Advice on Which MP to Buy

[motor_magic]

Hi there,

I'm not totally sure whether I'm posting this in the write place but hey it happened.

I'm wanting to get a MP for commuting to work instead of a car.  I'm getting a bit old but refuse to let in and buy a car - for one reason I'm not sure whether I can afford one!  Some days I want to cycle assist some days I want just sit and pretend to cycle.  I want to fit it onto my mountain bike which currently has hydraulic disc brakes front and back.  I've included an elevation of my trip to work.  My trip back is the same in reverse.  I'm fairly skinny and weight about 70Kg (11 Stones).  Some days I want to barely peddle at all (bits of my body are giving up .

OK my questions:-
1) What motor and battery do you recommend? 
2) The laws in my country may change - if they do is it possible to detune your recommended MP motor and battery using the PC controller so that it has a lower wattage, and if so does that mean I need to keep the PC controller attached when I'm cycling?  I'm guessing that I need to change the battery...
3) As I have hydraulic brakes will I need to replace the mechanism so they now use wire actuated disc brakes or do I only need to replace one of the brake mechanisms?  There isn't a system to retro-fit the system within existing breaks?
4) Do you think I'll need to change my gear mechanism for the rear cassette as its a 9 speed at the moment and I was considering using the 6 speed cassette?
5) Can you switch between PAS and finger throttle without plugging it into the PC?

I'm moving offices in the next few weeks so I'll need to make a decision soon so any help is very grateful

Cheers,

Neill

[Morgen 3Eman]

Those street names make me think of Glasgow!  Yes?  No?



TTFN,
Dennis

[Pinner]

You might as well get the MP III they seem to have fixed some of the problems with the MP1 and MP2 and you'll want to get the 48 volt battery.  The 24 it's just too slow maybe the 36volt as it will be cheaper than the 48V and faster than the 24V.  The 48 on my steel frame bike goes 43kph according to my phones gps app and I'm 185lbs (on flat land).  I'm very happy with mine and it climbs hills really good too.  I pull a kid trailer and I don't even notice it there even on hills.  The nice thing with this kit is the hub wattage does not need to match the battery volts like on all the other brands kits and yes you can govern the speeds with the usb cord and program.  The regen breaking on mine is so strong that you don't need to have disc brakes and even if you can't fit your disc on the hub for some reason the front one will be enough.

[Pinner]

The usb cord just goes to your laptop then you unplug it after you save your changes not sure how the PAS works I didn't hook that up.  Don't think it even came with that, but you can peddle and/or use throttle.  I used a 5 speed freewheel and it was a tight fit (and I have the standard 135mm dropout space) so I would get a different gear cluster and the freewheel tool that removes them which is pretty cheap but needs to match your brand and year of freewheel (says on the package at the bike stores) as there are about 7 different tools.  And you will want a rack for your battery I recommend the one that attaches to your seat post and rear forks as the battery is very heavy.  Also, if you buy one of GM batteries in the silver case get the rack or at least the battery plate as the battery case has a key lock that mates with the plate to lock the battery and has a sliding rail attachment to hold the battery down and slide it off.  Then you don't need to mess around with bungee cords or velcro straps and it won't shake and rattle when you go over curbs etc.  Also, Gary told me that you should put a washer on the inside of the dropouts and the other tabbed washer on the outside.   These washers on the inside take up dropout space but I think it should be done that way to be stronger and tighter.  And if you ever want to remove your freewheel such as if it binds and you need to put a washer behind it you will need to die grind the hole bigger in the tool because the axle is twice the diameter and long....took me 5minutes to do.  Cassette gears wont work on this hub you need freewheel gear clusters that thread on.  High psi tires help too as the set up is very heavy...you will not want to peddle that much except at low speeds and on real steep hills that are pretty big to help out the motor.  If you need to stop on a large steep hill and then go such as at a light you will need to peddle as it will grunt and be hard on the motor until you get going.  If you are moving all the way up hills it seems to work much better.  The cruise control on these hubs is nice on long commutes you just press the red button and it stays at that speed until you brake.

[truly_bent]

Neill;

Not wishing to rain on your parade, but I think your biggest problem is the UK power limitation for electric bikes. As per http://en.wikipedia.org/wiki/Electric_bicycle_laws the legal limit in the UK is a somewhat anemic 200 watts. I believe  the MP motors' lowest rating is 500W at 24V. If you're like me however, you'll be ignoring the local legal limit (is this posting traceable?).

Your chart seems to indicate relatively large changes in elevation. Whether this is due to the compression of the graph I'm not sure. If in fact your route takes you through extreme elevation changes, you might consider a completely different type of electrical assist. At the risk of raising a chit-storm of protest, you might consider turning away from hub motors toward mid-drives.

As you are probably aware, mid-drives combine your pedal power plus the motor's power through a common jackshaft arrangement, and from there on to the rear gear cluster. This allows the motor to be run at a more efficient speed (and therefore with greater power) on those particularly steep and slow sections of your ride. Granted, mid drives are a somewhat more complex animal, but the benefits in your case may warrant such an approach.

Having said that, I went with the hub drive for a couple of reasons. One is that I don't live in an area with many hills (south central Ontario Canada) and two, because hub motors are considerably quieter than mid-drives. It's difficult to get away from the chatter that the necessary extra gearing makes with mid-drives.

Good luck in your quest...


By the way, how did you generate that elevation chart?

[Bikemad]

I've just entered the return trip details for one of my local trips into http://bikeroutetoaster.com and this is the result:



When my modified MKI Pie was still alive and drawing up to 60 Amps, I could manage this route by using ~80% capacity of my 51.8V 5Ah LiPo pack, although the battery warning device did indicate a low battery voltage under load on the last steep part of the trip.  On a 25.9V 10Ah LiPo pack I can manage this route using less than 30% of the pack's capacity.

Climbing steep hills will suck the power from the battery pack fairly rapidly, but at least they also allow the regen to help put some capacity back into it again when you're going down them.

I recently tested my MPII (with a slightly modified shunt) using a pair of watt meters with one connected in reverse to measure regen current, and here are the results of a short test run using the 25.9V 10Ah LiPo pack:

Units Measured	Under Power	During regen
Voltage (Volts)	27.41 min	29.47 max (@ 22mph)
Current (Amps)	36.39	16.37 (@ 22mph)
Power (Watts)	997.4	482.5 (@ 22mph)
Capacity (Ah)	0.626	0.042

         

I calculated the regen to be ~6.7% of the power used, therefore the range should also be extended by an additional ~6.7%.
I'm still not sure whether the regen on the MPIII works in the same manner as the earlier Pies, but when I finally get my MPIII on the road, I will try to do the same test as above as a comparison.

Hi andto the forum Neill, my main concern for your intended use is the range you're likely to get without pedalling with all those hills. If you can recharge the pack while you are at work, you should be able to manage with a 48V 10Ah pack.
If you are not able to recharge at work, you may have to consider using a lower voltage pack with a higher capacity.

Alan