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Well I did a search and found nothing specific, so here goes. Since I recently got a warranty replacement of my IMA battery at only 72,000miles, I have begun to wonder what advice/tips our more experienced Insight 1 owners might offer to best preserve the life of the IMA battery. I've done some reading over on Insight Central and there is a lot of talk about grid chargers and their importance to maintaining cell ballance, particularly as the batteries get older.

It seems to be pretty much uniformly agreed that letting the car sit for periods of more than a few days damages the battery. One battery expert even says "2-3 days." I do believe that long storage spells have been a problem for me and I'm resolved to avoid that in the future.

I practice Sean's FE technique of staying out of assist as much as possible for best FE. I've gotten so good at that that I seldom drop below 18-19 bars, so my battery is getting very little "exercise." Good or bad?

What are the early indications that a battery is beginning to lose its effectiveness or capacity?

Does anyone care to offer a list of important "survival" considerations?

Maybe this is an old topic but I couldn't come up with a thread:confused:

Hi, Jim -- I'm no battery expert but my understanding is that as long as you don't let the battery sit idle for long periods of time so that the age related differences in self discharge give the pack a chance to get unbalanced you'll be fine. The grid chargers do what is known as a "top balance" -- it gets all the cells up to the same voltage and helps keep them better in balance. This won't help if the actual capacities vary much but as long as the batteries haven't been damaged in some fashion they should be pretty well matched.

As for exercising, I've seen enough data from refurbishing efforts to know that the capacity can suffer from lack of "exercise." This seems to be related to the formation of large crystals in the NiMH chemistry -- which can only be broken up by "exercising" the cells through charge and discharge cycles. Along those lines I've seen recommendations to run the pack down to the bottom and then let it charge back up again once a month -- in context this seems not unreasonable to me. With a clutch switch this is not difficult to do without much of a hit to FE if I don't mind it taking a while -- engine starts and autostop will slowly drain the battery down if I keep the clutch mod enabled, then I can dole out the regen to charge it back at will by disabling the modification whenever I wish to slow down. Without MIMA this is not possible in the 2006 model, but you could use aggressive P&G and then get the battery topped back up with one of the above mentioned grid chargers without an FE hit.

As for early indications, I've read that the effective capacity (apparent duration of assist per bar on the SoC gauge) is reduced noticeably before recals begin to make a nuisance of themselves. I think that is about as much early warning as you are going to get.

For survival, I think in your particular case a grid charger would be a good investment. Keep in mind that self discharge and imbalance states by themselves are not harmful to the battery -- the damage is done when IMA tries to make use of the battery in these states. Cell reversal/overheating/venting can't occur without current being pulled from the pack. Any time you've left it sitting a week or more, just charge it up before you drive and you shouldn't have any issues. Note that self discharge rates are significantly lower in cooler temperatures so you could safely extend that interval to something more like a two week timeframe in the middle of winter.

To my knowledge there is no other (in-depth) thread here on CleanMPG about this topic, though it has come up a couple of times in other threads.

I suppose this would hold true for a CR-Z as well ? ! ?

I have been a bit concerned over the temperature of the battery. With 100+F every day I have been running with AC on, for the sake of the batteries not me :-). As I understand, high temperatures can be harmful to the batteries. Anyone have info on this?

My FE has dropped form ~55mpg to ~46mpg with AC use. The AC starts to struggles in econ mode with 100+F temp. One must really drive in normal mode for the AC to be effective.


KD

Without MIMA this is not possible in the 2006 model, but you could use aggressive P&G and then get the battery topped back up with one of the above mentioned grid chargers without an FE hit.


I think this is a very good strategy in my particular case. I have a test circuit already laid out, that I have tested on before, so I could test the FE hit. If it were just of the order of 5 MPG once/month, then the economics of a grid charger wouldn't seem to make sense. But with my long duration storage cycles, I'm definitely at risk of unballance and lack of exercise, so that definitely argues for a grid charger.

Hi, KD -- you are correct that high temps can damage the batteries but the cooling fan doesn't even come on until the temps reach 104F inside the pack in my Insight. Somewhere in the 125-135F range is where cells start venting and that's when you've got the (non-recoverable) damage mentioned above.

I wouldn't worry about it too much -- particularly if you don't actually use the battery much (good for max FE!). Because I barely touch my battery state of charge I haven't bothered with the AC -- even with temps inside the car noticeably higher than 100F. I've driven it a couple of times in 100+F ambient temps and didn't even hear the IMA fan come on.

Thanks, I have heard the fan kick on a few times. It has been 110+F here for the past few weeks. It cooled down today but no rain.

KD

As for exercising, I've seen enough data from refurbishing efforts to know that the capacity can suffer from lack of "exercise." This seems to be related to the formation of large crystals in the NiMH chemistry -- which can only be broken up by "exercising" the cells through charge and discharge cycles. Along those lines I've seen recommendations to run the pack down to the bottom and then let it charge back up again once a month -- in context this seems not unreasonable to me. With a clutch switch this is not difficult to do without much of a hit to FE if I don't mind it taking a while -- engine starts and autostop will slowly drain the battery down if I keep the clutch mod enabled, then I can dole out the regen to charge it back at will by disabling the modification whenever I wish to slow down. Without MIMA this is not possible in the 2006 model, but you could use aggressive P&G and then get the battery topped back up with one of the above mentioned grid chargers without an FE hit.

