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Friends,

I found something curious over the weekend and think it might have a big impact:

Turning on the headlights makes the car charge the IMA battery more aggressively!

This seems counterintuitive at first and I don't quite understand the reasoning behind it. It's almost like turning on the A/C. However, the lights use significantly less power so there should be no noticable mpg hit. Don't forget to turn them off when parked or in idle-stop for longer periods.

When I turn the lights on, charging starts within 10 - 30 seconds and stops immediately when I turn the light back off. If the car was charging already, turning the light on makes the charge current go up 1.0 to 1.5 Amps! This works both for forced charging and hidden charging (forced charging without green bars lit). It works for most levels of battery charge, except when full (19 or 20 bars).


To all those who suffer from recals, never get their SoC gauge to read full, or have other battery problems: Try driving around with the lights on at all times and see if you notice a change!

No, I'm not drunk and it's not a late April fools joke.
 

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This makes sense. The interface between the 12 volt and 144 volt system is one-way. The 144 volt system works like an alternator to charge the 12 volt system. When the 12 volt system has higher voltage, the link between the two is switched off. If the 12 volt system voltage goes low (like when you turn your lights on), then there is a demand on the 144-volt system to charge it.

Since the transformer that steps the 144 volt power down to the charging voltage for the 12 volt system has one fixed step-down ratio, that means that the control system would want the 144 volt system topped off in order to provide that power to the 12 volt system.

I would expect it to have a minor negative effect on gas mileage, but still quite small. It just depends if the 144-volt generator's drag on the engine affects the threshold for lean-burn mode, and that also involves how fast you are driving and whether you have a head-wind or tail-wind, if it's raining, etc.
 

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not quite

Will M said:
Since the transformer that steps the 144 volt power down to the charging voltage for the 12 volt system has one fixed step-down ratio, that means that the control system would want the 144 volt system topped off in order to provide that power to the 12 volt system.
Sorry, Will, but I think you are a little off. The DC-DC converter that provides 12V power is not a transformer at all. And it does not have a fixed conversion ratio. (This wouldn't work, since the NiMH battery's voltage varies between 120V and 180V during driving!)

The DC-DC really provides very well regulated constant 13.9V output. Also, the charge current that I measured and talked about in my earlier email is the current going into the 144V battery. This should not be affected by current drains in the 12V system, since those are usually supplied by the IMA motor/generator while the engine is running. Also, the effect is opposite what it would be, if it was just the current supplying the load. (it would be a discharge on the battery, or reduced charge current).

No the only way to explain the symptom is that there must be a software feature that says "when there is x load on the 12V system, increase charging the 144V system." For whatever reason.
 

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Re: not quite

Armin said:
Sorry, Will, but I think you are a little off. The DC-DC converter that provides 12V power is not a transformer at all. And it does not have a fixed conversion ratio. (This wouldn't work, since the NiMH battery's voltage varies between 120V and 180V during driving!)
It's always good to learn. Thanks for the info, though it still seems a bit vague yet. (I've returned to edit this down quite a bit, since much of the discussion was more appropriately moved to personal messages...)

Armin said:
The DC-DC really provides very well regulated constant 13.9V output. Also, the charge current that I measured and talked about in my earlier email is the current going into the 144V battery. This should not be affected by current drains in the 12V system, since those are usually supplied by the IMA motor/generator while the engine is running.
You doubt the accuracy of the Encyclopedia on this list in reference to the details of how the system charges the 12 volt system. Until we can resolve who has the more accurate model, that ends most of the discussion.

Armin said:
Also, the effect is opposite what it would be, if it was just the current supplying the load. (it would be a discharge on the battery, or reduced charge current).
We are miscommunicating... All variables are managed by the control system and if it's priority is on maintaining a 13.9 volt charging current, then it will manage all the other variables in order to acquire that value.

Armin said:
No the only way to explain the symptom is that there must be a software feature that says "when there is x load on the 12V system, increase charging the 144V system." For whatever reason.
I'm only suggesting that the reason is to maintain the charging voltage at 13.9. If you have a better reason, let's hear it.
 

