Anyone got a Hybrid?

[guest2872]

However, I do have several grumbles with the hybrid system on my Jazz (registered March 2011:

(i) I've never seen the battery charge level drop below half;

Hi John,

The manual says some interesting things about the battery charge level and gauge:
"The battery level reading may drop near the bottom under driving conditions that require IMA motor assistance for a long time, such as prolonged acceleration or climbing a long hill."
   Perhaps it's the case that you really need to give it the beans for a prolonged climb up a particularly long, steep hill before you see the battery charge drop so low? Either way, it can't be a bad thing that the battery may be so hard to drain.

"The battery level gauge does not read the battery level directly. It calculates the level continuously by measuring the current flow, voltage and temperature. Since the level is not read directly, small sensing errors can, over time, cause the gauge to read higher than the actual battery level."
    This may also add to why we don't see the battery charge level indicator drop to nearly empty very often. However, the manual does also state that when such a sensing error occurs, the system will perform a correction, and the battery level gauge reading will drop suddenly (temporarily disabling IMA assist and the auto stop function).

Perhaps the car is just managing itself more efficiently than we might expect, and maybe one needs to put the car under considerable and prolonged loading before we see the battery reading drop to below half in response to the immediate driving conditions?

I don't think what you're seeing on the display has anything to do with any part of the battery being reserved for when the battery starts to lose capacity. The manual clearly states that the charge indicator can display 7 stages of charge, from empty to full, so it's certainly worth probing the dealer for their view on this. I haven't driven ours enough to know whether it's the same, but I'll keep my eyes open.

(ii) But on long hill climbs I've seen the IMA mode switch from assist to charge while still going up the hill;

When this happens, do you notice a drop in performance? If so, that might be an indication that the system isn't responding correctly to your driving demands, and could indicate a problem. But if the engine and CVT are continuing to provide the power and response that you're demanding, then the IMA system could well just be taking that opportunity for a quick recharge?

(iii) The trip computer bar display showing the past 3 trips MPG seems to have a limit of 62MPG.

Yes, you'd have thought Honda would have put a longer scale on there, just to encourage us all to see how much we could squeeze out of our hybrids! They should definitely recalibrate this to display up to 80mpg. 

The Honda agent did offer to look at these problems but I only want to go round if I know that the newer Hybrids behave different. What do you folk see on your cars?

I need to do the 'hill test' before I can compare my battery charge indicator performance with yours. As for the charge indicator, I'll need to wrestle the car off my wife for a bit to see if I can get ours to display less than half a charge.
   

As for the 8 year warranty on the IMA, I think that is what it used to be, and then Honda reduced it. However, if the website still says 8 years then we we need to keep the evidence.

I've checked this in the service handbook for my car, and you may well be right: the IMA warranty is listed as 8 years or 100k miles for model years 2003-2010, and 5 years or 90k miles for model years 2011 onwards. So in spite of what the website says, it does appear that we only have 5 years IMA cover from 2011 onwards. I wonder why.

[John Ratsey]

On that occasion my photos say 65.9 MPG, but here's another one:



That's the best MPG I've managed to get. My Jazz doesn't like the winter weather and is struggling to get over 60 MPG at the moment. And I would note that my fuel filling calcs give 2 to 5 MPG lower than the computer.

John

[guest2872]

Wow, 71.6 mpg is great going. How hard (i.e. 'soft') did you have to drive to pull such an excellent average?

It's interesting that you're struggling to better 60 mpg at present, as that's also the best we've been able to achieve since we took delivery almost a month ago. Can only be the weather.

Looking forward to the summer...

[John Ratsey]

Yes, 71.6 MPG is good going. That was A road driving so typically 50 MPH. The Jazz is not very aerodynamic (one can't get the space and high driving position into a sports car profile) so 60+ MPH does start to hit the fuel economy. Windy conditions aren't good news since they substantially increase the wind resistance. 60 MPH into a 10 MPH head wind = 70 MPH wind resistance but the corresponding 10 MPH tail wind doesn't reduce the wind losses by as much.

Regarding the battery assist / charge behaviour and long hills, I have felt a slight loss of power on occasion although the level of boost or charge is quite small. One does need a long hill such as the climb up the M4 going eastwards to the top of the Cotswolds. The behaviour I am seeing has two annoying features: (a) that the battery gauge never goes below half and (b) the computer then decides to immediately start to recharge the battery instead of waiting until the vehicle starts to accelerate or the driver eases off the accelerator (either of which indicate the top of the hill). The computer ought to be able to figure out the road conditions based on engine power and change in speed.

I do wonder whether the computer is actually using the battery over the planned range of capacity with the bottom half being reserved for when the battery progressively wears. However, the display should reflect the working range of the battery and not reveal that only half the capacity is being used.

John

[Ozzie]

71.6 very impressive ! 

[John Ratsey]

71.6 very impressive ! 

Don't forget that what the computer reports. Deduct maybe 3 to 4 to get the real MPG. (I've got between 2 and 5 MPG difference between computer and actual, presumably due to differences in "full" when refilling the tank).

