Building my first ebike, would appreciate some advice

[I4N]

I've been a long time lurker here and finally decided to take the plunge and build my own ebike.

I was considering buying the Burisch GT250 on ebay, but I'm tempted to convert my old Specialized hybrid so I can spend more on the kit and then buy a new bike when the sales start. The only concern with my old bike is it has v brakes and no suspension!

My current bike (someone elses photo though!)

The Burisch.. apparently he can sell an uprated controller which would be great for me off road out here, but not sure the battery would make the journey.
http://www.ebay.co.uk/itm/BURISCH-Synergy-GT250-LARGE-Ebike-e-bike-pedelec-electric-bicycle-/171031884340?pt=UK_Bikes_GL&hash=item27d24b7234

I need the bike to commute on around 10-12 miles, I'd say 90% of which would be off road on dirt tracks, I'd love a full suspension bike to soak up the potholes and vibes from concrete surfaces but that may have to wait. I'm tempted by a cheap 500EUR bike from the local Decathlon store, the frame looks good but the components would need upgrading,.. then I may as well get a frame off ebay.. so I'm sticking with my current bike to start.

I have a set a budget around 1000USD + customs & taxes so fairly healthy but I want to get the most bang for my buck. I've decided on 48V system LifePO4 12-15Ah (using a 36 torquey motor). I was tempted by the LiPos from Hobbyking but couldn't be bothered with the myriad of charging issues and then I heard their cycle life is half that of LifePo4 so they're more expensive in the long run anyway..

I'm pretty heavy 100Kgs but the bike is light ;-) There are two 12-15% hills, I live at the bottom of each so going anywhere I must tackle one of them, 200-300 meters, last year I'd cycle it almost every day (bottom gear of course!) but I haven't been on the bike this year at all yet!

Also the bike is highly geared, I'm not sure whats on the front but I could pedal pretty much up to 45kph probably more but I am not focussed on the speedo at that point!

Ideally I'd like the bike to do around 20-25mph, I can recharge at work if necessary I might buy two chargers.

I think that covers my wishlist.. a bit longwinded sorry.. now I have a few questions before I place an order..

Think thats it for the mo, I'd appreciate any advice from veterans, I've tried to digest as much as I can from reading these forums..

 

[I4N]

Ok I think I've narrowed it down to a Mac motor from Paul cell_man from Em3ev, it seems like a better built kit and comes properly setup in a decent rim. My local bike shop seems a bit run down and I'm not sure I'd trust them to put a wheel together properly!

Just got to decide on the 8t or 10t motor..

 

[I4N]

Thanks to having great communications with Paul (cell_man) I've placed on order with EM3EV.com for a fully built MAC motor in a decent quality Alex rims wheel, it should be here within in a couple of weeks.

I decided to go for the 10T motor for the extra torque, after measuring some of my gradients are around 20-27% If I need more speed I'll upgrade the battery to a 60V system. I've also bought a Cycle Analyst and the GRIN tech V4 torque arms from Paul.

I'm placing an order with Eclipse ebikes for the Headway batteries, call me old fashioned but I prefer the cylindrical type batteries, plus they have screw on connectors.. no risk of my dodgy soldering blowing a cell up!

 

[mxer125]

Can't wait to see this!!!.... Can't go wrong with a Mac. Good luck and plenty of pic's

 

[I4N]

The batteries arrived today, the motor has been stuck in customs for nearly two weeks now! It's supposed to be arriving tomorrow, fingers crossed!

 

[I4N]

I've made a few upgrades on the bike.. gone are the super skinny and rock hard hybrid tyres, in are a new pair of Schwalbe Big Apple balloon tyres.. so far they do give a more comfortable ride. These aren't the widest tyres in the line-up but are almost the widest I can get on my bike.. I'm going to order a pair of Kenda 8 Small Blocks as the Big Apples are not great on loose gravel which covers most of my commute.

 

[I4N]

The batteries have arrived!

The battery box arrived yesterday, really pleased with the service I received from Eclipse Bikes (eclipsebikes.com| bikes | electric bike kits | Pedal | Power) really keen prices too. The box came well packaged, the batteries are sitting under all that gubbins..

I've quickly taken the batteries out and placed them on the frame.. they are big! I'm not sure where they're going to go at the moment. I do have a frame bag on it's way, I'm going to have to decide to mount them in that, put them in a backpack (stealthy and easy to charge) or mount them to the frame somehow..

The main issue would seem to be placing the BMS, it has to be close to the batteries as the balance leads are fairly short. I'm feeling nervous about soldering all this up!!

 

[I4N]

Commute detail

I've ridden the bike a couple of times without the motor so I can compare apples with apples once I've got motor assist!

My commute is 16km which I can cycle in 30 mins dead. The same route in the car takes 20mins (and costs me €35/week in petrol alone).

There is a faster route I can take by bike but it's mainly off road, I'm pretty sure I was doing this in 25 mins last year, but my mind is a bit foggy now..

The fastest route in the car takes just over 15 mins.

I'm not too bothered about beating any of those times with the bike motor, I'd like to be able to take the off road route to work so I can avoid the traffic and fumes.. but there's a couple of 25% hills to contend with and I always end up getting to work needing a shower..

My top speed cycling on the road run is 55km/h. Top speed so far on the bike 65.8km/h! just on pedal power alone.. well that and a bloody great hill!

 

[Mike63]

....I wish you luck with this and I can't wait to read more.

.....Mike

 

[I4N]

I've managed to have a quick look at the batteries, I'm thinking of charging the individual cells in series using a DC converter. The idea is to get them fully balanced at ~3.6V before I build them into a pack.

