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Hello, I have had a problem with the IMA battery for a month. Sometimes when I stand at traffic lights the battery bar goes to zero. It recharges after a short drive. I am concerned about this sudden drop in charge. Has anyone had that too?
 

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If you do not drive it enough and the battery never gets fully charged that is normal. Have you had under hood battery load tested? What year is it and how many miles on it any added electrical equipment?
 

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It just has never happened before. Now I can not fully recharge the IMA battery (one bar is always missing, sometimes it will work in sport mode but it drops quickly).

I have had a new battery for several months.
It seems to me that it all started when I left the lamp on weekend. The battery ran out and I used jumper cables.
My Honda is 2010.

62646
 

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My car from new has very infrequently had all 8 bars. Now that you have left the lights on even though the under hood battery was replaced you may have damaged it. Batteries when fully discharged can have some cells reverse polarity and even if charged on a charger not recover. If you have or can borrow a battery charger put the car on the charger for as long as you can to ensure the under hood battery is fully charged. If the battery has the caps where you could add water to it, add distilled water to it but not many batteries are like that any more. I would suggest you have it load tested and or replaced again. These cars are not very tolerant of battery issues considering how we have no alternator and the way the under hood battery is charged.

If you can, take it for a longer than usual drive and see if you can get the IMA to 8 bars. Let us know what the load test shows.
 

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Yes, remove the battery and charge it fully. The IMA does not charge it to 100% which is also the case for 99% of vehicles with an alternator.
The take the car on a longer steady drive, not using any assistance if possible, and then see what the SOC meter reads.
If there are any long hills, coast down in gear with slightest pressure on the brake pedal. This should maximise the charging and quite quickly get you to 100% charge.
Its probable that your 10year old NiMh batteries now have reduced capacity which will show up as quick charging and quick discharging but the SOC meter should still have 6-7bars lit up frequently.
 

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There is no reason to remove the battery to charge it. All that will do is reset everything that it has learned since he jump started it and he will then need the codes etc. Even though he needed to jump start it it may have had enough available to maintain the items in memory and not have to relearn.

Please stop suggesting disconnecting the battery for any reason other than to replace it.

Yes ,charge it and take for a long drive as I said above.

Yes, remove the battery and charge it fully. The IMA does not charge it to 100% which is also the case for 99% of vehicles with an alternator.
The take the car on a longer steady drive, not using any assistance if possible, and then see what the SOC meter reads.
If there are any long hills, coast down in gear with slightest pressure on the brake pedal. This should maximise the charging and quite quickly get you to 100% charge.
Its probable that your 10year old NiMh batteries now have reduced capacity which will show up as quick charging and quick discharging but the SOC meter should still have 6-7bars lit up frequently.
 

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Discussion Starter #7
OK thanks. My road to work lasts 10-15 minutes, so maybe there is no time to fully recharge.

Tomorrow I will go check if the battery is ok.

But is it normal for the charge bars to suddenly drop very quickly? and not slowly gradually?
 

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IMO with a discharged under hood battery yes. Beg, borrow or buy a charger and use it(over night). Then take car for a long drive at least 30 minutes ,longer is better. See if that changes the behavior.

OK thanks. My road to work lasts 10-15 minutes, so maybe there is no time to fully recharge.

Tomorrow I will go check if the battery is ok.

But is it normal for the charge bars to suddenly drop very quickly? and not slowly gradually?
 

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Im sure it is not normal. I've fully discharged my IMA battery a few times on the highway and it never drops to zero bars. I've gotten it to the point where it provides no assist even with the pedal to the floor, but it always had that 1 bar.

As for the 8 bars, the car will try to keep the battery below 80% charge. That way it can prolong the life of the battery and still have some 'room' to charge when you brake. To get all 8 bars you need to either go down a very long hil or deccelerate very slowly with regen only from a very high speed (over 70mph/120 km/h) which isn't easy.

It is possible that the IMA battery is simply worn out. It is true that batteries in series can be subject to 'reverse charging' when discharged too much. However, leaving a lamp or a headlight on will only discharge the 12v battery, and not the IMA battery. Plus, you said you got a new 12v battery, which further confirms that the 12v battery is fine.

Its probable that your 10year old NiMh batteries now have reduced capacity which will show up as quick charging and quick discharging
I agree. Not only are the batteries literally a decade old, they work hard since they have to handle huge currents, both in and out.
Please stop suggesting disconnecting the battery for any reason other than to replace it.
It is true that the battery can be recharged in place, and it is better to do so. It is easier, and there's no reason to reset all the systems in the car. However, there's no adverse effect to removing the battery either, and there are many reasons why you would disconnect your battery other than replacing it. I've disconnected my battery many times, sometimes for days at a time, and the car fires right back up as if nothing ever happened when I plug it back in.
OK thanks. My road to work lasts 10-15 minutes, so maybe there is no time to fully recharge.
While 10 minutes is not a long drive by any means, it should be enough to keep the 12v battery topped off, especially since the CR-Z doesn't use it for starting most of the time. I don't think that your issue is battery charge.
But is it normal for the charge bars to suddenly drop very quickly? and not slowly gradually?
No, it isn't. That is a sign of high internal resistance within the batteries, which would mean they are bad. High internal resistance would make the voltage of the battery decrease drastically when it is under load, whereas a battery in good shape with low resistance would have a more consistent voltage that doesn't drop as much.
 
