[Motty82]

Hey people,
I saw my first recal of the IMA Battery today. I am curious if anyone can tell me if they know if the system is supposed to allow assist durring the recharging process...? It is my understanding that it's best for the life of the batteries to fully cycle; meaning deplete completely, then recharge completely before allowing any charge to drain from the recharging batteries.

~Martin
Recycled
2000 5 Spd

 

[Mitch53]

Motty - Can't answer your question and will watch this for others ideas. I also have a 2000 5Spd and need to know .... what is your mileage, and when you had the REC did your battery gauge drop off too 0 :?:

 

[Insightful Trekker]

A recal, short for recalibrate occurs when the battery gauge becomes
out of sync with the available charge in the IMA pack. Measuring the
capacity of a battery pack is not like a liquid in a tank. You must
calculate that amount of charge removed and added. There is an error
factor in such a system. The packs capacity will deteriorate with time
an vary somewhat by temperature. At a certain point the voltage at rest
and or under a known load is clearly out of spec for the calculated
level of charge as shown on the dash. The pack must then be force fed
until its voltage falls into the known "full" range.

Then IMA pack's temperature must also be monitored because excess
charging or discharging when its out of an optimal range causes rapid
deterioration of the cells. Ni-MH packs frequently stored at higher
temps deteriorate somewhat faster even at rest. The Insight's BCM
(Battery Control Module) takes all these factors, and possible a few
more into consideration when charging or discharging the pack.

Unlike NiCD batteries NiMH's do not have the same memory effect. Therefore a routine deep discharge is unnecessary.

There is an interaction with the rate of charge for the IMA battery
pack and whether or not the headlights are on (for US models anyway).

And a good way of reducing a forced charge event (different from the
dreaded regeneration or recal event). If your routine commute regularly
requires a forced charge for less that the most severe hill climbing you can
prevent the occurrence by turning on the headlights. Simply anticipate
the event by watching the charge indicator. My commute routinely (but
not daily) demands more of the IMA then I can replenish through
regenerative braking. Turning on the headlights for the last 10 miles or
so recharges the pack from 60-70% to 90-95% (1 to 2 bars from the top).
Without this intervention I get a forced charge regularly.

I believe Armin had originally documented this behavior (in this forum)


John K. Bullock
aka. Insightful Trekker

 

[Delta Flyer]

Last year, some one e-mailed me if hot weather affects the battery life (I live in the Dallas area). I said no, although last month had me wondering. Some stop-and-go rush hour traffic totally discharged my battery a couple of times.

Driving like a Pizza delivery person with the frequent stop-and-go seems to be one of the best ways to discharge the batteries.

 

[Rick]

I think heat deffinitely will lower pack life. Nimh do not like heat much and that constant baking inside the car doesn't help much. I think that is one issue with the Insight is they designed it to take winters just fine, but they did not design it completely with heat in mind. Put an Insight thorugh a couple of hot summers and you'll notice that the pack starts to develop problems. You'll get recals more and more often. I seem to experience thermal cutback more than anything. Plus to make the problem worse is the fact that I have a 2002 which is basically the same ecu that they put in the older ones on recall, so it's assist assist assist. Sometimes for the sake of batteries I wish I could turn the assist off temporarily until I get the car cooled off enough.

As far as draining the batteries down, I've seen that as well. The trick is to let it rev up more so you take more power form the engine.

Frankly thats one thing I'm concerned about. Are my batteries going to be on their way out, but just holding on enough to not give me a IMA code so I can get a new pack before warranties up.

 

[Insightful Trekker]

quote Motty82 :

[I am curious if anyone can tell me if they know if the system is supposed to allow assist during the recharging process...?]

I can see I didn't completely answer your question. And your timing couldn't be better. My second recal happened just last week. And yes, I could/did get IMA assist during the recal. In the early stages it wasn't as much (fewer bars, and less oomph) and increased as the SOC indicator climbed.

Perhaps another way of thinking of a recal is simply a forced charge from near zero on the SOC gauge. The only difference being that the SOC drops spontaneously, not in response to a sustained IMA load.

To minimize the duration of a forced charge/recal you would be wise to limit the need for IMA assist. At some point thermal cutoff will occur in response to heavy IMA charging/discharging which will then require additional time in this low MPG/power operational mode.

John K. Bullock
aka. Insightful Trekker

 

[Mitch53]

Insightful Trekker -

GREAT explaination, it all makes sense to me now. I'm happy :lol: to say I now believe what I'm seeing is not a recal as I thought, but just the normal drain on the battery pack as I do my regular driving on the hills ( some pretty steep ) around Denver. One climb at C-470, approaching I-70 depletes my battery to 4-6 bars, but within 15-20 miles I'm back to 85% of a full charge.