The voltages are not too far out of line max is 3.45V lowest is 3.31V

Is this necessary when the BMS should be doing the balancing? I've heard that a BMS won't work optimally if the individual cell voltages are too far out of equilibrium?

The DC converter can supply 1 amp (2 amps I think), when the cells are almost charged I've heard each cell will draw about 20 milliamps so the converter should be able to supply enough power, but not too much to melt any of the cells.

I'm planning on just setting the convertor to 3.6V and leaving the batteries connected up for however long it takes. The motor is still stuck in customs so there's no rush to get them charged quickly.

Obviously I'll connect a volt meter and monitor the amp flow, I'm expecting to see the amp flow drop as the cells reach max capacity, is that right or do I need to time the charge duration and disconnect at a certain time?

 

[banbury frank]

Hi 14N I have been building headway packs for 5 years now

you are doing the right thing fully charge each cell The BMS must be connected correctly or it will destroy itself

a tip is to go around the battery and number the cell ends with the positive ends the first one is the positive end off the cell you are using with the main negative connection I then using sticky labels

Number the BMS balancing leads and split them into odd numbers and even numbers as one side off the battery pack is odd number the other even

The other think to be AWARE off Is the outside case off the battery is POSITIVE so keep it well insulated we cover the outside with 4 mm plastic sheet

Charging the cells can be charged at 10 C so so if you are using 10AH cells that is 100Amps

3.6 Volts is OK

The Pack should balance out at 3.2 volts per cell

Frank

 

[I4N]

Hi Frank,

Thanks for the info, I'm going to have a go at putting a few cells together tonight and charge then from a 1amp DC convertor to about 3.6V

Question - Am I correct in thinking the cells will stop pulling current when they are saturated at 3.6V?

Thanks,
Ian

 

[Deleted member 4366]

Am I correct in thinking the cells will stop pulling current when they are saturated at 3.6V?

No. You need a charger with an automatic cut-off at 3.65v. If you're going to do it with a non-voltage-controlled charger, you should aim lower because once over 3.4v, they start to climb rapidly, so don't leave them charging unwatched at that level.

 

[I4N]

In other news...

After three and a bit weeks in customs in Lisbon the motor kit finally arrived.. all present and correct wayhay!!

I managed to get the motor together okay, it's smaller than I expected, it all looks good quality and the Alex Rim looks smart..

I had a little time this morning to do a test fit, it all slotted together nicely, everything is tight and I didn't need to do any filing.

It's starting to come together now, I'm planning on keeping the controller in the seatpost bag, I'll put a few holes in it for airflow, plus I need to butcher it a bit so the wires come out the front and down the seatpost rather than spewing out over the back wheel as in the shot..

 

[I4N]

Now I show my mechanical ineptitude!

So the motor fits nicely, the wheel is true and everything looks good..

I've got a bag full of washers and bolts.. the bolts are easy.. they go either end of the motor shaft..

What are the washers for? I have two circular washers and two washers (torque washers?) with a lip on them.. I've put them on as I think they should fit..

Torque washer first, then normal washer, then bolt.. is that right?

 

[I4N]

Which leads me on to my next question...

I've test fit the torque arms, these are the V4 Grin Tech arms from ebikes.ca

However with the torque washers on the cassette side the torque arm is pushed too far out and doesn't rest centrally on the seat stay.

Is it okay to leave the washer out here, I guess the torque washer would be redundant on this side, but should I use the normal washer between the torque arm and the frame?

 

[I4N]

No. You need a charger with an automatic cut-off at 3.65v. If you're going to do it with a non-voltage-controlled charger, you should aim lower because once over 3.4v, they start to climb rapidly, so don't leave them charging unwatched at that level.

Thanks d8veh,

I wasn't going to use a charger, just a simple DC converter.

It would put out a constant 3.6V at 1amp (it's adjustable from 3-30V)

I thought if I left it on long enough it would eventually saturate the cells at 3.6V and they'd stop pulling current, am I wrong in thinking that?

I don't understand how the voltage would keep rising if the input charge is constant? Obviously I don't understand battery chemistry!

 

[patpatbut]

So the motor fits nicely, the wheel is true and everything looks good..

I've got a bag full of washers and bolts.. the bolts are easy.. they go either end of the motor shaft..

What are the washers for? I have two circular washers and two washers (torque washers?) with a lip on them.. I've put them on as I think they should fit..

Torque washer first, then normal washer, then bolt.. is that right?

Hi there,

I have similar rear dropout but with the torque washers from GBK (the top set)

e-bike brushless dc hub motor anti-torque washers for fixing engines-Greenbikekit.com online store for electric bicycle components-GreenBikeKit.com

This fits nicely on my bike.

You can buy it from GBK and it costs you about 2-3 pound

Pat

 

[Deleted member 4366]

You need to fit the disc first to check that it lines up with the caliper, then you can move the washers around to suit. You don't need the anti-rotation washers with torque arms, but you have the option of installing them inboard of the drop-outs if the disc and gear spacing will allow.

If your charger is fixed at 3.6v, it'll be OK. I thought that you were just going to charge at 1 amp with no voltage cut-off, and stop when you saw 3.6v. The charge and discharge curve is "S" shaped, being nearly flat between 3.0 and 3,3v, but climbs/drops increasingly more rapidly either side of that.

 

[banbury frank]

Hi just one problem you need to fit a washer on the inside with the round cut out with the 2 flats as if you just tighten up as you show the motor shaft can pull through the aluminum frame as the difference between the slot in the end off the frame and the diameter off the shaft is very close and the aluminum frame is very soft


And remove the caliper from the bike before you fit the wheel and the offer up the caliper to the bike or you can buckle the disk they are quite soft

Hope that Helps

Frank