Saracen / MXUS, 1000w build thread

[averhamdave]

Hi,

I have just completed a build using a Saracen 700C wheeled roadster and a MXUS kit. The MXUS motor is a copy of the Bafang CST, ie strong, geared, brushless motor.

Whilst I have completed the build I am going post on the thread in bite sized chunks. The purpose of posting is for general interest of forum users but also to share some of my thoughts about the process of building the bike. If you could hold off with questions until I've finished it may keep it tidier.

I'll start at the end! Here is a picture of the finished bike:


http://s958.photobucket.com/user/averhamdave/media/Saracen MXUS/image_zps2f788e82.jpg.html?sort=2&o=19

 

[averhamdave]

I ordered the Kit from the supplier in China. I had no problems whatsoever with them. It cost me £265 delivered (although Fedex my still send me a customs bill). It was ordered and was with me 10 days after placing the order.

It consisted of:
MXUS 01A motor built into a 700c wheel using 12swg spokes. the wheel is true and tensioned correctly.
22a Controller
Pedelec components
LCD display - to display mph, distance travelled, time travelled, battery meter, assist level
2 brake cut off levers
Thumb throttle.

The bike runs on 48v / 15ah of RC Lipos

The box was opened and this was how it came:

image_zpsb06b30d3.jpg Photo by averhamdave | Photobucket

image_zps66d3ec32.jpg Photo by averhamdave | Photobucket

 

[averhamdave]

The bike is a Saracen Roadster with 700c wheels. It is in very good order but I carried out the following mods:

I wanted a single large front chainwheel - so I wasn't peddling like mad at speed. I bought a 52T, single wheel chainset off e-bay for £13.

It has 155mm arms, now I have tried it I wish I had sought out one with 175mm arms.

Having removed the original 3 ring chainset to fit this one, it became apparent that the bottom bracket was too long (122mm). The alignment of the new chainwheel was not so good. I fitted a 110mm bottom bracket. £8 from e-bay.

I needed to remove the 3 ring set, firstly because you don't need 24 gears on an electric bike but particularly because the bike was fitted with rapid shifters. I removed the left one (with the 3 change shifter, brake lever etc) and fitted one of the electrical cutout brake levers (Which I think is essential to fit at least one on a Pedelec bike).

I refurbished the brakes and fitted new cables also.

The picture below shows the thumb throttle fitted along with the supplied brake lever and LCD meter

image_zps6fb2afd4.jpg Photo by averhamdave | Photobucket

 

[averhamdave]

Before I was able to fit the front chainwheel I had to fit the pedelec sensor. This was straight forward, the pick up being clamped by the bottom bracket "locknut" and the magnet disc just pushes on the crank square.

I did however have a problem in that having fitted the shorter bottom bracket for alignment purposes, I now had insufficient clearance to accommodate the magnet disc. I therefore had to skim a small amount off the clamp ring in the lathe. The picture shows the whole bottom bracket in my Boxford lathe!

image_zps23658035.jpg Photo by averhamdave | Photobucket

Rather than use the old rear cassette I purchase a new one. 8 speed Shimano, 11T to 32T. I also purchased a new chain 116T (which was just right)

The wheel was fitted with a new Schwalbe Marathon Plus tyre.

image_zps2dd5a461.jpg Photo by averhamdave | Photobucket

Because of the beefier centre of the cassette shaft - due to it having to accommodate wiring - my cassette tool would not enter the cassette - see picture.

 

[averhamdave]

The rest of the bike was then mechanically assembled - wheel in, chain on, harness fitted etc.

The harness provided for the use of two (supplied) brake cut off levers. I only used the left hand one. You don't need to do anything to the harness except I taped over the exposed end of the waterproof plug.

The picture below shows the anti rotation washers. There was one for each side:

image_zps02d67a74.jpg Photo by averhamdave | Photobucket

This picture shows (not very clearly) the new cassette fitted and the wheel in the bike. Standard (for today) 9 pin motor plug.

image_zps18d76042.jpg Photo by averhamdave | Photobucket

 

[averhamdave]

The wheel and wheel build is of good quality. Badged up "Champion" the sticker is already peeling off!

image_zps7f615f4a.jpg Photo by averhamdave | Photobucket

The batteries are housed in the top compartment of this Raleigh pannier which was purchased at Argos.

This was at the stage where I had temporarily cable tied wiring into place to see how things worked out

image_zpsd334bad8.jpg Photo by averhamdave | Photobucket

 

[averhamdave]

I use Lipos in my other hobby - flying RC Helicopters. I am very experienced with them and understand their plus and minus points. I'm happy with them, they are relatively cheap and can delivery high levels of current without voltage sag.

