nano brompton

[jerrysimon]

That battery looks like the lithium polymer packs used in the model aircraft hobby world.

Regards

Jerry

 

[barrycoll]

hi folks..

as the original proposer of this thread, I am fascinated in the twist and turns it has taken, and also about just how much knowledge is 'out there'

the latest take is Freedom ebikes offer of the nano conversion, and as Tony at electricwheel never seems to be there to take a call, I am very interested in this new possibility...(but if he doesnt take calls, heaven knows how I could expect a return of deposit!)

as Daniel says, the battery seems to be an unknown quantity at the moment, and the details of the kit as given on the website (to me) seem a little vague...
the actual location of the supplier is not given which is a tad worrying

any more info from anybody?????

cheers from barry c.

 

[daniel.weck]

as Daniel says, the battery seems to be an unknown quantity at the moment, and the details of the kit as given on the website (to me) seem a little vague...
the actual location of the supplier is not given which is a tad worrying

The batteries are small (91 Wh), but that's a design feature. You can purchase 2 extra batteries from Freedom e-Bikes, which gives you a total of 273Wh, so on a 36V system it's 7.58Ah, which is closer to the Nano's 10Ah configuration. (I am talking about the Brompton-specific kits, not the 26" ones)

The extra cost when you purchase extra batteries brings the total cost to about the same as the Nano kit. By the way, the Freedom e-Bikes kit doesn't use LifePo4 batteries on the Brompton kit due to their size and weight, but I'm sure you can discuss your needs if you want to purchase the 26" wheel option.

As for the location of the seller, I have my idea based on his personal email address, but I'll let you work this out with him directly. He told me he is a new business, based abroad, but I have no other details.

 

[daniel.weck]

That battery looks like the lithium polymer packs used in the model aircraft hobby world.

Andy (Andrew Hamilton) told me that it's Lithium but not Ion or Polymer
He also told me that it is safe, and with a life of 1000 cycles (claimed) it's on a par with LifePo4.
However we know that it's not LifePo4 or LiMnO4.
What is this "nano-technology" exactly ?

 

[jerrysimon]

Looking at that battery again it seems VERY similar to the Lithium Polymer batteries I have used in RC. You can see the balance plugs and a deans connector I think

http://www.freedomebikes.com/vp/JS-Lib/CustomerSites/Common/view_larger.htm?src=http://www.freedomebikes.com/0_0_0_0_250_333_csupload_12025304_large.jpg?u=633869906626188750

This means all the BMS will be in the charger. Interesting stuff.

Regards

Jerry

 

[daniel.weck]

from the photos on your website, it's difficult to tell but it looks like the black Brompton has got a front wheel laced into a 1-cross or 2-cross pattern, whereas the red Brompton (which is shown on most of the pictures) has got spokes laced into a direct/radial pattern. This makes quite a difference to the wheel strength, especially due to the torque generated by the motor. Maybe the photos are from prototypes, so how do you build the wheel in you current product ?

Building Bicycle Wheels by Sheldon Brown

"
Wheels with hub brakes and drive wheels should never be radially spoked. Due to the near perpendicular angle of the spoke to the hub's tangent, any torque applied at the hub of a radial spoked wheel will result in a very great increase in spoke tension, almost certainly causing hub or spoke failure.
"

 

[jerrysimon]

I like the little protector for the cable entry though

Regards

Jerry

 

[daniel.weck]

I like the little protector for the cable entry though

That's a Brompton feature, and it's not meant to protect the cable spindle-entry, it's a "hook" that rests on part of the frame when the bike is folded

In fact, the Suzhou Bafang (8-Fun) SWXK offset side-entry design is much better, because it doesn't compromise the folding abilities (it's better for other reasons as well, but my point is about this black plastic "hook").

Cheers, Dan

 

[barrycoll]

thanks for all the extra gen on Andrew Hamilton...

an email says that the wheel/fork build up is done in Israel, but I personally am not too happy with the radial spoke arrangement...just basic physics would suggest that a powered hub could put some nasty torque through an 'unprepared' spoke...bit similar to a disc brake??

power to the motor also folks

does not come through the bag block, as it does on the nano, so that means more connections that arent rigid..

having tested the Sparticle from the London branch, I wasnt impressed with the cable run through frame fold pivots, which seemed a future problem in the making...less connectors imply less problems?

as I failed physics at school (and uni!), my understanding of the battery size in relation to the electricwheel joby is non-existent, but from what I have read then battery for battery, the costings of the 2 conversions come out the same, despite the low(-ish) 'teaser' price..