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The Honda Nimh based IMA cars battery system all operate in the same basic manner.

Nimh useable capacity slowly goes down as the cells are cycled and the activate material inside deteriorates.
Nimh cells also get lazy with shallow cycling and develop the memory effect.
Calculated versus actual SOC drifts with variable self discharge when stood and due to individual variances when in use.
A pack of 84 series cells has variances between individual cells causing imbalance and SOC variations between cells in use.


With a Nimh pack if when assisting the SOC bars drops suddenly step down over a few seconds from a higher level to a much lower one and
the car stops assisting and starts regenning, that is called a 'Negative recalibration'

It is not a sign of high internal resistance per se.
(General pack voltage sag or spiking under load is a sign of high resistance, and the car deals with that by cutting back assist or regen to keep within permitted pack voltage levels)


What is happening in the OP's scenario if reported accurately is that the BCM via the battery voltage taps has detected an imbalance of at least 1.2V indicating one of the 84 cells has reached empty. The car acts to protect the empty cell from reversal by immediately cutting assist and starting a forced charge.

Whatever the calculated/stored SOC was before the event is declared null and void and the BCM adjusts the SOC to around 20/25%
(That's the step down over a few seconds to 1 or zero bars)

The car then force charges for a set period counting current in and then stops when it has reached a few bars or ~30% SOC.
Assist then returns and the car builds up soc gradually as normal.


The same effect also occurs to prevent the car overcharging the NIMH pack and you can get a 'Positive recalibration'
The gauge can suddenly step up over a few seconds from a lower level to a much higher one (normally 7/8 segments)
during steady regen or after sitting with a high static voltage.

Again if the SOC has drifted the pack as a whole or individual cells might actually be higher charged than the SOC indicates.
The car watches the unloaded pack voltage and if it is above a certain level for a certain time it assumes the pack is charged and sets the SOC to 75%
If a cell voltage tap gets very high and/or above the others, again to protect a full cell it will cut regen and recalibrate the SOC to 75%

It's normal in Nimh IMA cars to get very occasional recalibrations as the pack/cells drift.
The better the pack is managed and the better balanced and condition it is in means the less recalibrations you get.
If you drive daily/regularly you might see no recalibrations as the cells don't get time to drift apart due to the natural balancing effects in use.

If you don't use it much you will probably see occasional recals every now and then.

The car also uses the counted Ah gap between when a positive and negative recalibration occurs to work out the useable capacity of the pack.
The useable capacity reduces as the pack cycles/ages and you get a smaller and smaller window of capacity to use.

The car hides this from you as I have already explained on another thread by rescaling the display bars to cover the smaller useable capacity window.
The bars go up and down faster but they still cover the full range 0-8 segments. As the change is very slow over years people don't notice it.

Once your pack useable capacity gets below ~10% of the original new 5.75Ah the car will set an IMA code for battery deterioration.

Do not confuse the battery useable capacity % with the calculated or displayed instant SOC.
 

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Why are you disconnecting the battery? As I stated that resets everything on the car and under normal circumstances there is not a need to disconnect it. Yes, the car will still start just like replacing the battery but some things may get reset and car may have to relearn or re-calibrate. If you turn everything off and let the car sit the battery should not get discharged unless you leave something on. If my car was to sit for a long time it would be on a smart charger and I would turn everything off including the dome light switch to off from door.

The OP had an under hood battery that was discharged enough so car would not start. In a CR-Z as we all know this can be the death of the under hood battery. There is a small chance that using an external charger will bring it back but usually when discharged that far no matter how new the battery is, it is done. Hence my suggestion of a load test and a charger over night. Ultimately it is probably a battery that needs to be replaced again.

I was thinking IMA battery issue maybe related to the under hood battery discharge but after reading PeterPerkins's posting this maybe the first member to need a replacement IMA battery or repair to the IMA system. As there is no IMA warning light on the dash yet then the car maybe needs to be looked at for the IMA once the under hood battery is fully charged. Any errors may have been cleared by the under hood battery getting fully discharged but should have reoccurred after he has driven it.

In summary Underhood battery needs at minimum a charge and probably replacement. Once that is done and car gets a long drive then the IMA performance needs to be evaluated. As car is driven such short distances and times the IMA system is not getting fully exercised and may show odd behavor till it gets a longer trip after under hood battery is proven OK or replaced.