Rick said " Sometimes for the sake of batteries I wish I could turn the assist off temporarily until I get the car cooled off enough " This question was brought-up in another forum I think - I have not seen anyone that has figured out how to do it.

Comments :?:

 

[Motty82]

Thanks for the great posts peeps!
I especially want to thank Insightful Trekker for addressing my question directly in his second post. And to answer everyone else's comments, I knew all that other stuff about heat affecting the NiMH batts and that NiMH batts don't have the memory loss that NiCD batteries do.
Thanks again,
~Martin
Recycled
2000 5 Spd

 

[Tim Maddux]

what I'm seeing is not a recal as I thought, but just the normal drain on the battery pack as I do my regular driving on the hills

I have found that every zero-out of my battery SOC (state of charge) gauge is at some point the result of a recal, i.e., even when hammering up a hill the reported SOC will suddenly drop off at some point rather than decrease smoothly through the last few bars to zero. When the recal occurs simply depends on how far off the expected charge level is. We just don't notice when it's not off by much or when we expect a drain (like going up a hill).

On the other hand, for the first 50k miles I never saw 100% SOC reported. The first one I saw was after a big climb on I-10 eastbound in the Arizona desert, presumably because there was a long sustained charge on the downhill side. I have seen a few more in the sub-freezing temps this past winter in New England, presumably from the car force-charging the IMA batts to warm them up.

 

[Insightful Trekker]

Quote Mitch53:

[Rick said: " Sometimes for the sake of batteries I wish I could turn the assist off temporarily until I get the car cooled off enough " This question was brought up in another forum I think - I have not seen anyone that has figured out how to do it.]

Well,

The risks are not zero in regard to voiding the warranty and there is the potential for erroneously second guessing the BCM's logic causing premature battery failure, but theoretically "reducing" IMA operations would be a safe hack.

It should be relatively simple. All that appears to be needed is to modify the IMA's thermal sensor circuit. Causing it to "lie" to the BCM in regard to being too cold for charge/discharge. This modification _must_ me made to fail safe such that if the modification fails the IMA pack will not be incorrectly "lied" to and overheat the pack.

According to the ETM there are two different types of sensors in two groups. One a positive coefficient sensor "strip" that is in physical contact with each battery cell group (2 "D" cells) and is "read" through its entire length.

http://www.insightcentral.net/encyclope ... ttery.html

The second group of four sensors that appear to be IMA ambient case temperature sensors.

Substituting a resistance that indicates subfreezing or thermal cut-off conditions should cause the BCM logic to disable IMA operations until the false value is switched off. However, since two independent groups of sensors are used it remains to be seen whether or not the BCM cross checks the resistance values to possibly determine a sensor fault. And there is both the known battery logic in regard to subfreezing and thermal cut-off and the unknown.

Subfreezing will cause the backup starter to be used. Its designed durability for frequent use is unknown. Thermal cut-off is known to cause the battery pack fan system to run. The newly discovered increased charging to the battery pack with headlights on is an example of a previously unknown logic. What battery management logic that may be beneficial and would be defeated by enabling user "control" is still a big and potentially _VERY_ expensive "discovery."

Independent of a thermal "hack," forcing the battery pack fan(s) on should be relatively risk free. Simply add an additional switch to the relay control side. But I would think that the fan logic is generous in regard to fan on operation. Adding fan on indicator lights so the driver can see fan operation is a risk free hack. A solar driven cabin air cooler can be as simple as a solar vent that hangs in a front window.

http://amos.catalogcity.com/cc.class/cc ... 9&ccsyn=22

I've personally used one of the above years ago. Durability was only 2 years and wind noise was annoying if left installed at highway speeds.


http://www.americanautoparts.com/599-607V.PDF
(see page 8, Nicro 3" MiniVent 1000)

Something interesting from a nautical application that may have greater durability, but require much greater installation effort. I can see this potentially fitting through a hole made somewhere behind the rear bumper. It would also require disassembly of the fan and remote mounting of the solar array. And some type of manual closure for winter days if not already equipped.

Finally, preventing solar gain from some type of cover would be the first line of defense. Maybe simply a clam shell "cap" that covered only the upper glass portion(s) of the Insight. Possibly using the home insulation material of reflectorized bubble wrap. With a bit of ingenuity it probably could be done at a relatively low cost and look good too!

