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Discussion Starter #1 (Edited)
All the Honda IMA cars try to minutely manage the 12V battery voltage and SOC (State of charge).

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Unfortunately this quest for ultimate micro mpg gains and efficiency is to the long term detriment of a standard 12v lead acid battery.
Lead acid technology simply does not like being at this low SOC for long periods.
With modern 12v starter batteries a couple of excursions down to really low level with a light left on overnight can kill them off.

If you plug in one of those cheap voltmeters into the aux power socket you can monitor the 12V battery voltage fluctuations for yourself.
The 12V battery spends a lot of time in the low voltage doldrums during normal daytime driving as the DC-DC converter is switched to a lower output.

Our batteries are lucky in that generally they don't have to do much except power up a few auxiliaries when we turn the ignition on.
The IMA battery at the back does the actual engine cranking. Unfortunately this masks the steady decline of the neglected 12V battery at the front.

If the lead acid has to jump in and do 12V cranking with the emergency starter this weakened state and low SOC will show itself very quickly.
You will get dimming headlights, the 'click click click' of relays unable to energise, and a starter unable to start the car!

It also means if the IMA fails for any reason and you lose 12V charging you don't have much time left to get home or to a safe place as the 12v battery is already low.
If it was fully charged as it should be you might be able to drive for an hour or more. But with our abused batteries you might be lucky to get 15 minutes.

So what can we do about it? Well a few basics first.

1) The earth & battery leads are vital in these cars, so step 1, ensure they are perfect.
2) Have your 12V battery charged and load tested. If it's beyond recovery then replace it now before it lets you down.

The DC-DC Converter.

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The DC-DC converter is the alternator for the IMA cars and converts the high voltage DC from the motor/IPU into a low voltage high current supply.
The IMA motor and DC-DC combo is much more efficient and reliable than a traditional automotive alternator.

However to improve the charging of the 12v battery we need to raise the DC-DC converter output voltage.
As you may have seen from my static testing of the CRZ DC-DC when powered up on the bench it defaults to a higher voltage output which goes from about 13.8-14.5V.

The ECM monitors the 12V load using the ELD load detector and does increase DC-DC output when you turn the lights on etc.
But the problem is the long periods the car spends during daytime driving in the DC-DC low voltage mode.

The actual DC-DC output voltage in use is controlled by a serial datastream from the MCM on the SCIMD line, which is a Green wire on MCM connector A pin 27.
If you interrupt this datastream (cut the wire) the DC-DC should default to the higher voltage output mode at all times without giving any errors.
You can add a simple switch if you like so you can flip the higher output or OEM mode on/off.

So what are the pro and cons of this mod?

Pros.


1) It will result in a better charged and longer lived 12V battery.

2) You will get slightly brighter lights, better wipers or louder banging tunes (Maybe)

3) If the IMA fails your 12v battery will have a higher SOC and reserve capacity to either start the car or get you home.

Cons.

1) It's a bit of a pain to do as you have to get into the IMA to access the relevant wire.
(Note. You do not need to remove the IMA unit or take out all that interior trim, you just take the covers off.)

2) There is a potential microscopic mpg penalty that I defy someone to measure and quantify.

Conclusion.

We/I/many have used this type of mod on several different IMA car variants over the years and it does help a lot. (y)

Feel free to try it and report back. I'll keep you updated with my testing.
If it proves to be unreliable or has some unforeseen problem in the CRZ, then this can all be deleted if necessary.

This video shows the CRZ DC-DC operating on the bench.


This video shows the relevant wire on connector A27 to cut or insert the switch into.

 

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Discussion Starter #2
Stand by your beds!

I've been testing this hack on a few drives today and it appears with the CRZ it sets a non fatal temporary DTC which takes several drive cycles to trigger the IMA light. :(

Even with the IMA light on the DC-DC functionality is as expected (high output = good for 12v battery) and the IMA works normally but it is annoying the light is on.

So some more work required on the serial comms.

The MCM is probably sending a check byte or something in the data it sends to the DC-DC, and expects to see this echoed back in the data from the DC-DC.