It is true that the battery can be recharged in place, and it is better to do so. It is easier, and there's no reason to reset all the systems in the car. However, there's no adverse effect to removing the battery either, and there are many reasons why you would disconnect your battery other than replacing it. I've disconnected my battery many times, sometimes for days at a time, and the car fires right back up as if nothing ever happened when I plug it back in.
 

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No, I have seen this before. See my notes about cells reversing and other issues after battery is fully discharged. Battery could be defective maybe warranty replacement but it is possible to discharge a battery beyond its capability to recover.

You should not have to replace a newish battery just because it went flat unless it was left discharged for months.
 

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Discussion Starter #14
I checked the battery. It charges fully, and charging is no problem either. Before my battery ran out and I charged it with jumper cables, I always had 8 bars. I must go to the car service
 

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see also this thread for a similar issue

Have your under hood battery at minimum load tested since you know you discharged it.
 

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As I have said all along my car since new it is very unusual to get 8 bars. With that being said has your car had the update I detailed in the other posting above? All owners of CR-Zs have noticed that 8 bars no matter the year is unusual. You do not have a problem in my opinion.

I checked the battery. It charges fully, and charging is no problem either. Before my battery ran out and I charged it with jumper cables, I always had 8 bars. I must go to the car service
 

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Discussion Starter #17
now 7 bars is a strange sight for me :) but if it's the norm, I'm calmer. I bought my Honda in 2015. I haven't done any update since then. I didn't even know they were.
 

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Update may have been done before your purchase or not. If not it is a free update.

2011 and 2012 CR-Zs are listed in this technical service bulletin:

See all the postings I referred to in the other thread. He actually had the code and the CEL and IMA Light that this update prevents. It is a free update and is much discussed. It affects calibration of the charge status on that gauge.

now 7 bars is a strange sight for me :) but if it's the norm, I'm calmer. I bought my Honda in 2015. I haven't done any update since then. I didn't even know they were.
 

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The Honda Nimh based IMA cars battery system all operate in the same basic manner.

Nimh useable capacity slowly goes down as the cells are cycled and the activate material inside deteriorates.
Nimh cells also get lazy with shallow cycling and develop the memory effect.
Calculated versus actual SOC drifts with variable self discharge when stood and due to individual variances when in use.
A pack of 84 series cells has variances between individual cells causing imbalance and SOC variations between cells in use.


With a Nimh pack if when assisting the SOC bars drops suddenly step down over a few seconds from a higher level to a much lower one and
the car stops assisting and starts regenning, that is called a 'Negative recalibration'

It is not a sign of high internal resistance per se.
(General pack voltage sag or spiking under load is a sign of high resistance, and the car deals with that by cutting back assist or regen to keep within permitted pack voltage levels)


What is happening in the OP's scenario if reported accurately is that the BCM via the battery voltage taps has detected an imbalance of at least 1.2V indicating one of the 84 cells has reached empty. The car acts to protect the empty cell from reversal by immediately cutting assist and starting a forced charge.

Whatever the calculated/stored SOC was before the event is declared null and void and the BCM adjusts the SOC to around 20/25%
(That's the step down over a few seconds to 1 or zero bars)

The car then force charges for a set period counting current in and then stops when it has reached a few bars or ~30% SOC.
Assist then returns and the car builds up soc gradually as normal.


The same effect also occurs to prevent the car overcharging the NIMH pack and you can get a 'Positive recalibration'
The gauge can suddenly step up over a few seconds from a lower level to a much higher one (normally 7/8 segments)
during steady regen or after sitting with a high static voltage.

Again if the SOC has drifted the pack as a whole or individual cells might actually be higher charged than the SOC indicates.
The car watches the unloaded pack voltage and if it is above a certain level for a certain time it assumes the pack is charged and sets the SOC to 75%
If a cell voltage tap gets very high and/or above the others, again to protect a full cell it will cut regen and recalibrate the SOC to 75%

It's normal in Nimh IMA cars to get very occasional recalibrations as the pack/cells drift.
The better the pack is managed and the better balanced and condition it is in means the less recalibrations you get.
If you drive daily/regularly you might see no recalibrations as the cells don't get time to drift apart due to the natural balancing effects in use.

If you don't use it much you will probably see occasional recals every now and then.

The car also uses the counted Ah gap between when a positive and negative recalibration occurs to work out the useable capacity of the pack.
The useable capacity reduces as the pack cycles/ages and you get a smaller and smaller window of capacity to use.

The car hides this from you as I have already explained on another thread by rescaling the display bars to cover the smaller useable capacity window.
The bars go up and down faster but they still cover the full range 0-8 segments. As the change is very slow over years people don't notice it.

Once your pack useable capacity gets below ~10% of the original new 5.75Ah the car will set an IMA code for battery deterioration.

