Hi all,

I'm in possession of a 2005 HAH that has sat idle for quite a number of years (5? 6?). The IMA battery was switched to OFF at some point, but I think it is unlikely to simply come back to life. Tomorrow morning I intend to get into checking it out and am wondering about the best way to do a check on the individual modules and replace them.

The first question is whether I should attempt to check the total battery voltage at the terminals connecting it to the rest of the car. This seems dangerous, but I've got some class 0 rated insulating gloves. But is this even useful to do? My instinct is not really, as cells are likely to be individually dead and possibly not even well below the rated voltage if so. I would guess it gives me a sort of rough estimate of how many cells might be dead at best.

To test the individual modules, by my understanding, I would need to pull the battery out of the vehicle and disassemble it's cover to get at the individual modules to perform load and no-load tests of their voltage. I think that the cells are supposed to read 7.2v and are rated for 6.5Ah. I would guess I could declare a module "bad" if it reads below 7v on either test—does that seem reasonable?

This last part is what I struggle most with... say I find a bad module: how do I go about replacing it? I've had a look around online and haven't really found much in the way of vendors with individual modules for HAH. I saw some ebay pages with HCH and plenty of options for Toyota Prius Hybrids, but nothing came up for the HAH. Any recommendations?

Thanks all, I've extracted lots of useful advice browsing the forum over the last couple of weeks trying to solve all the other problems with the car.

 

I've got an update.

The unlikely happened, and by flipping the breaker to ON the IMA system was recognized and the P0AC4 code was simply gone. No new codes took its place, and the starter battery was being charged up during idle. The green charge meter was up about 40% of the way for a couple of minutes before reducing to zero when the SoC meter showed 2 bars.

We let it run about 50 minutes to make sure nothing was going on insofar as the starter battery being run down like it had been without the IMA system connected. So far so good, idled shockingly smoothly around 650RPM which is, as I understand it, within the range of normality if a bit low.

I've learned a few things over the last couple days researching and figured I would catalog them here for anyone looking in the future. Firstly, if the pack is fully discharged I believe it should still read 120V (source: the prolific S Keith in this thread). Second, the SoC meter will normally show 2-3 bars in idle, and by revving the engine to ~4000RPM for a period extra bars should be be shown as the hybrid battery charges (source: tedson in this thread). Further, the cells inside the HAH IMA battery are identical to other Honda Hybrids (also from S Keith). Finally, I did actually find sellers for individual modules advertised as for the HAH, before knowing that the modules are identical. Either way, that problem is solved.

However, not everything was super smooth. I later the same day went out to the car and started it to make sure the starter battery wasn't draining while connected and checked out the voltage again. The starter battery was fine but my SoC meter was now showing as completely full. This is not how it should be by the above understanding I have.

As a bit of context, one of the few obvious issues remaining to me is that my spedometer is acting as a tachometer when the car is in park. Shifting into reverse and depressing the brake has the spedometer accurately drop to zero, but shifting out causes it to resume its RPM-based behavior. I'm looking into ways to fix this problem, but this oddity led me to the following thought. My best guess (and it is absolutely just a guess) explanation is that the prolonged time idling (while "moving" at 20mph for 50 minutes) gave the IMA computer system time to determine that because the charge was never increasing during operation, the battery was actually at its new maximum state of charge. Then after restarting the car, the dash updates with this information and because nothing has changed, the battery displays as fully charged. /shrug

It takes about a minute or so of idling for the SoC meter to gain a bar in both cases.

I plan to drive the car tomorrow after giving it a reasonable cleaning and hopefully no IMA warning lights are thrown up. Will continue to update as things happen.

 

Resting empty will be from 120-144V for healthy NiMH cells. That 120V response was context specific.

I don't have direct knowledge of the HAH battery indicator, but ALL other Honda gauges tend to operate in the upper 25% of their range with full indication being common. Forced charging by high rpm or charging by idle can easily drive the indicator to full. An imbalanced battery can also indicate full due to some cells hitting "full" before others.

A troubled battery sitting for extended periods many months/years will experience self-discharge. This self-discharge is a very effective means of a form of "reconditioning" that improves cell capacity; however, it does not improve the other conditions that contribute to failure. It's not uncommon to experience improved function after reactivation from a long dormant state, but this improvement is temporary, and in almost all cases, the battery troubles will return.

 

Hi Keith,

I'm glad you're still ridiculously active. Starting the car today at idle, the battery indicator was full immediately and there was no activity on the green charge meter. A pretty neutral sign, I think.

I've been doing research on reconditioning and that gives me some hope to hear. I'm not against grid charging the system, but I read in other threads that a grid charging harness needs to be installed. Is this a relatively easy install in general? I'm slowly becoming more confident working on the car so would be willing to give it a go myself if so.

I do expect the car to have problems. I hope to eke out another year or two while I nail down a job and save up some money for a slight upgrade. So far I've spent ~300$ resurrecting this thing, and am looking at a number of other maintenance issues (new brake pads, new tires...). If I can get the IMA system working for the ~500$ worth of cells to replace then I'll be over the moon.

About to give it a wash and a drive.

 

Post drive test information...

Initially there was some noise from the wheels that went away over time. We've chalked that up to the rust on the brake pads and other components getting knocked off. Things were a bit creaky but seemed mostly fine for neighborhood driving, which is all we did.

The charge meter would fill up and decrease in what looked to be a normal fashion. When braking, when idling, etc. The SoC meter behaved as it had when idling, going from empty to 2 bars over the course of a few minutes, and then rapidly up to 6 bars in maybe 15 seconds. The assist meter would go off occasionally, when the SoC meter was very full, and the SoC meter would drop down to 2 bars very quickly as well. The auto off feature of the engine seemed to be working as well. This continued for maybe 15 minutes throughout some variation in driving speed. Can't give accurate MPH numbers due to the spedometer problem I described (apparently we were doing 60mph in a school zone despite visually going maybe 20mph). Throughout this period the transmission was acting a bit funky. It felt very sticky, and sometimes when braking the automatic gear shift would struggle. The car would hiccup before coming to a stop. But then the IMA light came on. Nothing in particular had happened, but we drove home and got the OBD reader out again to find 2 new codes. On the way back the charge and assist system seemed to still be working, and I was able to hear the electrical whine of the HV system charging and discharging as those meters would light up.

P0AC4 is back, and now P0A7F. Starter battery voltage remains normal.

Some questions...

Transmission misbehavior: can the IMA system impact this? Should I start trying to diagnose the transmission separately? I will do a fluid change regardless and see if that helps.

Should I be worried about the ECU? What things can I try before springing for replacing all the modules that are likely to work?

Thanks.