Well Sean, that seems to have worked pretty well. I took the car out on the interstate and accelerated up all the hills and fas 'ed down the other side. In 6-7 miles going west out of Richmond I was able to get the IMA battery down to 2 bars, just at an exit:D

I turned around and in the 6-7 miles of return, I got back to 20 bars.

I was kinda interested in the nonlinear nature of the SOC guage, or perhaps the nonlinear nature of the discharge/regen. On assist, it dropped slowly at the top and like a rock in the botton third. Pretty much the reverse on regen. It was very slow to regain 1/3 and somewhat slow to regain the middle third, but the last third seemed to come all at once.

I've been reading the grid charger thread over on Insight Central - all 53 pages of it:eek: There seems to be a fair amount of confusion as to what really kills battery life, but for sure a high imbalance, where one cell in a stick goes negative on assist demand or startup, is a killer. Beyond that there are lots of different views, some from folks who sell "corrective" equipment;) It is thought that Honda only uses the middle 60% of the battery capacity, reserving 20% at each end as a battery life enhancement. Many of the grid chargers "stuff" the top 20%, but I gotta wonder if that is actually healthy, since Honda didn't do it that way.

Hi, Jim -- it actually is possible to stuff past the top (~82% or so IIRC) as long as you don't overheat or interrupt the regen when you hit full on the SoC gauge. The main concern with topping all the way up is the fact that essentially the internal resistance goes up as you reach full and all the power is converted directly to heat. Since you've read those threads about grid charging you know that the max current thrown at a pack during topping is 350mA -- this won't damage the cells as long as there is moderate airflow (easily accomplished by the running pack fan -- which is why it is highly recommended to have this powered up during charging). In cooler weather, you could do without the fan and still be fine. Regen involves much higher currents, though -- and that could cause overheating and venting of the cells.

The simple problem here is that you can't accomplish a balancing charge unless you let the cells bump up against the top. If you limit to total voltage, this is no different than what the car does anyway and we already know that it doesn't balance the cells at all.

I wouldn't be too concerned by a gentle charge that doesn't risk venting your cells.

As for early indications, I've read that the effective capacity (apparent duration of assist per bar on the SoC gauge) is reduced noticeably before recals begin to make a nuisance of themselves. I think that is about as much early warning as you are going to get.

I think this is the state of my batteries. It used to be that it was very hard to get the SoC to come down even one or two bars (on a CVT). Now I have to watch it all the time as the charge state varies wildly and quickly. I had similar symptoms right before my first pack went bad. That was at 4.5 years from purchase. I am at 9+ years ownership now so call me hopeful but expecting.

I don't know if the charge state is because of the heat or the age. Like I said, hoping cooler weather will prevail.

A good balancing charge would likely get most of the lost capacity back for you. I think Chuck might have a charger you could hook up temporarily?

I think this is the state of my batteries. It used to be that it was very hard to get the SoC to come down even one or two bars (on a CVT). Now I have to watch it all the time as the charge state varies wildly and quickly. I had similar symptoms right before my first pack went bad. That was at 4.5 years from purchase. I am at 9+ years ownership now so call me hopeful but expecting.

I don't know if the charge state is because of the heat or the age. Like I said, hoping cooler weather will prevail.

Assuming your batteries are kaput, can you tell us what the mileage was on the two sets? I'm going to try to start a poll on the subject so please respond if it get it going.

Bump to bring up the poll.

I am at 109K right now. The first went bad right around 50K, but I put 50-75 in the poll. I will have to look at my records to be sure of it.

Just a nudge. I know there are a lots of IMA battery data out there. Please take just a second to add your data to the poll. We would ALL benefit:D

From a HAH owner perspective.
Jim as I'm sure you are already aware letting the soc get low and leaving it there is enough of cell killer that Honda spent the money on a sticker to tell you not to do that. To bad they didn't just put in a decent SOC gauge instead of that thing that tries to guess at it. Making the real pack numbers available via diagnostic port would be equally nice.

Oddly I've never had a Honda tech tell me to do anything special in regards to non use. Two of them said the 12V might not run down.

I "store" my 07 HAH for periods that are long enough that if parked with a low SOC I'm pretty sure I would eventually find some bad cells. So I force the HAH to 100% before leaving it lonely. I also don't drive the car very often, sometimes only a couple of time a month. On the HAH this is simply a matter of turning off all electronics and while in park simply bringing the rpms up until it starts charging at about 2500 rpm, max forced charge rate happens at about 4000. I can also take the battery down quickly with the electric a/c compressor if I want to cycle it.

The firmware in the HAH will not let the pack stay full long if you drive it but it will leave it alone until the next drive. I also keep a charger on the 12V battery whenever the HAH is in the garage, which is most of the time. Numerous internet post indicate the HAH has proven to be hard on 12V batteries and my opinion is that the converter charges at to low a voltage for flooded battery chemistry and the battery is in a hot spot. Honda gave me a new one or mine would now be a agm, instead of the flooded.

Passed on buying a really nice 06 MT Insight a couple of weeks ago. Wants just didn't justify it. enjoy yours.

Don't know what the pack warranty is on the 06 Insight, but the HAH has a 10 yr 150,000 mile on on the pack thanks to the AT-PZEV CA requirement. As gently as the car uses it may well make it.
Mike