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By maurtis
Finally got around to getting the Razor MX500 back in action this weekend. We originally picked it up for $80, in decent shape with working original batteries. We got about another year of use from the stock batteries before they finally died. Due to working on other projects, the poor MX sat in the corner of the garage gathering dust and cobwebs. Being scavenged for parts for other projects (mainly for the 36V E300 build).

Using a 48V YK42-4 controller I picked up from Rob, four 12V 12AH Max Life eBay batteries, and new red throttle/grips the build was ready to go.

Mounting the extra battery was pretty easy. Mounting the top batteries sideways I was able to lift the front battery up using a piece of 2X4, the rear battery was lifted a bit as well in order to avoid bending the battery tray. I used industrial strength velcro to stick the wood to the bike and the batteries to the wood spacers.
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I used copious amounts of zip ties to secure the batteries in place. I also used velcro and zip ties to mount the controller.
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The white connectors with smaller gauge wire are for the charge ports.

I mounted a 300A battery disconnect inside the fake gas tank like Rob (great idea!), along with a 130A volt/amp meter. While the whole process is straightforward, it was many hours of cutting, crimping, and heat shrinking to get everything wired up nicely. But well worth it!

Since I have plenty of 24V chargers but no 48V, I just added another charging port next to the stock one and have each charging two of the batteries. I had to cut most of the top of each of the plastic side cases to get them to fit, but only a little of the wiring near the back is visible.
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The good news, the volt meter worked great and I saw that on full throttle startup I was pulling 66A, which leveled out to 26A as I reached a nice cruising pace. 21 MPH on flat road, 23 on a slight downhill. About what we expected. The new controller definitely has more grunt than the stocker, but not uncontrollable for my 8 year old.

The bad news, the volt meter stopped working after about 5 minutes, LOL. Oh well, at least the controller has an LVC, so no worries. I believe the issue was my fault. I wired the meter between the controller and motor since I wanted to see what was actually going to the motor and not what was being potentially wasted in the controller. This meant that when off the throttle, the meter would switch off. I think the on/off/on/off/on/off is what killed it so quickly. On the next build I will mount it between the batteries and controller.

By Saintmythi
nice. you gonna do a little headlight on that guy?
User avatar
By maurtis
Yeah, thinking of going with a headlight where the number plate is and a small tail light to go for the enduro look. And a horn since my boy likes to make noise ;)
By Saintmythi
strap on saddle bags to get the mail
By robnewyork
remember i said i ran this setup at 67.5 amp breaker and never tripped, 66amp controller it is@@@@@@@@@@@@@ man this is exciting to hear.. looks great,, a new amneter would be cool too , maybe from china for 10 bux.
User avatar
By maurtis
This is how they should have come from the factory. The extra speed is fun but not enough to be uncontrollable for a kid. The extra amps makes it feel like it could tackle more than just grass. I bet my son could get a wheelie out of it if he pumped the front suspension and pulled back under power. Me at 215 lbs, a lot less likely :lol:

As I like to tell myself, if I cannot be thin I might as well be strong! My homebrew hobby has seen to the end of any plans to be back to my college BMI, but at least I get a good workout moving kegs and fermenters around.
By robnewyork
that controller fits lots of loose ends we have not been able to tie the 50 amp vs 100 amp reliabilty question, and yes the mx looks awesome..did u inboard the chargers, if so or not it may be a nice touch
User avatar
By maurtis
Agreed, that controller is definitely a step up from stock but not a motor killer. I did not mount the chargers inboard, but easy enough to do :)
User avatar
By maurtis
Hey fellas, been a while!

Quick update on the 48V/66A MX500. Replaced the batteries a couple months ago, one battery in the old set gave out and instead of just putting one new one in I just replaced them all. The bike was going fine until last week when my son (who is 10 now) and a friend were riding two-up at the park and said they "smelled something funny". That did not keep them from riding until the batteries died, though.

Once they got it back to the garage and told me about the smell, I went to check it out but knew what I would find. It was the motor, stank up the entire garage and blazing hot to the touch. I guess two years of running at over 2X the rated power took its toll and the extra strain of two kids start/stop/start/stop was just too much.

After the motor cooled and batteries charged my son took it back to the park but this time only one rider at a time. The motor was still blazing hot at the end of the run, so pretty sure it is about to go. It seems a little down on torque with me on it, but not astonishingly. But it is heating up a lot quicker now, so time for a replacement.

I am thinking of just dropping in one of the replacement MY1020 800W versions and rigging up two cooling methods. 1) a covered endcap with fan to pull air through the motor holes on the non-chain side and 2) fan cooled heatsink for the outside of the motor.

Not quite ready to go crazy with a big motor yet, it was working great as is until he released the magic smoke. I think with a motor the same form factor but rated for higher amps and some fan cooling will probably get us by until he is fully a teen and ready for a bigger rig.
By robnewyork
sounds good , u been missing a while .. I figured a terrible scooter mod sealed ur fate (-'
ANyway , yea , an 800 should slap right in and save some headache.. And since he still uses it the thing , the bigger the better. i think the 800w have gotten cheap on ebay
User avatar
By maurtis
LOL, just got absurdly busy with other things so electrics just fell away for a while. No serious physical harm done, yet. Although I am thinking about building an electric or gas drift trike. That might get me hurt :D

I am seeing the MY1020 36V 800W in two versions, the 28.5A for $63 shipped and 29.2A for $83. Thinking the extra 0.7A is not worth $20 more, and $63 seems a decent price.

I picked up a 5 pack of squirrel cage computer blower fans off Amazon for $5.70, figured if at least 3 show up not DOA they should work out ok.
User avatar
By maurtis
Wow, just checking in on the board again. The MX500 is still hanging in there on the same motor! 10 months later and that motor he smoked in January is still going. It gets HOT easily now, but still going.

I saw Larry's post on going 1800W brushless which looks super easy, so will probably go that route next when this one finally does die.

Since my last visit earlier this year we finally moved into a new house! After two years of building two new houses and cancelling the contracts for various reasons, we finally found the one my wife wanted :)

The batteries in the Dune Buggy finally gave out and since my son only rode it once every 2-3 months he agreed to sell it. I told him either he ponies up the $100 of his cash for the go-kart batteries, or he sells it and he keeps the money... It went to a college student and his little brother who wanted to fool around with it, LOL.

I also sold my wife's electric bike which was still in perfect shape but she never rode it and I sold my fast electric bike since the batteries were about to die and I did not want to dump $400 into it again for more batteries.

So down to the Mongoose eBike and the MX500 now. Looking to build another project but not quite sure what yet.

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