Help needed on Bafang mid install problems!

[silver50]

If any experts could PM me a phone number that would be great but I'll explain:

Had my BBS02 90% buttoned today. All seemed to be working ok.

Had battery off/disconnected and then went to alter power cable and connections. Didn't anticipate live cables exiting the motor! I unfortunately got a brief short circuit when I snipped a pair of connectors off. Unexpected and not great.

I thought things were dead but I can get the system started up if I connect the battery when it's live. I can then switch the display on/off as normal. However, if I switch the battery off before the display, things won't come back on (after switching the battery back on) as they should. I seem to often get a momentary flash of display but that's all.


I've battery concerns though. Is there much operational circuitry inside the battery? There have been times I disconnect the battery and am seeing no voltage. Also, should a battery show no voltage at the cabling when it's switched off? I seem to be seeing 40.6 volts (or something close..) when the red switch is off. Lastly, my red battery switch at "O" is my on 54V position and "I" is off (showing 40.6v..). This is the opposite of a friends almost identical battery. Output at the connections on the back of the battery itself (rather than from baseplate are ok at 54V.

Not been the day I hoped it would be. Hopefully someone can help! Thanks

 

[peter.c]

Do not panic if you remove the battery power it is normal operation that you have to switch the display back on .The battery has a pcb a battery management system in side

 

[silver50]

Thanks for your reply. What seems odd is that I can’t connect the battery and get operation if the battery starts off in it’s “OFF” (at its red switch) position (obviously I turn it on before trying to turn on display). I seem to have to do the live hard (get a spark) connection before things operate.

If I switch off the battery before switching off the display, I again need to do the same hard reconnect or it won’t come on.

 

[Woosh]

your problem is in the BMS which trips when you switch on the LCD.
Where did you get your battery from?

 

[peter.c]

From your second post it now sounds like a bms fault in the battery

 

[silver50]

Apologies for no reply. Found first reply in spam and marked as not spam on my iphone. Now at 1145pm I see on my laptop that these replies are also in spam!

I was looking at it again tonight. Still puzzled as to which side at fault but I appreciate the input that it might be the BMS. Got battery from a UK ebay seller with good feedback. Hailong sticker on it but no labelling whatsoever and it's on'off switch seems to be the opposite way round from my friend's similar battery.

When I looked again tonight, when it wouldn't switch back on I read voltage at the battery to motor connector. Saw only 11V at the connector with battery ON.

A friend coming after work tonight with his bike and almost identical 48V battery. Trying his battery ought to clear up what’s going on (I hope!)

 

[vfr400]

Hailong makes theplastic case with the switch and connector already installed. The battery and all the wiring can be done by anybody from the latest high-tech factory to a bloke in his shed. Two batteries that look the same on the outside can be completely different on the inside.

I'm not sure if it's possible to wire the switch backwards, but it might have been assembled with the rocker the wrong way round.

When that switch is off, you can get any voltage on the terminals from zero to the actual battery voltage. Typical is around 10v to 25v. It's not real voltage. It's just a bit of leakage through the mosfets. You can't take any power from it like that, not even enough to light an LED.

 

[PC2017]

Am I being thick again??

Would I be wrong to assume when he cut the motor power cables the internal controller CAPS discharged, if so can anyone recommend a CAP discharger? Secondly if the battery was not on the system how did this effect his BMS?

Had battery off/disconnected and then went to alter power cable and connections. Didn't anticipate live cables exiting the motor! I unfortunately got a brief short circuit when I snipped a pair of connectors off.

 

[Woosh]

what happens is the on/off switch toggles a circuitry inside the BMS to enable the output. The BMS itself has a protection system which shuts down the output if the current exceeds certain preset level (over current protection) or flows in the wrong direction (reverse current protection) and on/off over current.
When you switch the LCD is off, it takes about 5 seconds to discharge the large power smoothing capacitor on the controller. When you switch on again, there will be a large inrush current to charge up that capacitor.
In some cases - like this one here, one of the three protection systems is triggered. The solution is to replace the BMS.
You can carry on using the bike by installing the battery only after it's switched on.
The design fault is in the chip and happens frequently so that many batteries don't have on/off switches anymore.

 

[silver50]

what happens is the on/off switch toggles a circuitry inside the BMS to enable the output. The BMS itself has a protection system which shuts down the output if the current exceeds certain preset level (over current protection) or flows in the wrong direction (reverse current protection) and on/off over current.
When you switch the LCD is off, it takes about 5 seconds to discharge the large power smoothing capacitor on the controller. When you switch on again, there will be a large inrush current to charge up that capacitor.
In some cases - like this one here, one of the three protection systems is triggered. The solution is to replace the BMS.
You can carry on using the bike by installing the battery only after it's switched on.
The design fault is in the chip and happens frequently so that many batteries don't have on/off switches anymore.

Thanks for all this. All noted and helpful. Yet again no reply notifications for me for some reason!)

Trying my friends battery later today should be a nice definitive test for me.

Does this make sense if it’s the BMS: With battery switched ON (everything connected prior) and I don’t get powered up (at display) I’ve been reading voltage at the power connector-
Voltage creeps up and up slowly from about 11v. I left it doing this for 15 minutes expecting it to reach 45+V. When I went to switch on at the display it did light up for slightly longer than a flicker but still wouldn’t power on.

If I disconnect the battery I seem to have 50+V ok at its cables

BTW certainly makes sense that things would actually work ok if prepared to do the hard wire but looks as if you’d need to be careful not switch the battery off before the display (or you’d have to do the power live reconnect up)

 

[silver50]

To update after a definitive test with my friends 48V battery. Definitely my battery at fault. Prefect operation and no problems on/off at battery etc.

Question though. Disconnected and switched off, my friends battery voltage drops away at a nice steady rate. You watch it dropping down quite quickly on multimeter. Mine on other hand sits at a steady 40.6 volts when off and disconnected. It doesn’t drop. Is this just down to different BMS type or significant in relation to its fault?