Chaos 2008 !

Part 4

I start 2008 with a " Giro- Mad Max S " Full face helmet !

Why ?

 

Well, a problem was discovered with the 72v 20ah Lithium " BMS " battery management system.

 

The job of a BMS is to prevent you from damaging the battery pack. To do this, it needs to do the following.

 

- Ballance the cells during charge

- Over-Discharge protection ( with LiMn chemistry this is 3.0v per cell )

- Over-Current protection ( On this bms board, 35 amps, at any given time, if the system detects a spike in power that goes over 35 amps, it opens the cirsuit and shuts you down )

The controller, Crystalyte 36v to 72v, 20 amp, single speed, in theory, should have worked without any problem as the bms limit was 35 amps.

 

However, at low rpm, below 5 to 10 km/h, the BMS would trip and cut the power. This required pulling over, getting off the bike, disconect the battery for a second and reconnect it , power then returned after a reset. Some research online and with help from a few friendly forum members, I was advised that at low rpm, even if you have a 20 amp controller, short spikes of higher current do happen well over the rated limit and this short duration was enough to make the BMS shut down..

My solution !

Remove the problematic BMS !

I replaced the tiny wires that originaly came with the pack with 16 gauge taps, this way i can monitor and ballance the packs externally. And eventually retro fit it with some LVC boards ( Low Voltage Cutoff ) circuit boards. But for now, considering that these packs provide a 20ah capacity, i never go even near full discharge, so making sure I fully charge before a long trip will be enough to keep the packs safe for the time being.

 

A test on the LBD shows a capacity of 15ah holding 70v, this is 3.5v per cell, well within allowable discharge levels. and as much as i need for a solid 60 km range !

The discharge wires were also changed to 10 gauge with 45 amp Anderson Powerpoles..

All the potential sharp edges were covered in commercial grade hot glue to prevent any possible shorts, and to keep things solidly in place, covered in plastic, re-installed the original shrink wrap.

 

( May 02, 2008 )

The battery packs having been sorted out, I decided to get working on the motor.

Above, on the left is the outer " can " of the motor, the magnets inside are placed in such a way that the North and South poles alternate.

In the middle is the stator, this part of the motor stays stationary as the wires exit the axle inside the bearing for the " can " .

On the right, motor cover for a front wheel motor. ie: No collar for a freewheel.

 

I have a stock of spare motor covers with threaded collars, so wanting this motor to be a rear wheel drive with a disk brake, i taped up the threads to protect them and got to work with the 100 grit sand paper.

Sanding unknown paint, metal and rust, wearing a good mask is imporant ! ( Sandy was not very amused, the Darth Vader voice thing.. )

 

 

Before I got into this E-Bike stuff, I was restoring a Honda 250SX 3 wheeler ( still have it, but that project has been sitting a while ! ) .

Above is a bearing puck kit, very handy when pressing bearings in or out. Using a 7/8 puck, and a hammer, removed the bearing from the original motor cover. I wanted to get some high-end bearings and see if it would make any real difference, but for now i'm going with what I got. !

 

Since i'm using the stock bearings, and have the motor open, bare minimum I could do was inspect them. With a small jewlers flat head screwdriver, carefully poked under the seal and removed it. Very minimal amount of grease in there..

 

Not anymore ! Filled it up and installed the seal rings again.

 

Using clear " G.E. Silicone-1 Multi-Purpose " applied a thin layer all around the motor cover. Gotta keep water out of the motor !

A dab of silicone in the wire channel of the axle for more water protection, and installed the 2nd motor cover !

 

Since the Chaos is a bit of an urban assault machine, it's only right to paint the motor dark to match the rest of the bike. Anytime you want to paint anything, it's important to use a solvent like rubbing alcohol, varsol, paint thinner etc.. to remove any grease, fingerprints, rust residue and so on , otherwise the paint will not last and will peel off in no time.

 

A few coats of black primer, then at least 5 coats of Dupli-Color " Mystify " oil patch paint.. And 5 more coats of clear .

In low light, the paint is almost an exact match to the frame, but in the sun, it turns into a multicolor mix.. a bit more flashy than I wanted, but looks ok.!

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