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Discussion Starter #1
Hi all.

Well my trusty 2001 MT that I love to brag about because I never have to fix anything...has been giving me headaches.

I put in a ticket with Hybrid Automotive because recently when connecting their automatic discharger, the voltage read zero and it would not start the discharge sequence, obviously. A couple days later, the car set a P1444 code. I did some reading and decided to probe for the voltage leak to the chassis. Indeed, I found current between the HV battery and the chassis. Quickly the multimeter would ramp up to 50v then taper slowly down to about 1v over the course of 10 seconds or so when reading across the positive terminal and chassis. The voltage seemed to build back up with the leads removed, as the voltage would be higher with increased time between re-reading the voltage. The result was similar between both positive and negative HV terminals.

What I did NOT expect was ZERO voltage across both HV terminals. I had the breaker off, so I flipped it on real quick to check again and indeed zero voltage. This explains why the discharger is reading zero, I think. However, with the HA grid charger connected, it reads 181v. Strange. Also, it reads zero mA, assuming because it cannot charge due to whatever the problems is/are.

I inspected the grid charger wiring as a couple threads suggested and saw no evidence of abrasion but also didn’t put the meter to it.

Neither the charger or discharger were connected when driving and the code was set.

I read a lot of P1444 threads and most seemed to go down different rabbit holes and none had these symptoms. I don’t have a shady shop or garage to leave the car in for days so I’m looking for some guidance or even elimination procedure before ripping the battery out to get at the sticks. As usual, any help is appreciated!
 

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What I did NOT expect was ZERO voltage across both HV terminals. I had the breaker off, so I flipped it on real quick to check again and indeed zero voltage. This explains why the discharger is reading zero, I think.
When you say "HV terminals" are you talking about the two big terminals on top of the pack electronics board, with usually orange-painted nuts? If so you won't get voltage there unless the key is ON... Also, you need to have that switch in the ON position to charge/discharge...

However, with the HA grid charger connected, it reads 181v. Strange. Also, it reads zero mA, assuming because it cannot charge due to whatever the problems is/are.
When you say "it reads 181V," I assume you mean the charger voltage meter?... It probably shouldn't read 181V - unless it's unloaded, i.e. if it were really charging/connected to the pack the voltage would likely be lower, unless the pack were totally chock-full of charge...

I inspected the grid charger wiring as a couple threads suggested and saw no evidence of abrasion but also didn’t put the meter to it.
I'd double check the harness install, make sure it's connected at the right places.
 

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Discussion Starter #3
When you say "HV terminals" are you talking about the two big terminals on top of the pack electronics board, with usually orange-painted nuts?
That's correct. I didn't know the key had to be on for voltage to appear there, that's a simple explanation. Thanks for that. So apparently not having voltage across those terminals does NOT explain why the auto discharger is reading 0v, because the discharger normally works and sees high voltage regardless of the key position. So that's still an issue. I read elsewhere on the forum that the HV relay will not engage when an IMA code is set; but the way the harness is wired in...an IMA code should not prevent grid charging/discharging, right?

When you say "it reads 181V," I assume you mean the charger voltage meter?... It probably shouldn't read 181V - unless it's unloaded, i.e. if it were really charging/connected to the pack the voltage would likely be lower, unless the pack were totally chock-full of charge...
Yes, the voltage reading on the charger. It reads ~181 volts, and the car has been sitting for a week as well, without being driven and no charging taking place. Hm. It's possible the breaker was off, and the install instructions of the grid charger do say the voltage will be about 180 until it's turned on. Will check that again tonight, with the breaker on.

The grid charger harness has been installed and working reliably for years so it's connected at the right places, and didn't seem to be abraded or damaged at all. Since both the charger and discharger not working properly, we have a short to chassis code and that seems to be more commonly caused by a harness fault than battery sticks... the harness certainly warrants further probing.

Thinking through this out loud, check me on this.
  • I'm going to probe for voltage between the red + black pins of the harness, and the chassis.
  • If voltage is found, include/exclude the harness as the offender by removing it and seeing if the code clears. Is this the easiest way to determine if it's the harness or if the problem is deeper inside the pack?
  • Ideally there should be ~144v across the red and black pins with the breaker on?
 

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Discussion Starter #4
Also...Hybrid Automotive has suggested that the fuse in the harness may be blown. Still trying to figure out if these two issues are related...
 

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So apparently not having voltage across those terminals does NOT explain why the auto discharger is reading 0v, because the discharger normally works and sees high voltage regardless of the key position.
That's right.

I read elsewhere on the forum that the HV relay will not engage when an IMA code is set...
Depends on the code, in general that's probably more often the case than not... In your case it probably is the case.

...but the way the harness is wired in...an IMA code should not prevent grid charging/discharging, right?
If the harness is wired correctly - that's right.

