700c conversion?

[Geoff_L]

My wife and I want to convert our existing bikes (we don't have storage for these and new pedelecs). My wife's bike is no problem - it's a hybridised MTB with 26" wheels, so the Alien Ocean road-legal kit will do the job fine.

However, my bike is a different story as I have a hybrid with 700c wheels and, according to Jim at Alien, he no longer sells a 700c version of the road-legal kit. So, I can either buy a 26" version and have the hub laced to a 700c rim or look for a kit that's 700c 'out of the box'. I live in Cornwall (think hills) and I'm not thin as I used to be - so the potential torque reduction from upsizing a 26" kit to 700c is of concern.

Any recommendations?

TIA, Geoff

 

[Alan Quay]

As long as you are reasonably handy, a BPM or CST kit from BMSbattery should cover it. They will deliver it in 700c format.

The CST 500w will have enough torque for you. If you want to stay strictly legal, you will want the 250w BPM.

The fact is, if you run skinny tyres on 700c I reckon you are pretty close to the same diameter as 26" with monster tyres (my preference), so it probably will be a small % difference.

 

[jackhandy]

If it's of any interest, you're welcome to come over to Roche & try my 8fun & Ezee kitted bikes over my alpine test route:
The difference between the 2 bikes, although both rates at 250w is considerable.
There's a very good reason I ride the Ezee - Cornish hills

Should add that the Ezee-kitted bike is a Trek Mamba 29er, so similar (identical, some would say) wheel size to yours.

 

[Geoff_L]

Thanks chaps, that's two recommendations that are poles apart price-wise. I reckon that the 250W BPM with battery, rack, controller, charger, and throttle works out to about £300 + shipping and taxes (but no pedelec sensor?). In contrast, the Ezee kit sells for about £800 and comes with everything. However, at that price it's not much more than the Alien kit plus a new rim and labour to build the wheel. Certainly something to think about - thanks again.

 

[Alan Quay]

.... I reckon that the 250W BPM with battery, rack, controller, charger, and throttle works out to about £300 + shipping and taxes (but no pedelec sensor?).....

The BPM kit will be something like £450-500 by the time you add shipping and tax. (edit, checked with website, closer to £450 with taxes)

You can order a pedelec sensor as and extra, which will only add a couple of quid to the total. Likewise with most options.

The BMSbattery route is really only suitable if you are comfortable with the DIY route.

 

[falmouthtony]

If it's of any interest, you're welcome to come over to Roche & try my 8fun & Ezee kitted bikes over my alpine test route:
The difference between the 2 bikes, although both rates at 250w is considerable.
There's a very good reason I ride the Ezee - Cornish hills

Should add that the Ezee-kitted bike is a Trek Mamba 29er, so similar (identical, some would say) wheel size to yours.

Hi Mike

This is exactly what I did when I wanted to convert my hybrid with 700c wheels. JH let me ride his ezee conversion against the 8fun, I was sold on the sheer grunt of the Ezee kit. Cornish hills - bring them on. Do it if you can.

 

[falmouthtony]

Sorry - should have said Hi Geoff

 

[Elecman]

I've just bought a 700c road bike with one of the Cyclotricity kits fitted and an uprated controller.
I really can't fault it for the money at all. Pulls 20mph on the flat, really smooth with both pedel sensor and throttle.
It's made a good conversion on a 700c bike. It's not too heavy either compared to some of the kits which works well on a lighter road bike.
The only problem is it's not massively torquey on the hills, but still very impressive for a plug and play kit you can buy in the UK for £400ish. (I have no affiliation with Cyclotricity BTW, I bought this second hand already fitted to my bike !)

 

[Deleted member 4366]

If you decide on the BPM kit, make a shopping list and post it here so we can check it and advise. There's lots of potential mistakes you can make.

 

[Geoff_L]

Thanks again all. FWIW, I'm fairly good with DIY and so wouldn't anticipate anything insurmountable with the BMS Battery route. However, I wasn't expecting the difference that jackhandy describes. I appreciate the offer of a shopping-list check also, that's probably a good exercise even if I don't eventually go the BMS Battery route. Thanks again.

 

[Alan Quay]

Does anyone have experience of the Ezee kit against the BPM and CST? While I can believe there's a big difference between an 8fun and an Ezee, I'm not convinced that the Ezee has more torque than a BPM/CST.

 

[Deleted member 4366]

Torque depends on current.

The standard Ezee kit is 20 amps. There's also an optional 25 amp controller, but I don't know if Cyclezee stock them, although I'm sure he can get one if that's what you want. You can go a bit higher still if you use your own controller and do a bit of wiring. You have to choose an Ezee battery that can provide those currents.

With a BPM kit, it's easy to choose the right power controller and battery to suit your needs, and the motors come in a large range of RPMs, so you can have whatever speed, torque and power that you want.

Naturally,a BMSattery 201 rpm BPM kit with a 30 amp controller will out-climb a standard 20 amp Ezee kit from Cyclezee, but you're not comparing like with like. If you compare the 350w BPM kit from BMSB with the standard USA Ezee kit, the Ezee one will win.

