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In an IMA system the 12V gets charged from the battery. Is it necessary for the pack to be functioning, or can it charge just using the dc/dc converter and a dead pack in place?

Hi Tom:

___Yes, the pack needs to be functioning from my understanding. The inverter/transverter is not directly hooked up to the MGSet so it would have too. I have never heard of a pack completely dead (even those with the dreaded IMA light) so why do you ask?

___Good Luck

___Wayne

I ask because it was brought up over at greenhybrid. I wanted to hear from a reliable source like Mike or whoever that has actually tested this or knows the details of how it works, vs guesswork. I've heard rumors of how it works, but I don't think anyone with any actual knowledge on how it works has answered the question.

Hi Tom:

___PM Mike or MSantos as they know the details down to the busses.

___Good Luck

___Wayne

My answer at GH was based on Mike once saying the IMA is the alternator. If the IMA goes - it's a situation similar to a conventional car with a dead alternator. In other words, the 12-battery would need overnight recharging if the IMA failed, according to Mike.

I understand that Delta Flyer. But IMA is a complete system. I'm wondering if parts of the IMA system can fail, but the 12v charging will still work.

When I take my car to the dealer, the service is excellent, but the explainations are sometimes non-existant. They have told me little about the IMA system or battery care. When my IMA failed, they just replaced the hybrid battery pack, the MCM, the BCM wholesale (i.e. everything in the back of the car electrical). I should be happy they did this just past warranty - and I am.

Information is hard to come by. Mike's answer makes sense.

The 12V can be charged from either the 144V pack or the IMA motor. You can see this on the MIMA display. The DC/DC converter must naturally be on in either case. The question then becomes: Will the DC/DC converter be active if the pack is completely inop? If the BCM thinks the pack is bleeding demised, I'm betting the DC/DC will not come on.

This question has been asked many times.
The IMA MG is always spinning, therefore it is outputting voltage, and with a load will output lots of power.
The IMA power inverter uses that output to charge the IMA battery, which via the DC/DC converter keeps the 12V system charged.

When the IMA pack is dead, or turned off, the DC/DC will not operate, even though the MG is cranking out voltage, it cannot get to the DC/DC except via the IMA HV battery.
This means that the 12V system will not be charged when the IMA battery is bad.

In response to the next question which you will ask, of how one may get the 12V system to work if the IMA is bad, I suggested that one may disconnect the IMA mG from the power inverter, and put a 3 phase diode bridge right on the 3 MG leads. this will generate a varying DC volts of between 50 and maybe 200V, depending on RPM.
The DC/DC converter is designed to operate from 120 to 180V.
If it were connected right to the rectified output of the IMA MG,with a capacitor to filter the ripple, the DC/DC may work just fine with no HV battery or any of the rest of the IMA stuff in the car.
It will likely be more complex than that, as the output voltage of the MG will need regulation if it tried to go too high, but in theory the car should work without the IMA. We rode around in a Civic hybrid at our hybrid class, with the complete IMA electronics and battery pack sitting on a table in the shop. The MG was outputting well over 200V. We connected some 1500W shop lights right to the MG leads to see what would happen. Poof! there went the magic smoke.;)
I thought this was familiar:
http://www.cleanmpg.com/forums/technical/t-12v-battery-maintainer-with-no-ima-4628.html

Now that you explained in detail I seem to remember :)

As a final note:
I am making an assumption about the DC/DC being off when an IMA light is on.I have not had the oppertunity to test that directly, and it may be different than when the switch is simply switched off.
In theory they could allow operation of the DC/DC while the engine is running, even with the IMA fault, but it is very unlikely, since the DC/DC is connected directly to the battery output which is also the MPI input and output. When the IMA light comes on, the relays in the battery control board turn off, but that would not prevent current from being sent to the DC/DC right from the inverter.
Will have to put that on my list of things to confirm should I see an Insight or Civic with the IMA fault condition.
;)

Can't you just "create" an IMA fault condition ;) Curious minds want to know :)

This curious mind is willing to wait for a real opportunity, rather than trying to fake it.
Too many other things to do.
;)

Maybe when I move back to MA I can take a trip to see you and while working on MIMA for my civic we can find out ;)

HEH. Seriously though. Thanks for the info you have reported so far. Can't wait to see what the results are from some of the other experiments/projects you are working on.

when my IMA battery died last year i still drove it. even when it was showing no charge/assist (the last week before all my parts sowed up) it kept charging the 12 volt battery. lost about 3 mpg though...

Interesting.
When it was showing no assist or regen, was the IMA light on the whole time?

Before I replaced my pack, when the IMA light came on I lost all assist and regen.

Mikes question was, was the IMA light on the whole time or did it go off at times.

