Help troubleshooting electric mini bike that intermittently blows fuses

[bigedgar]

Hello, I have a Monster Moto electric mini bike (model MM-E1000). This is not an electric bike – it's a beefy electric mini bike (all battery powered, no human power). This machine has never really worked properly as it intermittently blows fuses and eventually destroys the controllers. I'm trying to decide if it's worth putting any further effort into trying to fix or if I should just give up on it. The manufacturer is out of business, so no help available from them any longer. People have posted similar problems to mine on reviews of this machine, so I know I'm not the only one, but some people have also posted solid reviews of the machine, indicating that not all machines have the same problem.

The problems I have had are mostly centered around this thing constantly blowing the 30amp blade fuse, and then occasionally blowing the controller (I'm on my 3rd controller, and have also replaced the wiring to the battery and the blade fuse holder). I've had it running "well" twice, and it has lasted for maybe 5-10 hours of use over a few weeks each time, and then the fuses start popping, and eventually the controller blows. The metal female connectors in the holder for the blade fuse has also melted once. So the root cause is not super obvious - it's one of those frustrating problems that doesn't have an easily repeatable pattern that can be used to troubleshoot.

Here are the rough specs:

• 36v, 1000 watt motor
• 3x 12v, 14ah lead acid battery pack

The setup is pretty typical of an electric bike – see the diagram below for rough schematics of the key pieces.



Where I could really use some help is trying to troubleshoot the root cause of these problem. I'm no electronics guru, so learning as I go, but at the most basic level it seems that there is a mismatch between the power supplied and the capability of the internals to handle the requested load.

I've spent many hours trying to figure out how to get this running again and what component could be the root cause of the issues. Here's my best guesses as to what components could be at the root of the problems – what am I missing?

1. Poor quality controller (undersized wiring, resistors, etc.). I could get a different brand of 36v controller, but I know other people with this same equipment have not had my problems.
2. Faulty motor – is it possible that the 1000w motor could be bad? Maybe it's occasionally drawing more current than the controller can handle?
3. Batteries? What's the likelihood that bad batteries are to blame for this? I've measured the at-rest voltage and it seems fine.
4. Throttle – Is it possible that the throttle occasionally calls for more current than the internals can handle? The throttle has three connections - "to put", "indicator", and "power locks". The throttle itself has an on/off button, a twist grip and a batter level indicator.

I know that's alot of info, perhaps too much to digest But thanks in advance to anyone who has the patience to read this and provide thoughts - much appreciated!

 

[Balmorhea]

What's the current rating of the controller? For a 1000W nominal scooter, the controller should peak at significantly more than 36V*30A.

You need to allow headroom between your controller's rated current and the fuse value.

 

[bigedgar]

Thanks for the response. The controller says:

• Rated voltage: 36v
• Rated power: 1000w

There's no mention of amperage on the label.

Here's a link to the controller: https://megamoto.co/products/70-10003-00-controller-36v-1000w.html

 

[amberwolf]

if it's a brushed motor (two wires to motor from controller) then the most common cause i know of for controller failure that also blows fuses, that "gets worse" over time, is a bad connection in either battery or motor wires.

both of those are high current, so poor connections can result in arcing. that can generate high energy rf, which can then damage the fets in the controller, which can cause them to behave differently than they should, including the possibility of overlapping on times for the two halves of the fet bridge that drives the motor, so that if it's a full-h-bridge type you can get "shoot thru" from battery positive to ground which causes high current spikes that could blow a fuse, and can latch on and destroy the controller if the fuse doesn't blow fast enough.

often the connectors have high resistance to start with, so they heat up from current flow and then distort, loosening the connections and making it even worse, until eventually the arcing can happen.


so the first thing i would do is ensure all connectors are replaced with reliable ones; right now they're probably all cheap "tamiya" white plastic things with poorly fitting blades, or they're cheaply made stamped-form bullets, etc.

or you can solder the connections directly (or use wire nuts, as long as you can secure them against vibrationally loosening over time).

anything that eliminates the possibility of a bad connection or arcing would fix this particular problem.


note that the fuse holder itself can also cause this. so changing to a type that bolts on instead of a blade type may help.