 

[Geoff_L]

Torque depends on current.

The standard Ezee kit is 20 amps.

I'm now confused - much of what I thought I understood has just gone out the window!

I thought that the Ezee kit was 250W. Since power = volts * amps, the current drawn from a 36V battery at 250W (ignoring losses) should be 250/36, which is a tad under 7 amps. Why does the Ezee controller have such a high current rating? Does the controller etc. absorb a massive amount (i.e. are they that inefficient)? Is the battery pack voltage nominal 'no-load' and drops massively under load? Something else?

TIA, Geoff

 

[jackhandy]

I'm now confused - much of what I thought I understood has just gone out the window!
Why does the Ezee controller have such a high current rating?

Shhh... Don't tell anyone.

I'll leave it to others to explain the technicalities, but 250 watts CONTINUOUS rating is achieved in different ways, to keep within the uk rating, by various manufacturers.

 

[Deleted member 4366]

250w means nothing. The Ezee bike has a 36v battery (42v fully charged) and 20 amp controller, so 840w comes out of the battery when hill-climbing. When cruising at 15mph, the controller will only give about 10 amps, so 420w from the battery. The system efficiency varies anything fom about 15% to 80%, so the output power would be a lot less than what goes in to the motor. Efficiency is low when you go slow, so the Ezee's 840w in might be as low as 160w out depending on speed. The whole concept of how much power the motor makes is very complicated. You have to have all the aspects in your head at the same time to understand how powerful a motor is. Generally, you can say that the larger the diameter of the same type of motor, the more torque it will produce, and then the more current it gets, the more torque it will produce. Then the speed of the winding (motor RPM spec.) affects the efficiency, which determines how much input power gets converted into motive power, and it also determines how rapidly your motor will overheat, which is why you can't simply pump more amps into a small motor to get more torque.

 

[Deleted member 4366]

I can't delete this on Tapatalk!

 

[Alan Quay]

You have to apply D8veh's law, which states:

V x I = 250w

This is because a sticker applied to the outer casing of the motor will regulate the power output to a legal 250w, no matter what the voltage or current.

I have ahem... Heard of.... a 250w motor that will happily pull 30a at 40v.

Welcome to the confusing world of electric bike law!

 

[falmouthtony]

250w means nothing. The Ezee bike has a 36v battery (42v fully charged) and 20 amp controller, so 840w comes out of the battery when hill-climbing. When cruising at 15mph, the controller will only give about 10 amps, so 420w from the battery. The system efficiency varies anything fom about 15% to 80%, so the output power would be a lot less than what goes in to the motor. Efficiency is low when you go slow, so the Ezee's 840w in might be as low as 160w out depending on speed. The whole concept of how much power the motor makes is very complicated. You have to have all the aspects in your head at the same time to understand how powerful a motor is. Generally, you can say that the larger the diameter of the same type of motor, the more torque it will produce, and then the more current it gets, the more torque it will produce. Then the speed of the winding (motor RPM spec.) affects the efficiency, which determines how much input power gets converted into motive power, and it also determines how rapidly your motor will overheat, which is why you can't simply pump more amps into a small motor to get more torque.

I'm afraid the complexity of the technical stuff about the Ezee motor is a bit lost on me - but I do know that I recently pedalled my 103kgs plus TWO 14AH batteries and heavy kit bag up a nearly one mile long average 20% hill - mostly needing to be in next to lowest out of 29 gears - huge assistance all the way from the motor - and at the top the motor wasn't even warm!!

 

[falmouthtony]

Correction - 27 gears! One day I'll get a post right first time

 

[Geoff_L]

Thanks again all.

I've had a good look at the BMS Battery site and the choice of 250W front wheels with spoke patterns that reasonably match my rear wheel seem limited. All I can find is the SWXU V-Brake and the K5, so I'd probably be better off getting a kit. However, I want a rack-mounted battery with more than 10Ah, so my potential shopping list is:

• 36V250W Front SWXU V-Brake Motor E-Bike Kit with LED Meter
• High C-Rate 36V15Ah Li-Ion Alloy 07-Case Battery Pack

I'm not sure whether the battery comes with the charger and rack that appear in the photos on the relevant page, but if not then I need to add the rack and an Alloy Shell 900W LiFePo4/Li-Ion/Lead Acid Battery EV Charger.

That said, I'm a little concerned about using a charger that doesn't automatically stop charging when the battery is full - and I'm not sure this charger has that feature.

@falmouthtony: You say you carry an extra couple of 14Ah batteries around, so I have to ask what range you get out of the Ezee for 14Ah? FWIW, I'm heavier than you, and have been known to tow a trailer, so I'd expect less than you're getting - but it would be good to have an idea of how many batteries I need to buy!

At the moment, I'm wondering whether I'd be better off getting the Ezee kit without charger and battery (is this possible?) and going to BMS for those components.

Thanks again, Geoff