Hi

I just inherited a 2007 HCH with the understanding that the IMA battery needs to be replaced. I am looking for advice on how to delay the inevitable.

I am new to hybrids and have spent a few hours reading this and other forums and have picked up some understanding, and hope to avoid asking questions that have been answered a thousand times.

I have seen several references to the process of disconnecting the negative terminal of the 12v battery, then starting the car (but not driving it) and leaving it to idle until it stops charging, repeating this procedure 3 times. I have just done that, but haven't driven it yet and don't plan to drive any more today, so I can't offer any report of results yet.

Assuming I notice some improvement after this, what else should I do until I am ready to replace the battery?
I don't need to drive this car at all until I turn my Golf TDI in to VW as part of their buyback of cheating diesels, which is when I will have money to buy a battery for this car.

So meanwhile, should I leave the Civic parked most of the time?
Unhook both or either batteries/battery and leave it parked entirely for the next several months?

Or should I drive it regularly to maintain a charge, repeating the procedure [12v disconnect 3x] frequently?

Here's some background if it helps:

The few times I have driven the car, I have sometimes seen the engine light illuminated, but never the IMA light (other than at startup when all indicator lights are illuminated). No service codes have shown up.

However, the car behaves in all the ways frequent contributor (here and elsewhere) S Keith attributes to a "severely deteriorated" battery:

The display for the charge status is erratic; sometimes increasing and decreasing steadily bar by bar, other times jumping suddenly up or down from 2 bars to full or vice-versa. Sometimes assist is indicated, other times not for the whole drive. Auto stop usually engages, but not when only 2 or 3 bars of charge are showing. The engine seems to cough/hesitate at times. MPG is in the 30's.

Thanks in advance to any guidance anyone might offer.

 

You have codes. You need to get them read by a professional grade scanner. O'Reilly uses Bosch brand code readers that frequently read more codes than others.

Based on my interpretation of the information presented:

1) No more 12V disconnects until you get codes read - by Honda if you have to. You need to know what's up.
2) Disconnect 12V, put it on a float charger, or fully charge it every 3 months.
3) Just let it sit until about 2 weeks before you anticipate needing it. THEN make sure the 12V is healthy and do the 3X 12V resets BEFORE ever attempting to drive it. It may take more than 3.

A several month sit may actually improve the battery by having it self-discharge its voltage depressed capacity.

Furthermore, when the time comes to really dig-in, there are measurements you can take that will help you determine if a new battery is needed, or if a grid charger might be an option.

 

Thanks for the reply.

When i said no service codes I meant on the maintenance minder screen - I appreciate you clarifying I someone with a need a scanner to read them. The less expensive scanners available on amazon would not be advisable here?

 

Thanks for the replay. I was looking for service codes on the maintenance minder screen - thanks for pointing out a scanner is needed. I take it the less expensive ones on amazon that you sometimes recommend would be insufficient in this case?

 

Those bluetooth/wifi ELM327 readers or cheap handhelds are always good to have to get the more common codes or to reset codes of a known issue with which you can live, but a trip to O'Reilly for a free code reading can give better insight into the issue(s). The cheap ones frequently can't pick up a lot of the hybrid specific codes.

I can't stress it enough to you and anybody who might read this... the proper response to a check engine light or an alarm/warning light is to immediately divert your drive to the nearest diagnostics location. If that's not possible or practical, it should be done as soon as humanly possible.

Please don't think I'm chewing on you. I encounter so many people that dismiss warnings and want to ignore the issue altogether, or diagnose based on murky symptoms.

One kid had Prius warning light (red triangle of death), went to Autozone after a few days to read the codes - no codes. He continued to drive it even with severely deteriorating power until one of the cells in the hybrid battery literally exploded two weeks later. It disabled the car until the hybrid battery could be replaced.

A check engine light or other warning light ALWAYS means: get your codes read IMMEDIATELY if not sooner.

 

Understood. Thanks again!

 

Update:

I drove to O'Reilly to have the car scanned for fault codes. No codes showed up. I did notice it was a Bosch scanner.

The engine light was not on, if it comes on again, I'll try to have it scanned while the light is on. The guy at o'Reilly said the codes are often stored but not always if the car 'thinks' the problem is has been resolved.

If it means anything, for the few weeks I have had the car, the engine light has come on only if the car sat for a couple of days or more between use. If driven daily, the engine light doesn't come on.

I have also observed that when the engine light is on, the gauges indicate no IMA assist happening, only charging. After several miles are driven, the assist resumes, but the engine light only disappears after a few drives. For example if it is on when I leave for work (17) miles, it is still on when I go to lunch and back to work (about a mile each way), but will not appear when I start the car after work that evening.

Also I was wrong about the MPG in my original post as I was reporting what was stated on the instrument panel with "trip A." I refilled the car today and divided the mileage I had driven with the fuel consumed and I have averaged 41.5 MPG combined town and highway. I don't drive like a teenager, nor do I drive like a hypermiler.

Is any of this meaningful? My plan now is to let it sit for a few days, and if the engine light comes back on, I'll take it for another scan. Any better ideas?

No noticible difference today after disconnecting the 12v yesterday, by the way.

 

He is correct. If the issue detected meets the "resolved" criteria, then the code is sometimes wiped. In most cases, it is retained as a "historical" code, but those are treated differently with every manufacturer.

Sounds like a good plan. Moving forward, I would not disconnect the 12V unless it's absolutely necessary.

Extended sitting permits weak cells to self-discharge most of their capacity. On a deteriorated HCH2 battery, 1-2 days of sitting can be enough.

Recalibrations consist of:
1) car terminates all assist
2) SoC bars march downwards to 2 bars at 1 bar/second.
3) charging commences and does not vary with driving in most cases.
4) once charging is complete, it terminates and marches to full at 1 bar/second
5) normal use resumes

The drop to 2 is a "negative" recalibration. The charge termination and march to 8 is a positive recalibration. A positive recal may not occur. You might get to 3-4 bars after charging, and the car just starts working normally again. A recalibration occurs when battery imbalance triggers the upper and lower limits of the pack's operating range prematurely.

In my experience one recalibration per drive does not have a major impact on mileage for highway or combined with maybe 15-20% city mixed in. It will impact heavy city driving.

It will eventually deteriorate to multiple recalibrations per drive, which destroys mileage - particularly in city or combined driving.

Given the current state of things, a ~$450 grid charger is looking like a viable option. Once you know what codes are being thrown, you will have a better idea of how to proceed.

 

Can you elaborate on this please?

Thank you

 

Pull the IPU lid and check the 11 block voltages after sitting 10+ hours. If they have a small deviation (<0.2V), grid charging is likely a solution.