[bfivelover]

I like to put the car in neutral going downhill. Once in a while, more often lately, I will get 3 or 4 bars of charging while in neutral, even if the battery is nearly fully charged, which is where I try to keep it. Is this normal? It's a 2002 manual with 106,000 miles.

 

[Insightful Trekker]

With a few "mysteries" of the IMA system probably still out there its possibly normal under some unusual set of conditions.

An IMA reset would be indicated. And since your trying to maintain a "High" SoC stop coasting in neutral :!:

HTH!

 

[b1shmu63]

If the battery is "fully charged" then it cannot accept futher charging without damage. For this reason it is not normally a good idea to have the battery fully charged, as it disallows any savings in energy when slowing down. Use some of this excess charge for accelleration to actually increase overall efficiency! :wink: If you know you have a big downhill grade coming up you should again try to deplete the battery by the amount that the down grade will restore it.

 

[Rick]

You do realize you will use more gas by putting it in neutral right?

 

[Double-Trinity]

You do realize you will use more gas by putting it in neutral right?

Not necessarily... if the downhill is a gradual descent, then the engine braking often requires more gas to overcome than running the engine at idle. I'm not sure about this, but it seems like it would be possible for the car to be charging when in neutral for this reason: since the motor and engine are connected to one another, the motor could harness some of the power from the idling engine... I've never seen that behavior on my IMA civic, though.

 

[Insightful Trekker]

<snip>

Use some of this excess charge for accelleration to actually increase overall efficiency! :wink: If you know you have a big downhill grade coming up you should again try to deplete the battery by the amount that the down grade will restore it.

All true if your a MIMA equipped Insight However, since the IMA system is programmed as an electric "supercharger" and its ratio of assist is fixed. In other words to get at some of that electrical energy you _have_ to burn some dino juice.

Its been proven that _hyper_ MPG comes from little or no use of IMA on the highway.

HTH!

 

[Aaron Cake]

Not necessarily... if the downhill is a gradual descent, then the engine braking often requires more gas to overcome than running the engine at idle. I'm not sure about this, but it seems like it would be possible for the car to be charging when in neutral for this reason: since the motor and engine are connected to one another, the motor could harness some of the power from the idling engine... I've
never seen that behavior on my IMA civic, though.

At zero throttle, above 1000RPM, all fuel is cut from the engine. So while descending a hill in gear you will be using NO fuel. Idling the engine will of course burn fuel.

 

[kapps]

At zero throttle, above 1000RPM, all fuel is cut from the engine. So while descending a hill in gear you will be using NO fuel. Idling the engine will of course burn fuel.

Agreed

 

[IamIan]

neutral charge

I have noticed the same thing... If I am going down a hill at a good speed like over 40 MPH for a little while in neutral the regen lights come on just a bit like 3 or 4 lights....

As for useing more gass in neutral it depends on the conditions... If the braking that the ICE friction will cuase will slow the car and in gear the IMA with try to regen brake which will slow the car even more... and being in neutral will not slow the car you can use less gas to build up speed going down the hill then to be in fuel cut going down only to then need to apply more gas to go back up the next one... momentum of the situation may make it better MPG.... especialy if in gear you will have geatter fiction not only from ICE but also you will have REGEN from the IMA.

I have also personally noticed that at low speeds with a cold engine coasting in neutral will sometimes give me better MPG on the instant display than being in gear will....

I have not yet figured out all the variables in the 2 situations to figure out how to 100% of the time replicate them... but I know under some situations and drivign conditions being in gear can reduce MPG .... but all the data I have collected so far indicates that those are rare and very specific conditions and the difference between the two is not much.

My 2 Bits..

 

[nemystic]

While coasting in neutral, I've seen the small indicated regen condition many times over the 3.5 years I've had a 5 speed. The conditions that lead to this may be predictable, but the pattern has never been clear to me.

I'd agree that there are a few cases where coasting downhill in neutral is more economical than driving "in gear", despite the fuel cut condition.

The regen indicator isn't necessarily proportional to the actual recharge current. In fact, it can be quite misleading at times.

Now having the ability to monitor the system current somewhat precicely with a DVM, I continue to believe that hidden/background regen is based on some "intelligent" algorithm that probably considers trend as well as actual SoC, such as the rate of discharge. The hidden/background regen (at relatively low current) can sometimes continue to a nearly "full" indicated SoC, even without the headlights on, and with no indication on the regen bar graph.

Because in most downhill conditions I'm now usually in the MIMA mode, I haven't been able to observe the actual current associated with the regen-while-coasting-in-neutral phenomenon. If I do, however, it will be posted on this thread.

 

[ncnightowl]

Here's my strategy :

First, pull #18 fuse for 10 sec. to initiate a recal...

Second, allow car to charge back up (positive recal)...

Then, discontinue using IMA assist as much as possible, taking every opportunity to charge pack.

I can routinely get 20 bars of charge with no parasitic charging this way.

When cruising downhill on interstate, I just let off gas while in gear, very little drag from engine and no fuel used. Seems easier to maintain momentum this way. I get about 10% better mpg on my commute doing this.

 

[bfivelover]

And since your trying to maintain a "High" SoC stop coasting in neutral :!:

HTH!

I do maintain a high battery even though I coast. It's rarely down more than three bars.

 

[bfivelover]

You do realize you will use more gas by putting it in neutral right?

I don't buy that. If I'm coasting down a hill in neutral at 75MPH, I'm going to go a lot further before I have to put it in gear and give it gas at around 60MPH than if I coast in 5th gear at a slower speed, say 65MPH, then hit the gas around 60MPH. I'll hit the gas much earlier because I'll slow down to 60MPH much earlier and won't travel as far as when I'm in neutral thereby causing me to use more gas. Explain to me why that's not correct.

 

[Insightful Trekker]

Hi Bill,

Don't think you misunderstood my razz = But just in case:

It was a "play" on the old cliche:

Doc it hurts when I do this. Doc's reply, Then don't do that.

In regard to coasting only your MPG indicator will know for sure.

HTH!

 

[flunkysama]

To get back to the main topic, I have noticed it too. I only seen it when coasting down hills at >50mph. It seems the idle is raised a bit to around 1200 rpm. I've seen it before and after my battery, BCM, MCM change.
The biggest thing is that it only does it sometimes and its (currently) totally unpredictable.

It's at times like those, I wish I have a real ampmeter rather than the God-knows-what units the chrg/asst indicator uses.

 

[bfivelover]

To get back to the main topic, I have noticed it too. The biggest thing is that it only does it sometimes and its (currently) totally unpredictable.

I'm glad there are others that have experienced it also, so perhaps it is "normal" under certain circumstances.