 

[dogman dan]

I would also like to add, enough load on the motor would make it overheat, and then that's also hard on controllers, weak connections, and such.

So its not helping if a 200 pound or more dude is riding it.

 

[Balmorhea]

Thanks for the response. The controller says:

• Rated voltage: 36v
• Rated power: 1000w

There's no mention of amperage on the label.

Here's a link to the controller: https://megamoto.co/products/70-10003-00-controller-36v-1000w.html

If that “1000W” rating is accurate in terms of motor output, then the controller will draw something like 1500W if the battery allows it. That’s over 40A. You need more than a 30A fuse. I’d go with 50A.

 

[bigedgar]

Thanks for all the thoughts!

Amberwolf - your explanation makes alot of sense. I didn't put this in my original post b/c I didn't want to add confusion, but we've had at least one instance (and maybe two) of what I'd call "sudden acceleration" where, with the machine stationary and supposedly in the "off" position, swapping in a new fuse or re-connecting the battery pack to the rest of the machine has caused the motor to kick on and the machine basically takes off on its own. The machine was in the "off" position from the perspective of the throttle control, and the twist throttle was not activated, yet the machine still started spinning the motor and drivetrain. Pretty scary. I neglected to put this in the original post b/c it's hard to explain and this is likely more of a symptom of the bad electrics in this thing, but your explanation seems to offer some explanation as to why this might have happened.

Based on the feedback, here's what I'm seeing as a path forward:

1. Per Amberwolf's suggestion, replace the Tamiya connectors for the motor and battery with either soldered connections, or something more reliable than the Tamiya connectors.

-- Would crimped butt connectors with heat shield over the top be acceptable for connectors? I can definitely use wire nuts with alot of tape to help with the vibrations.

2. Per Balmorhea's suggestion, I can replace the 30amp blade fuse with a 50 amp fuse. FWIW, we've tried 40 amp fuses and those have blown as well. We have not tried 50 amp.

-- Will the 10 gauge wire that's currently used for the wiring between the battery and the controller be sufficient for a 50 amp fuse?

Dogman Dan - that's definitely a consideration. All the riders on our bike have been 175 lbs or less, and I've seen other reviews of the bike where people have noted that they are significantly over 200lbs and have not had issues. Thanks for the thoughts.

 

[amberwolf]

Amberwolf - your explanation makes alot of sense. I didn't put this in my original post b/c I didn't want to add confusion, but we've had at least one instance (and maybe two) of what I'd call "sudden acceleration" where, with the machine stationary and supposedly in the "off" position, swapping in a new fuse or re-connecting the battery pack to the rest of the machine has caused the motor to kick on and the machine basically takes off on its own. The machine was in the "off" position from the perspective of the throttle control, and the twist throttle was not activated, yet the machine still started spinning the motor and drivetrain. Pretty scary. I neglected to put this in the original post b/c it's hard to explain and this is likely more of a symptom of the bad electrics in this thing, but your explanation seems to offer some explanation as to why this might have happened.

the two most common reasons for "full power" at power on is a broken throttle ground (for either brushed or brushless motors/controllers), or shorted (failed) fets (brushed controller/motor *only*).

the failure modes of brushed controllers are noted in a bunch of places, but if they're still around, http://4qd.co.uk has a lot of good technical info on them.

-- Would crimped butt connectors with heat shield over the top be acceptable for connectors? I can definitely use wire nuts with alot of tape to help with the vibrations.

if you use wire nuts, i'd ziptie (at least two places within an inch of the wire nut entrance) the wires together, after installing the wire nut. then you can use tape if necessary to ensure the wire nut can't come off and allow a short from the bare wire tips to something else.

for the butt connectors, it depends on the type of crimp. if it's the typical automotive "squish" crimper...they dont' usually make a very good crimp. if it's a "real" crimper that's specifically designed for that particular butt connector size and type, and it's either a ratcheting or hydraulic crimper, or one with *really* long arms to allow immense leverage from your hands, then it will probably make a good crimp. the idea is to make a crimp that actually cold-welds all of the metal together: (wire strands and butt connector tube).

