The only time you will have 14V at the battery terminals is when the 12V light is out. When the 12V light is on, the car is NOT charging the battery. The only way you could have measured 14V is if you had a separate charger on it.

All symptoms you've described with a 12V that goes dead after some driving is consistent with the 12V light being on all the time and the 12V never being charged.

By measuring the IMA pack at the terminals, you are not measuring battery voltage as they are normally isolated from the vehicle. 40V is a concern as you shouldn't have much of anything when the key is off. I hope you may have an auto-ranging voltmeter, and it was actually 40mV.

When you measured 80V, you were measuring the output of the IMA motor at idle speed. Had you revved the engine, you would have seen the voltage follow engine rpm. The fact that you measured 80V further means you're not getting any 12V charging as 80V out of the HV system is too low to activate the DC-DC converter for 12V charging.

At no time did you measure the battery pack voltage. That can only be done manually on the hot side of the junction board relay and the opposite terminal. Since you are having MCM/BCM/OTHER issues, the relay is never being energized to allow main battery voltage at the terminals. The IMA battery is always isolated from the car.

If you have a scan tool that will read the 11 tap voltages, that is extremely rare. That scanner is far more capable than the vast majority of consumer grade readers. I would tend to trust the CODES. If you're trying to use the definition presented by a code reader vs. what the Honda manual says, I really don't know what to say about that other than the Earth is round, not flat.

Which light was giving you 10-7 flashes?

 

When it said 40V, the key was in the ON position, but yes my meter does automatically detect so it's possible it was mV.

No flashing light gave me 107, I was trying to find a way to read the flash codes but so far I have not figured out how. Jumping pins 4 and 9 only gives me body codes.

What I was saying is that there is an app that works in conjunction with my scan tool, and one of the places where it lists code U0110, it gives the description for code U0028 (107), BUS OFF MCM, instead of the lost communication description it gives as an explanation for every single other place it reports the U0110. Since the service manual says if you have code U0028 with codes U0110 and U1205 deal with that one first, I thought perhaps I should try to find out if I can get the flash codes just to be sure.

Thanks for the explanation on the HV voltage.

 

Are you saying that when you short 4 and 9, you don't get any blinks from IMA or CEL?

U0028 resolution is update PCM or substitute known good PCM. I'm pretty sure the PCM are VIN encoded.

 

Okay, nevermind, I figured out the flash codes and they do match the scanner. Probably just got distracted by the codes in the odometer display before LOL.

 

There actually is a new code now, P1435. I'm thinking now perhaps I need to figure out how I'm going to charge and discharge my pack before moving on to anything else. This is with the substitute BCM installed so I'm wondering if this indicates progress.

 

Yes. Progression to P1435 indicates you have likely fixed the U codes by replacing the BCM. I'll have to take note of that. The system can now properly communicate with the BCM and is now sensing issues with the tap voltages. Time to charge the HV battery.

 

That's kind if what I was thinking, even though the U codes are still there (temporary and confirmed despite removing the 12V to charge it every night). It also made me think that's possibly why my 12V won't charge now--because it's like now the DC-DC converter knows the HV battery pack is low and before it didn't. I think it died when I was driving it 2 years ago because 99% of my driving was in town, stop and go traffic going 35 mph or less. I could certainly be mistaken, but I do remember my Dad checking it with his multimeter when I revved it up and the voltage was increasing then.

Anyway, thanks for confirming my thoughts that charging is the next appropriate step.

 

Correct. Once the tap voltages drop below a certain point, the HV battery is isolated and the DC-DC converter is disabled.

I don't know the criteria, but following an IMA battery failure, the DC-DC will work in approximately the 1600-3500rpm range, so you get intermittent 12V charging. Holding the rpm at 2000 for 30 seconds should make the 12V charging light go out if that's the case. If you're receiving battery related error codes, and your 12V is never charging with the 12V light never going off, the DC-DC is inoperative, and/or the 12V battery has dropped a cell (won't hold over 12.6V).

Once the HV battery is charged and in the working range, you may also find the DC-DC converter is inoperative, but they don't fail that often (way less than 12V or IMA batteries).

 

I took my 12V battery in to get tested again and this time it tested bad. They gave me about $45 that I was able to put towards a new 51R battery. Put it in the car, and checked things again just in case the new battery would make a difference, but as I expected, no change.

I'm now waiting on the arrival of the power supplies and diode to put together my own grid charger. Do I use just any polarized plug and cord to connect the power supplies to since they don't appear to have a ground wire? And is using a surge protector sufficient protection if I'm not certain that my outlet is GFCI? Some of my outlets are labeled as such but the one I planned on using isn't.

 

Most of the power supplies just have L and N inputs and don't need/can't use a grounded plug, so GFCI outlet wouldn't do you any good anyway.

Which supplies did you get?