The battery fires at ECU sense connector thread

The wire harness is cheap enough to replace that attempting to clean one is just not worth the effort.

 

hey strawbad. could you share a link to purchase the conector. it seems like it would be hard to find one that fits in the mother board. I would really appreciate it. Thank you!

I wish I would know how to post pictures so I can send the close up of the female connector that I think there is a way to open it up to replace the pins.

 

This is the male adapter that I am referring to. the one solder into the HV ECU. Where can we find one of this? I looked a few websites online with no luck.

 

here is the male adapter soldered into the ECU. You can see where the little corrosion was removed leaving some discoloration in the corner pin.

 

As far as the female adapter. Can the white plastic jacket tab be opened up or the pins be removed and put new ones? it seems like it would be much easier to fix one or two wires than splicing 14 wires on a new adapter. although probably just easier to buy a new harness since someone mention they are not too expensive.

 

hi texas hybrid. have you had any luck finding adapters and/or pins replacements? what have you done with the big collection of ECUs that you have? thanks

 

thanks chapman, so would you replace the whole ECU in my case? Did you see the condition of the pin on post 124? it hardly had any corrosion before it was cleaned.

 

There are 1k-ohm resistors for each line - also the ECU does use opto-isolation to keep the HV from the low-voltage side; the ECU is well designed except for the 'environmentally friendly' zinc-dip coating which causes whiskers to grow; the circuit does connect the wires one at a time to read them - so low voltage, low current). The issue is mainly when a short-circuit occurs anywhere before the 1k-ohm resistors; basically the connector, or the metal pins of the ECU (whether on the inside or outside of the ECU).

Imagine if the ECU had been made without the 1k-ohm resistors, and instead they had been included just prior to where each sense wire connects to the battery? The only reason they *didn't* do that, was probably because the looms are much simpler to make without resistors in them, and the ECU allows the resistors to be added there for basically zero cost, especially with the relationship between Denso + Toyota.

 

I would keep the ECU. give it a good clean, and get rid of those fibrous whiskers that are visible on the detailed photo

On the slightly corroded pin, look very carefully to ensure the base of the pin, where it enters the orange plastic connector, isn't covered in corrosion, and doesn't have any whiskers. The pins get thicker at this point - so less distance between each one.

If you could check the ECU, say every 6 months (which can be done in the car, access is quite easy, just be careful re: electrocution), then you could see if anything is getting worse.

Finally, while not posting recently I've done some research into this issue and experimented with a few things. My suggestion to dramatically reduce this problem is to, where possible, use the air-conditioning in the car, on a low setting to reduce the impact on fuel economy. Basically, keeping the car dry inside (using the air-con as a dehumidifier) will, I think, *dramatically* slow down the development of this issue. Toyota did take this into account when designing the Battery ECU firmware (as can be seen from watching live data, I still cant get the actual ROM off of the ECU). The worst situation is if you are driving with that car filled with hot, humid air; the ECU fan control detects this but only after periodically moving said air through the battery (and contributing to a number of issues which, in time, result in connector fires).

I've left my Prius parked up for 4 weeks. Oops. Due to inverter water pump failure (getting fixed next week for free!!!!! by Toyota NZ). Will go and check if I have any issues at the Battery ECU :O

 

<bump> having tended a small fleet of 3 Gen I Prii for several years, I have seen the sense harness corrosion/charcoal on the connector in every car when I look at the battery ECU (which requires pulling the traction battery out of the car).
No fatalities or fires, yet...
The failure mode is sufficiently serious that I suggest that Admins move this thread to a sticky at the top of this forum.
Or start a new one (stickied) with traction battery "best practice" for hybrid cars.
The task of pulling the traction battery out and inspecting the ECU sense harness connection should be part of an annual inspection.
From the discussion, there seems no particularly good remedy except to replace parts.
This thread is populated by folks who prefer high mileage, long vehicle life and to have their parts "run to failure".
I would hate to lose any of these good folk.

 

“Report” your own post, ask that the info be stickied?

