2008 civic. Different than 05-07 and 09-11?

From what I read, you can disable IMA simply turning off the breaker, then 12v should charge with limits, low power, dash lights, but all good.

Did that, worked great as long as I tested it (weeks). Let my niece drive it and within 24hrs, 12V died while driving.

I checked it out, dc-dc had no output. Replaced it, back to normal operation. Added volt meter to lighter socket.

Worked great as long as I tested it (about a week). Let niece drive again, again died while driving within 24hrs. Now no output from dc-dc again.

What is going on here?

 

03-05 is gen 1
06-08 is gen 2a
09-11 is gen 2b

They changed the battery in '09 to try and fix the horrific abortion that is the 06-08 battery, but they actually made it far worse.

Your experience is typical.

Even with the breaker off, the tap voltages are fed to the BCM. Once they deteriorate enough, DC-DC will be disabled.

 

I was reading that 05-07 (I think) you had to disconnect connector "A" to get dc-dc to work without IMA battery, but for 08 to just turn off main breaker. I've read where others have driven with IMA battery completely removed and dc-dc worked for extended periods. In that case, taps would all be 0.

So you are saying that dc-dc is probably just disabled due to low or unbalanced tap voltages? If so, I should be able to fix that with forced Regen to test (battery does work well enough) then replace IMA battery, right?

I was assuming that the dc-dc failed twice, which would mean there's another problem.

If tap voltages are disconnected, I assume the dc-dc will be disabled as well? Would it be possible to fool with something like a capacitor tied to all tap wires and the dc-dc output to keep it charged, then leave breaker off?

Anyone ever find a simple alternator setup for these?

 

Again, 06-08 are identical.

The bypass method to which you refer is for the 03-05, and it works.

For 06+, the only bypass method I'm aware of is the master switch off. You can try to disconnect the sense harness (orange plug), but I expect DC-DC will be disabled due to 11 voltages now reporting 0.

Your capacitor idea won't work. You would short the battery internally.

12V disconnect and reconnect may trigger forced regen and temporarily enable DC-DC converter operation in all or just the 1600-3500 rpm range or not at all.

 

My idea with the capacitor was to disconnect from the battery, then feed a capacitor into the tap wires so that it sees identical voltage on all cells, not to just add it while connected to the battery.

If forced regen doesn't make the dc-dc work, it sounds like neither will replacing the IMA battery.

I need to be able to test it. Is there a relay somewhere that enables dc-dc, or how is it being disconnected? Why would it work fine when replaced if it was just because of tap voltages?

 

These are sequential, not isolated, voltages:

(-) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+) 12 cells (+)

The (-) for taps 2-11 is the (+) of the prior tap. You can't feed a single source to it.

The ability to do forced regen also depends on the taps. Batteries can be so bad that they immediately re-trigger the DTC even after clearing codes.

I assume you have a P0A7F code?

Have you actually checked the taps?

I can't speak to your particular situation, but I have seen a dozen HCH2 with disabled DC-DC converters due to hybrid battery deterioration. Have seen zero that failed due to the hybrid battery. I have seen one DC-Dc that failed because they sometimes fail. Hybrid battery was good.

 

I get what you are saying about not feeding one source to the taps, but it would still be pretty easy to do with 11 capacitors and diodes.

However, doing more research, it looks like these dc-dc converters can be used without any computer controls as others have done it on the bench and the BCM is not signaling it off/on. Also, the charging that they provide when working is the same with taps unplugged.

I've done multiple forced regens now.

I get P0A7F pending after bogging the engine in gear.

Checking taps while running gives pretty consistent results around 16.4v. How long after a regen should I wait to get accurate results?

 

With no IMA light/active DTC, do you have DC-DC operation in the 1600-3500rpm range?

 

I do not. It's been the same way with both dc-dc converters. Both worked fine until niece drove it, then failed overnight.

If they aren't being deactivated, there's likely something killing them, but what??

I checked pin 2 on the 4 pin plug to the converter, and it has battery line voltage. HV is around 180. Output side only had battery voltage, no charging.

I've driven it a bit with IMA active and everything seems fine except 12v charging.

I'll check taps this evening, but doesn't seem like that is the issue with 12v. It's very likely unbalanced, but don't want to build grid charger or replace IMA battery if the dc-dc is just going to fail repeatedly.

 

Did you clear all codes?