if you're not sure how good a splice you're making, take some spare wire and connectors, and crimp it. then carefully cut it in half right thru the crimp, and examine it. it should be hard or impossible to tell where the individual strands are, vs the surrounding tube or each other; they should be essentially one piece of metal. if it's not quite that good, but there's no air gaps in there, it's still ok, but if it's got air gaps in it, strands that aren't within the crimp, etc., then it's not a good crimp.

some good pics of good vs bad here
https://www.google.com/search?newwindow=1&q=what+does+a+good+crimp+look+like+vs+a+bad+crimp&tbm=isch

even better:
https://hackaday.com/2017/02/09/good-in-a-pinch-the-physics-of-crimped-connections/
good pics and explanations

-- Will the 10 gauge wire that's currently used for the wiring between the battery and the controller be sufficient for a 50 amp fuse?

yes. but...what is the current limit supposed to be on the motor controller? (a lot of cheap brushed controllers don't actually *have* a current limit, so they can't protect themselves or the motor against overcurrent, and that's why a fuse rated below teh failure point of the controller/etc may be used instead).

 

[bigedgar]

Thanks, Amberwolf. I went and did some research on mosfets, which I didn't know anything about. I'm glad to have learned something new!

This is a two-wire motor, so it sounds as if it's a brushed motor (you can see the motor here: https://megamoto.co/products/70-10001-00-motor-36v-1000w-base-mount-ccw-rotation.html).

Based on this info, I think it's likely that the mosfets in the controller are dodgy and it's probably best to order a new controller (currently on sale for $20).

And thanks for the detail on the crimp / wire nuts. Wire nuts seem much easier and more suitable to the likelihood that I'll screw something up and need to take everything apart at least a few times, so I'll go that route.

My current plan is to order a new controller, use wire nuts for the connections between the motor, battery, controller and throttle, and hope for the best. It sounds like there are mosfets in the brushed motor which could also be kaput, so that's a risk that I'll be taking.

Thank you again for all the help on this!

 

[amberwolf]

if you get a better controller (will cost more) then you'll get better results.

look for one that specifically says it does current limiting, and has a current limit that is within the 30a of the original fuse.

not just one that says it can handle 30a (or some other current amount), but that actually measures current, and then limits that current by pwm once it reaches that limit.

cheap brushed controllers don't always have this feature, and it's a good feature to have, to protect the system.

 

[bigedgar]

Thanks again for the thoughts. I considered getting a better controller, but wasn't sure how to measure "better" - this info helps me determine what "better" could look like.

Here's an option for a controller that claims to limit current to 32 amps: "Current limiting feature helps prevent controller and motor damage due to over-current conditions.". https://electricscooterparts.com/hookup/SPD-361000B.htm

TBH, from the picture and wiring diagram, this one ^^ looks exactly like my existing controller (although I obviously can't see the inside of the controller).

Here's a look at one of my blown controllers - is there any way to tell if my blown controller has any current limiting capabilities based on the images below? (You can see one of the blown components - not sure if that's a capacitor or what...).

 

[amberwolf]

Here's an option for a controller that claims to limit current to 32 amps: "Current limiting feature helps prevent controller and motor damage due to over-current conditions.". https://electricscooterparts.com/hookup/SPD-361000B.htm

TBH, from the picture and wiring diagram, this one ^^ looks exactly like my existing controller (although I obviously can't see the inside of the controller).

most controllers look pretty much the same from the outside, even the insides look a lot alike, and the only differences may be component choice or quality of parts, or firmware if it's run by a microcontroller (common).

Here's a look at one of my blown controllers - is there any way to tell if my blown controller has any current limiting capabilities based on the images below?

it probably does, based on the three thick wires in parallel around the middle of it--those are shunts, used to detect how much current is flowing in a system. no reason to put them there if it didn't have the ability to use them.

it might not be very *good* current limiting, meaning it might not kick in soon enough, or have some other limitation, but it is probably there.

