new IMA battery, recognized by car, but not charging?

[S Keith]

My DIY design can go together in less than an hour.

With your terrain, I doubt the pack will out last the car. Hills are murder on the IMA system.

I'd keep the original as a spare.

The grid charge/deep discharge/charge process essentially "refurbishes" the pack with results similar to pulling all the sticks, cycling them and then reinstalling. However, you can do it in a long weekend with a couple hours of bench time vs. taking weeks and many hours of bench time at the stick level.

Personally, I'd keep both packs and swap them out every six months for grid charging.

Many people attempt to piggy back Lithium packs for your stated purpose. You could do it in parallel, but the potential complications in service could be problematic. It would take a lot of know-how to do right - way beyond my expertise. You could splice in all the taps, thermistors and main terminals to put the pack in parallel, but the danger would be if cells fail.

In series, the only issue is the voltage drop of the failed cell. Packs in parallel will transfer current back and forth as needed depending on their relative voltage. If one pack has a failed cell, the other pack will discharge into the pack with the failed cell until their voltages are equal. Given the very low internal resistance of the cells, this current could be pretty high. Not explosively so, but potentially damaging if not actively cooled.

Personally, as much as I like the concept, I wouldn't pursue it.

Steve

[rpearson]

Steve,

We've now done 12-14000 feet of hill climbing/descending and the IMA system seems to be working correctly. No error codes have been thrown during since doing the charge/discharge cycling. I am going to declare victory and seal it up. I'm sure I'll have more questions as we will follow your advice and keep that other battery pack as a spare. I think I'll build my own grid charger since we presumably are not in a hurry at this point. I think our drive train is in pretty good shape so we might well get another 100-150K miles out of the car provided we can keep the batteries going.

I want you to know how much I appreciate your help. I think you saved us at least $1,000 and maybe double that. I've looked at some of the other threads where people faced some of the same issues/error codes/etc., and were throwing expensive parts at the same problems. I believe they were using dealer mechanics. Our dealer (Honda of Santa Fe) didn't even find our blown fuse although they told us they checked them. I HATE throwing parts at systems I don't understand which seems to be a fairly typical strategy for dealer mechanics. The fact that we were able to make this work for the price of a single 20 Ohm resistor is awesome! Is there any kind of ranking system for contributors on ecomodder? You've been incredibly helpful. Your attitude was wonderful: helpful, friendly, understanding, clear and very knowledgable: one of the best experiences I've had on the internet. If you get points or something for people up voting you I would up vote you to the max.

I'll report back in a few weeks how the new battery is holding up.

Best, John

One more question. What is the idea behind the charge/discharge cycling? Does the IMA battery actually discharge when you disconnect the 12 Volt? Is there a writeup somewhere that explains some of the underlying principles a bit?

[S Keith]

I'll put that in the "passes a torture test column."

It's a very good sign. Double-plus-good if you noticed long periods of assist and regen when appropriate.

Given the uncertain history of your "new" pack, I would put a priority on getting a grid charger on it for 24 hours, particularly given the torturous driving conditions. Ensuring the pack is top-balanced will extend its life. You can get the parts in 10 days and assemble it in an hour plus the time needed to remove and install pack. Simply charge it for 24 hours, put it back in and let it rest for 30 minutes before driving.

You're very welcome. It's my pleasure. I'm only sorry I didn't think of it before. I'm aware of the circuit issue, I've posted on it multiple times, but I just didn't connect the dots. I'll put that on my "always check" list.

Not sure of any ranking, buy many are more helpful in many areas than me. Any post you feel was particularly helpful, you can just hit the "Thanks" button at the bottom right.

To your last question, the 12V disconnect resets the BCM, and it loses it's state of charge information. Upon restart, it reads the tap voltages and initiates a charge to see how the taps respond. It uses an algorithm based on charge current and voltage tap response to decide when the pack is at or above 80% SoC and then terminates the charge and sets the SoC to 80% (full gage).

The lower limit is then established in the future by an algorithm based on discharge current and tap voltage response. For a given current, if a tap voltage drops below a certain threshold, the pack is at or below 20% SoC, and the car terminates discharge. It may initiate a forced regen to bring the pack SoC higher or it may begin background charging at levels that don't show on the gauge.

The recals occur when these tap voltages hit their limits sooner than expected.

The multiple resets just force the car to make these SoC assessments multiple times, and it enables you to get a little more charge in the battery to start at a higher SoC. That's why the final one usually terminates very quickly because the tap voltages max out almost immediately.

[rpearson]

The first battery lasted only 65K, that one was of course replaced under warranty. The second battery started failing at 165K, same terrain, however I was no longer doing a daily commute down and up and down and up mountains (4K+ feet of gain round trip). And somehow we still got another 20K out of it after the IMA light turned on. Plus it's a manual transmission. bad combo with the mountains.

Anyway, we (royal we) are going to build a grid charger, components have been ordered. looking forward to it, and to reconditioning the old battery with it, too. Wish we had read up here before ordering the new battery, we assumed that sticks had to be reconditioned separately in order to recondition the old one! Ah well. And two batteries isn't a bad problem to have.

[S Keith]

Spares are good. I have 4 packs and 2 extra sets of sticks for our HCH2 fleet. Realistically, I have about 3.5 good packs worth of sticks, and I'm in the process of sorting them.

There is some benefit to stick cycling, but IMHO the reward to effort ratio is off the charts better when working with the whole pack vs. stick. Stick work requires a lot of bench time and coordination to make completion occur at a convenient time to start the next stick. Repeat X20.

With the pack charge and discharge, you get 95% of the same benefit for dramatically less bench time and much less calendar time.

Since you're in no hurry, you could discharge with two very low watt (25-40W) bulbs in series, and you could do multiple cycles. The hardest part will be remembering to check it every day.

I don't have a wiring diagram for the charger, but the second tab in the sheet shows pictures with and without the 12V supply.

Again, I'd make getting your new pack on a 24 hr grid charge the priority. Extended sitting adversely impacts the pack balance, and that's what kills the cells - because it causes the car to run the most imbalanced at the SoC extremes - near 0% and near 100% where cycling can cause rapid deterioration.

Good luck!

Steve

[rpearson]

It's 11 days after I first declared victory on this and the IMA continues to function properly.

[S Keith]

You have won the battle, but the war remains undecided... grid charge?

[rpearson]

Originally Posted by S Keith

You have won the battle, but the war remains undecided... grid charge?

I'm going to build a grid charger and rebuild the old dead battery and keep it as a spare. Hopefully I'll get the grid charger built over the holidays.

[S Keith]

When people say "rebuild" that conjures images of pack disassembly and stick-work.

Please don't. So much of the information out there is about how to do it wrong.

Grid charge your new pack. Done.

Grid charge your old pack. Discharge it with 2X 40W light bulbs for a couple days until it's < 60V. Grid charge for 2 hours. Put it on a shelf until you need it. Done.

Stick work is painful, and it takes an investment in time and equipment to do right.

Steve