John

[whoopster]

Yes, I have a Honda Jazz Hybrid... picked it up at the dealership on 1. October 2011.

Great car...

[guest2872]

The behaviour I am seeing has two annoying features: (a) that the battery gauge never goes below half

We've been watching our battery gauge closely and so far can confirm that, until yesterday (see below), ours also hadn't dropped below half. The car is still being run in gently, and driven with economy as a priority, so we haven’t pushed it too hard at all yet.

(b) the computer then decides to immediately start to recharge the battery instead of waiting until the vehicle starts to accelerate or the driver eases off the accelerator (either of which indicate the top of the hill). The computer ought to be able to figure out the road conditions based on engine power and change in speed.

Yes, on the face of it, it would seem reasonable to expect the battery to continue to provide assistance to get you over the hill.

But what if that hill was so long and steep that the battery just kept on assisting until it almost ran out of charge, consequently requiring a significant follow-up period of appropriate driving conditions to recoup sufficient charge to fully reinstate the hybrid operation again? As I understand it, fully charging and discharging NiMH batteries on a regular basis also affects their longevity.

Could it be that the computer is making allowances to avoid such a scenario by using whatever opportunity it considers reasonable to go back into recharging mode to keep the battery topped up, at least to half charge? I suspect this may be a factor.

A simple experiment
Being curious, I found a stretch of uphill dual carriageway yesterday and had a little play with the battery. I first kept the car under gentle but continuously increasing acceleration uphill to see whether I could force the battery to stay in assistance mode. Like yours, it frequently dropped back to recharging even whilst the load on the car was gently increasing as I continued to accelerate lightly up the incline.

So I tried once more, this time applying greater acceleration to keep the car under greater loading with an increased rate of acceleration compared to my first attempt. With this approach, I found that I could keep the battery in assistance mode longer, and reduce the instances of the computer dropping it back into recharging mode.

This slightly more aggressive driving also succeeded in reducing the level of charge shown on the battery charge indicator to below half, and I have no doubt that if I had been prepared to be even more aggressive I could have held the battery in assistance mode even longer and reduce the level of charge shown even further. However, it seems that I would have had to drive unacceptably hard to achieve this.

Hence, the impression I get is that the 'charge window' within which the battery switches in and out of recharge under normal driving conditions is, perhaps deliberately, relatively small and that one would effectively have to thrash the car to keep it in assistance mode and run the battery charge down to a really low level.

But why?
I suspect the reason is not just to ensure you always have adequate battery power reserves in case of need, but may also be connected with maximising the life of the battery itself. I understand that it’s a characteristic of NiMH batteries that, to prolong their service life, they should be kept at just above half charge for the most of their operational time.

In addition, NiMH batteries can suffer damage if they are allowed to become completely discharged, particularly if they are allowed to become ‘over-discharged’ which can cause the polarity to become reversed.

So maybe the frequent recharging instances are essentially the result of a fail-safe design aimed at keeping the battery topped up to an optimum level to maximise the service life of the system?

However, the display should reflect the working range of the battery and not reveal that only half the capacity is being used.

Fair point – I think this is where Honda’s approach differs with that of Toyota:  the Jazz manual seems to indicate that the battery charge indicator shows a reasonable estimation of the charge present in the battery, i.e. from ‘zero’ at the bottom of the gauge to ‘full charge’ at the top.

However, Toyota’s Prius takes a different tack, which is more in line with your preference, i.e. the top of the battery charge indicator apparently reflects a 75 percent charge, and the bottom of the gauge represents a 45 percent charge, being that Toyota believes a 60 percent charge +/- 15 percent (max) to be the optimum working range of the battery under normal operating conditions. I think this may be the key.

Hopefully this goes some way towards an explanation of why we see what we do on our cars with regard to the battery charge, and the charging versus assist scenarios.

If correct, and being that our HS is demonstrating similar characteristics, this would suggest that you don’t have a problem as such with yours in this respect.

It probably doesn't take away the annoyance, though! 

Cheers,

Head

[John Ratsey]

Thanks for your lengthy observations. I've always been under the impression that Nickel based batteries didn't mind being fully discharged (Ni-Cd batteries needed regular complete discharge to avoid the charge memory effect which resulted in loss of capacity). Lithium-based batteries, however, prefer to avoid the extremes of the charge range. Anyway, it seems that I'm not pushing my car up the hills hard enough. Do you use the Eco or normal driving mode?

To me, going up a long hill means the probability of soon going down the other side which provides the opportunity for recharge (on some roads one needs to slow the vehicle down. Having a nearly full battery at the top of the hill reduces the potential to store some of the energy instead of wasting it as heated brake discs. I'm thinking that the hybrids realling need to have a GPS system linked into the computer so they known if they are going up or down. The next step would be to have a digital elevation model in the computer so it could look at the road conditions ahead and plan accordingly. I feel that the IMA concept isn't being used as efficiciently as it could be.

Does your HS also have the same scale for the last 3 trips MPG display (see my photo in a previous post)? That would seem to be a simple thing for Honda to fix.

John

[guest2872]

Thanks for your lengthy observations.

