Help needed

[Skyline5709]

Hi all need some advice l'm not new to bafangs as l've built 5 bikes but l've come across something l've never experienced and can't really find anything online l've got a bbs02 and recently it's showing a full battery drain
from 100% to 50% in less than half a mile I can literally counting down like a clock then it'll go back to 100% when I stop I know about battery sag but this is silly it's never done that and yes it's not the battery as I have 3 different batteries and it does the same on all which it doesn't on my other bike I've replaced the controller
and the wiring harness could it be the hall sensor or something else any advice would be great thanks

 

[RollingChunder]

Hi all need some advice l'm not new to bafangs as l've built 5 bikes but l've come across something l've never experienced and can't really find anything online l've got a bbs02 and recently it's showing a full battery drain
from 100% to 50% in less than half a mile I can literally counting down like a clock then it'll go back to 100% when I stop I know about battery sag but this is silly it's never done that and yes it's not the battery as I have 3 different batteries and it does the same on all which it doesn't on my other bike I've replaced the controller
and the wiring harness could it be the hall sensor or something else any advice would be great thanks

Percentages never tell the full story and are often wrong. Can you switch the display to volts? Also, some punctuation wouldn't go amiss.

 

[Skyline5709]

I put ot in voltage same results.

 

[RollingChunder]

I put ot in voltage same results.

The cold weather makes batteries sag more, as does any resistance so hills or brakes rubbing or extra weight. If it bounces back to full straight away it sounds quite normal. Do you have a lower top speed on a full charge?

 

[Nealh]

Could be a faulty display ?

 

[Skyline5709]

No I've tried 3 different displays aswel.The only electronics left are the hall sensor and it's not normal battery sag as its only very recently started, I've ridden through 2 cold winters and it didn't happen

 

[saneagle]

Hi all need some advice l'm not new to bafangs as l've built 5 bikes but l've come across something l've never experienced and can't really find anything online l've got a bbs02 and recently it's showing a full battery drain
from 100% to 50% in less than half a mile I can literally counting down like a clock then it'll go back to 100% when I stop I know about battery sag but this is silly it's never done that and yes it's not the battery as I have 3 different batteries and it does the same on all which it doesn't on my other bike I've replaced the controller
and the wiring harness could it be the hall sensor or something else any advice would be great thanks

Sounds like a dodgy MOSFET in the controller, though it could be just a bad phase wire connection. Either way, it would be worth taking the controller off to look at the connections and test the MOSFETs.

There have been a couple of instances where water got into the controller, even though it's potted,which would do the same. The MOSFET test would give some indication of that.

 

[Skyline5709]

Thanks for the advice but as I said I have replaced the controller last week and its still doing . That's why I was wondering if it could be a dodgy hall sensor board as its the only electronics that haven't been replaced

 

[saneagle]

Thanks for the advice but as I said I have replaced the controller last week and its still doing . That's why I was wondering if it could be a dodgy hall sensor board as its the only electronics that haven't been replaced

I doubt that it's a hall sensor. the motor would screech. Best thing you can do is put a wattmeter between the battery and motor to see how much current is flowing. that'll tell you whether it's the battery or the motor.

Logically, for some reason, a very high current is coming out of the battery, which implies a short somewhere. If there were something wrong with the motor, it would get hot, if it's the controller, that would get hot.

Another possibility is a bad battery connector that can't conduct the current. Check your solder joints on any connectors and in the battery receiver/base.