Gen II Prius Individual Battery Module Replacement

Replying to my own question here -

Drove to exactly to the 35 mile mark - triangle came on, problem was indicated on the mfd, and check engine light came on. I quickly plugged in the code reader and P0AC0 was the error. Searched around and here is what I found

P0AC0 - Battery current sensor malfunction
· HV battery assembly (wire harness or connector)
· Battery current sensor
· Battery ECU

The problem I had was a complete blowup of my modules by "increased resistance" per dealer and melted the two modules beside it . I replaced 3 modules, reconditioned all cells, I cleaned the copper connecters of the harness, but did not replace that or the Battery ECU. I have no Idea with the battery current sensor is and if that could have been damaged.. any thoughts?

 

My thoughts are... THAT'S CRAZY!?

Posted via the PriusChat mobile app.

 

Hmmm, IDK so the following is just a suggestion. Double check orange safety plug and retest. If that doesn't work, remove the safety plug and small left battery cover and check all harness connections inside which includes the battery ECU.

 

I bought a couple new remote shells on ebay. The old ones are glued together - probably super glue. I used a hobby knife (Xacto) to start cracking the old one along the glue seam. I followed up with my Swiss Army knife to avoid breaking the hobby knife blade. Moved contents to new shell, carefully applied a few drops of super glue to the edges, sanded off excess glue (when good and hard) around the edges with 400 grit wet-or-dry. Cleaned up the old key and re-used that but you can buy key blanks on ebay and have them cut as well. The best deals I found were from China (slow mail) but there are also resellers in the U.S., some with competitive pricing. Buying used remotes is a caveat: smart remote is different from the simple remote.

 

Ok that is a good idea. When I had it diagnosed at the dealer, info on thread here Smoke from rear interior after acceleration | PriusChat they said "found orange connector at hv ecru melted. One of the cells in the hv battery has melted and split open" in their notes. When I opened everything up, I didn't find any melting. It was also very new to me so I don't know what it looked like originally but this could an issue.

 

If you neglected to attach the wiring harness from the sensor to the battery ECU you would get that DTC. Difficult to see how you would have overlooked that. Probably wouldn't function at all unless it is plugged in.

 

I never disconnected them when I rebalanced. There was current flow, like I said drove 35 miles since the rebuild, averaging 51 mpg so it is clearly working. Just stupid code. Perhaps i'll pull the orange connector out and put it back in and reconnect the harness wires.

 

Crazy...keep us updated

Posted via the PriusChat mobile app.

 

How many months ago? I'm asking only because mine has been off-line since May while I am playing with the hv battery and hobby charger.

When you disconnected the 12V battery, all the codes and the computers should have automatically reset. This should have been done before disconnecting the hv battery and the 12V should not have been reconnected until after the hv battery was in place. I hope you are not mistaking the computer system test of all the diagnostic lights on the dash for actual codes. If you did, then that would explain why your scan tool found no codes. I'm assuming you read some codes with the same scanner before you pulled the battery.

 

Yes, could have been a brain fart <<please excuse me!

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I pulled the battery out on August 15th and started with the chargers a week later. When I installed, I did it in that order hv battery and then the 12 v. When I powered up - I heard some clicking and saw the MFD loading for about 5 seconds before the red triangle and check engine light came on. I then plugged my code reader in and it found no codes which I thought was odd. But I could clear the light so I did and it came back on today. I checked the reader and it through out that code.

 

Well, my wife says I can't buy a C. And I quote "We'll look like those weirdos around the corner with his and her Gen4s".

So the race car I finally got back in the garage this past weekend is going to be displaced by the hobbled Prius while I pick through the modules. Wish me luck.

Jay W

 

Unfortunately drove the car to work so thought was in the green. When down on my lunch, car is in permanent limp mode. I can't even get it to run correctly when I clear the codes. Even with no error indicators, car wont go above 10 mph. Through the same code though again. "P0AC0" and "P0AC0 P"

Here is the connection at the ECU from the harness, If you look closely it looks a little dark maybe from some high heat, a little stinky to the touch. Also, I was unable to pull it out . New harness and ecu?

 

Have you read this thread about battery ECU fires? The battery fires at ECU sense connector thread | PriusChat

I think your harness and ECU are toast. It is much easier to get the harness out of the ECU by removing the ECU from the case. With the ECU loose you can release the brown plastic cable hold down. That will give you enough slack to remove the orange connector.

The big black negative battery cable goes though a white current sensing ring just before it connects to the main relay. There is a small wire plugged in to the ring that connects to the ECU wire harness. If that wire is disconnected it could cause the P0AC0 code.

Brad

 

This looks very similar to the problem I had with the first pack I worked on. I also could not disconnect the orange sense plug from the ECU with the ECU still bolted into the pack. As suggested by Brad, I ended up unbolting the ECU from the pack. This allowed me to get enough leverage to pry the orange plug loose. Once it was loose, it was evident the connectors had partially melted/fused together. See the following picture, which was taken after I pulled them apart.