Israel or Wiltshire, that is the question???

any thoughts folks
......and thanks to everybody, once again...barry c.

 

[daniel.weck]

an email says that the wheel/fork build up is done in Israel,

Yes, that's what I thought.

but I personally am not too happy with the radial spoke arrangement...just basic physics would suggest that a powered hub could put some nasty torque through an 'unprepared' spoke...bit similar to a disc brake?? power to the motor also folks

Yes, you *really* want at least a cross-1 pattern (I'm going for cross-2) on small wheels with strong hub-originating torque.

does not come through the bag block, as it does on the nano, so that means more connections that arent rigid..

That being said, you can make this appliance yourself It's not rocket science. The provided convenience is great (take front bag on/off), but I personally prefer robust proven water-proof connectivity. I don't mind the extra effort involved.

having tested the Sparticle from the London branch, I wasnt impressed with the cable run through frame fold pivots, which seemed a future problem in the making...less connectors imply less problems?

Yep, I just don't understand why they decided to put the battery at the back ? It adds weight to the high seat post (high center of gravity, higher risk of tube bending), it requires a longer seat post, and it requires longer cables that affect the fold. The front luggage block would have been a much better location.

Also note that the Sparticle kit is more expensive than the Nano from Freedom e-Bikes or from the Electric Wheel Company (once you add the cost of wheel build to match the products).

My advice: contact the ETS/Sparticle and work-out a custom order without their default battery setup. I'm sure they would be happy to sell the rest of the kit anyway.

as I failed physics at school (and uni!), my understanding of the battery size in relation to the electricwheel joby is non-existent, but from what I have read then battery for battery, the costings of the 2 conversions come out the same, despite the low(-ish) 'teaser' price..

Israel or Wiltshire, that is the question???

Another option is to purchase the parts from other trusty sources (Europe or Asia), and if you're not great at DIY, you can hire the services of your local bike shop for wheel building and fork widening.

You may be able to save some money this way, have more flexibility, and pay for local labor. I am not denying the appeal of an off-the-shelf solution, I am just going through the options.

Let us know how it goes.

 

[apshamlton]

Wow. This is a busy forum.
I'll try to answer all the questions raised.

1. Radial vs Crossover spokes. We can do either cross over or radial spokes depending on what is the customer preference.

The radial design looks better in the photos and in our prototype the radial build has not proven problematic.
Radial build is a problem when there are large torque forces (disc brakes or US style 1000 watt hub motors) and large wheels.
Sheldon Brown is an American (ie much more powerful hub motors) and is, I think, talking about bigger wheels.

The torque from a UK compliant hub motor is much less than from disc brakes and on a small wheel the radial configuration isn't the issue its made out to be.

2. Batteries - The plugs and balancing connectors are typical of RC but the battery packs use A123 cells (nano phosphate lithium) not lithium polymer. They are extremely robust and safe - we've had a pack shot 4 times by a bomb disposal robot and half the cells were recoverable. They also have very high charge and discharge rates and long (1000+) cycle life.
They also don't need BMS circuitry, which means they are not subject to BMS failure which is a big reason for premature failure of many other type of ebike battery.

3. Connections - I can't go into detail about the connections right now but it is more robust than the Nano / Electric wheel and much easier to install. The problem with the baggage block connector of the nano is that the copper connections eventually break because of wear (I've had this experience personally) and the copper strips are very difficult to affix to inside of the luggage bag block holder and can come away and short out against each other.

4. Price - The one battery pack headline price is not a teaser - it reflects the fact that most ebike commutes are less than 15km between charges, especially when the charger is around 400gms can be carried with you and recharge while you stop for a quick coffee. I only use more than one pack when I'm dragging a trailer with kids. Otherwise one pack gets me anywhere around Jerusalem which is a very hilly (but quite small) city and back.

