Smoke from battery

[Justin.Clements]

Hi all,

My girlfriends bike (em3ev conversion) had a problem cutting out the other day just after we had set off.

Whilst I was doing the usual checks for loose connections there was a puff of smoke from the battery so I immediately disconnected it and we walked home.

I've since tested for continuity across the +ve and -ve terminals going into the controller (Infineon) and got zero resistance, this was with the controller still connected to the motor/throttle etc. When I did a similar test on my bike there was an initial resistance that started to reduce, presumably due to capacitors filling up in the controller.

So my conclusion is that there must have been a short somewhere either in the controller or possibly between the phase wire bullet connections.

The battery is a 50v 16S 20Ah A123 pack from em3ev and is 2 years old. It currently shows 55.3v (batteries charged with a 58.4v charger). I assume it has been damaged possibly having lost some cells but I really don't like the idea of cutting off the shrink wrap and taking it apart to find out.

I have changed the controller on the bike for an old one that I'd replaced a mosfet on a year ago and connected it up and the motor seems to run fine. I've also connected the battery to a charger for less than a minute to see if there was any smoke or heat from the battery and all ok there too.

I can't see any damage to the battery externally and it doesn't smell excessively other than a gaffer tape/battery smell.

So should we just take a chance and use it? Obviously with me cycling at a safe distance from her in case she goes up in a puff of smoke ;-)

Thanks,

Justin

 

[Deleted member 4366]

The battery is protected by the BMS. If there were any problems with a cell, it would shut off. It also gives over-current protection. Are you sure the smoke came from the battery?

The main capacitor is directly across the battery wires, so there will be no resistance between them until the capacitor is charged, which will take a long time with the low current from the meter.

 

[Justin.Clements]

Are you sure the smoke came from the battery?

Hi d8veh,

Yes pretty sure, the battery is just kept in a side pannier and the controller was on the rear rack. Kelly is also convinced the smoke came from the pannier bag which was open at the time.

I agree it would make a lot more sense if it was the capacitor in the controller that had blown. I'm pretty sure the cause is water ingress in the controller. I've not opened it up yet but the controller had been left on the rear rack in torrential rain. She normally stores it away in the pannier bags when not in use. When this controller is connected there is a strong resistance to rotating the wheel backwards which is what I felt with the old controller when it blew a fet.

Is there any way to test the battery? Could the bms have failed?

 

[Justin.Clements]

Well I went down the lane on it and it seemed ok. No smoke.

I think I'll just take a chance with it and maybe we should recharge it outside after next use.

 

[Nealh]

Reading through your posts it sounds like the battery is ok and for what ever reason ( moisture/damp ?) you have smoked the controller, you do say that you swapped controller and all is well. I would open the controller up and have a look.

 

[Justin.Clements]

Hi Nealh,

Thanks for reply, I'm quite sure it was the controller that caused the problem but the smoke definitely, (well as definitely as I can be) came from the battery. Maybe it was just the insulation though as the battery seems ok.

I will open the controller up and try and repair.