The bad news is that such a situation is caused by a short which effectively shorts out some of the modules. However, the pins effectively act as fuses and *may* burn out before the module voltage drops to levels that are likely to damage (reverse voltage) cells within a module.

The potentially good news is that I was able to repair my pack without too much pain and, the last I heard, that Prius was still running fine. As suggested by Brad, you probably need to replace the voltage sense cables/connectors, the voltage sense ECU, and, possibly, one or more battery modules. Note that used cables/connectors and the ECU have a reasonably good supply, since many packs are parted out primarily for the modules. I recommend contacting a couple of the professional rebuilders on PC to see if they won't sell you those parts. I have also seen these parts on ebay sporadically.

For more details regarding the problem my pack had, check out the thread: Gen II codes P01AF P3030 P3056 | PriusChat

 

Eww... scary!

What caused this again?

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Probably moisture. There is no dielectric grease in the connector, as you would typically find in a connector under the hood, to protect against arcing/shorts. I presume the Prius designers figured that would not be necessary, since the battery is inside the car cabin where you would not expect water to accumulate.

See the thread Brad posted above regarding fires for more details.

 

Figured I would post answers/updates to my questions in case it helps someone else out. I compared capacities, at 20A discharge, between my modules with the best and worst self-discharge rates (.03v per week and .1 per week). There didn't seem to be a noteworthy difference between the two. I got about 1000mAh difference max(and these showed about a 500mAh difference in capacity at 2A discharge. Looks high discharge rates are not a way to bypass a self-discharge test, at least according to my quick and dirty, data meager approach.

I charged my modules at 1C. Ambient temps were between 90F and 100F. Cooling could probably be characterized as inadequate, but the batteries were optimally spaced. Didn't have battery surface temps that surpassed 96F. Didn't see any negative consequences during balancing from this, but those would most likely show up later anyway.

Discharged each module to a uniform voltage and chucked the pack back in the car. Been driving it for about a month; have gone at least 1k miles. Seems great so far. Haven't had a chance to try S Keith's real world pack capacity test yet or techstream, but will do when I have time and can get techstream installed on a laptop. Will try to update with results then.

Also, definitely recommend the Turnigy chargers: high discharge rates, forming charge, and reduce discharge are nice. Might try the data logging next time.

Thanks all, happy balancing.

 

Manufacturer's patent suggests that the lost electrolyte in NiMH traction batteries can be added in the vacuum in controlled environment. You are brake opening sealed modules to get to the individual cells in open air.
Tell me that you are doing that for learning and experimentation and not for sale?
If you are reselling those previously broken open modules - you are insane. Those modules present huge risk to the public.
Useless time wasting practice IMO. Making statement again, refrasing it - you must not get to the individual cells in NP2 modules the way Brad does. It is not safe, unnessesary and those modules previously opened must not be reused in the car. Ever. You proved it is possible to open the module One idiot was cooling the pack with the compressed air and proved it is possible to open 6 modules at a time even without touching them. I saw the photo...

I do not have get to the individual cells in those modules. I can see with my Battery Complex and Software straight away which modules have weak cells in them.
This week had tested:
- Prius 30 ~1/2 pack is dead (Auckland Taxi);
- Prius 2006 - my scanner revealed in front of the owner in 30 seconds that his pack had previously being worked on by the amatures - there was one non-conforming module from 2005 (the rest of the pack was genuine from 2006). The 40 minute test on that pack on the individual module level revealed 8 dead modules.
Also tested Lexus 2006 - 40 module pack on my 20-channel Analyser under 6A load - in 60 minutes the whole pack was tested on individual module level - 2 dead modules discovered.
As for what type of load to choose - one of the garages has decided to use 70A load with my Analyser - nothing wrong with that approach if you are testing the module performance close to live test conditions. But if the goal is to measure URC and compare with the design capacity - you have to use the current as per design specs, hence do not call test at 2 or 6 amps "meaningless" as it has its purpose.
I do not call what you do with breaking modules "meaningless" - for you to learn the ropes - it has its purpose. I simply passed that learning curve ages ago... So play safe and do not offer those previsouly opened modules to the general public...

 

Pretty sure Brad said he was testing individual cells not selling them lol, don't recall any mention of the test environment either I guess open air was yet another of your submissions.

test a 40 module lexus pack in 60 minutes and only diagnose two bad modules? really? lexus packs are well known to have almost no surviving modules due to inefficient cooling system issues, designed to fail!.. Lexus usually has 2 good modules not 2 bad!

60 minute complete tests? pffft..NO WAY obviously no C/D wait time? no SD testing? this is just not thorough! and you talk about Brads "attention to detail" there's no way you are "properly" testing those 40 modules in 60 minutes its almost an impossibility.


discharge tests of 2-6 amps are meaningless unless you have incorporated a separate load test that you have failed to mention, prius requests 100+ amps of these modules periodically sure you can count "proposed capacity" at such low rates but its meaningless data if the module has not passed a real world load test, some modules will give you false hopes of 6000+mA @ 2a then when you re-test at 20a or 60a your 6000 module can be up to ten times less.

your entertaining if nothing else.