Ok first of all forgive me... it's been YEARS since I've posted. I'm a happy owner of a 2004 Civic Hybrid and my battery was replaced once with previous owner in 2010. I purchased it in 2015. Since then I've been successfully balancing my pack once per year using HYBRID AUTOMOTIVE products. I've had just one IMA light, last year, and was able to recover from it using the HYBRID AUTO charging and discharging system. So to be clear, the IMA light is NOT on at the moment. But what I'm noticing now is wild swings of the battery capacity meter. It will be full one minute and then almost drained the next. Acceleration also seems to be to be very poor. Soooo..... is it time to replace the pack?? The body is still in reasonably good shape and the mechanics are all sound. And given the recent chip shortage used cars are extremely expensive which makes this car kind of valuable to keep. One other question, when you get a replacement pack, does the acceleration performance get better? And what about the "hesitation" this car always seems to have when I press the gas pedal? Does that get better? Because frankly it's always been that way and I've just dealt with it. If both those things get better with new pack I might go out right now and do it! Thoughts? And thanks in advance.

Nate

 

The 1.3L of the HCH1 is pretty gutless. It relies on the torque of the IMA motor for "launch." An under-performing battery is definitely noticeable.

Good gas mileage in city/combined driving is a sign that the IMA battery is "healthy enough."

Given your description, it sounds like you may be dealing with other issues.

Gauge behavior appears to be indicative of "recalibrations" due to imbalance/deterioration.This is indicated by the gauge bars "marching" at a constant rate to near full or near empty that's not consistent with operation, e.g., not charging, but the gauge "marches" to full with bars being added at a constant rate.

Recommend you give the car a 12 hour overnight CHARGE to see if the gauge behavior and performance improve. Also recommend a full 30 hour full grid charge over the weekend.

It is important that you confirm the battery fan is engaged during charging.

 

It’s funny, that’s almost exactly what it is like. It marches up to full even while you’re just driving, and then if you use it a little bit, it will swing way back down to the lower half and then maybe go back up again a little bit later. But it never seems to be able to make up its mind or follow any pattern. I will try a 12 hour charge first. Thanks

 

It's not funny. It's by design, and it's the typical behavior prior to a failure. The big swings are reactions to operation. The "marches" are the results of forced calibrations.

The pack is monitored every 12 cells, so there are 10 "taps" reading 10 voltages.

In a healthy battery, all cells will be at almost exactly the same voltage regardless of siting, charging or discharging.

In a deteriorated/aged battery, those voltages diverge as the individual cells begin to vary. Charges and discharges amplify these differences.

The BCM is continuously comparing these tap voltages to a table of current, temperature and state of charge. When one of those taps drop below a given threshold for "empty battery," it's seen as an outlier, and a negative recalibration is forced. That's the march down, forced charging and poor performance until it recovers. In the worst cases, the forced charging actually triggers the opposite - a positive recalibration. One of the taps has exceeded the upper limit for "full battery", forced charging is terminated and the gauge marches back up to full/near full.

The 12 hour charge should input 0.35 * 12 = 4.2Ah minus efficiency losses. This should force all cells well into the operating range and eliminate/minimize/reduce the frequency of recalibrations in a battery with some life left. If you see an improvement after 12 hours, recommend the 30 hour ASAP as that guarantees all cells are driven to true 100% charge.

If performance is improved, conduct grid charges when you encounter recalibrations. Increased grid charges may require that the pack be discharged every 3-6 months. Never conduct a discharge without a 30 hour charge immediately prior.

Replace battery when you can no longer achieve acceptable function.

 

Excellent explanation and advice! Thanks very much I will proceed and post my results. Nate.

 

I forgot to mention it again... make sure the fan is moving air.

 

Update. First of all, yes my grid charger does move the fan so that’s good. After a 12 hour charge there is some improvement. The battery no longer swings up and down the way it did before. It’s more like I remember, gradual increases and relatively gradual decreases depending on the load. However I still feel like it’s just not performing that well. Take offs are just so sluggish, like there’s no oomf behind the battery itself. I will try a 30 hour charge next.

 

Another update! I followed up with a grid charge of approximately 42 hours. The readout on the Grid charger topped out at 180volts. I have to say that now there is a BIG PERFORMANCE increase! Acceleration is MUCH smoother and doesn't hesitate or "gulp" like it did before. What a difference! In fact all "transitions" from accelerating to decelerating are much smoother too. I'm VERY PLEASED! So my only question now is how long with this last and when will I likely have to do it again? I guess we'll have to see. Also, when is it appropriate to DISCHARGE? I've got the Hybrid Automotive automatic discharger that has something like 90/60/12 volt discharge cycles. They recommend stepping down the discharge cycles after each grid charge. Thoughts? Thanks.

 

It's impossible to say. It depends exclusively on the state of the single worst of the 120 cells.

Generally speaking, CHARGE when needed to restore performance. When charge-only doesn't get you there, charge + discharge. NEVER discharge without a 30+ hour charge before hand. The 3 progressive cycles are rarely needed. Discharging below 60V is rarely warranted and can do more harm than good on these aging packs.

If you just want to do things on a schedule, 30+ hour grid charge every 90 days with 1 discharge/year.

 

Excellent tip. I think I’ll do your last recommendation and just continue to keep an eye on it. Thanks so much for all of your help with this. I really really appreciate it. Have a great day!