Unknown e-bike brand busted up

[E-bike Maine]

Hi - I bought this e-bike from a local high schooler and at the beginning it ran nice. Up to 22 mph. Great on our back-roads.

I'm hoping there is a simple answer to my issue. I can get technical but I've been trying to find the "simple" fix and not get too involved.

I hope you can help.

Here's what happened. I had a little accident -- it fell off my bike rack -- and the bike hasn't run correctly since.

When I twist the throttle, there's no power. It wants to go, but it has no power.

When the bike is on a rack, the throttle will get the front wheel spinning, but as soon as there's any resistance, it stops spinning.

I think it is an early Voilamart rig, or a clone as there are no brand names on anything. The bike is likely something that came from WalMart.

Sorry folks, can't seem to get these images to upload. Maybe they'll be OK.

 

[amberwolf]

Here's what happened. I had a little accident -- it fell off my bike rack -- and the bike hasn't run correctly since.

What fell off the bike rack? The controller? battery? The entire bike off a rack on a car/truck/bus/?? Or??

When I twist the throttle, there's no power. It wants to go, but it has no power.

What exactly do you mean? Normally "no power" means no lights, no operation at all. Since the below happens, that can't be the case:

When the bike is on a rack, the throttle will get the front wheel spinning, but as soon as there's any resistance, it stops spinning.

When this happens, what voltage do you read at the connection from battery to controller? If it drops low enough (perhaps because of physical damage to the battery), the controller will shutdown to protect a low battery from damage.

If power is completely lost (no lights, etc) when this happens, then it's almost certainly an internal battery problem, where the BMS turns off the output to protect the cells.


Does the wheel spin at it's normal full speed until it is loaded down? Or is it spinning only slowly?

the latter could also indicate a battery problem, but it can be just a broken throttle that is not outputting the full signal it should (usually because of magnets broken off inside).

If the motor does spin only slowly, what voltage do you measure from battery negative to each of the throttle wires, with throttle off, and then with throttle all the way on?


A fall-damaged battery would be safer to replace than repair, because cells could be damaged and that can lead to a fire at any moment in time now or any time in the future. It could just be broken cell interconnects, etc, which may be relatively easy to fix with the right equipment and expertise.

If it's a broken throttle, that's cheap and easy to replace.

 

[E-bike Maine]

Amberwolf, thanks for getting this started.

Entire bike fell off the bike rack. it was fairly spectacular and totally idiotic as I had not put on the safety straps.

The battery was not on the bike at the time of the accident. I have two batteries and they both generate the same conditions.

Yes, I get "lights" on the throttle when the battery is plugged in and I turn the switch on.

Will have to get out my voltmeter to answer your next question but the answer may be moot.

With no resistance to the wheel - (literally hanging the bike in the air) - the front wheel spins at what seems like normal speed.

I believe the axle end where the cable enters the motor through the axle was hit during the accident and there's a minor short somewhere in those wires but as I have no way to diagnose this without taking the whole thing apart I am hesitant to do without more clues that this is the problem.

Could also be the throttle?

I'm likely in need of a 101 as to what and how to test these theories.

 

[amberwolf]

Entire bike fell off the bike rack. it was fairly spectacular and totally idiotic as I had not put on the safety straps.

Oops.

Stuff happens. Were the wheels / rims damaged? That's common even when lightweight regular bikes fall off like that. Does'nt have anything to do with your issue but is another thing to check for.

Magna brand bikes are pretty cheap "BSO"s (bike shaped objects); I've used them for parts to build my own bikes from (the front half of CrazyBike2 used to be a Magna about the same color as yours
), so they don't always have the toughest parts...and factory-built kit-hubmotor wheels are also not usually well-built or of great rims/spokes....

Also check the pedals/cranks as they often get bent (can damage the bearings too), and if yours had a suspension fork that could also be damaged (the nonsuspension U forks I've seen on them are a bit tougher).

The battery was not on the bike at the time of the accident. I have two batteries and they both generate the same conditions.

Good--that eliminates a lot of things to check, so no need to check battery voltages.

With no resistance to the wheel - (literally hanging the bike in the air) - the front wheel spins at what seems like normal speed.

That eliminates the throttle and the battery, most likely.

I believe the axle end where the cable enters the motor through the axle was hit during the accident and there's a minor short somewhere in those wires but as I have no way to diagnose this without taking the whole thing apart I am hesitant to do without more clues that this is the problem.

That's a really common problem, even from bikes just falling over on their sides. Even happens during shipping of the mtor kits when the wheels are poorly packed (most of them are this) and the axles poke thru the box side.

If there's wire damage it could short halls to phases which usually destroys the motor's hall sensor (s) affected, and can also damage the FETs in the controller. If it's just a broken wire that didn't short to anything (like a cut phase wire) then it would just need reconnection.


The first thing to do is remove the tape(?) covering that area and examine the wiring for insulation damage on the outer jacket, and then inside on any wire. If any is evident, then the easiest way to fix that problem is to open the motor, pull the cable from the inside of the motor thru the axle further into the motor until the entire damaged section is accessible and cut that away, leaving some of the colored part of the wiring attached inside the motor for reference to reattach the undamaged wires to.

There are a a number of threads and posts around here with more specifics on opening hubmotors, replacing or modifying wiring, etc., but it's usually not too tough. If you need to do it I can try to find and link some of them.

 

[E-bike Maine]

Did a bit of cheating with ChatGPT and see there's virtually no voltage on the Hall effect circuit.

Sort of want to double check this with you guys.

My voltmeter says there's 1.3 volts there and there should be 5.

Smells to me like I need to replace the controller??

 

[lnanek]

You mean the hall sensor in the throttle? There should be 3 wires to it, minimum. +5V, ground, and signal. Volt meter between +5V and ground should give you 5V. Volt meter with signal to ground should range from 0.8 to 4.2V as you turn the throttle.

The motor hall sensors should have 5-6 wires. +5V, ground, motor position hall sensors A, B, and C signal wires, and potentially a speed hall sensor signal wire. Volt meter between +5V and ground should give you 5V. Any of the signal wires and ground should range from 0 to 4.9V as you turn the wheel.

 

[amberwolf]

Did a bit of cheating with ChatGPT and see there's virtually no voltage on the Hall effect circuit.

which hall?

there are halls in most motors, there is one in most throttles, and some ebrake levers have them as well, and some wheelspeed sensors.

there are different types of hall sensors and they have different output ranges and behaviors.

don't trust any of hte ai things because they don't "understand" anything. if you ask questions here and provide informaiton when requested then we can help you much more accurately than those chatbots.


waht were the results of checking the axle wires?

My voltmeter says there's 1.3 volts there and there should be 5.

Smells to me like I need to replace the controller??

1.3v where? On exactly which pin or wire, in reference to what other wire or pin? Under what specific test conditions?

All of those are required to tell you an answer.