For this build I am using 6 off, Turnigy 4S, 5000mah packs, 3 in series, twice then paralleled up to give a nominal 50v, 15ah. These are hard cased lipos as well. Specifically built for RC Cars where they have to take a series amount of physical abuse.

This picture shows them on the bench with the harness I have made up. Note I have used EC3 connectors for the packs (they came with bullets ugh!), the main outlet to the controller is via a 40a fuse, through EC5 connectors. In there I have my Turnigy watt meter as well.

image_zps5ef22db9.jpg Photo by averhamdave | Photobucket

I made up a support base out of wood and aluminium angle. The batteries have Velcro on their underside and are sat on a Velcro base. they are further secured with an over strap.

The top bag on the pannier is wide enough to accommodate the packs, wiring, spare loom (bundled and cable tied), watt meter and a cell checker. You may think it looks like a dogs dinner but its no big deal to me and quite neat when all zipped up.

image_zps4275c2a8.jpg Photo by averhamdave | Photobucket

 

[averhamdave]

I have included a picture of my battery charging equipment just for interest.

I have this anyway to charge batteries for my flying hobby. I don't think RC lipos on this scale are a viable option unless you have the gear and to buy it just for an e-bike would seem to be expensive to me. My charging equipment you see in the picture below would cost today over £300.

That said I can charge these 6 lipos on a parallel board as in the pic, in about 45 minutes - and that's without pushing it.

image_zpsdc5ac299.jpg Photo by averhamdave | Photobucket

 

[averhamdave]

Got the bike finished yesterday and have done a couple of short runs and a 12 miler this morning. In total just over 20 miles on it. My views:

2. The bike will power on to 25mph with help. Without pedalling and on the flat it will reach 20mph. I am disappointed in its speed. I had hoped for 5 mph more.
3. The motor whines a little. Much more than the Bafangs or Ezee motors on my other bikes. Similar to my old Powerbike of some years ago. Its not a problem though really.
4. The freewheel is good and as I have said the rear wheel runs true.
5. I am riding the bike in 3rd,to 6th gear. I have ridden it along the flat and up and down some seriously steep hills. The 11T and 32T gears are never going to be used! Furthermore the chain angle is such on those gears that you can feel the chain rubbing hard on the side of the front chainwheel.
6. Its hill climbing ability I would describe as adequate, providing you make some effort it will get you up any hill.
7. I am unused to "pedelec" so I don't know if these characteristics are typical or not? The pedelec power takes about 1 to 2 seconds to come in. If you chose to pedal a bit and then freewheel a bit and so on the bike lurches in and out of power. Change your style of riding and you'd get used to it.
8. The LCD offers 6 settings, ie 0 to 5. Zero is bike switched on but no power available. 1 to 5 offer 5 levels of assist. IMO 1 and 2 are useless, offering negligible assistance. 3 is OK if you feeling the need for a workout. 4 and 5 are good to be fair.
9. In levels 1 to 5 inc the throttle will over ride the pedelec, ie you can accelerate the bike to it maximum whilst in pedelec mode. I know this is not always the case with this type of set up.

I have some data to post in the next installment

 

[averhamdave]

I did 11.4 miles on the bike this morning. It was over hilly terrain but I put quite a bit of effort in myself as well. I guess I averaged about 18 to 20mph.

The packs were fully charged when I left home and were showing as containing 46% power when I returned. I'd guess on an easier ride the range of the bike will be about 20 miles at 20mph.

The packs are Turnigy's. They claim to be 5000mah each but I doubt they are - which is pretty usual for Turnigy!

My watt meter (which is also Turnigy and therefore of spurious accuracy) showed I had used 257watt hours. The lipo package should theoretically have around 700 w/h capacity. That doesn't square though with the 46% left in the packs. The 46% was accurate, being measured by a good cell meter and my Cellpro charger. So I had used 54% of the stored energy.

That all means I either used about 380wh (not 257) or the pack assembly is more like 13.8ah.

To be fair the packs are new and they do usually improve after the first few charges. Its not a big deal.

The peak wattage reached was 1142

The peak power draw was 21.7a (the controller is rated at 22a)

 

[averhamdave]

Overall I am quite happy with the bike. It rides well, it'll keep me fit and it looks very much like a "normal" bike.

Inevitably you make comparisons with previous experiences. I am a Ezee bike man through and through and this is my first deviation for some time. My old Torq (I have 3 plus a Liv) is on 48v (overvolted and also using RC lipos), has a non standard controller that has the shunt soldered. Whilst its delicate it is a faster and sharper bike than this. It is around 1200w. However it it is front wheel drive and dangerous in the wet.

