# Failures and Horror Stories for Halloween



## GoElectric (Nov 15, 2015)

Hi. A friend of mine and I were talking about a battery fire and I thought an accounting of common EV issues/failures might be informative. 

I'm wondering for example about solder joints - actual breakage, not just "thou shalt-not...."


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## onegreenev (May 18, 2012)

Quality Solder joints should be just fine. What is the context of your statement? Batteries, Electronic Circuit Boards?


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## dougingraham (Jul 26, 2011)

Solder joints are not much of a problem. You can run into situations where solder wicks up a wire and causes a stress riser at the end of the wicking where the high vibration environment in a car will eventually cause the wire to break. But this was not a fault of the solder joint.

The largest failure I know of in DIY cars is improperly tightened battery terminals. A loose connection will be higher resistance and will get hot. One reason top of cell BMS boards are a bad idea. They make getting and keeping a tight connection problematic.


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## madderscience (Jun 28, 2008)

I credit top of cell BMS boards (with individual temperature sensors) for being able to detect bad connections. With the right display unit or data logging, you can see a particular cell heating up faster than the others under stress like long freeway runs and hills, then fix it before bad things happen. Even without temperature sensing, a cell that registers higher internal resistance or more voltage sag might also actually be a result of bad terminal connections.


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## GoElectric (Nov 15, 2015)

RE Solder joints, I need to connect 24 gauge copper from the Tesla modules to the slightly larger wire(s) going to the BMS to monitor the cell voltages. I have soldered an intermediate wire to the module leads (as they are too short), and then soldered to a connector on the bulkhead of the battery box. BMS wires are soldered to the other end of this connector. 

It all came down to not being able to find a 10 pin bulkhead connector with crimps.

I'll shoot some pics.

I didn't realize that was a major area of failure. Aren't "Nordlok" washers the best way to connect terminals? I had a mechanical engineer over here the other day, and he got a memo not to trust lock-washers, but use Nordlok instead.

Ah, the debate over cell-level boards. Why don't the battery manufactures come build something into their bricks? Or at least make it an option. I have an Orion, but will be bottom-balancing.


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## GoElectric (Nov 15, 2015)

What-about pre-charge resistors? I was just reading a thread on them. I assumed the Controller would not leave itself vulnerable, but has this been an issue which could damage your Controller? 

I admit, I did not read all of the threads which came up when I searched "pre-charge resistor."


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## EVfun (Mar 14, 2010)

Somewhere on this forum is me writing about what happens when a Curtis 1221 controller fails on! Those little MOSFETs are able to pass a lot of current, making more torque than my brakes could handle. The front tires where locked and the rear tires where burning rubber and launching the Buggy.


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## Moltenmetal (Mar 20, 2014)

Fortunately my list of horror stories is short, so far:

- I was stranded during one of my early drives by the action of my inertial switch- the car just suddenly went dead after hitting a pothole. Took a few minutes to figure out what had happened. The switch is just too sensitive for its location and the harsh ride of a little British sportscar, so I've bypassed it permanently now

- I was startled to hear my BMS low voltage alarm on an early drive this year, well short of my battery capacity. Turns out one cell in my rear pack was likely defective from the factory, dropping from 180 to 135 Ah capacity likely as a result of gradual loss of electrolyte through a defective celltop vent. No other cells were affected, and I was able to get a replacement. It was the reason I smelled electrolyte in the trunk. Good thing I had a BMS...

I didn't bother with Nordlock washers in my build. I periodically check the tightness of my battery terminal bolts and never find them loose, despite using the marginally better than useless split lock washers.


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## GoElectric (Nov 15, 2015)

I have since heard that the Curtis 1238 does not need a pre-charge resistor, but a 1239 does. I just bought an AC51 AND 1239, so good to know.

Keep 'em coming.


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## WolfTronix (Feb 8, 2016)

Never use cheep battery connectors:


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## onegreenev (May 18, 2012)

WolfTronix said:


> Never use cheep battery connectors:


Yes, Never Ever use cheap connectors.


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## Moltenmetal (Mar 20, 2014)

...and don't use a cheap crimper, either!

Even on 12VDC connections for the old car's lights, horn etc.!

I bought a decent crimper actually capable of solid crimps on spade lugs etc. for 12VDC wiring, but did that too late in my build to avoid problems. It was only $7 at Harbor Freight in the US, but we don't have Harbour Freight here in Canada- and Princess Auto, our Harbour Freight knock-off, doesn't carry decent crimpers nor does any local hardware store. Go to an electrical distributor/supply house and you'll pay serious money for them.


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## WolfTronix (Feb 8, 2016)

Yeah, I re-crimped (borrowed the crimper from work) all the connectors in my truck, they all were terrible from the factory... All the intermittent electrical problems went away. 
Before:








After:


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## onegreenev (May 18, 2012)

WolfTronix said:


> Yeah, I re-crimped (borrowed the crimper from work) all the connectors in my truck, they all were terrible from the factory... All the intermittent electrical problems went away.



Wow, whoever did that repair job did not know what they were doing. I guarantee it was not a factory job on that. That looked rather hacked and that is a back yard hack job. 

Glad to see you cleaned it all up and looking nice and factory again. Nice when you have good connections that problems seem to melt away.


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## WolfTronix (Feb 8, 2016)

I think the bad crimps are factory, from Solectria.
Other trucks I have worked on had similar bad crimps.

They do use plastic hobby boxes for all their electronics enclosures.


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