48v upgrade

[Hightechpete]

I recently acquired a full size Dahon folder with a front wheel kit fitted by C H White of Malvern. I love the way the bike rides but not the power delivery. It has an 8fun unsensored motor which has a 3 level speed controlled pedal assist. I'd like to change the controller and display to 5 speed current control.
After doing some research on this board, it appears that I need a square wave controller and corresponding display.
While I'm about it I thought I might upgrade to 48 volts, I don't need the extra speed but a little extra torque and range might be useful at times (I'm the wrong side of 70, I live in Wales and it's a heavy bike).

Apart from the legal issue which doesn't concern me, am I likely to encounter any problems with a conversion. Any thoughts or advice ?

 

[saneagle]

There's no legal issue with using 48v.

If you want more torque but not more speed, you need more amps, not volts. Those motors can handle up to 22 amps, but would be noisy with a square wave controller.

The controller upgrade is a good idea, but square wave is not as good as sinewave. You get sinewave for sensored motors and square wave for uncensored.

 

[Hightechpete]

There's no legal issue with using 48v.

If you want more torque but not more speed, you need more amps, not volts. Those motors can handle up to 22 amps, but would be noisy with a square wave controller.

The controller upgrade is a good idea, but square wave is not as good as sinewave. You get sinewave for sensored motors and square wave for uncensored.

So your advice would be to stick with 36v and use a high amp controller?, I don't know the discharge capacity of the battery. I thought a 48v battery could handle more amps.
It's an unsensored motor so I'm stuck with a square wave controller.

 

[saneagle]

So your advice would be to stick with 36v and use a high amp controller?, I don't know the discharge capacity of the battery. I thought a 48v battery could handle more amps.
It's an unsensored motor so I'm stuck with a square wave controller.

48v gives more torque, so you can run with fewer amps. The downside is that it decreases efficiency at low speed. That's not a problem if you use the extra speed, but if your speed remains the same, you lose efficiency. For best efficiency and suitable operation of any motor, you should design your system such that the maximum rpm of the motor is 1.25 to 1.3 times your modal speed. After that, you choose a controller that gives the current for whatever torque you need.

In summary, torque and maximum speed of the motor increase in proportion to voltage if everything else stays the same, and the efficiency curve moves up the rpm scale.

 

[Hightechpete]

48v gives more torque, so you can run with fewer amps. The downside is that it decreases efficiency at low speed. That's not a problem if you use the extra speed, but if your speed remains the same, you lose efficiency. For best efficiency and suitable operation of any motor, you should design your system such that the maximum rpm of the motor is 1.25 to 1.3 times your modal speed. After that, you choose a controller that gives the current for whatever torque you need.

In summary, torque and maximum speed of the motor increase in proportion to voltage if everything else stays the same, and the efficiency curve moves up the rpm scale.

Thanks for the explanation, I'm recovering from a broken leg and using the bike to aid recovery, even so I'm finding the hill climbing power adequate so staying with 36v seems sensible.
There are 36v 15 Ah batteries available made from 21700 panasonic cells which I assume would have a good discharge rate, maybe you could recommend a suitable controller.

 

[saneagle]

Thanks for the explanation, I'm recovering from a broken leg and using the bike to aid recovery, even so I'm finding the hill climbing power adequate so staying with 36v seems sensible.
There are 36v 15 Ah batteries available made from 21700 panasonic cells which I assume would have a good discharge rate, maybe you could recommend a suitable controller.

The battery sounds OK, but always check the spec incase they put an under-powered BMS in it to save money. Aim for a battery that can give 25A continuous, sometimes listed as 1000w batteries.

We always recommend KT sinewave controllers, which you can find everywhere. If your present controller is 15A or less, a 17A one would give a 13% improvement in torque, and a 22A one about 50% improvement. Occasionally, you can find 20A ones. The 22A ones are bigger than 17A, so check sizes or you might have to make a new box to put it in. I'm pretty sure that all the ones above 15A are dual voltage, which gives the option os switching to a 48v battery later if you need more power.

If your motor is sensorless, you have to get a KT square wave controller.

 

[Hightechpete]

Thanks for all the advice, seems like those 21700 cell 15ah batteries are in short supply at the moment. I'll report back when it's all done.

 

[guerney]

I recently acquired a full size Dahon folder with a front wheel kit fitted by C H White of Malvern.

Another Dahon conversion! They're pretty rare on this forum: AFAIK it's just you, me, @saneagle and @RogerA (who has a very similar framed folding Dahon to yours and mine, but rear hub motored). I was curious about what C H White's special build conversions comprised of exactly, but not enough to enquire. I shall be reading about developments with interest.

 

[Hightechpete]

It's the Dahon espresso virtually as new, 26 inch wheels, 8fun front wheel motor labelled 250 watt, unknown controller (label missing), big apple tyres. Got the original receipt for £973 , rides nicely. It's a keeper.

