E-bike randomly stopped working

I have an e-bike with the cyclone 3000 kit and a 20AH 52v lunacycle battery and after completing it I took it for a test ride for about 15 miles.
It worked great no problems.
The next day I went around a few blocks and all of the sudden the entire thing shut off.
I rode it home and checked the wiring, everything was okay. The engine was only warm to the touch. The battery was very hot. However the battery was only at a few volts even though it was just fully charged.
To be sure I unplugged the battery from the controller and remeasured the voltage and it was now at 45v.
After plugging it back into the controller it turned on and worked fine.
I took it out again and after only a few minutes it cut out again and after disconnecting an reconnecting the battery from the controller again it did work but this time it was showing a very low battery indication on the throttle.
After bringing it back home I measured it again and it was at only 1.2v when connected to the controller and 40v when disconnected.
I concluded that there was a short in the controller but today I plugged it back in again and it once again works fine. I only rode it through the yard for a few minutes at low speed but after checking the voltage it remained stable.

I'm not sure what sort of fault could cause this issue but I have to assume the issue is with the controller.
Does anyone have any input on this issue?
I don't want my battery turning into a bomb, it was pretty darn hot for a very long time after I stopped riding it. No surprise if it was shorted.

Sounds like the bms is turning off your battery for some reason. That's why you get a low voltage on the output. Then it resets when you unplug it.
If you're battery is hot that points to a problem.... I'd start with measuring the voltage of all the cell groups, checking over the connections, and giving it a bench test to see what is happening under load.
But it could be a short somewhere else that is causing a big load on the battery ( causing heating and the bms to trip) and its independent of the controller cause it wouldn't be working if it was an internal controller short.
Check all external wiring for chaffing.
Stick a watt meter in line with the battery to measure current to controller.
Something is definitely amiss.

I don't see how it can be a short within the battery.
The voltage goes from near nothing to near full voltage when disconnected from the controller and the battery gets very hot after this. Both indicating a short within the load.
After charging the battery it reaches almost 59v at full now.
A short in the controller would also explain why the voltage dropped from 45v to 40v after my second run on the bike.

All that aside there's no way the BMS can suppress the battery voltage at the battery terminals which is where I'm measuring the voltage.

Roger....

45V no load on a 14S pack is 3.215V per cell group, which is actually pretty near dead. It will have been dropping lower than that under load before it shut itself off. Not sure what BMS Luna uses in these packs but I think most will cut off at around 2.8 to 3.0V. Cutting it off drops the load, the voltage rises again and the BMS will reset (some automatically, most after disconnecting the load). So I'm pretty sure the BMS is just doing it's job. They use FETs to switch the power off and on, so there is some leakage which is why you're reading a small voltage at the output. There's not much energy between 45V and 40V, you basically rode it from dead to more dead, 40V is like 2.86V per cell. Quite dead.

A short internal to the controller or in it's supply wiring would be pretty easy to spot when you connect the battery. There would be a hell of a sparky flashy whooshy fizzy plasma like event as the connectors neared one another. You'd know trust me.

If you managed to get the two connected without aforementioned sparky flashy stuffs happening, the controller would at best get really hot, because all that energy would need to go somewhere. Most likely smoke would come out and it wouldn't be shorted for long. Sparky flashy stuff would happen inside the controller, for a few seconds at most.

Another way to rule that out is with an power meter of some kind between the two, you'd see abnormally high amperage being pulled from the battery while the motor wasn't doing anything. Power meters are a great way to answer to all kinds of ebike related questions, including if your battery is performing properly.

Which is a good question in your case, you said you rode 15 miles, with a 2000W (or so) capable motor/controller combo. So if you were riding hard, it's quite possible you used very near the 1000Wh or so that battery holds. You said the battery was very hot, was it hot all over or in one particular area? What is the amperage rating on it? I think the cyclone kit has a 40A controller, that load could really heat up a battery depending on what cells it's made from and how many of them are in parallel. That will also reduce the amount of Ah you get out of the pack, because instead of the energy going out the battery terminals and powering your bike, it's being dissipated out of the cell casing as heat.

After running the battery dead like that, particularly at high amperage, you should really get it on the charger ASAP. It's very bad for those cells to be stored at such low voltages. Also, make sure you at least occasionally let the battery sit on the charger after it shows "full" so the BMS can balance the cells properly, especially after you fully drain the battery. You'll get more range from the battery, as you won't have one cell group hitting LVC way before the rest do. It can take hours sometimes for a pack to balance, depending how far out it is and how quickly the BMS can do it's job.

When I road 15 miles that was the day before I had problems.
It was fully charged the next day before it started to fail on me. I left it on the charger over night.
I had used it for about 30 minutes around the streets near my house before it started to fail, there's no way the battery could have died that quickly on mostly flat roads when the previous day I road 15 miles and it still showed it had over 75% battery.

When I measured the voltage and it was showing only a few volts that was directly at the battery terminals, not on some external gauge, then it would bounce back when I disconnected it from the controller. I don't know what else other than a short could make a battery behave like that.
Unfortunately I don't have a power meter that can measure over 10A.
The battery was hot all over after the incident, like too hot to touch. It stayed hot for many hours after I stopped using it.

I took the bike out for another ride of about 6 miles and no big issues while riding except I can't help but feel it's going noticeably slower then before.
However the battery went from 58v to to 48v during that time and the roads were mostly flat other than 1 small hill.
The battery is also extremely hot again.
This isn't good.

If you can get to the balance wires that go to the BMS, check the voltages of each cell group. It does sound like a problem somewhere in the battery. Either a bad cell or maybe a bad spot weld. I'd really encourage you to get in contact with Luna support over this, they'll know way more about how the battery is put together, etc. It's not a dead short though, that would be far more dramatic than just peacefully shutting off.

coinmaster said:

The battery was hot all over after the incident, like too hot to touch. It stayed hot for many hours after I stopped using it.

Click to expand...

That's a real danger sign. It's entirely possible the battery was damaged by the heat. The motor is apparently drawing way more than the battery is good for. This kind of heating greatly increases the risk of battery fire and drastically shortens the life of the battery. I would be highly concerned about the battery heating. The battery should get barely warm at the most.

It's possible the BMS has a bad channel and is constantly draining one of the cells. That cell will go low and trip the BMS before the pack voltage gets noticeably low.

Your voltage measurements indicate the BMS is tripping. The actual cells might have 48v, but output from the pack will drop once it trips. Unplugging the controller will reset the BMS (usually). BMS will trip if any cell drops below about 3.0v or if the current is above the set point or if the temperature of the BMS goes over 60-70C. In your case, it sounds like a cell is dropping too low.

It seems like you got a false positive on the hall/phase sequence to me. That can make the controller draw massive currents. Go through some more combinations. Unless your controller is specially matched to your motor, you can't rely on colour to colour connections.