BB02 500w - cuts out under load - help!!

[Jouboy]

Have a self build running a 500w Bafang BB02 mid (crank) motor with 48v battery.

System has developed a fault whereby all runs fine when back wheel raised and throttle applied. However, as soon as load of a rider is applied, motor cuts out and system shuts off i.e. VDU turns off. Removal and reinstatement of battery gets system back on until again load is applied.

Have checked all battery/power connections - all good

Can you assist by way of either diagnosis or, better still, solution

 

[Fordulike]

Have a self build running a 500w Bafang BB02 mid (crank) motor with 48v battery.

System has developed a fault whereby all runs fine when back wheel raised and throttle applied. However, as soon as load of a rider is applied, motor cuts out and system shuts off i.e. VDU turns off. Removal and reinstatement of battery gets system back on until again load is applied.

Have checked all battery/power connections - all good

Can you assist by way of either diagnosis or, better still, solution

What battery are you using? A link to vendor would be useful.

 

[Jouboy]

Hi Fordulike

In short, not sure of the name of the battery manufacturer (if that is what you mean) and acquired it from the same Chinese company that sold me the Bafang 500w motor. Its a 48v 10.6 A/h

 

[Fordulike]

Hi Fordulike

In short, not sure of the name of the battery manufacturer (if that is what you mean) and acquired it from the same Chinese company that sold me the Bafang 500w motor. Its a 48v 10.6 A/h

Depending on how the Bafang is programmed, it can draw a lot of current from the battery under load. It may be that the battery is sagging badly under load and tripping out the BMS' low voltage cut-off.

It's not the Bafang's low voltage cut-off, as this produces a stuttering sensation in the motor unit, plus the LCD display stays on.

 

[brightonebikes]

How old is the battery too?

Sent from here to there with computer wizardry.

 

[Jouboy]

Battery is old, but can confirm that a new BMS was fitted recently, and fault started almost immediately after that.

 

[Fordulike]

Battery is old, but can confirm that a new BMS was fitted recently, and fault started almost immediately after that.

Oh right, I assumed the battery was new. Most likely the battery can't provide enough amps for the Bafang then.

 

[Jouboy]

Whilst I must bow to your knowledge of these things, can I check - when the bike is tilted onto its side, and I run the system on throttle only, it works absolutely fine. Would this still fit with your theory?

 

[Jouboy]

to clarify last comment, i.e back wheel is off the ground and able to free wheel under throttle power

 

[brightonebikes]

Why was the BMS replaced?

 

[Jouboy]

Hi Brightonebikes - Battery insides slid out of their aluminium sleeve. On trying to re-insert, there was a small "pop", fizzying and smoke. Took it to a battery builder here in N London (UK), who spotted another burnt bit on the old BMS so replaced it.

 

[Fordulike]

Whilst I must bow to your knowledge of these things, can I check - when the bike is tilted onto its side, and I run the system on throttle only, it works absolutely fine. Would this still fit with your theory?

With rear wheel off ground, the Bafang will only draw a few amps maximum to spin the wheel. With the wheel on the ground, a person on the saddle and starting from standstill, it could require 20 amps+. This condition can cause an old worn battery to sag to BMS low voltage cut-off point.

 

[brightonebikes]

Hi Brightonebikes - Battery insides slid out of their aluminium sleeve. On trying to re-insert, there was a small "pop", fizzying and smoke. Took it to a battery builder here in N London (UK), who spotted another burnt bit on the old BMS so replaced it.

I see. Do you know if they checked any of the strings or individual cells within the battery at the same time? Kind of false economy to replace BMS if the cells are near to the end of their usable life.

 

[Jouboy]

Afraid do not know, Brightonebikes. Battery was old, but hadn't been used that much.

 

[Jouboy]

Seems like a battery problem from what I can ascertain from you guys, and others on other forums. Will have to find another 48v to see if that resolves it

 

[brightonebikes]

If you have access to another 48V battery, try process of elimination starting with the battery. From what you say and coupled with Fordulike's input it does sound like battery issue rather then the BBS02.

 

[Nealh]

One of my bug bears on here peeps wanting advice but won't tell us where they live.
Sounds like the battery is sagging and can't cope however the LVC on the BMS could also be to high or is asking for to many amps to be supplied.
What is the full charge voltage hot off the charger and do you have a programming lead ?

 

[Fordulike]

Seems like a battery problem from what I can ascertain from you guys, and others on other forums. Will have to find another 48v to see if that resolves it

Although pricey, I can vouch that the dolphin style frame batteries from Eclipse Bikes, work perfectly with BBS02's.

http://www.eclipsebikes.com/116ah-lithium-frame-battery-samsung-cells-p-1105.html

 

[Jouboy]

Hey Nealh - I've no problem telling people where I live - SW London, United Kingdom.

 

[Jouboy]

Ah - nice suggestion Fordulike, but there is a very good reason why it has to be an old-style cylindrical battery - I had the frame modified to have a 100mm diameter seat post which houses the battery