Smart pie 4 vector instantly drains battery

[Martins108]

After I got replaced controller (http://goldenmotor.com/SMF/index.php?topic=5475.msg31201#msg31201) I was finally able to test my Smart pie 4. At the beginning all was ok and I use it daily for one month. In total I drive ~ 200 km (~ 125 miles) until I got my second big trouble with this kit.

Previous week when going home I notice strange behavior. From time to time motor started to twitch on bumpy road. Feeling was that if power is cut off and then again back.
So my first idea was that there is poor connection between battery and motor.
So I rechecked wire and all seemed perfectly fine so I went for another test drive. And power cuts occurred more frequent as I kept driving.
What I also notice that more frequent twitches influenced battery capacity that dramatically decreased until on display it showed that battery is empty.
So I put bike for night and tried to turn on it on next day. Unfortunately no signs of life…

I rechecked all connections – all ok
I measured output from disconnected battery – all ok ~ 36v
But when I measured output from battery when its connected to motor then voltage instantly dropped to ~ 2v.

I disconnected all wires except battery (throttle, display etc) and same result. As you connect battery to motor its instantly drops voltage in the system.

Has anyone experienced similar issue?
I suspect that its again faulty controller and again I will need to replace it.

[Bikemad]

The problem you are experiencing could be caused by several different things including water inside the battery's BMS, incorrect voltage setting on the charger, a single faulty cell inside the battery, a poor contact on the keyswitch or possibly a short within the controller.

I would first check the voltage stated on the charger and ensure that the charged battery is somewhere close to the set charging output voltage.
Some chargers have a switch to select the incoming mains voltage which is used to set the voltage to either 110V or 220V. if this is not set correctly the battery will not charge properly on 110V supply.

Make sure the battery is nice and dry as water can get inside if it has been exposed to rain or water thrown up from the tyre etc.

Unfortunately, without having an ammeter or a small fuse it will be difficult to see if the controller is shorting out the battery and causing the BMS to shut off the power.

Check the obvious first and see if the charging voltage is correct.

Alan
 

[Martins108]

I checked charger it gives 42v and ~2 amps output (according to specification on it).
I charged fully battery and when not connected to system and it gives me 41.9V
What is interesting that if I turn off switch on the bottle battery then I still get 21.1V reading. Should not it be 0?
So I opened bottle battery to inspect is there any issues with wiring inside and notice that red wire coming from connector to fuse has burned a little. This could be caused by controller training too much power?

[Bikemad]

In your initial post you said that the output from the battery was ~36V.

Your battery is made up of ten groups of 3.7v cells in series to produce a nominal voltage of 37V and a fully charged voltage of 42V (4.2v per cell).

If you look at the following graph you should be able to see that when your battery only read 36V (3.6V per cell) it must have been almost completely empty.



Connecting a very low battery would cause the voltage to drop even further, causing the BMS to shut off the power to prevent damage.

What is interesting that if I turn off switch on the bottle battery then I still get 21.1V reading. Should not it be 0?
So I opened bottle battery to inspect is there any issues with wiring inside and notice that red wire coming from connector to fuse has burned a little. This could be caused by controller training too much power?

The voltage on the output will depend on whether the switch disconnects the feed to the outlet or the feed to the BMS.
If it disconnects the feed to the power outlet it should read 0V but if it disconnects the battery feed to the BMS unit you may well pick up a voltage reading through the balance leads of the individual cells.

As the battery appears to have both a fuse and a BMS, it should not be possible to damage the internal wiring by overloading the battery. If the wire is "burned a little" and the fuse has not blown there must be a poor connection causing a high resistance resulting in a build up of heat.

Alan
 

[Martins108]

a poor contact on the keyswitch

Alan

Thank you for this hint. Seems that this caused problem. I welded wire back into the place and today all worked. So hope burn on the wire was caused by poor connection not issues with controller or battery it self.

[Bikemad]

It's good to hear that you have been able to sort the problem without too much trouble.

Soldering a wire is much easier than removing the wheel and replacing the controller.

Alan