VEC200 Not working

[Saranrazz]

Hi,
I have bought 3kW frame mount golden motor along with VEC200 controller. It was working fine. But, right now I am facing an issue where if I connect the battery to the controller, the system voltage suddenly drops to ~5V. I am using 72V lithium ion battery pack. Kindly let me know what I am missing here.

Thanks,
Saravanan

[Bikemad]

Hi Saravanan andto the forum.

If the battery voltage is dropping to ~5V when you connect the controller to the battery, then there is probably a fault with one of the following:

• The battery or its BMS
• The battery supply wiring
• The controller itself

Try connecting a 110/220V 100W incandescent light bulb across your battery and see if it lights. A 110V bulb should light much brighter than a 220V bulb on a 72V battery as it will be drawing a higher current due to its lower resistance.
If the bulb lights up (and the battery still reads more than 72V) then connect the controller to the battery as well as the bulb.  If the bulb then goes off and the battery voltage drops completely, it could be a short circuit somewhere in the battery cables or possibly a short within the controller itself causing the BMS to cut the power from the battery, but I would expect this to be accompanied by a big spark when the battery wire from the controller was connected to the battery.

Disconnecting one of the battery leads from the controller's battery terminals should cause the bulb to light up again if the problem was being caused by a fault inside the controller.
However, if the bulb remains unlit, it is more likely to be a short circuit between the "+" and "-" battery cables.

Alan
 

[Saranrazz]

Hello Alan,
Thanks for the reply. The controller started working fine now. I have connected the bulb initially with the battery pack and after that along with the controller. In both the cases the bulb glow. Later when I checked the controller voltage it was fine.
But I am really confused on why this has happened. Its clear that no short circuit with the battery pack and with the BMS. So my guess its to do something with the controller. If you could give your thoughts on this, it would be really helpful on understanding why the voltage drop happened and how it got rectified by itself.

Thanks,
Saravanan

[Bikemad]

If there's no physical sign of any short circuits on the battery cables (insulation chaffed away allowing internal copper wire to touch) then it could simply be a poor/loose connection on the battery supply cable (or even a poor connection between separate cells within the battery if it is made up of large capacity single cells in series instead of multiple smaller capacity cell groups.)

If you are using a contactor or heavy duty switch to connect the battery to the controller, it could be poor contacts within (or poor connections onto) either of these items, resulting in a high voltage drop when power is required.

An electrical power circuit is a bit like a chain, it can only transmit as much power as the weakest link can withstand, therefore a poor connection on an electrical circuit is effectively a weak link. 

If you had full battery voltage at the battery, but not at the controller, it would have been a poor connection somewhere in the main battery supply circuit. Checking the voltage at each connection point should have located the connection causing the problem.

Where exactly were you measuring the "system voltage" when it suddenly dropped to ~5V?

Alan
 

[Saranrazz]

I measured the system voltage across the controller's B+ and B-
I can understand your point on the loose connection, but I have checked that twice and even changed my contactor and it was still the same.

[Bikemad]

If I connect the battery to the controller, the system voltage suddenly drops to ~5V.

Where exactly were you measuring the "system voltage" when it suddenly dropped to ~5V?

I measured the system voltage across the controller's B+ and B-

If you were measuring the voltage on the B+ and B- terminals on the controller, I don't understand why it would have been higher than 5V before the battery was connected. 

If you only have ~5V at the controller's B+ terminal, what voltage do you have on each of the contactor's main terminals in relation to B-?

It might be worth checking out this thread, as I'm wondering whether your problem might be the same as Pcgayan's. 

Alan
 

[Saranrazz]

Hi Alan,

Thanks for your response!
I am using circuit breaker and not a contactor. When the circuit breaker was not closed, I measure the voltage across controller B- and the terminal of the Circuit breaker, it showed the same voltage as the battery pack. But after the circuit breaker was closed, the same voltage drop happened across the circuit breaker and the B- of the controller.
It was so confusing. I even checked connecting the communication cable with my pc for the LED blink. The LED blinked 13 times and I couldn't find anything related to 13 blinks from the guide/manual.

Saravanan

[Bikemad]

According to page 5 of the Motor Controller Guide the 13 blinks indicate that the "Motor temperature is higher than default value", but I seem to recall that 16 blinks is sometimes observed when the USB lead is connected.
If you don't have battery voltage across the controller, I would not expect the controller to be able to obtain the temperature sensor value.   

If you measure the battery voltage directly across the battery's main connections, does the battery voltage also drop to ~5V, or is it just the controller and circuit breaker voltage that drops?

If the battery voltage does drop to ~5V, then it is either a poor connection in the battery/BMS or the battery's BMS is going open circuit because it is either overloaded or faulty.

If the controller was internally short circuited and completely overloading the battery's BMS causing it to open the circuit, I would expect to see ~0V across the controller's B+ and B- terminals.

Alan