 

[daniel.weck]

The problem with the baggage block connector of the nano is that the copper connections eventually break because of wear (I've had this experience personally) and the copper strips are very difficult to affix to inside of the luggage bag block holder and can come away and short out against each other.

Yep, my concern too.

 

[jerrysimon]

apshamlton,

I think the busyness is down to a couple of us newbies being over keen and with two much time on our hands at work, well me anyway

Thanks for the feedback.

Re the battery packs I totally agree I have a 36v 10ah 5kg Li-Ion pack and commute 10 miles to work and back. So a smaller pack would be fine. I have been looking at using 3*12V 4600mah NiMh about 2kgs.

I don't understand how your A123 pack does not need a BMS ? is this taken care of by the charger using the balancing tabs ?

Regards

Jerry

 

[daniel.weck]

2. Batteries - The plugs and balancing connectors are typical of RC but the battery packs use A123 cells (nano phosphate lithium) not lithium polymer. They are extremely robust and safe - we've had a pack shot 4 times by a bomb disposal robot and half the cells were recoverable. They also have very high charge and discharge rates and long (1000+) cycle life.
They also don't need BMS circuitry, which means they are not subject to BMS failure which is a big reason for premature failure of many other type of ebike battery.

Interesting. I have been in touch with someone who experimented with A123 batteries for a Brompton and a 80mm Tongxin motor. For those interested in the technical details, here's what he said:

...running with a 12 cell A123 pack (they are nominally 3.45v/cell straight off the charger), so 12 cells gives 41.4v at full charge. This compares to the standard pack, which gives 42v initially, dropping to 38.5v at 'half discharged', down to 36v being fully discharged. The A123, won't be hurt by discharging down to 2v/cell.

The A123 cell drops within a very few minutes to about 3.25v/cell, then discharges almost linearly, to about 2.95v/cell (under the sort of load used for the bikes), at which point it has delivered about 2.2Ah. It is considered fully discharged at 2.5v/cell, having delivered about 2.36Ah.
After about 2Ah has been delivered, the motor output starts to noticeably drop (speed down to about 12mph), slightly lengthening the battery life, but reducing the effectiveness at this point...

The batteries supplied with the Nano actually give more power for their weight, than the A123. About 20% more.
But, if you use small batteries of this type, and load them relatively 'hard', their output degrades more quickly (even though you see claims like '30S', the performance curves look awful at such rates....). The Tongxin, draws typically 6A under normal use, rising to just under 12A during pull-off, and hill climbing - for a 2.3Ah battery, this is just over 5S, making the A123 the better 'choice' for a smaller battery, but weighing more per Whour than the standard Nano battery.

 

[apshamlton]

I also forgot to mention that we can supply complete new electric Bromptons (ie with the kit installed and tested) delivered to anywhere in the world (for surprisingly low cost).

Thanks for the battery tech stuff Daniel - from the practical side I can testify that, after 18 months of heavy, hilly use my first A123 cell pack is still going strong. I had to replace a cell that got physically damaged but after that it was as good as new.

The 6 saved cells from the pack that was shot up by the bomb disposal robot are in my second pack that has also had heavy use for about 15 months total.

Suffice to say that from both the techy and practical perspective the Freedom Ebikes battery packs work really well with the Tonxgin motors & controllers.

 

[AndyOfTheSouth]

I am sure this has been answered before and apologies for asking again, but I can't find the thread.

How easy is it to widen Brompton front forks to take an 80mm Tongxin? I seem to remember a picture of a fork being widened using a long bolt and set of nuts, but I may be misremembering.

Secondly, once it has been done, would it be safe to reverse the process to put an ordinary wheel back in?

Thanks.

 

[apshamlton]

Hi Andy.
Its very easy to widen the Brompton Forks to take a 80mm Tonxgin.
As you described you just need a 110mm bolt and some nuts and you just screw it out to widen it gradually.
You also need to file or dremel the dropouts a bit to fit the wider axle. Again very easy.

The forks have quite a lot of spring so putting an original front wheel back in will not be a problem from the widening perspective. Once you screw the nuts tight you'll effectively reverse the process.

I even know of someone who has successfully widened titanium Brompton front forks via a similar method.