(You can see one of the blown components - not sure if that's a capacitor or what...).

looks like the cap exploded, and the one next to it was ready to, but didn't.

that comes from two things. overheating inside the ocntroller that causes electrolyte to boil, or lots of current spikes / changes in current that the caps have to smooth out, which means they get hot from current flowing in and out of them.

that could mean just inadequate caps, bigger ones that are rated for higher voltage and temperature, with lower esr, might fix that.

could mean that there's a lot of rf (which is higher energy, more currents, etc, than the usual stuff inside a controller), usually caused by bad connections but brushed motors do generate this naturally at the brushes (the arcing you can see in a dark room inside the motor), and that eventually causes stuff to fail that wasnt' designed to handle it.


often when the caps fail, the fets no longer have anything to smooth out current (and voltage) spikes, so they fail or are damaged by the voltage exceeding their limits.


so...what you could do is replace this controller with the one you link to, or any other that has around a 30a current limit (to stay within the 1000w continuous rating of the motor at 36v, 36v x 30a = about 1000w (1080).)

then fix all the wiring connectors in both the battery to controller wiring, and the controller to motor wiring, so there can't be any bad connections.

if you like you could also replace the capacitors with better (better brand (panasonic, etc) lower esr, higher temperature rating) and bigger (higher capacitance) ones, which may prolong their life inside the controller.

or just do some periodic checks on them. if your original controller system failed after say, 6 months, then this time at 3 months you could open the controller top, and see if the caps look flat on top, or bulging even a little bit. if they're flat, they're probably still ok. if bulging, they need to be replaced. then do this check every so often, as often as you feel the need, or as soon as any of the same problems appear to crop up again.


fwiw, if this controller does not have the full-motor-power at power on problem, it might be fixable by replacing the caps and cleaning up the mess inside. probably not, but it's a few dollars worth of parts if you feel like trying it.


the caps in this controller are 470uf (microfarad), so you could go to 1000uf each, higher if you find ones that will physically fit in place there, but that might be tough.

they're rated at 50v, so you could use 100v versions instead, or at least 63v, depending on what will physically fit.

can't see the temperature rating, if they evne have one, but i'd use the 105c versions.

some good brands, i bolded the two i usually use (copied from this site:
https://www.tomshardware.com/reviews/power-supplies-101,4193-5.html rather than typing them out):
Rubycon.
United Chemi-Con (or Nippon Chemi-Con)
Nichicon.
Sanyo/Suncon.
Panasonic.
Hitachi.
FPCAP or Functional Polymer Capacitor (ex-Fujitsu caps segment, which was bought by Nichicon)
ELNA

i get mine from digkey.com or mouser.com ; they can cost 50 cents to a couple dollars each for good ones, which is one reason cheap controller manufacturers use cheap ones (that cost a tenth to half of that, but only do their job a tenth to half as well, if that).

 

[dogman dan]

So much for my suspicion, that one ride with that 350 pound guy cooked the motor.

I had a brushed motor, mid drive bike that ate controllers constantly. It would eat the controller when you rode with too much weight, my 200 pounds, and started in too high a gear.

More or less, it just needed a much more powerful controller, so it could then eat the motor just as quick. Bottom line, the motor was too small for the duty.

 

[bigedgar]

Dogman - that's funny. Here's hoping I don't do a bunch of work to solve the problems with the controllers, only to find out that the motor is a piece of junk (definitely a possibility).

Amberwolf - this is terrific info! I'm going to look through the other blown controllers and see if the caps all look bloated or blown. That would definitely give me something else to look for in an improved controller. At this point I'm thinking I'll follow your suggestion of getting the "better" controller and solidifying the connections for the motor-->controller and battery-->controller, but while I'm at it I'll get better caps for one of my other controllers and see if can retrofit that. As you said, it won't cost much and it could give me another controller (or maybe even two) to play with if the mosfets aren't trashed as well. And if the new controller comes with the same caps, I'll know to inspect these periodically to see if they are getting bloated - if so, I can look to replace those on the new controller.