I guess that if the battery was "bad" (many ways it can fail), and he was waiting for the pack replacement, that the "bad" condition did not stop the DC/DC from keeping the 12V system charged.
IMA light or not.
The pack can be turned off, but since the path for the output of the MG to get to the DC/DC is still intact, even with the relays off, charging of the 12V can still operate. Keeping the DC/DC running with no IMA pack, may be as simple as opening the DC/DC enable line like I do on the new FAS system. Randall or anyone else with the DC/DC enabled FAS system can test this by simply flipping the IMA switch off, then opening the FAS enable line (white/black wires at the ECM side of the new harness). If the 12V system stays at 13+V with the lights on, we would have the option of operating the car indefinitely with a dead IMA pack.
I cant easily test this as I have not installed the DC/DC enable on the Batmobile yet.
Will keep this in mind the next time I have the opportunity to get in the IMA box of an Insight.

Sorry for the delay in contributing with my 2 cents. I just returned from a small vacation and I am just now trying to catch up to the fun stuff that's been going on. :)

This time I don't know how much I can add to what Mike and crew have already mentioned, but since my forte would be the HCH-II and can perhaps report on what would happen if the battery pack or BCM failed.

Essentially the DC-DC converter on the HCH-II derives its input directly from the BCM's HV lines on Pins A19 and A18. Then the DC-DC module drives all the remaining downstream components from it (12V stream, AC, power steering, etc).

So would an HCH-II remain drivable for very long when confronted with a severe HV failure? Not likely, but I find the prospect intriguing if not hilarious. Fortunately, a total failure of the pack is also very unlikely since the system will hopefully detect a bad cell bank long before the HV system is placed off line with a catastrophic failure code.

Again, just my two cents... and very HCH-II specific.


MSantos

Once my IMA light would come on it would not go off. I had the pull the fuse (per Mike's recommendation) and it would go 20 -30 miles before coming on again.

So for those 20 or 30 miles the IMA light was off. Maybe thats when the 12v was getting charged.

That could be. I did drive it 7 hours with the light on from Atlanta Ga. when I bought it. I had to use the wipers off and on most of the way.

I'll try it when I get home, Mike.
Won't take but a second.
Randall

Test results.
2001 Insight w/ recent extended warranty battery and modules.
The DC/DC in the Insight does not ingage, with the IMA breaker in the off position.
Sitting in the garage, ICE not running, near full SOC.
Turn IMA breaker off, ignition key on, check battery volts with scanguage II = 12.xVolts.
Hit the FAS button, volts remain unchanged at 12.x.

Key off, turn IMA breaker back on, retest....battery volts= just short of 14v.

Randall

So if IMA light is on the breaker is open right?

I didn't crank up the ICE, and, I have not driven with the breaker in the off position, that I can remember anyway. The only time I have seen the IMA light was when it coughed up the code of death. I was only verifying the operation of the DC/dc with the IMA breaker off. I'll have to go back and read the thread again.
Randall

I would think that IF the system was willing to run the DC/DC
when the IMA motor produced sufficient voltage to power it, that
as the engine RPM rose and fell the supply to the DC/DC would
be sporadic and might give it minor fits right near the transition
region. So testing its output under a variety of running
conditions would be useful. If it just deals and turns the
DC/DC output on or off depending on RPM, then you've got the
moral equivalent of an alternator.
.
_H*

I thought the Insight used the IMA to smooth out the vibrations of the 3-cylinder ICE so that a balance shaft (with its frictional losses) would not be needed. So if one removes or disconnects the 144v battery, wouldn't this system be inoperative (or at least the part where the IMA pushes on the ICE) and wouldn't the ICE therefore run a lot rougher?

sorry about the delay. i dont remember if the IMA light was on all the time or not. i think it was reset at the dealer when they read the code of death and ordered the parts. it stayed off until about a week from the parts replacement, but the 12 volt kept charging the whole time.

as for extra roughness, i didnt notice any.

I now have some new information about the DC/DC running without the IMA battery.
The DC/DC is pretty much self contained, and it connects to the HV buss on the IMA motor generator side, so electrically it can operate without the battery pack installed.
One of the last MIMA owners has been driving his insight for several years with no IMA battery installed.
He has all the modules plugged in, with the exception of the BCM connector "A".
He indicates that the 12V system is maintained at the proper level, except for when the engine is > 4000 rpm. (voltage is too high)
My reading of all this is that the MCM has a limp mode where it keeps the DC/DC enabled when it looses it's serial communication with the BCM.
Simply opening the DC/DC inhibit line (MCM connector A pin 27) as we do on the new FAS relay should also keep the DC/DC operational.
So if you extreme hypermilers that do not useassist want to drop some weight, and eliminate regen, you can run the car without the pack.
The P&G downside, with the engine off during a glide, the motor generator cannot power the DC/DC, so the 12V battery will be on it's own, and can only recharge when in the pulse mode.