i9 shuts down after while

[uas66]

Hello,

My i9 scooter shuts down with full battery after 100-200 meters. After that the scooter does not power on when pressing on the display button. If I disconnect the power plug from the controller and connect it gain, the scooter turns on. When I plug the charger it shows that the scooter is full.

All cells from the battery pack are checked and seems all OK.

The scooter runs fine when the wheel is in the air, but on load it powers of after a while.

What could be the problem?

Thanks!

 

[E-HP]

How are you riding the 100 meters? Slow, full throttle, etc.?
How old is the battery pack?

 

[amberwolf]

If it actually powers off, it's almost certainly a battery problem--one or more cells (groups) has a problem (low capacity, high resistance, etc) so the BMS turns the pack off to prevent damage that could lead to a fire.

For this case, replacing the battery pack is your safest and easiest option.

 

[uas66]

How are you riding the 100 meters? Slow, full throttle, etc.?
How old is the battery pack?

Yes, full throttle.
Battery pack is about 1 year old.

 

[E-HP]

Yes, full throttle.
Battery back is about 1 year old.

Do you charge it to full or run it to empty often?
I believe amberwolf’s advice is sound. I’m guessing the pack is made of low quality cells, given that the whole scooter costs around what a decent battery might cost.
Get a pack with brand name cells, and don’t fully discharge or charge it in order to keep it healthy.

 

[uas66]

Yes, the battery is always fully charged. And there is no way the battery could fully drain, because the scooter turns off.

 

[E-HP]

Yes, the battery is always fully charged. And there is no way the battery could fully drain, because the scooter turns off.

Even if the cells seem fine, assuming you measured them, they could still be bad/weak. Weak cells will appear to “charge” faster (and “discharge” faster) than good cells due to their higher internal resistance (so the voltages may look good until they are subject to load). Running full throttle makes the weak cell voltages drop faster until the BMS trips.

 

[uas66]

Even if the cells seem fine, assuming you measured them, they could still be bad/weak. Weak cells will appear to “charge” faster (and “discharge” faster) than good cells due to their higher internal resistance (so the voltages may look good until they are subject to load). Running full throttle makes the weak cell voltages drop faster until the BMS trips.

Thanks for the replies! But why does the scooter run again if I disconnect and reconnect the power cable from the battery to the controller?

 

[E-HP]

Thanks for the replies! But why does the scooter run again if I disconnect and reconnect the power cable from the battery to the controller?

The battery BMS trips under full throttle due to voltage sag. After it trips and the pack is no longer under load, the voltage recovers above the cutoff voltage. Disconnecting the battery, or turning it on and off, if the battery has a switch, allows the BMS to reset.

 

[Chalo]

Thanks for the replies! But why does the scooter run again if I disconnect and reconnect the power cable from the battery to the controller?

The battery BMS trips under full throttle due to voltage sag. After it trips and the pack is no longer under load, the voltage recovers above the cutoff voltage. Disconnecting the battery, or turning it on and off, if the battery has a switch, allows the BMS to reset.

I will add, when you run until it faults out again and again, you might as well be stomping on it. Fix the problem instead of worsening it.

You'll have to open up the pack and check cell voltage until you find the one(s) that's out of line. Then you'll need to balance it with the others and change your charging and discharging habits so the issue doesn't immediately reoccur.

 

[uas66]

I will add, when you run until it faults out again and again, you might as well be stomping on it. Fix the problem instead of worsening it.

You'll have to open up the pack and check cell voltage until you find the one(s) that's out of line. Then you'll need to balance it with the others and change your charging and discharging habits so the issue doesn't immediately reoccur.

Thanks. I will check the pack again. Also, I tried today to run the scooter with half throttle, and the scooter didn't shut down. So, I can confirm that it happens on full throttle.

 

[uas66]

Update: removed the whole pack.

Checked all batteries for resistance, capacity (average 2700 mAh) and voltage. Two batteries were 0 volt. I think that was the problem!

 

[uas66]

Replaced the bad cells today. The scooter runs fine and does not power off anymore. The only strange thing is that when I plug the battery into the charger, the red LED stays on for a couple of seconds and then turns off. Even with the LED off, the battery still draws 1.4 amps, so it is charging (I think).

What is the reason that the LED goes off?

 

[amberwolf]

What does the system manual say about charger operation? (if the charger didn't come with the system, then the manual for the charger itself, or perhaps it's label, as some have info printed on those).

How are you measuring the 1.4A?

 

[uas66]

The manual says: red = charging and green = full.

For measuring the amps I used my multimeter in series.

 

[uas66]

Update: After a while, the battery charged fully to 42.44V, and the green LED lit up. All fixed!

 

[amberwolf]

Sounds like the charger is built incorrectly, such that whatever runs the red LED is triggering off at too high a current.

Usually that LED should be run from the same trigger that actually turns the charging current off, so that ought not to happen.

As long as it still works, and does correctly shut off once the battery is charged, doesn't really matter.

 

[uas66]

Well, I'm back Unfortunately, the scooter stopped again after 200 meters today. Strange because I drove about 3 days without problems. I immediately checked all the cells and they're all testing at 4.1V, whereas before the repair, two cells were at 0.5V (which I also replaced). So now I'm not sure what the problem could be. Any ideas?

 

[amberwolf]

Are they all at 4.1v under load equal to when it stopped?

If any of them are high resistance, then even though they are identical in voltage in a static test (no load) they may be very different voltages under load, sagging in voltage enough to trip the controller LVC (if it doesn't actually turn off) or the BMS (if you actually lose all power)

 

[uas66]

I am not able to monitor the voltages under load, don't know how to do that. The resistance could maybe be the issue. I checked all cells with my OPUS charger, but I am not sure if that is an accurate measuring.

What is a good way to measure resistance?

 

[E-HP]

I am not able to monitor the voltages under load, don't know how to do that. The resistance could maybe be the issue. I checked all cells with my OPUS charger, but I am not sure if that is an accurate measuring.

What is a good way to measure resistance?

Probably something easier to determine on the bench. You need a known resistive load and a way to measure the voltage with and without it. I have a charger that imputes the cell resistance, but it’s for lipos.