Huge voltage drop on BBS02

[Wullen]

I rode my bike just fine for an hour, and the day after when starting the bike it said that the battery was empty. Showing about 30v. The battery works just fine on my other BBS02 bike.

So a couple of days later when I was checking the bike again and the bike starts upp with 52 volts but as soon as I start the motor it drops to 30 volt, and then it turns off. I checked the xt60 connectors and wiggled around couldnt find anything obvious.
Also changed the fuse on the battery connector.

Have to fix the bike outside so I gave up after an hour in the freezing temperatures.

Has anybody had this problem? Can a bad connection on a XT60 really show lower voltage?

 

[docw009]

I think the big clue is the drop to 30V. A 52V or 48V battery with a BMS cannot show 30V on the output. If you see that, it's just residual charge, The BMS has shut off the battery because it detected a low voltage on a cell group from volt.. Sometimes voltage sag from high current on a weak cell group will do this, or a cell group was just undercharged.
,
With that in mind, if you immediately move your battery to your other bike, does it power up again. If not, does it restart on its own or do you have to put a charger on it?

 

[Wullen]

I think the big clue is the drop to 30V. A 52V or 48V battery with a BMS cannot show 30V on the output. If you see that, it's just residual charge, The BMS has shut off the battery because it detected a low voltage on a cell group from volt.. Sometimes voltage sag from high current on a weak cell group will do this, or a cell group was just undercharged.
,
With that in mind, if you immediately move your battery to your other bike, does it power up again. If not, does it restart on its own or do you have to put a charger on it?

No, im sure its not the battery. It works just fine directly afterwards. Measure the right voltage and works on another bike. Went full blast 1300w with other bike without any problems.

 

[docw009]

Maybe the power wires behind the XT60 have frayed down to a few strands? That could drop 10-20 volts.

 

[amberwolf]

With the battery still connected to the controller, what does a multimeter show for voltage on the battery immediatly after the system shows the low voltage?

If it also shows a low voltage, it means the battery's BMS has turned the output off because some limit has been exceeded. If the battery works fine on a different bike, then that means this bike has something wrong that is doing it, and the most likely thing is excessive load, such as shorted motor windings or blown FETs in the controller.