I toasted my old Bafang battery, short circuited it. So I got a new battery from China. It worked great for about 100mi and then went intermittent and total death. When I test the volts for the new battery I get 41.5 at full charge should be 48 I think. I think the battery is good because of this but not sure. Since I have no display I don't know what else could be wrong. Is there anyway to tell whats going on with out buying a new $400 battery Anybody have a clue
Broken bike
- Thread starter Stu
- Start date
rich c
Well-Known Member
How did you short circuit the old battery. Many of those have fuses in them, and that be all that needs to be replaced. You don't know if the battery is supposed to be 48v? It should say right on it. Batteries directly from China are notorious for being poor quality. Hard to suggest what is going on because you give so little information. I suggest you find a local ebike mechanic.
J.R.
Member Since 2014
- Region
- USA
A 48 volt pack hot off the charger should be somewhere around 54.xx volts and a 36 volt pack is 41.xx fully charged. It almost sounds like you have a 36 volt battery pack and you're trying to run a 48 volt kit with it. Is your kit/drive 48 volt? And are you sure your new battery is 48 volt?
harryS
Well-Known Member
The maximum values at full charge are 54.6V and 42.0V respectively for 36 and 48 volt batteries. I am going to assume you have a 48 volt ebike.
The controller in a 48V ebike has a low voltage cut-off between 41 - 42 volts, so if you are seeing 41.5V on the battery, that explains why the ebike won't power up. It could be that your battery is not taking a charge. That's either a broken battery management system (BMS) or a bad charger.
Is your charger working? Its voltage with nothing attached should be that 54.6 volts mentioned above. Does it act like it's charging and do its usual behavior with the LED's? Bad BMS requires taking the battery apart and measuring the voltage on the 14 cell groups inside for a start. Only electrically competent people should attempt that.
The controller in a 48V ebike has a low voltage cut-off between 41 - 42 volts, so if you are seeing 41.5V on the battery, that explains why the ebike won't power up. It could be that your battery is not taking a charge. That's either a broken battery management system (BMS) or a bad charger.
Is your charger working? Its voltage with nothing attached should be that 54.6 volts mentioned above. Does it act like it's charging and do its usual behavior with the LED's? Bad BMS requires taking the battery apart and measuring the voltage on the 14 cell groups inside for a start. Only electrically competent people should attempt that.
It is a 36V battery that replaced the 36V bafang battery I short circuited by trying to hook another gauge to it Where the charger plugs in I clipped the wires and continued using it by jury rigging the charger to it. Worked great for several months but I just kept shorting it, My bad I know, Eventually it wouldn't charge.
Now the new battery is a 36v, 13Ah battery from China which may be the problem. I have not taken it apart yet I am looking for better direction before I do surgery.
Maybe it is the BMS The charger seems to be working I am showing 41.5v coming out of the battery and after the last failure it was down to about 39.5v after 1/2hr or so of running Then it kicks off and runs intermittently. I am thinking maybe it gets to hot and kicks off Sometimes the display will come on and last a few seconds before dying. I think the charger is working ao if thats the case it would be the BMS,right?
Now the new battery is a 36v, 13Ah battery from China which may be the problem. I have not taken it apart yet I am looking for better direction before I do surgery.
Maybe it is the BMS The charger seems to be working I am showing 41.5v coming out of the battery and after the last failure it was down to about 39.5v after 1/2hr or so of running Then it kicks off and runs intermittently. I am thinking maybe it gets to hot and kicks off Sometimes the display will come on and last a few seconds before dying. I think the charger is working ao if thats the case it would be the BMS,right?
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