This is a good cruiser that will get the job done efficiently and quickly without getting the adrenalin going!

(I do see a 60v upgrade on the horizon though!)

Thanks for taking the time to read the article.

 

[103Alex1]

Very interesting read - thanks for posting .

Must admit I'm very surprised that the motor didn't give you more at 48V. It sounds like it doesn't have as much guts as the Bafang CST 500W rated (even at 36V ... although run at 30A) and that by going to 48V you aren't getting the speed increase you'd hope for. Also the power consumption stats are surprisingly high... were you expecting less consumption for the performance obtained ?

 

[averhamdave]

I'm not sure what to make of the data or the feel of the bike yet Alex.

Its different to what I'm used to but I'm not sure if its better.

I had hoped to see 25mph minimum and with some effort 30. I was also surprised to see how much it was pulling the batteries down but I don't think it will cause me a problem. My rides are rarely more than 20 miles anyway.

 

[averhamdave]

BTW the quoted revs/min of the motor at 48v was 300. I think that equates to about 27mph (?? - not done the calc to be exact)

 

[103Alex1]

I noticed watching the Cycle Analyst on the CST power use profile can make a huge difference to the consumption sometimes with very little impact on additional speed. Full throttle all the way is very hungry. Was using a throttle not PAS so much easier to fine-tune during the ride and turn down power e.g. when it was doubling consumption for 1mph extra speed, but with a bit of practice and decent effort in a hilly area got 13.7Wh/mile over 22miles (300.6W/h total used) with an average speed of 20.4mph. Only a short 1/2-mile section of very fast downhill riding @ max 48.2mph - so effect of this shouldn't skew the results too much. Full throttle that ride would have used more like 20Wh/mile and probably averaged no more than 21mph.

The one thing which absolutely hammers consumption, far more than moderate hills, is hard acceleration from stop or lower speeds at junctions, lights, etc. The motor gets supplied with over 1000W continuously and even with relatively light throttle use, a few of these on the ride cumulatively this adds up into many W/h.

 

[Deleted member 4366]

Nice work and nice write-up.

I was thinking the same: Swap three of your 4S packs for 6S ones to give an extra 8v.

300rpm is 22mph. If it's a 36v motor, it will do 29mph. If it's a 48v one, you're stuck with 22mph. I average about 3 miles per amp-hour with my 500w CST, which works out at about 13wh/mile. I'm quite heavy and my journeys are relatively hilly, but I only average about 14 mph. Flat out with moderate pedalling into a slight head-wind with a net climb of about 300m over 15 miles I used 12 aH, which works out at 32wh/m. Flat out in the other direction, I only used 4 aH, which is 11wh/m. Average speed was about 19mph one way and 21 mph the other for an all-over average of 20mph.

 

[averhamdave]

Thanks d8veh and also thanks for your help with the project away from the forum.

I may look at swapping two of the 4S packs out for 6S and see if it does much in the way of improvement. It would mean though that I couldn't parallel charge all 6 packs together (as they all have to be the same to do that).

Its all in the future but I may look to just add two more 4S packs and push the voltage up to 67v which will give a theoretical 30+% increase in speed but also a 33% in battery capacity. No doubt FETs will blow and the LCD will go into meltdown. More on that later though.

BTW, having now done the calc I make a 700c wheel running at 300 rpm to be doing 24mph (??)

 

[103Alex1]

I seem to get much more performance / speed for less W/h consumed than d8veh. Should really have put the net climb in for context on the figures above - 592m net climb over the 22 miles at an average 20.4mph using about 8.5Ah/300W/h. Me @ 62kg + about 8kg of stuff strapped to the rack that ride. Bike total weight including me and everything on it must total about 95kg. Wonder if that's the key ? Didn't think it would make that much difference though !

 

[averhamdave]

I'll weigh the Saracen and work out a total weight. I'm 90kg alone though but reasonably fit.

What are you using to determine altitude climb? I used to use the android app "Sports Tracker" and whilst it was/is good for all other data it's altitude plot was useless - you could be 200m below sea level at times!

The data I published was from this first ride and I did use the throttle heavily as I was pushing the bike to test both its hill climbing abilities and speed. I'm hopeful that the range could be considerably extended with more careful use.

I'm away now until Sunday pm. I can read posts but not post myself until then.

Thanks so far.

 

[Deleted member 4366]

My calcs were based on a 26" wheel, so you can add about 10% for 700c.

Don't forget that I'm relatively heavy, which is why my power consumption is a bit higher. It makes quite a difference when it's hilly as well.