Mongoose CX24v450

[16v4nrbrgr]

That's great to hear Maurtis!

I'm going to run a 44v 18 Ah auxiliary pack on my pit bike, and I'm glad to hear that they have such strong current delivery since I will be running mine at a lower voltage than the onboard SLA's.

You should check out the hard cases that Harbr Freight sells, I used a couple similar cash boxes from Walgreens that have combo locks so I can toss a smoking pack if I need to lol.

 

[maurtis]

Okay, made a lot of progress this weekend. The short version, mounted the batteries and went for a quick ride (not too long since I am still waiting on my volt gauge). The torque loss with the new 16T southpaw rear sprocket was not as bad as I thought, it felt about the same as the stock 20T on SLAs... You could still take off from a standstill without pedaling. I still like to help getting going, though...

GPS reported 27 MPH cruise, 29 MPH on a flat if I tuck down! I was shocked... We will see how the little motor holds up to the abuse.

I mounted my batteries to a piece of 1/4" pegboard that I cut to fit. I figured the holes in the pegboard would be nice for using velcro straps, it worked out great! The board is secured to the bike with 6 velcro straps, the kind that sticks to itself. The batteries are mounted with industrial strength velcro on the back and held down with velcro straps and foam rubber padding, so the straps would not damage the soft packs.

I also used a Durolast battery cutoff switch before the fuse, so if there are any sparks they will be taken by the switch, which is easily replaced. It also lets me turn it off and take the key with me.

Here is the board, after cutting, painting with Plastidip, and running the mounting straps:

And a picture after mounting the batteries, the 5s on one side, 4s on the other. I still need to attach the lipo buzzers in place...

Left side of the bike after mounting:

Right side of the bike:

Closer picture, with the key inserted:

So, still waiting on my eBay volt gauge, mount the lipo buzzers, and need to tidy up the wiring and make a pebble guard to cover the batteries. I picked up a black wire mesh trash can from Target for $1, I figure I can cut and shape that to fit over the batteries. Using the velcro straps to mount the battery board worked well since they hold it tight and make it easy to remove for charging. So far, I am pleased with the way it turned out!

I am also thinking about the cooling mods people have done, at least passive cooling with holes in the motor covers. I fear that the motor will not last long at 36V and the 16T rear sprocket. But then again, maybe it will? Most of my trips are, at longest, 3 miles each way. With lots of stops, so not a lot of long distance high speed cruising.

 

[16v4nrbrgr]

The only way really is to try. The cooling modifications really do work though, and passive ducting helps as well. Just make sure to only duct one end, preferably the end with the brush mount on it.

I really like your bike a lot, it couples the best of a motorbicyle with the best of a Razor MX bike, I bet its so light!

 

[paul]

awesome battery set up. great idea

 

[maurtis]

Thanks guys! It was one of the few things I have made that actually turned out like I envisioned

The bike is pretty hefty steel, so definitely heavier than a comparable BMX bike. The top tube is actually two tubes welded side-by-side. So a good, strong frame, but heavy. But I cannot complain, that describes me too

 

[maurtis]

Finally got my $6.50 eBay voltmeter in, so pretty much have the bike where I want her for now. I am contemplating going with a dual motor setup, but that will be a little ways down the road. I have a couple other projects calling my name first... My son wants more speed out of his Razor Dune Buggy, so that is next

So for the battery cover, started with my $1 trash can:

Trimmed it with my Dremel and added some rubber door molding:

Not 100% happy with it, but it keeps the wires from being accidentally pulled and helps protect the batteries from flying debris, so good for now.

Added my volt meter to the plastic side cover, it turns on when the "ignitiion" switch is flipped to connect the batteries to the controller:

It is a little hard to see in direct sunlight, but still good enough for a spot check while on the move

I made a quick video riding around the neighborhood today. I apologize for it being crooked, I zip tied an old digital camera to my handlebar and it was not quite level, LOL. At least you get an idea of the gear whine of the motor. I hit 28 MPH on this ride, so comparable to a stock China Girl. I did not pedal in the video to give people an idea of how the little motor behaves on its own...
Modified Mongoose CX24V450 28 MPH test ride

 

[motortriker]

I like your bike. Bet it is great off road !

Nice !

 

[maurtis]

I like your bike. Bet it is great off road !

Nice !

Thanks! With the smaller rear sprocket for more top speed, it killed some of the torque. The bike still does well in grass and gravel/dirt bike paths, but I would not take it on a mountain trail.

I am definitely pleased with it for a first easy build, and it lets me know that I really do like higher speed electrics. I was tempted to add another motor to go with a dual motor setup, but think I will always be wanting more speed than the little brushed motors can reliably give me in this setup.

So instead I am going to pretty much leave the bike as is and use it as my errand runner while I build a higher powered e-bike with a brushless hub motor

 

[16v4nrbrgr]

I'm going to keep a lookout for one of these Mongoose, its such an awesome bike!

I'd like something like the MX but with pedals, if I can find one of these I might just have get it and do something like yours.

I really like the mesh screen protection for the batts, perfect so you can keep an eye on them and keep them cool too.

Thank you for sharing this build with us Maurtis!

 

[maurtis]

I'm going to keep a lookout for one of these Mongoose, its such an awesome bike!

I'd like something like the MX but with pedals, if I can find one of these I might just have get it and do something like yours.

I really like the mesh screen protection for the batts, perfect so you can keep an eye on them and keep them cool too.

Thank you for sharing this build with us Maurtis!

Excellent! They are definitely a neat platform to build off of with a lot of potential. If you do find one and want to add a second stock-style motor, I think the iZip/eZip mounting plate that mounts to the back axle would work with very little modification.

It mounts on the eZip bikes like this:

I figure if you mount it vertically with the motor above the freewheel sprocket on the rear wheel, the chain should line up well between the two motors and wheel...

With that route and 36V you would get wheelie popping torque and keep the top speed around 30 MPH. With that setup they might take 48V, but not sure. Since I am after a 35 MPH cruise with a 40+ top, I figured I would go with a different setup...

But then when I think of how easy it looks to be to add that extra motor, I get that itch

 

[16v4nrbrgr]

I think you should try a geared hub or derailleur instead, since I went to two motors, the range is significantly reduced. Adding the geared hub to mine helped the range and hill climbing, and I didn't need crazy battery packs like I'll need now with so much power consumption.

 

[maurtis]

Since the hub uses a regular freewheel on the right side for the pedal drive and southpaw freewheel on the left for the motor, adapting a geared hub to fit would not be all the straightforward. BUT... if you could find a way to make a geared hub work, it would turn this little bike into an EXCELLENT runner.

In the end I think I am better off in my search for more speed by going with a hub motor on a different frame and leaving this one as is. Now, a hub motor in a 20" wheel would work great on this bike but I would have to get creative with where I want to put 72v 20AH worth of batteries. On a bigger bike with a larger center triangle it will be easy.