John K. Bullock
aka. Insightful Trekker

 

[Rick]

Ohh no, your giving me good, probably warranty voiding ideas. :?

I would probably do that if there wasn't such a generous warranty on the IMA stuff. Actually, looking at the design I've been starting to wounder how the air flow through the box is as there are the fans that blow air in, but nothing that really pulls it out very well. I've been contemplating potentially making myself a clear plastic cover for the box, which would make an awsome display to begin with, and put a couple fans to suck air out of the back of it. Considering the only place I can see where air goes out of the box is in the holes that are in the bottom of it so I wounder if cool air is entering the box and just falling out of the bottom more than it getting rid of hot air that rises to the top. Thoughts?

The other thing that bothers me about thermal cutback is that it will limit charge, but will not limit assist. You can still get full assist reguardless of how hot you seem to get the thing. Eventually if you get it hot enough it will stop auto stopping to prevent that fast inrush needed to crank over the engine.

The other thought is if I still have the car out of warranty and the pack dies I might just have to find a way to fit some prismatic cells rather than the cylindrical ones. They are made for higher currents so they shouldn't heat up as much.

 

[Insightful Trekker]

<replied inline>

Ricky Suiter wrote:

> Ohh no, your giving me good, probably warranty voiding ideas. I would
> probably do that if there wasn't such a generous warranty on the IMA
> stuff. Actually, looking at the design I've been starting to wounder how
> the air flow through the box is as there are the fans that blow air in,
> but nothing that really pulls it out very well. I've been contemplating
> potentially making myself a clear plastic cover for the box, which would
> make an awsome display to begin with, and put a couple fans to suck air
> out of the back of it. Considering the only place I can see where air
> goes out of the box is in the holes that are in the bottom of it so I
> wounder if cool air is entering the box and just falling out of the
> bottom more than it getting rid of hot air that rises to the top.

> Thoughts?

Any convective air currents will be easily overcome with forced air. Opening the lid on the power pack and using a clear cover _will_ increase the greenhouse effect when the cover is exposed to direct sunlight. (read add heat to the battery pack)

> The other thing that bothers me about thermal cutback is that it will
> limit charge, but will not limit assist. You can still get full assist
> reguardless of how hot you seem to get the thing.

Well it theoretically reduces the thermal load by at least 50%, and there may be a difference in charging vs discharging in NiMH chemistry that further reduces the thermal load during discharge.

> Eventually if you get it hot enough it will stop auto stopping to
> prevent that fast inrush needed to crank over the engine.

Which as I remember is the highest current load on the pack, 80A +- and its cutoff is reflection of the BCM's thermal management.

> The other thought is if I still have the car out of warranty and the
> pack dies I might just have to find a way to fit some prismatic cells
> rather than the cylindrical ones. They are made for higher currents so
> they shouldn't heat up as much.

An interesting challenge. However, the thermal management of these different batteries will also need to be changed for maximum battery life.

A better approach will be to attempt to manage the overall interior temperature of your Insight and reducing (or in winter increasing) its interior temperature and thereby allowing better battery operation.

Secondary to that is improving the battery pack's internal temperature. Accurate temperature measurements need to be made as a starting baseline so that it can be seen if there is room for improvement. This might be done through manual operation of the existing fans. And or improvement of the existing intake and exhaust points, possibly directly ducting some of the Heat/AC directly toward the existing intake(s) for more rapid cooling/heating (in winter).

An accurate thermocouple probe with readings adjacent to the existing thermo sensors will define the sensor resistance value(s) as they relate to temperature and allow easier gathering of data identical to the BCM's input. After the internal sensors are mapped you would simply need to take an Ohm reading at a relatively easy access connector to determine its thermal value. The most difficult readings will be the cell surface sensor in that you will be dangerously close to a 144v source and that this sensors value is an average for all cells. Any specific point will likely be different and may require multiple points before an accurate sensor resistance correspondence to temperature can be mapped. Fan on operation would also need to be mapped to see if more aggressive fan operation could be of benefit. And cabin air temperature data will need to be time synchronizable with all of the above.

I would think that the batteries thermal mass and the corresponding time factor in warming or cooling the battery pack could be reduced by one or both of the above. And could be anticipated for those in areas that require heavy IMA assist for hills and the like. Anticipation being something that the existing battery management logic simply can't do.

But as you can see without some expensive automated charting equipment its not a weekend task.