 

You can always tell who were the pioneers...they're the ones with arrows in their backs.
Gen I owners are now pushing the longevity envelope of a new technology (automotive hybrid batteries) for >20 years, about 3x the design life of the vehicle. We are seeing a failure mode which is probably more widely spread than realized, and potentially fatal (car fire). The inside of the hybrid battery pack is (1) NOT easily accessible, (2) NOT an inspection item and (3) NOT in the maintenance knowledge base of most drivers. Hopefully, a failure at that point will shut down the system before something more serious happens. At minimum, I propose that anyone driving a Gen I (and maybe also Gen II) Prius make the HV sense connector of the hybrid battery pack an annual inspection item.

 

I bought a 2002 Silver NWH11 for my mum, December 2019; then along came a covid. My mum still can’t come to New Zealand because covid (she is sheltering in place);

The Prius ended up garaged from Jan 2020 till yesterday; the battery self-drained to 2.5v per two-module block, but no connector fires! I expected a charred connector.

I use the air-con advice in my Gen2 2007 Prius and no further burnt connectors

 

Thinking about this further; this failure mode is almost certain to happen with all electrified vehicles. Probably the only safe EV is the Nissan Leaf; you can cut battery cells in half with an angle grinder - and it doesn’t catch fire.

Auto manufacturers historically are used to using 12 volts; increasing the voltage opens up a whole world of electrochemical reactions / galvanic reactions etc.

I tore down my NWH11 battery today; the ECU had clean pins??! But the bus bars were all blue. I’ve put NWH20 cells in it. A question I asked myself : why wasn’t the ECU fries? I left the car parked up from Jan 2020 till yesterday?

The guy I bought it from garaged it (and seriously they had a carpet down and seriously somehow it wasn’t muddy). I didn’t realise how good it is; no wear and tear on the interior or boot lining. And the battery was ‘working’ with two modules with 1 dead cell each, when I parked it up, and most of the modules were low (interestingly, 2.5 volts seems to be the ‘self-discharged to zero’ voltage; the two at 1.2 volts wouldn’t take any charge at all). However even with that mistreatment - no burnt connector.

I seriously think it is due to humidity around the ECU combining with the corrosion which is worsened by the high voltages involved. I’m still running my original battery in my NWH20, my ‘ECU sense connector’ plasma event happened when I left the Prius parked up for 2 weeks and it was damp inside; the NWH11 I have has been cared for very well; no ECU corrosion?

 

Did you ever find a number for the PCB connector?
Mine is fried, but I tend to think the computer is still good - so I want to replace just the connector and see if it works.
I'm just having a real hard time finding the connector number.

 

I’m actually not sure! I think someone may have had part numbers?

Can you post a photo? (If you haven’t already); it may be possible to desolder pins one at a time from the ECU, and only replace the bad ones.

That would involve some (possibl huge) risk if they short later. A solution would be resistors added in to the loom.

I am going to make up a test look with 1k resistors in-line (I will start by splicing a 1k resistor in to 1 of the sense cables on my NWH20 to see what it does in terms of reported voltage and internal resistance.

it may be possible that splicing an x-Ohm resistor in could stop all these fires. But if the BMU reads the wrong voltages it could overcharge chronically and reduce battery life :/

Right now I am sitting in my NWH20 checking out my NWH11 battery with NWH20 cells. 2 of them lost one cell resting for a week. Then comes the road test :O once I get this done I will dig into my NWH20 (my actual daily driver hence the caution).

Dont dispose of the ECU; almost all ECUs will be fine after even severe arcing events (because Toyota put the 1k-ohm resistors inside each channel on the ECU.... and not on the connection between each sense cable on the battery modules. That is a design error (well not really, given they last well over a decade before this happens, most other brands of cars are scrapped and crushed before the mileages we get our Priuses to!)

 

Watching Gen 3 battery rebuild videos on YouTube, the bus bars still have heavy blue/green corrosion; has anyone seen a Gen 3 connector short yet? (Or any pics of the BMU circuit?)

 

My Gen 3 has similar issues, and it proves impossible for me to obtain a new connector on the wiring loom or loom! It was available for gen 2 but gen 3 has(had) 10 pins across and not 11 and different config. I might have to bite the bullet and buy a used one, but the sellers are crazy.

 

from my 2017 post... Found the AMP receptacle part number for the orange battery sense harness.
316836-1 tin, gold is available but 6k min. digikey has inventory....

Seems a combination of electrolyte leakage from the negative post and humidity/condensation liquid moving the electrolyte down the sense wires to the connector where it corrodes(accross the bus bars too). Since there is no current limiting on the sense wires, corrosion-short-heat-fire.