentially grey area - I'm sure someone else will know how grey - about whether 50V is intended to mean 'nominal' or 'maximum' when applied to battery systems. If nominal then a 13s lithium ion pack is OK, but if maximum it is not as fully charged voltage is 54.6V.
 
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saneagle

Esteemed Pedelecer
Oct 10, 2010
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Probably best to ignore most of the first post as found out most of that over the last couple days, thanks. . Just making a decision on the motor, and battery now
IMHO, your first ideas were pretty sound, and you could have done a pretty good legal conversion. Your second ideas are great if you want a throttle-only electric moped that will probably get seized by the police sooner or later. The third idea is even better, and if you need a bit more oomph, you can always upgrade to 48v battery and KT controller and still be legal.
 

Catchmydrift?

Finding my (electric) wheels
Mar 15, 2025
7
3
IMHO, your first ideas were pretty sound, and you could have done a pretty good legal conversion. Your second ideas are great if you want a throttle-only electric moped that will probably get seized by the police sooner or later. The third idea is even better, and if you need a bit more oomph, you can always upgrade to 48v battery and KT controller and still be legal.
Awesome thanks... Woosh it is then, assuming it's as good as he says it is!
 

Peter.Bridge

Esteemed Pedelecer
Apr 19, 2023
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Oh very nice - I think that would be my choice as a "do it all" e-bike - and you can get a new battery when you need it from Woosh for a reasonable price
 
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Bikes4two

Esteemed Pedelecer
Feb 21, 2020
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.........I'd like you to point out the law that states 52v is illegal though ....
As I understand it this stems from BS EN 15194 which is the European and British Standard for EPACS and defines the max voltage for an EPAC as 48v, thus running a bike at 52v puts it outside the definition so if riding a nominal 52v machine then it's an electric motor bike I'd think.
62373

But I'm no expert on the EPAC laws as I always ride legal ebikes e.g 250w/36v/no throttle etc etc and therefore rarely delve into the finer points of the legal side so apologies if I've got something wrong here (and happy to be corrected - every day is a school day as they say).
 

matthewslack

Esteemed Pedelecer
Nov 26, 2021
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As I understand it this stems from BS EN 15194 which is the European and British Standard for EPACS and defines the max voltage for an EPAC as 48v, thus running a bike at 52v puts it outside the definition so if riding a nominal 52v machine then it's an electric motor bike I'd think.
View attachment 62373

But I'm no expert on the EPAC laws as I always ride legal ebikes e.g 250w/36v/no throttle etc etc and therefore rarely delve into the finer points of the legal side so apologies if I've got something wrong here (and happy to be corrected - every day is a school day as they say).
Another opportunity to discuss what 'rated' means!
 

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