Perhaps its best to simply let the experts do their job. I've lost the link but I remember some technical site reviewing the Honda IMA battery pack design. As I remember their harshest finding of fault was that the lowest cell group in the array may not be sufficiently monitored for temperature thus allowing damaging current loads _if_ frozen.



John K. Bullock
aka. Insightful Trekker

 

[Will M]

Just to add one more element to the explanation of the recal stuff:

The computer that manages the batteries has what is essentially a built-in chart that says, "At this state of charge and this temperature and this load, the voltage should be between X and Y" encompassing all functional states of charge, all temperatures and all loads. The state of charge is a guess based on how much current has gone into the battery and how much has been pulled out.

If the system notes a voltage level that is out of bounds for the chart (lower than X or higher than Y), then the system knows that its guess for the State of Charge is wrong, so it has to start over.

Most of the time this happens because the voltage dipped below what it ought to be, since that can happen a number of different ways. So, the recalibration is the assumption that the battery must be at a lower state of charge than expected, so the computer just assumes it is bottomed out and starts putting a priority on charging it until the voltage hits the maximum voltage for a 100% charge.

The system then assumes that it is at 100% charge and continues its calculations from there. People in mild climates, gentle driving habits and few hills may go a very long time without recalibrations, even if the SOC calculation becomes inaccurate, because it won't tend to hit the boundaries for the voltage that trigger a recalibration.

People who drive serious hills or accellerate a lot and generally push the system toward its extremes will naturally trigger recalibrations more often, and as a result will tend to report a more accurate SOC.

Also, when the battery chemistry starts to fade, the batteries will no longer hold as much electricity, and so they, too will tend to hit an extreme voltage more often and trigger a recalibration. Meanwhile, a recalibration is not a system failure. It is simply the system bringing itself back to more accurate reporting of the SOC.

Driving the car gently will make it last longer. This is true for most devices. There probably aren't any modifications you can make to the system to make it last longer if you don't drive it gently. There probably isn't a cheat that will get around this simple fact.

It is not unique to the Insight, and the Insight is not an exceptional device that can be habitually abused without a shortened life.

 

[Insight Driver]

I have about 73K miles on my Insight. I work on power conversion equipment used on passenger trains. They have a system similar to the IMA, in that batteries accept a regen current and provide current when the main power is interupted momentarily. Having that experience with batteries, and knowing the Insight has a very conservative charging algoritm people who fear the batteries will wear it is somewhat unwarranted.

My driving style has changed tremendously. I used to drive mostly on interstates. I had battery recal event occasionally. I now drive stop and go in the city most of the time. I now rarely ever get a full charge on my battery pack and I don't recall the last time I had a recal event.

I personally think the batteries will last well over 100K miles, conservative estimate. Replacement cost is not much of a factor at all. That said, you can drive the Insight without assist, but then it's a wimply little car that gets good gas mileage.

 

[The Citrus Smoothie]

I have only had one recalibration, but then with the 'mild' climate in the UK this is none too surprising. However, the UK has been in a heatwave recently and went over 100F for the first time in meteorological records. Global warming perhaps? I made a point of opening the car up from time to time to let cooler air in and protect the batteries after reading this topic.

 

[Insightful Trekker]

Quote The Silver Streaker:

[I made a point of opening the car up from time to time to let cooler air in and protect the batteries after reading this topic.]

Of relatively small benefit. Except to help limit thermal cutoff during the initial drive off. Keeping the windows cracked would likely have a greater effect on moderating interior temperature.

And compared to Ricky Suiter's "144volt" in Glendale AZ, USA 100 degrees is just another nice spring day. <vbg>


John K. Bullock
aka. Insightful Trekker

 

[Rick]

And compared to Ricky Suiter's "144volt" in Glendale AZ, USA 100 degrees is just another nice spring day.

Hah, I wish it would only be 100 out, thats where the fun only seems to begin. Two days ago I was driving home and a business had a sign outside that displayed the temperature. 118! Recently it's been like that and it has just been a screw it type philosophy. Auto air 60, Ahhhhhhh! At the beginning of the summer my lmpg was 64.1, barely, and not even having put a few thousand on it since summer began I'm down to 62.7 at 19,000 miles. Doing mostly in town driving with the air on and driving to keep it off the IMA as much as possible (higher rpm's while accelerating) I've only been averaging about 55 mpg. All things considered thats not too bad considering it's rated for 61 in the city without the air. I can't complain. I also recently had the car aligned and I apparently had the front left off a bit and I seemed to gain some mileage after having it put back to 0 toe in.

Anyways, I recommend the windshield cover and car cover to keep the car cooler inside.