HV Battery Fan doesn't turn on

Those pics look scary...Have you checked for any loose connection in the power cable to the fan?May be the power cable got snapped when doing the first rebuild.

 

I think you dodged a bullet. The two photos show evidence of a traction battery short to the case on the ECU end, trunk-side. The smoke deposits suggests the gasses escaped out the connector interface on the ECU side. Your description also suggests another short on the other side.

• Is it possible the traction battery case was loose?
• Could you speculate on how the internal surface of the traction battery case might have contacted the buss bar?
• Do you have photos of the interior of the cover that might show arc spots?
• Do you have photos of the right edge?
• Did you have a book or manual guide on how to rebuild the pack?

I see significant damage to the modules on the left and the buss bar. Could you describe what parts were replaced?

Given the hot gasses that exited the connector interface, I am speculating that the wire(s) feeding the battery fan may be broken or a connector damaged. With a fan relay involved, both the energizer wiring as well as the relay operated circuit needs to be traced. However, I find the fan only comes on when the thermistors indicate the battery is too warm. Can you read out all four thermistor values?

I might rig up a pot connected to one or more thermistors and lower the resistance, spoofing higher temperatures, to see if the ECU activates the relay.

I know the temptation but this is very risky and could lead to two failed vehicles. I would recommend continue trying to find out if the relay energizer circuit is 'open' or the 'fan' circuit is open. I know how heavy the battery assembly is but I would recommend putting it on the bench and carefully testing.

A pilot, I read aviation accident reports and some of those involve pilots with thousands of hours. It is very easy, especially when working alone, to miss something that another pair of eyes might see.

I have seen only one other traction battery fire in Australia. The car had been sitting in the driveway and then caught fire. The photos clearly showed the ECU end but on the cabin side was involved. So now I'm wondering if case clearance might be involved in both yours and the Australian case.

At the time, I speculated that some critter might have gotten in via the vent and initiated the arc to the case. But now I'm beginning to wonder if the case itself might have somehow deformed and led to the initial short.

I'm going to send a not to David Taylor at ReInVolt and ask if he might have any ideas. David rebuilds traction battery packs using new modules and may have some ideas. It would also help if the folks at Lucious Garage might take a peek.

Thank you for sharing! It is never fun to bring something 'not good' for public viewing but it is also how we learn what works and doesn't work.

Bob Wilson

 

Bob,

I see definite evidence of very local high temperature, but I'm wondering what specific features in the photos indicate 'short' to you. I'm not necessarily disagreeing, it's just if there are particular visible features that are characteristic of short I'd like to learn how to spot them.

My first reaction was to wonder if there was somehow excessive resistance at the battery terminal to busbar connections in that area (corroded busbars, mistorqued nuts, something of that nature). Had there been total connection resistance adding up to even a quarter ohm in that area, during a 60-amp acceleration or regen nearly a kilowatt of heating would happen there, easily melting the bus covers as seen in short order and probably making some sooty vapor too. Whether short or IIR heating, it was probably quick enough and local enough to have had little effect measured at the thermistors in the central module wells ... and there's no way that whether the fan ran or not would have made a difference with the amount of local heating seen.

-Chap

 

The soot was the first clue but the metal 'beads' in the area of the second module are the 'tell' of an arc event. Welders throw them off.

I wouldn't rule that out either. But I also noticed what appears to be pine needles on the far side of the battery assembly. They get into everything and a little moisture and I could see one 'cooking' to become an arc source.

I've put the fan as a separate problem and possibly due to the current pack being at room temperature. If an OBD scanner shows them as being hot, the ECU should command fan operation. But I suspect they are just 'too cold' to command fan operation.

Bob Wilson

 

wow this is advanced expert stuff...would it help if he used SCANgauge? Obviously there must be a thermocouple somewhere that relays battery temp to the fan to get it going when needed.

 

The Gen III HV battery fan is controlled by the battery temps. The fan does not run until the temp gets about 95F and then goes through 6 different speed steps based on elevated temps.

My guess would be that the Gen I's would be somewhat similar.

 

There are four thermistors: three in module wells and one on the air duct. Yes, the NHW11 battery fan is temperature operated.

Bob Wilson

 

Well I don't see cover involvement either. Now the buss bar has copper tabs in an orange plastic, flexible assembly. I've seen some photos showing a 'fancy' metal strip on some. I wonder if that metal strip might have been the arc path?

You've really got me scratching my head.

Bob Wilson

 

...there is something called SCANgauge that the folks here use to get that type of data data, but I do not have one and not sure if it works for Gen-1

 

It works great with the Gen-1. You have to add XGAUGE definitions but thanks to "vincent1449p" we have a fairly complete set of codes (see the last post in the sticky.)

Bob Wilson