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back on topic

This thread went a little OT, but to come back on topic:

I confirmed that any load on the 12V system (lights, rear-window-defogger, fan, ...) has the same effect of charging the 144V battery more aggressively.

It does keep the SoC of my 144V battery almost always at 18-19 bars again. Before I turned the light on, it was frequently going to about half and recalibrating.

I'll have to wait and watch a little to see if my recals really get fewer.
 

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I have noticed that keeping the lights on does make the car charge the battery more agressively and the SOC higher... That's neat!
~Martin
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2000 5 Spd
 

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I'm just curious why people want to "force" recharge the batteries. I mean, you have to figure that Honda put some serious development into the BCM to develop optimal charging algorithms for both performance and cell life. There is a reason that the batteries rarely exceeed 80% SOC.

While recals are very annoying, I can't say that I have ever experienced one in the 15,000 KM that I have driven the car. Though I rarely bring the pack down more then 50%.

I did completely drain the pack twice two weeks ago (keeping up with a line of RX-7s on the way to Indiana), and even that did not result in a recal.
 

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Aaron,

one of the pecularities of the "recal" problem is that it only affects some cars.

We have tried very hard in the past in both yahoo groups to link it to something in driving style, environmental conditions, gas quality, driver weight, ... etc. without success. It is entirely random. Just because you don't see it doesn't mean it's not there.

Consider yourself lucky!
 

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this makes sense!
before i moved, i could reach a full charge about once a week, but that was also when i left my lights on all the time (for safety)

then i turned them off thinking it was hurting my charge, but i havent reached full since then!

i miss having a full charge because i can really coast quickly in fuel cut mode but without the IMA charging and slowing me down

ill try this and report back next week
 

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Aaron Cake said:
I did completely drain the pack twice two weeks ago (keeping up with a line of RX-7s on the way to Indiana), and even that did not result in a recal.
A recal is a reset by the Insight computer of reported IMA battery state-of-charge to 0 bars. What you experienced is a recal. It just wasn't an unexpected one.
 

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Speaking of recals. I have left my 2002 Insight in auto stop and ran the stereo for over an hour before. This drained the soc to about half, but the car started right back up and I was able to drive off. It force charged for a little while until it was back up to around 2/3 charge and it was fine. Now the other day I went for a ride in my frineds 2001 Insight with a non replaced ECU. He won't let them change it as it makes the IMA way to aggressive for Arizona summer climates. Anyway, we stopped at the bank so he could make a quick run to the ATM. He left me in the car in auto stop for a few minutes while he got his money. We drove off and as we were driving down the road all of a sudden we both noticed the bars on the soc gague were dropping off. I don't think I would put his comment here, but he says that happens when the car is left in auto stop for more than 2 minutes.

So we drove around for a little while eeking every last ounce of regenreative braking possible out of the thing, but it started going in to thermal cut back as the batteries were getting hot, and it kept force charging at lights. I'm just curious if anyone else has noticed this behavior if in auto stop for more than a couple minutes. I've tried to reproduce that in my 2002, but cant'. I wounder if they corrected that with the new ECU's also.
 

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Armin,

Great find! I periodically have this problem where my Insight will not trickle charge, even though it is way below 50%. Eventually it gets too low (recals, I guess) and then figures out it needs to charge. It was in this state when I read about the lights thing and I tried it this morning and sure enough, it started charging! Thanks!
 
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IHonda2002 said:
Armin,

Great find! I periodically have this problem where my Insight will not trickle charge, even though it is way below 50%. Eventually it gets too low (recals, I guess) and then figures out it needs to charge. It was in this state when I read about the lights thing and I tried it this morning and sure enough, it started charging! Thanks!
Glat to hear I'm not the only one that has experienced this. But I wish I had seen this post before I made my own yesterday. Guess I'll be driving with my lights on more often. :)
 
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