Always a little too lengthy I’m afraid! 

I've always been under the impression that Nickel based batteries didn't mind being fully discharged (Ni-Cd batteries needed regular complete discharge to avoid the charge memory effect which resulted in loss of capacity).

Me to, and I think that’s correct as far as actually damaging the battery is concerned (i.e. it’s over-discharging that can cause the damage).

However, although I can’t claim to fully understand why, from what I can gather it does seem that the service life of a Nickel Metal Hydride (NiMH) battery (as currently used in the majority of hybrid vehicles) will be maximised if frequent charging/discharging cycles remain relatively shallow. Apparently, NiMH batteries don’t suffer the memory effect that Nickel Cadmium batteries do.

Anyway, it seems that I'm not pushing my car up the hills hard enough. Do you use the Eco or normal driving mode?

We have the Eco mode engaged all the time.
I did once switch it of for a short while to see if there was any change in performance but noticed no discernible difference, so I put it back on and left it there.

There’s an interesting article here (http://batteryuniversity.com/learn/article/are_hybrid_cars_here_to_stay) about hybrid car batteries which, coincidentally, makes a couple of references to the hybrid owner who lives at the top of a mountain…

 

Having a nearly full battery at the top of the hill reduces the potential to store some of the energy instead of wasting it as heated brake discs. I'm thinking that the hybrids realling need to have a GPS system linked into the computer so they known if they are going up or down. The next step would be to have a digital elevation model in the computer so it could look at the road conditions ahead and plan accordingly. I feel that the IMA concept isn't being used as efficiciently as it could be.

I’d patent those thoughts real quick if I were you!

Does your HS also have the same scale for the last 3 trips MPG display (see my photo in a previous post)? That would seem to be a simple thing for Honda to fix.

Yes, exactly the same. I suppose it is a bit daft that the scale only goes up to 62 if you can manage over 70 on the trip readout. Maybe Honda never expected anybody would get such an impressive return, or perhaps they just left the scale large enough to reflect their published figure of 62.3mpg over the combined cycle? Who knows. But yes, I guess it would make sense if the bars tallied with the trip reading.

So: 71.6mpg?  You have clearly thrown down a gauntlet here, and I intend to do my utmost to try to top that come the summer – watch this space!

Cheers,

Head

[John Ratsey]

Thanks for that battery link.

The charge efficiency is best at 50-70% state-of-charge. Above 70% the battery cannot absorb the charge well and much of the charging energy is lost in heat.

That almost represents what I am seeing except that the battery is spending more time above 75% than it spends below 50%. It would, however, explain why the system is reluctant to go below 50% charge. [It's also possible that the steps on simple bar gauge doesn't properly represent the charge. Perhaps 50% includes 40%.]

It doesn't explain, however, why the system will switch from Assist to Charge before reaching the top of a long hill. I can understand Assist stopping when the battery charge reaches a certain level of discharge but I would then expect the system to wait until the top of the hill (which can be detected by either an increase in speed or easing off of accelerator) before starting Charge. Unless there's some clever stuff like the system being programmed with the most fuel efficient engine speed range for generating electricity, and that just happens to be my normal uphill cruising speed.

John

[guest2872]

I can understand Assist stopping when the battery charge reaches a certain level of discharge but I would then expect the system to wait until the top of the hill...before starting Charge.

According to Honda:
When cruising at a constant speed and the battery charge falls to a relatively low level, the IMA motor will use a small amount of engine power to act as a generator to recharge the battery. But even when the battery is charged, a small amount of electricity is still being generated, primarily to power any 12v accessories, but with any surplus still being used to slowly charge the IMA battery.

Perhaps this is the answer?

[guest3001]

Re; IMA warranty. Although I was told by the dealer the IMA warranty was 5yrs, I have read the Service Book (issued03/10) and it clearly states 8yrs, with no mention of date of manufacture.

Re; MPG  my best is 83.4, I've got no picture to prove it, I was driving at the time....

[John Ratsey]

I just stumbled across this article http://www.economist.com/blogs/babbage/2010/08/hybrid_cars about Honda hybrid batteries. Food for thought?

John

[guest2872]

I just stumbled across this article http://www.economist.com/blogs/babbage/2010/08/hybrid_cars about Honda hybrid batteries. Food for thought?

John

Yes, I saw this a while back, just after we bought our Jazz in December 2011. I guess we can only hope that Honda learnt enough from the Civic battery woes to ensure we don't have issues with our Jazz hybrids. That said, I do wonder why Honda has reduced the warranty on the battery and IMA system from 8 to 5 years with effect from the 2011 model year. 

Must admit, whilst I am fascinated with the hybrid concept from the technology angle, and currently have no regrets about our purchase, the question of resale values in 3 to 5 years' time has been one I have so far deliberately chosen to ignore!

For now, we're happy. My wife is gradually relearning how to drive for maximum economy and is pushing her mpg slowly upwards towards 60 on her local commute, and I managed just over 62 mpg last week. Still a bit short of your 83.4, Geocol, but we haven't taken it out of local traffic since Christmas.

Cheers,

Head