If you reconnect the green wire the DC-DC functionality is OEM with no error even with the HCH2 DC-DC so at least that works as expected.

I'll keep you updated..
 

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Stand by your beds!

I've been testing this hack on a few drives today and it appears with the CRZ it sets a non fatal temporary DTC which takes several drive cycles to trigger the IMA light. :(

Even with the IMA light on the DC-DC functionality is as expected (high output = good for 12v battery) and the IMA works normally but it is annoying the light is on.

So some more work required on the serial comms.

The MCM is probably sending a check byte or something in the data it sends to the DC-DC, and expects to see this echoed back in the data from the DC-DC.

If you reconnect the green wire the DC-DC functionality is OEM with no error even with the HCH2 DC-DC so at least that works as expected.

I'll keep you updated..
:( was afraid it was too easy a hack! Thank you for the update I had not taken my wire cutter and screwdriver to it yet.
 

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Discussion Starter #4 (Edited)
All useful info though. Onwards and upwards.. (y)

Looking at the data stream I have identified a suspect bit in the serial comms from the DC-DC to the MCM.
I think it's saying 'I can't hear you!' when there is no data coming into the DC-DC from the MCM i.e (The green wire has been cut.)

So to get rid of that it would probably need another tiny interceptor gadget in the data stream from the DC-DC to the MCM which clears the 'I can't hear you!' bit
It's easy enough to test that using the old IPU interceptor I made in the first week. A job for the weekend..

EDIT.

I've written the test code for the DC-DC so will try that tomorrow with luck.
 

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All useful info though. Onwards and upwards.. (y)

Looking at the data stream I have identified a suspect bit in the serial comms from the DC-DC to the MCM.
I think it's saying 'I can't hear you!' when there is no data coming into the DC-DC from the MCM i.e (The green wire has been cut.)

So to get rid of that it would probably need another tiny interceptor gadget in the data stream from the DC-DC to the MCM which clears the 'I can't hear you!' bit
It's easy enough to test that using the old IPU interceptor I made in the first week. A job for the weekend..

EDIT.

I've written the test code for the DC-DC so will try that tomorrow with luck.
Hi, dumb question here, would a grounding kit help with this?

"You will get slightly brighter lights, better wipers or louder banging tunes (Maybe)"
 

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If adding additional grounds fixes an issue then your OEM grounds are damaged or not connected properly.

Hi, dumb question here, would a grounding kit help with this?

"You will get slightly brighter lights, better wipers or louder banging tunes (Maybe)"
 

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If adding additional grounds fixes an issue then your OEM grounds are damaged or not connected properly.
No, IF adding helps improve, doesnt not mean damaged original is damaged many have added grounding kits to their cars. "grounding kits have evolved and now manufacturers have incorporated a voltage regulator into the mix. ... The grounding system allows all key components of the engine to receive the proper voltage, improving throttle response and overall performance. "
 

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I call Hype and BS but @PeterPerkins is more knowledgeable. OEM system should be well regulated without needing anything else and if it needs something else I go back to what I said and something is wrong but again I have never heard of such a product or need for it under normal circumstances with a stock vehicle and electrical system designed by real engineers. A ground is not a Voltage regulator. There is a voltage regulator on conventional cars at the Alternator and on ours built into the IMA system. Cleaning your contacts and terminals will do more . Maybe using some contact enhancer like I saw in public safety for Air bag connectors. Solder instead of crimps for added on circuits etc. Clean, Improve or protect the existing connections from corrosion or other damage.

No, IF adding helps improve, doesnt not mean damaged original is damaged many have added grounding kits to their cars. "grounding kits have evolved and now manufacturers have incorporated a voltage regulator into the mix. ... The grounding system allows all key components of the engine to receive the proper voltage, improving throttle response and overall performance. "
 

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Discussion Starter #9
Modern cars do need good grounds as many circuits are referenced to it at several places.
Bad grounds as we know do lead to problems.

However you do not need better than good condition OEM grounds.

A grounding 'kit' or 'system' that promises improved throttle response and overall performance over good standard grounds is at best marketing hype....
 

