New project MM-eRCH electric mini bike

[Texas Pete]

I was out riding my motorcycle continuing the slow and steady piling on of engine break-in miles when I spotted this on the curb for bin day.


I did some quick image searches and it looks like it is an MM-eRCH electric mini bike. I have not found user manuals or guides yet, as I don't think they sell it any more.


No batteries so it was a guess as to what it came with, I was thinking a lawn mower battery or something small. Turns out they sell them in two packs so its either going to be 12v or 24v depending on how they join the two batteries.


I'll have to get out my power supply and see about setting up some test voltage so I can see if the speed controller or motor is burned out before investing in batteries for it. If it is a goer, I'll give it to my youngest who tries to follow me down the street when I'm headed off on one of my daily motor break in sessions on my motorcycle.

[Texas Pete]

I gave the bike a quick once over. Nothing burnt looking, nothing burnt smelling. That is a good first step.


No batteries and missing the side cover that is normally installed over the batteries.


Also no battery harness, there are two 12 volt 7ah to 9ah batteries that are supposed to sit side-by-side in the tray and then are wired in series to 24 volts with a harness that includes a 30-amp automotive fuse. All this is missing so I'll have to rebuild a harness if the bike is a go.


For now time to build a test rig to see if the electronics are all still a go.


For the power I will be co-opting a data center tape backup power supply. This is a 48v high amperage power supply that gives me a huge amount of flexibility in powering any electrical project from low voltage microcontrollers to electrical motors.





To tame all that power I use a DC to DC digital converter to dial in specific parameters for the output electrical feed. Here I am just reading the raw electrical output from the data center power supply.





Now to build an output power harness. I need banana plug to spring clips. I had an old electrical cord from a dead washing machine hanging around so I cut it up and reused it for this project.






The banana plugs were mechanical screw connections against barrel for securing the wire. The other side I didn't have anything but some Harbor Freight? test clips that needed some soldering. All done.

[Texas Pete]

Now that I had a test rig, time to test the MM-eRCH electric controller and electric motor.


Time to get the mini bike itself onto the test bench.





Now to recheck the wiring circuit hook ups from wall outlet to mini bike battery connectors.





Satisfied with the circuit, it was time to start testing.


I initially programmed the electrical output to lock the current draw at no more than 1 amp and voltage at no more than 24 volts.


I found the main power switch and turned it on. The LED indicators on the throttle lit up so that was a good sign. Looking at the DC to DC digital converter I could take the parasitic power draw reading from the bike when it was switched on but had the throttle in the off position.





When the throttle was activated I had to lift the rear of the bike off the workbench to allow the rear tire to free spin. I didn't get any photographs of the electrical draw under load but I averaged the bouncing display numbers in my notes.


I also found an additional on/off switch under the battery tray. This was used as a speed limiter setting. Slow speed for small kids and Fast speed for bigger kids.



It looks like we have:

• 24 volts and 2.3 amps or about 55 watts with speed switch on fast setting.
• 24 volts and 1.2 amps or about 30 watts with speed switch on slow setting.
• 24 volts and 0.1 amps or about 2.3 watts with the power switch turned on but no throttle.

As you can see, forgetting to switch the main power switch to the off position after every ride you will drain down the batteries and if left that way will contribute to battery deterioration. One of the negative of battery powered kids toys.


But it looks like the bike is electrically sound outside of missing the battery harness and fuse. It will be a pain to properly recharge the batteries as they will charge better and be healthier overall when disconnected individually and charged. Series isn't as bad as parallel batteries for recharging but its still not as optimal as individual 12v batteries.

[McQueen216]

Ah - a data center tape backup power supply. Always keep that handy.

[Texas Pete]

Originally Posted by McQueen216

Ah - a data center tape backup power supply. Always keep that handy.

I looked at the sticker, it was built in the city I grew up in, made in the USA. It's a keeper for sure!

[Texas Pete]

I got in a few more minutes of work on the mini bike before the sun went down.


Removing the chain guard was fun. Here I found the typical homeowner lost a hex head bolt and shoved in a small wood screw and called it a day repair.


Look at that massive rear wheel sprocket


What is even more eye opening is the tiny sprocket on the motor, I swear without counting it looked like 5 maybe 6 teeth at most. Obviously these bikes are not made to last the long haul. That tiny sprocket will wear out rapidly.






Old chain removed, not completely caked in rust but in person the whole chain was rust covered which doesn't come out as well in the photograph above.


I spent some time on the bench grinder with wire wheel and manage to knock just about all of the surface rust off.





I just got these in from Amazon since the stores in my city don't stock it in store. So as the sun had set I quickly sprayed down the chain and hung it to dry and called it a day and will do reassembly next time.

[Texas Pete]

Got some more time to work on the bike.


Chain was dry, so I reinstalled it and reset the chain tension according to the specifications in the manual.





Multi-piece chain guard was reassembled and installed as a one piece unit. Yes even the prior owners wood screw





I put the final trim piece back on the right side and then looked at the tires. Zero pressure in both rear and front. Filled both to 40 PSI according to the manual. Then checked and filled all the bicycles in the garage and the motorcycle. Before I got to the car my wife came out and drove to to the supermarket so I'll check on that another day.





Not much left now. All switches checked out, the speed controller and motor checked out. Nothing left now except to order some batteries and a fuse and harness pack.

[McQueen216]

Whee-lees! Whee-lees! Whee-lees!