It reads ~181 volts, and the car has been sitting for a week as well...It's possible the breaker was off, and the install instructions of the grid charger do say the voltage will be about 180 until it's turned on. Will check that again tonight, with the breaker on.
You were probably just reading the unloaded voltage of the charger...

The grid charger harness has been installed and working reliably for years so it's connected at the right places, and didn't seem to be abraded or damaged at all. Since both the charger and discharger not working properly, we have a short to chassis code and that seems to be more commonly caused by a harness fault than battery sticks... the harness certainly warrants further probing.
Earlier you said you read 0V in the discharger mode. Forget the charger itself at this point - you should be able to probe your harness and measure a substantial positive voltage. If you don't, something's probably wrong with the harness...

You should probably open up the IMA compartment and measure voltage at the 2-wire connector at far right, with the pack switch ON. That will tell you what the actual voltage of the pack is. While you're there, you might as well check stick-pair voltages at the connector to the left - back probe the connector, here's a link to a diagram: The quintessential Insight NiMH voltage thread

Thinking through this out loud, check me on this.
  • I'm going to probe for voltage between the red + black pins of the harness, and the chassis.
  • If voltage is found, include/exclude the harness as the offender by removing it and seeing if the code clears. Is this the easiest way to determine if it's the harness or if the problem is deeper inside the pack?
  • Ideally there should be ~144v across the red and black pins with the breaker on?
That all sounds about right... Once you detach the harness from the pack connection points, I think you should be able to backprobe the 'right' connector red wire (+) with positive DMM probe, negative DMM probe to chassis, pack switch ON, to verify if there's a HV short between pack and chassis, rather than depending on the clearing of the code alone.
 

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Discussion Starter #6 (Edited)
Well...fun times, eq!

It started raining (Florida, go figure...) so I could do all the testing I wanted but here's what I got so far...

Between the red and black pins on the end of the harness, I was able to read about 152v with the breaker on. I turned the breaker off for the rest of testing for safety, however I'm now questioning if it needed to be on, because I don't know where the breaker is in the circuit.
Anyway, here's what I found:
Harness Red - Black, breaker on = 152v 👍
Harness Red - Chassis, breaker off = 50v, ramps down to 1v
Harness Black - Chassis, breaker off = 50v, ramps down to 1v
Battery 10mm Red, breaker off - 50v, ramps down to 1v
Battery 10mm Black, breaker off - 50v, ramps down to 1v

--Removed Harness --
Battery 10mm Red, breaker off - 50v, ramps down to 1v
Battery 10mm Black, breaker off - 50v, ramps down to 1v

So removing the harness doesn't seem to have affected anything. In addition, I checked for continuity along the red harness wire (because Hybrid Automotive was suggesting a blown fuse) and read about 1 ohm. This is suggesting to me that 1) the fuse is likely OK and 2) the harness isn't causing the short to chassis. Do you agree?

Also, you suggested to read the total battery voltage at the 2-wire connection at the far right. I'm facing the rear of the car, and the 10mm terminals I am measuring to the chassis are on the LEFT side of the battery pack as I'm standing. It would be on the right if you were working from the front seat of the car. Are those the ones you're talking about, or is there another set of terminals I haven't found yet? I hope I'm not measuring the wrong place.

I'm going to go measure the taps next. I assume that's across each tap, to HV battery negative. In this case, maybe to negative AND to the chassis?

Thanks for all your help!
 

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--Removed Harness --
Battery 10mm Red, breaker off - 50v, ramps down to 1v
Battery 10mm Black, breaker off - 50v, ramps down to 1v
When you say 10mm you mean the orange bolts, 'big HV terminals' on left side of pack, right? So above you're testing + to chassis and - to chassis, right? If so that says you got a short somewhere in the pack itself, including electronics, or maybe just the electronics...

So removing the harness doesn't seem to have affected anything....Do you agree?
Yes, it doesn't sound like the harness has an issue; the short itself obviously can't be the harness - if you measured voltage between pack and chassis with harness removed...

Also, you suggested to read the total battery voltage at the 2-wire connection at the far right. I'm facing the rear of the car, and the 10mm terminals I am measuring to the chassis are on the LEFT side of the battery pack as I'm standing.... Are those the ones you're talking about, or is there another set of terminals I haven't found yet? I hope I'm not measuring the wrong place.
You need to visit that link I posted earlier. The 'ones on the right' are at the connector on the MCM, there's one connector on the right hand computer, with two wires. With pack switch ON that will give you the pack voltage... At this point though I'm not sure what needs to be done -- besides taking the pack out of the car, breaking it down, and finding what's causing the short.