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Agreed those kits and regulators are BS. Any improvements can be had for free by cleaning up the existing grounds and replacing any corroded hardware.
I have a voltsge monitor on my power socket gizmo and it always shows 13.8 when driving. Battery resting voltage is a bit low but my tester (conductance) showed good CA capacity so I think it's ok for now. Recently the car sat for over a week in the cold and was fine when I got back in it. Anyway I always have my handy Li jumper pack in the toolbag just in case.
 

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Discussion Starter #11
I still need to do some work on fooling the stock DC-DC converter into outputting it's higher voltage. :unsure:

Actually I have just had an idea.

Fiddling with the serial dc-dc control signals is a pita and difficult due to the fact it's inside the IPU.

However if we fool/modify the 12V ELD (Electrical Load Detector) at the front of the car then the ECM will command the DC-DC to provide it's higher voltage output.
In the OEM configuration when you turn the headlights and other things on the ELD detects this and tells the ECM which turns up the wick on the DC-DC.

I'll have a look at that and document it here once the Supercaps are up and running. .

It's should be fairly easy to fake the ELD load to be active all the time... (y)
Then the 12v battery will be much better charged.. 90% SOC instead of 25% LOL.....
 

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Or just keep the lights on-
When I have them on the voltage is almost always 13.8. With them off, sometimes it is and sometimes it isn't.
I have another car with a conventional charging system but ECU-controlled with a sensor on the battery negative. If it doesn't see a minimum current load it throttles back the alternator to save a thimbleful of fuel (bloody CAFE) so I leave the parking lights on all the time to keep it charging.
 

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Discussion Starter #13 (Edited)
Hmm. Lights is ok for those who want to do that.. :)

The ELD is easily accessible and resides in the under dash fuse box.
It connects to the ECM on PIN A23 (Pink)

It has an output range from 0.1 to 4.8V
It has a pullup resistor on it's input inside the ECM to 5V
Need to work out the pull up value, then a simple series resistor might do it.

I suspect the voltage output of the ELD rises as the current load increases.
 

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Fortunately I have an EX with HIDs so the current draw is less than halogen lights after the initial turn-on surge.
My 12V battery is nowhere near full SOC at least judging by the voltage, I did put my conductance tester on it a while ago and it showed a good CA reading but said to charge it. I should check it again when it's not so darn freezing out, maybe dip a hydrometer into the cells. I'm not too concerned about it as it's been working ok and I've got the jumper box just in case, also I'm pretty sure it's not that old.
 

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I just replaced the 12v battery on my son's 2015 CRZ. He was having weak/dead 12v battery lately and had to jump start using the Li packs each time. This is the third 12v battery on this car in less than 6 years. I installed Bluetooth Battery Monitor this time, so I can check the voltage change on the 12v battery 24/7 without even starting the car. Will see if it has an excessive drain in the next few days.

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Yes, I installed a digital volt reader, cost 3 quid from Japan, in the cig lighter. I wondered why it kept getting stuck at 12.3 when I was just cruising about. It has been seen to go up to 14 on rare occasions. I will monitor those occurrences now, and try to do more!
 

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I justI installed Bluetooth Battery Monitor this time, so I can check the voltage change on the 12v battery 24/7 without even starting the car. Will see if it has an excessive drain in the next few days.
That BT gizmo will have a drain of its own so you might want to measure that. Hopefully just a few milliamps but you never know.
 

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Yes, I installed a digital volt reader, cost 3 quid from Japan, in the cig lighter. I wondered why it kept getting stuck at 12.3 when I was just cruising about. It has been seen to go up to 14 on rare occasions. I will monitor those occurrences now, and try to do more!
Try turning on the headlights when the voltage is low and you should see it go up to 13.8 give or take. After a while turn the lights off and see how long it keeps charging.
 

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That BT gizmo will have a drain of its own so you might want to measure that. Hopefully just a few milliamps but you never know.
Yeah, ~1mA. I have had this on my Prius Prime for 8 months. On a healthy 12v battery, it draws so little, it is negligible.
 
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