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My 2000 Insight recently decided to stop charging the 12v system. I have a freshly rebuilt IMA that was working fine for a short period of time, and now I'm unable to determine exactly why I'm having this issue. Doing my due diligence, I verified that ALL fuses were fine, ALL ground straps were in good condition (and tight), I swapped the BCM/MCM's with spares that I know to be good, and I was in the process of switching out the IMA for a known good one that I also rebuilt.
Here's where I ran into issue #2. Car was OFF, I then turned off the IMA switch and proceeded to remove all the bolts. I unbolted the high voltage cables that lead to the DC/DC converter and went to set them aside. It was at that point in the time where the two made contact, and I heard a sound that I would compare to a gunshot going off in my ear. I'm under the impression that there is NOT suppose to be power here when the car is OFF, but rather when the car is assisting/charging. But that wasn't the case for me last evening.
What in the heck is going on with my car?!
 

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Do you have any codes? If so what are they?

Issue 1. Probably a bad IMA Battery.
Rebuilding IMA batteries using used sticks etc is a black art that few master.
They are usually unreliable and relatively short lived unless you have good equipment and a lot of experience.

Issue 2. Assuming you mean the two big MDM too switchboard wires.

The MDM contains large unfused capacitors that store power.
If you turn the car off and then start fiddling around very quickly then there can be enough charge in the MDM capacitors to cause big sparks when the connections touch.
The car should always be left a few minutes for them to discharge after turning it off.

Also if you disconnect the DC-DC at the grey plug then the capacitors discharge much more slowly....
 

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Discussion Starter #3
Do you have any codes? If so what are they?
No codes, and all indications that the IMA is good. I've got around 165 volts, and there is little deviation when testing the voltage taps.

Issue 1. Probably a bad IMA Battery.
Rebuilding IMA batteries using used sticks etc is a black art that few master.
They are usually unreliable and relatively short lived unless you have good equipment and a lot of experience.
Issue 2. Assuming you mean the two big MDM too switchboard wires.
Yes, looks like I jumped the gun too quickly after the car was running. good to know! I'll proceed this evening with my spare IMA and hopefully by car starts charging again.
Thanks for the advice
 

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I've got around 165 volts, and there is little deviation when testing the voltage taps.
What do you call little deviation?
 

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Discussion Starter #5
What do you call little deviation?
Less than the 0.2V difference that would invoke an IMA light.
Either way, I've had that issue before and it never lead to 12v charging issues. It just caused the IMA light to come on.
 

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^ A 0.2V difference won't cause any codes in itself. But, a variation of 0.2V among taps is pretty big, it could easily mean a single cell that's self discharged much more than others. That'd be my guess - a cell has self discharged close to empty so the tap's voltage drops below about 14V under light load/no load and causes the DCDC to disable...

Here's a bit of math: assume all your cells are at about 165V / 120 = 1.375V (very typical).
One is responsible for the 0.2V variation: 1.375V minus 0.2V = 1.175V. That's a bit too low for typical, but it's in the ballpark. You could have a near empty cell if the variation were only say 1.375V minus 1.25V= 0.125V. And you have 0.2V variation...
 

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Discussion Starter #7
^ A 0.2V difference won't cause any codes in itself. But, a variation of 0.2V among taps is pretty big, it could easily mean a single cell that's self discharged much more than others.
Sure, but like I said, there's very little variance between the taps. that is not my issue.
I've load tested my 12v (1 year old battery), and it's fine. I've swapped my IMA with another one, let it grid charge for a day, verified the taps were good. still not charging.
Next up, I suppose I'll swap out the DC/DC converter itself tomorrow.
 

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Sure, but like I said, there's very little variance between the taps. that is not my issue.
Maybe you're misunderstanding what I wrote. I'm saying a variance of 0.2V is not "little." It could mean a single cell that's near empty.

edit: Here's a couple charts illustrating stuff. The top panel shows balanced taps, the bottom, not so balanced. Tap 7 has a problem - and the variation is 'only' about -0.15V. I know Tap 7 is problematic because I worked with the sticks and cells... Maybe this isn't your problem. But you definitely can't (or couldn't) rule it out based on the tap values. The symptoms you described earlier plus 0.2V variation point toward a tap being the problem.

BUT, if you swapped out the pack(?) and grid charged and the 12V still doesn't charge? - who knows.

86528
 

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So you are happy your IMA is ok but the DC-DC is not charging.

OK.

Is the dc-dc fuse blown? It has it's on special dc fuse on the switchboard.

Measure the voltage on the green/black wire and chassis ground on the dc-dc connector.
This is the MCM control control line.
If it is 5V then it should be working.
If it is 0V then the MCM is turning it off.
(If you cut this wire you will eliminate the MCM's ability to turn the dc-dc off)
 

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Discussion Starter #10
Is the dc-dc fuse blown? It has it's on special dc fuse on the switchboard.

Measure the voltage on the green/black wire and chassis ground on the dc-dc connector.
This is the MCM control control line.
If it is 5V then it should be working.
If it is 0V then the MCM is turning it off.
(If you cut this wire you will eliminate the MCM's ability to turn the dc-dc off)
I cut the green/black as one of my troubleshooting steps, and there was no change. I'll look for the dc-dc fuse (didn't know about that one) today. If that's good, I do have a spare dc-dc converter somewhere in my shed, thanks for the info.
 

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Discussion Starter #11
I found the issue. So often, it's the simplest thing.
 

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A 0.2V difference won't cause any codes in itself. But, a variation of 0.2V among taps is pretty big, it could easily mean a single cell that's self discharged much more than others. That'd be my guess - a cell has self discharged close to empty so the tap's voltage drops below about 14V under light load/no load and causes the DCDC to disable.
Laying in bed, it crossed my mind that it's not likely, or probably not even possible, to get a battery + brake warning light with just a near empty, self-discharged cell -- not without first getting a neg recal. I think the cell would have to be charged enough not to trigger a neg recal when driving, but have fast enough self discharge that the cell completely discharges by next drive. And it'd have to be really empty, not just near empty.
 
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