I'm going to go measure the taps next. I assume that's across each tap, to HV battery negative. In this case, maybe to negative AND to the chassis?
Again, consult that link I posted and get clear on what needs to be measured, where. Taps are measured at the connector on the back of the BCM - the connector on the left hand computer. I don't see a major diagnostic reason to do that at this point, because as far as I can tell the pack needs to come out and be inspected closely. But, it wouldn't hurt, you might see a glaring outlier that would suggest the problem...

...Thinking about this, not terribly deeply, those 50V readings you measured should narrow down what's possible, if I'm understanding what you're measuring correctly. You say 50V between + HV terminal and chassis, 50V between neg HV terminal and chassis, both with pack switch OFF, both with key OFF. That seems really weird to me.

For one, you shouldn't see any voltage at those terminals with the key OFF. I can't remember if voltage remains at those terminals for a short time when you key-OFF, I think it does. Key-ing ON engages a relay or 'contactor' or something like that and allows power to flow from/to the battery. There's some big capacitors that charge - so those hold some charge and it can take some time to drain them*... You'd have to look at a diagram of the electronics board to trace the path, find the components...

So, with the key OFF, how do you get voltage from the + HV terminal to chassis? And the same thing from the negative HV terminal to chassis? And then, how do you get the same voltage -- with the pack switch OFF?

The switch breaks the pack in 12 and 8 stick halves, so with a total V of 152 you're looking at 91V and 61V...

I don't know, it'd take me a lot of sleuthing to figure this out. Maybe someone else has an idea and will chime-in...

*...Off the top of my head, and again, I'm not thinking super deeply or critically here, not an electronics expert -- I'm thinking maybe 'those capacitors' are charging, somehow, and the voltage you're measuring is actually a short between stuff 'on the left side' of the IMA compartment and chassis. I guess you'd need some kind of failure between 'that side' and the pack, though, to begin with...

Maybe try this, two measurements at connector on back of MCM, pack switch ON:

1. Pos and neg probes to pos (red wire) and neg terminals on connector on back of MCM (the two-wire one). That should give you pack voltage.
2. Pos probe to pos at connector, neg probe to chassis. That should tell you if there's a short between the battery sticks and chassis. You shouldn't measure any voltage.

And then where does this get you? I don't know, if you measure a normal pack voltage and then no voltage between the sticks and chassis, at least you'd know there's no short between the actual battery sticks and the chassis...
 

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Discussion Starter #8
When you say 10mm you mean the orange bolts, 'big HV terminals' on left side of pack, right? So above you're testing + to chassis and - to chassis, right? If so that says you got a short somewhere in the pack itself, including electronics, or maybe just the electronics...
Yes. Facing the rear of the car, the two large orange terminals with 10mm bolts on the top of the pack, on the left side.
...Thinking about this, not terribly deeply, those 50V readings you measured should narrow down what's possible, if I'm understanding what you're measuring correctly. You say 50V between + HV terminal and chassis, 50V between neg HV terminal and chassis, both with pack switch OFF, both with key OFF. That seems really weird to me.
That's correct, +50v to chassis on both terminals with the breaker OFF. Zero voltage between positive and negative. To be clear, these are the orange 10mm terminals on the top left of the pack. I too thought this was odd, but didn't make too much fuss about that because I assumed it was because there was something I didn't know about how the pack works.
So, with the key OFF, how do you get voltage from the + HV terminal to chassis? And the same thing from the negative HV terminal to chassis? And then, how do you get the same voltage -- with the pack switch OFF?
Yes. I can check it again, and post a video if that helps.

I agree, there's not too much benefit to probing the taps, because it looks like the pack has to come out at this point. Although as you mentioned, it could still uncover a glaring culprit.

I checked out that thread you linked, and does have the info to record the tap voltages. The pack still has to come out, I think. I will read the rest of that thread for further context though. Back to it!
 

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Yes. I can check it again, and post a video if that helps.
No, those were just thinking-out-loud questions. I trust you measured stuff correctly... Basically, it seems like there's limited ways one can measure what you did under those circumstances. Just that I don't know the whole circuit well enough.

...Thought of one other thing you might do: Remove the cables leading to the 'HV' terminals, then measure voltage between those cables and chassis, and between the HV terminals and chassis. If you measure voltage between HV terminals and chassis with those cables removed, at least then you'd know the problem has nothing to do with the 'stuff on the left side' of IMA compartment.

Later... Your issue keeps bothering me. My brain is kind of drifting in and out of 'wondering' what the problem is. I just searched for something I vaguely recalled, that might provide a lead down the road. I'm linking to it here so I don't forget. I didn't even re-read it beyond what's at the linked page: High Voltage LTO Setup.. 96 Cells. Can it be done?