Again, thank you for all the excellent education on this - I so appreciate it!

 

[bigedgar]

I checked the caps in the three controllers I have:

1. One cap exploded, the other is bulging
2. Both caps exploded
3. Both caps are swollen (this is the one controller that hasn't "exploded" yet, but the fuse holder melted. It's possible that the controller is already toast, or it could be that it's functional with a new fuse holder, but will fail soon).

 

[dogman dan]

Sounds to me like the controllers can't do the load. The fuse is blowing when the caps go. Bigger controllers, so you can melt the motor.

It may not be so much that the controllers are too weak, as the controllers are just not performing to spec, since they are cheapos.

A bigger controller may handle the load better, but be too much for the motor. Solution, cut one of the shunts in a higher amps controller, which will leave you with moderate power, but a controller made to handle more.

 

[bigedgar]

Thanks, Dogman. What does a "bigger" controller look like? Still 36v, but something that can handle more than 30 amps?

 

[amberwolf]

more or less.

the main thing is that if something is "built" for 36v 30a, many of the parts will be close to the edge for that usage scenario.

but if something was built for 48v and 50a, but only used at 36v 30a, pretty much nothing will be run near their limits, so they will last longer and be much less likely to fail.


part of the problem youre havign is voltage (but also heat, and current). capacitors are voltage sensitive (as are fets). the closer they get to their voltage limits, and the more often it happens, the more damage builds up....it's worse with cheap ones, becuse they have crappy electrolyte, so it tends to boil more easily, and thus explode. better caps have better electrolyte, among other differences.

just for fun, you might want to look up "capacitor plague".




the catch with higher voltage controllers is sometimes they have a low voltage cutoff (lvc) that is higher than your battery's voltage, or at least high enough that you can't use all of the battery capacity you have (so it shuts off much earlier than it should). you have to find one with no lvc or an adjustable one.

higher current controllers, as noted by dogman dan, will have to be modified to lower the current or else risk overheating / damaging the motor. (but it will be more fun for the short time it may last ).

 

[dogman dan]

To clarify, what I meant was a 36v controller, with higher amps. Not a higher voltage controller.

It could be that like the bike I had, your controller just could not handle the load the motor is trying to pull, because of the load, and how it is geared. If the bike is geared too high, then the motor will pull max amps longer. The controller is supposed to be ok with that, but if its cheap enough, then it may fail with a lot less load than its supposedly designed for. This is not poor design so much as shoddy, cheap parts went into the controller to keep costs down.

Same thing tends to happen, when you put a very big hub motor on a bike, but run it with a not so big, cheap controller intended for a smaller motor. It works, but fails sooner than you would expect. It just doesn't like running maxed out so much of the time.

So look for a 50 amps controller, and then run it with a bigger fuse. And perhaps, if you mind risk to the motor, cut one shunt to make a 50 amps controller work with just 25 amps, if its a two shunt.

 

[bigedgar]

Thanks again for all the great thoughts, guys. It doesn't seem that simple to find a controller that is rated at 36v and > 30 amps while still being fairly plug-and-play. There are options out there, but it seems like most of them require additional parts to connect the throttle, power, charger, etc. I'm not sure I want to go through all of that.

The other option is to get a 36v / 1000w controller that is higher quality than what I have today, but it seems like it's tough to know whether the innards are any better than what I have today (I checked with one retailer to ascertain the size of the caps in their 36v / 1000 w controller but he/she didn't know).

With all that said, I'll just have to figure out whether I try one of the $50 controllers and hope for the best, or buy 2x the on-sale $20 controller and play with them (upgrade the caps, maybe look at changing out the mosfets if the caps hold but the fets blow, etc.).

Either way, it should be a fun project!

 

[bigedgar]

Hi, I'm back with an update and another question. If you'll recall, this thread was about an electric mini bike that kept blowing up controllers. One of the suggestions was to replace the controller with a higher capacity, higher quality controller, but I couldn't find one that fit my specs (there are not alot of 36v / 1000w controllers out there, and the ones I found don't appear to be any better than the stock controller that I have).