Do not confuse the battery useable capacity % with the calculated or displayed instant SOC.
Great info. I would have expected the battery meter to show the actual SoC of the battery, and not the calculated usable SoC. However, I have read that the CHRG/ASST and the battery meter kinda fudge the raw data a bit so it isn't obvious that the battery is not performing well. I also read that the IMA update makes the data fudging even more aggressive and makes it harder for an IMA code to be set. I'd absolutely love to monitor data about my battery, such as current, pack voltage, voltage of cells, temperature, etc. I'd also like to see what the battery health is. 10% to set an IMA code seems awfully low. at that point your battery is a paperweight, I think.

Why are you disconnecting the battery? As I stated that resets everything on the car and under normal circumstances there is not a need to disconnect it. Yes, the car will still start just like replacing the battery but some things may get reset and car may have to relearn or re-calibrate. If you turn everything off and let the car sit the battery should not get discharged unless you leave something on. If my car was to sit for a long time it would be on a smart charger and I would turn everything off including the dome light switch to off from door.

The OP had an under hood battery that was discharged enough so car would not start. In a CR-Z as we all know this can be the death of the under hood battery. There is a small chance that using an external charger will bring it back but usually when discharged that far no matter how new the battery is, it is done. Hence my suggestion of a load test and a charger over night. Ultimately it is probably a battery that needs to be replaced again.

I was thinking IMA battery issue maybe related to the under hood battery discharge but after reading PeterPerkins's posting this maybe the first member to need a replacement IMA battery or repair to the IMA system. As there is no IMA warning light on the dash yet then the car maybe needs to be looked at for the IMA once the under hood battery is fully charged. Any errors may have been cleared by the under hood battery getting fully discharged but should have reoccurred after he has driven it.

In summary Underhood battery needs at minimum a charge and probably replacement. Once that is done and car gets a long drive then the IMA performance needs to be evaluated. As car is driven such short distances and times the IMA system is not getting fully exercised and may show odd behavor till it gets a longer trip after under hood battery is proven OK or replaced.
One of the reasons was to try to reset the IMA system. I've complained about poor MPG and the IMA system doing almost nothing, so I tried to reset it by disconnecting the battery. Also, when working on electrical stuff, like installing a new radio, the numerous mods I've done to the headlights, as well as removing the steering wheel which requires the removal of the air bag, it is generally recommended to disconnect the battery. Also, If I need to let the car sit for long, disconnecting the battery is easy and just as effective as having it on a tender, and since I rarely let the car sit for long, a battery tender isn't worth buying for me because it'll just end up sitting unused in a box.

No, I have seen this before. See my notes about cells reversing. Battery could be defective maybe warranty replacement but it is possible to discharge a battery beyond its capability to recover.
Cell reversing probably didn't kill the battery. If an SLI battery, like the one in the CR-Z, is discharged, it will be severely damaged. The cells are made of sponge-like lead plates. they are very porous in order to increase their surface area. This is how many car batteries can deliver over 600 amperes. The problem is that when the cell discharges, the conductive lead turns into lead sulfate, which isn't conductive. This can 'clog' the porous plate, which prevents the lead from re-forming and thus from recharging. This is why a battery can last for over 4 years if properly cared for. But if you leave your headlights on, for example, you can easily kill a battery, or at least severely shorten its life span.
When I first read the post I thought the OP had killed his old battery by leaving the headlights on, then had a new battery installed, but now that I re-read it it seems like he had a new battery installed, then drained it by leaving the lights on.
You should not have to replace a newish battery just because it went flat unless it was left discharged for months.
if the latter was the case, then it is totally possible for his new battery to be dead or severely damaged. I doubt it got to the point where reverse-voltage would be a problem, but if he needed a jump-start to start a car that doesn't even use the 12v battery for starting, then it was drained pretty far, likely killing it. Load testing it is the only way to know for sure, though.


As I have said all along my car since new it is very unusual to get 8 bars. With that being said has your car had the update I detailed in the other posting above? All owners of CR-Zs have noticed that 8 bars no matter the year is unusual. You do not have a problem in my opinion.
now 7 bars is a strange sight for me :) but if it's the norm, I'm calmer. I bought my Honda in 2015. I haven't done any update since then. I didn't even know they were.
My car usually hangs aout between 4 and 6 bars. Sometimes I see 7 if I'm driving with economy in mind, rarely 8 when I'm on a freeway off-ramp. As I said, the car tries to not fully recharge the battery both for longevity and to always leave some room for regen braking.
 

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i feel as thou i am experiencing a similar issues to the OP.
only difference i can say with my 2012 ZF1 is there is no IMA light but there is zero charge and assist happening.
I am sensing my hybrid battery are kaput.

Even the 12v battery up front is loosing voltage of some kind.
 
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