OK, so I glanced over a couple posts, a few below the one linked above is this, here's the whole post (emphasis added):

This capacitor network is a high frequency snubber that references the IMA pack to ground. This prevents high frequency noise from the IGBTs from causing interference. You really should keep the center-tapped ground connected to the chassis. Also note that there are two of these capacitor packs, one on the junction board and the other inside the PDU.

The P1444 issue you're seeing could certainly be due to this capacitor network leaking... other possible causes:
-leakage inside the IGBTs
-leakage inside the larger capacitors (inside the PDU)
-insulation breakdown in the BLAC motor.
-fault inside the DCDC.
-leakage inside the MCM (you should measure more than 300 kOhm from both MCM connector E wires to chassis ground).

The proper method to test the capacitors for leakage is to test them while they have the full pack voltage across them. You'd place a small series resistor from each 'hot' leg, and then ground the capacitor bank. With the capacitors charged, you'd then place a DMM across both terminals on each resistor (one at a time). Using V=IR you can then calculate the leakage current. Ideally it should be pretty much 0 A.
OK, OK, here you go, start here: High Voltage LTO Setup.. 96 Cells. Can it be done?

Peter describes an unusual P1444 that turns out to be this capacitor 'snubber' unit. There's a vid there, watch it, read through the following posts, etc.

Looking at this a little closer I'm almost positive this is your problem. Forget all the other tests/measurements I mentioned earlier, but rather, do this: There's an orange-clad wire that crosses from pack electronics board to 'left side stuff', attached to top case of the DCDC converter, you can't miss it. It runs more or less parallel with those two larger cables.

That wire comes from the center tap of this capacitor snubber unit. Detach that wire then do your HV terminal-to-chassis voltage measurements again. Is the voltage now zero? if so, this thing has to be the problem... Re-attach, check again: Does the leak reappear? etc etc...

Here's an image of the electronics board with a few things labeled:
87517


Here's a link to another image of the board, this one has other parts labeled. Mine's missing a couple parts/connections: Insight Battery switching/current monitoring - MIMA Honda Insight Modified Integrated Motor Assist


hmm... I'm not seeing how this thing gets charged, though, if you have the pack switch OFF... With the switch OFF, those two busbar eyelets at lower right sever the pack.
 

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Just looked at this.

Is this an aftermarket pack?
Are the PTC strips fitted/in circuit?
Is this a leaky stick/s eating the heatshrink etc scenario.

Unplug the BCM Temperature sense plug.

Is there any voltage with the main switch on between the always HOT +/- live points on the HV battery and any of the connections on the BCM plug?

1) Check from the top negative terminal to each connection on the BCM plug

2) Check from the tricky positive terminal on the white resistor (grid charge connection point) to each connection on the BCM plug.

There should not be any voltage present....

If there is the pack will have to come out and apart for stick inspection.
 

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Discussion Starter #11
Thanks for all your input guys. I'm going to go back and comb through your responses, I scanned over them very quickly but I wanted to post up what I found on Friday, which wasn't much but I wanted to explain what I did so that we can be sure I'm testing and interpreting properly. I did snap photos when I measured the the tap voltages and I still plan on compiling that into something easier to analyze, but haven't done that yet.

So I opened up the pack, going down the road of chasing the voltage leak to chassis. What seems to be the next most talked about issue that causes this is the PTC strips, so that's what I intended to check. I removed the pack, and completely removed the orange plate on one side to access the sticks, which of course includes removing all the stick bolts and disconnecting the PTC strip. I checked for voltage between each stick and its respective PTC connection. No voltage found anywhere. On the flip side of the pack I did not completely remove the orange plate because it didn't seem necessary, I just disconnected the PTC strip and probed between it and its stick. In retrospect, I think I should have removed the plate to be able to isolate any current to a particular stick; but I found no voltage anywhere, anyway. So the PTC strips seem to be fine, unless I tested improperly.

As soon as I can get back to it today, I'm going to sift through the recent responses and follow any advice given and report back.

Peter, I can answer a couple of your questions real quick though. I do not believe this to be an aftermarket pack. I purchased the car about 5 years ago, I have only opened up the HV compartment to install the grid charger...until now. I seem to recall having checked the Honda dealer service records based on the VIN and found an IMA battery replacement having been done in 2004. So if it's not the original battery pack, it's a dealer-installed replacement. The PTC strips seem OK based on voltage tests, but I have not removed the sticks to visually inspect.

As always, thanks so much for your help guys.
 

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Discussion Starter #12
So it would seem that after reading your test suggestions that they must be conducted with the pack installed. Now that it’s out and assuming you agree with the idea that the PTC strips are OK since no voltage was measured between any of them and their respective strips... would you suggest re-assembling and reinstalling the pack and doing the recommended testing, or is there anything else I should look at or test while the pack is out and partially disassembled?
 
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