So I opted instead to try to beef up my existing controllers, starting with getting better capacitors. It's taken a few months, but I got two brand new "stock" controllers and some Panasonic 63v capacitors. I de-soldered the original 50v caps from one of the new controllers and replaced them with the 63v caps.

I then hooked the modded controller up to the mini bike battery and there's a short somewhere - it pops a fuse every time I try to connect the battery (FWIW, I removed the Tamiya connectors for the battery and am just using wire nuts to ensure a solid connection). Just to be sure, I tried the same setup with the other stock, new controller and the bike works fine - so the problem is most likely with my modified controller.

Which brings me to my request for some help. As I mentioned, the mods I made to the controller were to replace the stock 50v caps with new Panasonic 63v caps. I think there are two likely culprits to my short:

1. These caps were too big to fit nicely in the controller box, so I had to frankenstein them in there with really long posts so that I could bend them to fit into the enclosure. Is it bad to have long posts on capacitors? My googling for this specific problem didn't turn up any helpful info.
2. My soldering skills are very poor and I may have done a terrible job of actually soldering the caps to the board.

Given the pictures below, what do you think the most likely cause of my short is? Long posts for the caps, or bad solder job?

Thanks for any thoughts.

 

[amberwolf]

The leftside cap looks like it is installed backwards, with negative on the positive side.

The stripe with the - sign on it has to go to the circuit board pad that is battery negative / ground.

Also, you want to install those with the leads as short as possible, even if you have to drill a hole in the controller casing for them to stick up thru, they will work much better if mounted directly to the board surface vertically. The longer the leads are, the more they interfere with the job the caps have to do.

 

[bigedgar]

Well shoot, I had no idea caps had a positive and negative . I can fix that. And drilling a hole in the case for the caps to stick through is a good idea - I'll give those two things a shot and let you know how it goes. Thanks again, Amberwolf!

 

[amberwolf]

The hole in the case thing only works easily if the top comes off the case, not if the board has to slide into it from the end.

If it goes in from the end, you'd need a long slot as wide as the caps.

 

[John in CR]

Even more important than rider weight is how the bike is ridden as well as the terrain. The fact that it keeps blowing fuses with multiple different controllers is a big clue that it's being abused in a manner that stresses the system. Hills, muddy terrain, and repetitive acceleration from low speed or a stop will easily stress such a system and easily blow controllers, with going very slow on uphill grades being one of the worst things you can do to a controller without even knowing it. It doesn't help that everything is sealed up inside that cover severely inhibiting heat dissipation.

If it rides well for your use, then it's worth spending some money on to turn it into an EV with absolute reliability and significant range with any rider, so the only concerns are the brakes, chain and air in the tires. I say that because of the ample space housing the batteries, motor and controller, along with how easy things are to get to. The first stage in the upgrade path is a motor controller that is programmable and exceeds what the motor can handle, so the controller can handle whatever you throw at it. A relatively cheap solution if you can find one is a Kelly KDS48050E 24-48V 50A programmable controller, and be sure to get the programming cord if you can't make one up yourself, or already have what's needed.

If you want to go the ultra-cheap route that requires some learning about electronics, and you are willing to put the effort into tuning it to your system, you could DIY a controller using something like this as your base https://www.amazon.com/Controller-1...=psdc_306530011_t1_B07D31MGFF#customerReviews

Another cheap way to end up with a much better machine if you're now sold on electrics would be to find a used electric scooter for cheap with the same diameter tire on the hubmotor. Even a larger diameter wheel could be fit easily with a bit of metal work since you have no suspension. That would give you a virtually indestructible motor as long as you keep power conservative, and controllers are plentiful and cheap. That would free up massive space for the ultimate upgrade, which would be to go with lithium batteries instead of the lead anchors they come with which have limited capacity and short life if they aren't babied, and are big and heavy. 100+ mile range would be a matter of simplicity using lithium in the space on that bike.