 

[guerney]

They've got a big stash of new frames for their special builds. 2.35" Big Apples are a great choice for adding suspension, as there's none anywhere else. My (much older) Espresso might get those too, or Big Ben Plus. For extremely bumpy pothole blighted roads, you may be able to install a Redline Shockstop? @Nealh has one:

ShockStop Suspension Stem

The minimal design of the ShockStop Stem blends seamlessly with the aesthetic of modern bikes, while reducing fatigue and strain. Along with the ShockStop Suspension Seatpost, this system works together to suspend the rider and smooth out rough terrain on the bike you already own, making your...

redshiftsports.com

 

[Hightechpete]

What?, you cannot be serious, £189 !!. That's almost what I paid for the bike.
Interesting comment re. Big apples, maybe that's why it rides so good.

 

[guerney]

There was very noticeable improvement in ride comfort, after swapping out the original 1.5" for 1.75" wide tyres on my electrified Helios. My Espresso's front mudguard is missing, the rear mudguard is 60.1mm wide and a bit damaged. Trying to source full mudguards that wide, with clearance enough for wide tyres like Big Apples has been difficult. Is there a brand name marked on your mudguards (or receipt) and how wide are they? If unmarked, they're probably Dahon.

I was considering buying a new frame for my old Espresso, I still might. There's also the possibility of a folding handbar stem, for a thinner folded bike profile (rules out a Redshift Shockstop, if installed) - useful for carriage on pubic transport and to fit the bike into cars... but a shiny new frame would be a thief magnet, and for short unelectrified journeys, I intend to leave the Espresso locked up on bike racks if necessary, every so often. Outer gear and brake cables arrived yesterday, waiting for stainless steel inners. I'll put the now de-rusted groupset back on and see how it rides on the Continental Contacts it was delivered with (ebay bargain bike), next week probably. Talking of groupsets, my de-rusted Tourney seems likely usable... I see you've got an Acera derailleur, again, good to know - I wonder which? Do you know what freewheel is fitted? Could be this, like mine:

https://www.amazon.co.uk/Shimano-MFTZ5007428-FREE-TZ500-14-28/dp/B073XTMQQV/

Apologies for all the questions, feel free to ignore them. I really should have saved that CH White product page. I shall contact them for answers...

 

[Hightechpete]

Photos of mudguard and gear cluster


Mudguards look similar to those fitted to the Big bear, the last time I looked at CH White's website there was a bare frame for sale for like 80 quid.
Don't worry about all the questions, after all the good advice from members I'm happy to give something back

 

[RogerA]

This is my bike - A Dahon Matrix with a rear wheel AKM100cst motor. I think the only difference between our frames is that mine has front suspension forks, and a rear cassette (and yours is a lot cleaner). I removed the front triple and went for a single 42T chainring to simplify things. With a motor a 42 chainring and 11-32 cassette is plenty.

If you have any questions then I'll try to help, but I'm not here as much as others.

 

[saneagle]

This is my bike - A Dahon Matrix with a rear wheel AKM100cst motor. I think the only difference between our frames is that mine has front suspension forks, and a rear cassette (and yours is a lot cleaner). I removed the front triple and went for a single 42T chainring to simplify things. With a motor a 42 chainring and 11-32 cassette is plenty.
View attachment 54790
If you have any questions then I'll try to help, but I'm not here as much as others.

Nice bike, but I'd get rid of that rear bottle holder and rotate the battery a few inches forward for better handling. Your goal with a rack battery should always be to get it as low and far forward as possible. Even an inch can make a big difference.

 

[Hightechpete]

I love the way the bike rides but not the power delivery. It has an 8fun unsensored motor which has a 3 level speed controlled pedal assist. I'd like to change the controller and display to 5 speed current control.
After doing some research on this board, it appears that I need a square wave controller and corresponding display.

Further to the above, the KT controller and LCD4 was obtained and fitted, I'm getting an error code 3 (Hall sensor error). I wrongly assumed that the square wave controller would run in unsensored mode, not so.
There are cheap dual mode controllers available on ebay but I would like to stick with KT. Bearing in mind I would like a 36/48v 17 amp, can anyone suggest a supplier?

 

[saneagle]

You have to buy a sensorless KT controller. They don't have the connector for hall sensors. I don't remember ever seeing a dual mode one. Topbikekit has sensorless ones.

 

[Hightechpete]

Thanks saneagle, it seems that all their square wave controllers will run sensorless but all the 36/48v are 22a and too big to fit, so if I want to keep things neat it looks as though I'll have to settle for a 24/36v, it's a shame because I wanted the option of upgrading to 48v.
The KT website listing shows the one I need but I can't find a supplier.

 

[saneagle]

Thanks saneagle, it seems that all their square wave controllers will run sensorless but all the 36/48v are 22a and too big to fit, so if I want to keep things neat it looks as though I'll have to settle for a 24/36v, it's a shame because I wanted the option of upgrading to 48v.
The KT website listing shows the one I need but I can't find a supplier.

15A and lower are normally 24v/36v, but you can find 36v/48v ones on Aliexpress if you have the patience and creativity to search there. You need creativity to invent the correct search string. Even when you type in the exact listing title, it still doesn't find it. Their search has gone to shite.

 

[Hightechpete]

I'll give it go, this might be the last bike I ever buy so I want to get it right.